U.S. patent application number 12/016843 was filed with the patent office on 2008-05-15 for method and apparatus for arrhythmia classification using atrial signal mapping.
This patent application is currently assigned to Cardiac Pacemakers, Inc.. Invention is credited to James O. Gilkerson, Julie Thompson, Yongxing Zhang, Yunlong Zhang.
Application Number | 20080114258 12/016843 |
Document ID | / |
Family ID | 36568209 |
Filed Date | 2008-05-15 |
United States Patent
Application |
20080114258 |
Kind Code |
A1 |
Zhang; Yunlong ; et
al. |
May 15, 2008 |
METHOD AND APPARATUS FOR ARRHYTHMIA CLASSIFICATION USING ATRIAL
SIGNAL MAPPING
Abstract
An implantable medical device senses a plurality of electrograms
from substantially different atrial locations, detects regional
depolarizations from the electrograms, and analyzes timing
relationships among the regional depolarizations. The timing
relationships provide a basis for effective therapy control and/or
prognosis of certain cardiac disorders. In one embodiment, an
atrial activation sequence is mapped to show the order of
occurrences of the regional depolarizations during an atrial
depolarization for classifying a detected tachyarrhythmia by its
origin. In another embodiment, conduction time between two atrial
locations is measured for monitoring the development of an abnormal
atrial conditions and/or the effect of a therapy.
Inventors: |
Zhang; Yunlong; (Mounds
View, MN) ; Thompson; Julie; (Circle Pines, MN)
; Gilkerson; James O.; (Stillwater, MN) ; Zhang;
Yongxing; (Maple Grove, MN) |
Correspondence
Address: |
Schwegman, Lundberg, Woessner & Kluth, P.A.
P.O. Box 2938
Minneapolis
MN
55402
US
|
Assignee: |
Cardiac Pacemakers, Inc.
|
Family ID: |
36568209 |
Appl. No.: |
12/016843 |
Filed: |
January 18, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11000133 |
Nov 30, 2004 |
7328063 |
|
|
12016843 |
Jan 18, 2008 |
|
|
|
Current U.S.
Class: |
600/516 |
Current CPC
Class: |
G16H 50/20 20180101;
A61N 1/3622 20130101; A61B 5/7264 20130101; A61N 1/3956 20130101;
A61B 5/349 20210101 |
Class at
Publication: |
600/516 |
International
Class: |
A61B 5/0452 20060101
A61B005/0452 |
Claims
1. A lead for electrically coupling an implantable medical device
to a heart having a right atrium (RA) connected to a vena cava, a
left atrium (LA), a left ventricle (LV), a sinoatrial (SA) node, an
atrial septum, a coronary sinus, a coronary vein, the lead
comprising: an elongate lead body having a primary end and a distal
end, the primary end coupled to a connector configured for
connecting to the implantable medical device; first, second, and
third conductors disposed within the lead body and coupled to the
connector; an LA electrode coupled to the first conductor and
configured for placement in the coronary sinus or coronary vein
near the LA; an atrial septal electrode coupled to the second
conductor and configured for placement in the coronary sinus near
the atrial septum; and a high RA (HRA) electrode coupled to the
third conductor and configured for placement in the RA or the
superior vena cava near the SA node.
2. The lead of claim 1, further comprising: a fourth conductor
disposed within the lead body and coupled to the connector; and an
LV electrode coupled to the fourth conductor and the distal end of
the lead body and configured for placement in the coronary vein
over the LV.
3. The lead of claim 2, wherein the LA electrode, the atrial septal
electrode, and the HRA electrode are each a ring electrode
incorporated onto the elongate lead body.
4. A lead for electrically coupling an implantable medical device
to a heart having a right atrium (RA) connected to a superior vena
cava, a sinoatrial (SA) node, and an atrial septum, the lead
comprising: an elongate lead body having a primary end and a distal
end, the primary end coupled to a connector configured for
connecting to the implantable medical device; first and second
conductors disposed within the lead body and coupled to the
connector; a high RA (HRA) electrode coupled to the first conductor
and configured for placement in the RA or the superior vena cava
near the SA node; and a second RA electrode coupled to the second
conductor and configured for placement in the RA.
5. The lead of claim 4, wherein the second RA electrode is an
atrial septal electrode configured for placement in the RA near the
atrial septum.
6. The lead of claim 5, wherein the HRA electrode comprises a ring
electrode incorporated onto the elongate lead body.
7. The lead of claim 4, further comprising: a third conductor
disposed within the lead body and coupled to the connector; and a
third RA electrode coupled to the third conductor and configured
for placement in the RA.
8. The lead of claim 7, wherein the second RA electrode and the
third RA electrode are each an atrial septal electrode configured
for placement in the RA near the atrial septum.
9. A cardiac rhythm management system coupled to a heart having a
right atrium (RA) connected to a superior vena cava, a left atrium
(LA), a left ventricle (LV), a sinoatrial (SA) node, an atrial
septum, a coronary sinus, and a coronary vein, the system
comprising: one or more leads including a plurality of atrial
electrodes; and an implantable medical device coupled to the one or
more leads, the implantable medical device including: a sensing
circuit configured to sense a plurality of atrial electrograms
using the plurality of atrial electrodes; an arrhythmia detection
circuit configured to detect tachyarrhythmia; and an arrhythmia
classification circuit configured to classify the detected
tachyarrhythmia, the arrhythmia classification circuit including:
an atrial signal mapping module configured to map an atrial
activation sequence using the sensed plurality of atrial
electrograms, the atrial activation sequence indicative of an order
of regional depolarizations during an atrial depolarization; and an
atrial pattern analyzer configured to classify the detected
tachyarrhythmia using the atrial activation sequence.
10. The system of claim 9, wherein the one or more leads comprises
a first lead including: an LA electrode configured for placement in
the coronary sinus or coronary vein near the LA; an atrial septal
electrode configured for placement in the coronary sinus near the
atrial septum; and a high RA (HRA) electrode configured for
placement in the RA or the superior vena cava near the SA node,
wherein the sensing circuit is configured to sense an RA
electrogram via the HRA electrode, an LA electrogram via the LA
electrode, and an atrial septal electrogram via the atrial septal
electrode, and wherein the atrial signal mapping module is
configured to map an atrial activation sequence using the RA
electrogram, the LA electrogram, and the atrial septal
electrogram.
11. The system of claim 10, wherein the implantable medical device
comprises: an event detection circuit configured to detect an RA
event from the RA electrogram and an LA event from the LA
electrogram during an atrial depolarization; and an inter-atrial
interval measurement circuit configured to measure a time interval
between the RA event and the LA event.
12. The system of claim 11, wherein the implantable medical device
further comprises one or more of an atrial enlargement detection
circuit and an atrial conduction disturbance detection circuit, the
atrial enlargement detection circuit configured to detect abnormal
enlargement of at least one atrium using the inter-atrial interval,
the atrial conduction disturbance detection circuit configured to
detect atrial conduction disturbance using the inter-atrial
interval.
13. The system of claim 12, wherein the implantable medical device
comprises the atrial enlargement detection circuit, and the atrial
enlargement detection circuit comprises a comparator including a
first input to receive the inter-atrial interval, a second input to
receive a predetermined threshold interval, and an output to
indicate the abnormal enlargement of at least one atrium when the
inter-atrial interval exceeds the predetermined threshold
interval.
14. The system of claim 12, wherein the implantable medical device
comprises the atrial conduction disturbance detection circuit, and
the atrial conduction disturbance detection circuit is configured
to detect a variance of the inter-atrial interval and comprises a
comparator including a first input to receive the variance of the
inter-atrial interval, a second input to receive a predetermined
threshold variance, and an output to indicate the atrial conduction
disturbance when the variance of the inter-atrial interval exceeds
the predetermined threshold variance.
15. The system of claim 10, wherein the first lead further
comprises an LV electrode configured for placement in the coronary
vein over the LV, the sensing circuit is further configured to
sense an LV electrogram via the LV electrode, and the atrial
pattern analyzer is configured to classify the tachyarrhythmia
using the atrial activation sequence and the LV electrogram.
16. The system of claim 9, wherein the one or more leads comprises
a first lead and a second lead, the first lead including a high RA
(HRA) electrode configured for placement in the RA or the superior
vena cava near the SA node and a second RA electrode configured for
placement in the RA, the second lead including an LA electrode
configured for placement in the coronary sinus or coronary vein
near the LA, wherein the sensing circuit is configured to sense an
RA electrogram via the HRA electrode, an LA electrogram via the LA
electrode, and an atrial septal electrogram via the second atrial
electrode, and wherein the atrial signal mapping module is
configured to map an atrial activation sequence using the RA
electrogram, the LA electrogram, and the atrial septal
electrogram.
17. The system of claim 16, wherein the implantable medical device
further comprises: an event detection circuit configured to detect
an RA event from the RA electrogram and an LA event from the LA
electrogram during an atrial depolarization; and an inter-atrial
interval measurement circuit configured to measure a time interval
between the RA event and the LA event.
18. The system of claim 17, wherein the implantable medical device
further comprises one or more of an atrial enlargement detection
circuit and an atrial conduction disturbance detection circuit, the
atrial enlargement detection circuit configured to detect abnormal
enlargement of at least one atrium using the inter-atrial interval,
the atrial conduction disturbance detection circuit configured to
detect atrial conduction disturbance using the inter-atrial
interval.
19. The system of claim 18, wherein the implantable medical device
comprises the atrial enlargement detection circuit, and the atrial
enlargement detection circuit comprises a comparator including a
first input to receive the inter-atrial interval, a second input to
receive a predetermined threshold interval, and an output to
indicate the abnormal enlargement of at least one atrium when the
inter-atrial interval exceeds the predetermined threshold
interval.
20. The system of claim 18, wherein the implantable medical device
comprises the atrial conduction disturbance detection circuit, and
the atrial conduction disturbance detection circuit is configured
to detect a variance of the inter-atrial interval and comprises a
comparator including a first input to receive the variance of the
inter-atrial interval, a second input to receive a predetermined
threshold variance, and an output to indicate the atrial conduction
disturbance when the variance of the inter-atrial interval exceeds
the predetermined threshold variance.
21. The system of claim 16, wherein the second lead further
comprises an LV electrode configured for placement in the coronary
vein over the LV, wherein the sensing circuit is further configured
to sense an LV electrogram via the LV electrode, and wherein the
atrial pattern analyzer is configured to classify the
tachyarrhythmia using the atrial activation sequence and the LV
electrogram.
22. The system of claim 9, wherein the atrial pattern analyzer
comprises at least two of: a right atrial pattern matching module
configured to detect a supraventricular tachyarrhythmia of a right
atrial origin by comparing the atrial activation sequence to a
predetermined right atrial pattern template sequence; a left atrial
pattern matching module configured to detect an supraventricular
tachyarrhythmia of a left atrial origin by comparing the atrial
activation sequence to a predetermined left atrial pattern template
sequence; and an atrial septal pattern matching module configured
to detect one of a supraventricular tachyarrhythmia of atrial
septal origin and a ventricular tachyarrhythmia by comparing the
atrial activation sequence to a predetermined atrial septal pattern
template sequence.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. application Ser.
No. 11/000,133, filed Nov. 30, 2004, the specification of which is
herein incorporated by reference.
TECHNICAL FIELD
[0002] This document relates generally to cardiac rhythm management
(CRM) systems and particularly, but not by way of limitation, to
such a system providing for detection and classification of
tachyarrhythmias.
BACKGROUND
[0003] The heart is the center of a person's circulatory system.
The left portions of the heart, including the left atrium (LA) and
left ventricle (LV), draw oxygenated blood from the lungs and pump
it to the organs of the body to provide the organs with their
metabolic needs for oxygen. The right portions of the heart,
including the right atrium (RA) and right ventricle (RV), draw
deoxygenated blood from the body organs and pump it to the lungs
where the blood gets oxygenated. These mechanical pumping functions
are accomplished by contractions of the heart. In a normal heart,
the sinoatrial (SA) node, the heart's natural pacemaker, generates
electrical impulses, called action potentials, that propagate
through an electrical conduction system to various regions of the
heart to cause the muscular tissues of these regions to depolarize
and contract at a normal sinus rate.
[0004] Tachyarrhythmia occurs when the heart contracts at a rate
higher than the normal sinus rate. Tachyarrhythmia generally
includes ventricular tachyarrhythmia (VT) and supraventricular
tachyarrhythmia (SVT). VT occurs, for example, when a pathological
conduction loop formed in the ventricles through which electrical
impulses travel circularly within the ventricles, or when a
pathologically formed electrical focus generates electrical
impulses from the ventricles. SVT can be physiologic (e.g., sinus
tachycardia) or pathologic (e.g., atrial fibrillation). The
physiologic sinus tachycardia occurs when the SA node generates the
electrical impulses at a particularly high rate. A pathologic SVT
occurs, for example, when a pathologic conduction loop forms in an
atrium or both atria. Fibrillation occurs when the heart contracts
at a tachyarrhythmic rate with an irregular rhythm. Ventricular
fibrillation (VF), as a ventricular arrhythmia with an irregular
conduction, is a life threatening condition requiring immediate
medical treatment such as ventricular defibrillation. Atrial
fibrillation (AF), as an SVT with an irregular rhythm, though not
directly life threatening, also needs medical treatment such as
atrial defibrillation to restore a normal cardiac function and
prevents the deterioration of the heart.
[0005] An understanding of the nature of a detected
tachyarrhythmia, including its origin, ensures effective and
efficient treatment. For example, anti-tachycardia pacing,
cardioversion, and defibrillation are among therapies treating
tachyarrhythmias by delivering electrical energy to the heart. To
be effective, the type of tachyarrhythmia, including its origin, is
to be determined for selecting the right type therapy and the right
region to which the electrical energy is delivered. When the atrial
rate of depolarizations (or contractions) is substantially
different from the ventricular rate of depolarizations (or
contractions) during a detected tachyarrhythmia, the atrial and
ventricular rates of depolarizations (or contractions) provide for
a basis for locating where the tachyarrhythmia originates. However,
there is a need to locate where the tachyarrhythmia originates when
the atrial depolarizations and the ventricular depolarizations
present a one-to-one (1:1) relationship.
SUMMARY
[0006] An implantable medical device senses a plurality of
electrograms from substantially different atrial locations, detects
regional depolarizations from the electrograms, and analyzes timing
relationships among the regional depolarizations. The timing
relationships provide a basis for effective therapy control and/or
prognosis of certain cardiac disorders.
[0007] In one embodiment, a CRM system includes a high RA (HRA)
electrode, an LA electrode, an atrial septal electrode, a
ventricular electrode, and an implantable medical device. The HRA
electrode is to be placed near the SA node to sense an RA
electrogram. The LA electrode is to be placed near the LA to sense
an LA electrogram. The atrial septal electrode is to be placed in
or near the atrial septum to sense an atrial septal electrogram.
The ventricular electrode is to be placed in or near a ventricle to
sense a ventricular electrogram. The implantable medical device
includes an arrhythmia detection circuit to detect tachyarrhythmias
and an arrhythmia classification circuit to classify the detected
tachyarrhythmias. The arrhythmia classification circuit includes an
atrial signal mapping module and an atrial pattern analyzer. The
atrial signal mapping module maps an atrial activation sequence
based on the RA electrogram, the LA electrogram, and atrial septal
electrogram. The atrial activation sequence indicates an order of
regional depolarizations during an atrial depolarization. The
atrial pattern analyzer classifies each detected tachyarrhythmia
based on the atrial activation sequence.
[0008] In one embodiment, a tachyarrhythmia detection and
classification system includes a sensing circuit, a rate detection
circuit, an arrhythmia detection circuit, and an arrhythmia
classification circuit. The sensing circuit senses a plurality of
atrial electrograms and at least one ventricular electrogram. The
rate detection circuit detects an atrial rate from at least one of
the atrial electrograms and a ventricular rate from the ventricular
electrogram. The arrhythmia detection circuit detects a
tachyarrhythmia based on at least one of the atrial rate and the
ventricular rate. The arrhythmia classification circuit includes a
1:1 tachyarrhythmia detector, an atrial signal mapping module, and
an atrial pattern analyzer. The 1:1 tachyarrhythmia detector
classifies the detected tachyarrhythmia as a 1:1 tachyarrhythmia
when the atrial rate and the ventricular rate are substantially
equal. The atrial signal mapping module maps an atrial activation
sequence based on the atrial electrograms. The atrial activation
sequence indicates an order of regional depolarizations during an
atrial depolarization. The atrial pattern analyzer classifies the
1:1 tachyarrhythmia based on the atrial activation sequence.
[0009] In one embodiment, a CRM system provides for monitoring of
prognostic factors for atrial fibrillation and heart failure. The
CRM system includes two electrodes, a sensing circuit, an event
detection circuit, and an inter-atrial interval measurement
circuit. One electrode is to be placed in the RA or superior vena
cava near the SA node. The other electrode is to be placed in the
coronary sinus or coronary vein near the LA. The sensing circuit
senses an RA electrogram and an LA electrogram through the
electrodes. The event detection circuit detects an RA event from
the RA electrogram and an LA event from the LA electrogram during
an atrial depolarization. The inter-atrial interval measurement
circuit measures an inter-atrial interval between the RA event and
the LA event.
[0010] In one embodiment, a coronary lead provides for sensing of
one or more of an LA electrogram, an atrial septal electrogram, and
an RA electrogram. The coronary lead includes an elongate lead body
with a primary end and a distal end. The primary end is coupled to
a connector for connecting to an implantable medical device. At
least an LA electrode, an atrial septal electrode, and an HRA
electrode are incorporated into the coronary lead. The LA electrode
is to be placed in the coronary sinus or coronary vein near the LA.
The atrial septal electrode is to be placed in the coronary sinus
near the atrial septum. The HRA electrode is to be placed in the RA
or the superior vena cava near the SA node. The LA electrode, the
atrial septal electrode, and the HRA electrode are each connected
to one of a plurality of conductors that are disposed within the
lead body and connected to the connector.
[0011] In one embodiment, an RA lead provides for sensing of one or
more RA electrograms. The RA lead includes an elongate lead body
with a primary end and a distal end. The primary end is coupled to
a connector for connecting to an implantable medical device. At
least an HRA electrode and a second RA electrode are incorporated
into the RA lead. The HRA electrode is to be placed in the RA or
the superior vena cava near the SA node. The second RA electrode is
to be placed in the RA in or near the atrial septum. The HRA
electrode and the second RA electrode are each connected to one of
a plurality of conductors that are disposed within the lead body
and connected to the connector.
[0012] In one embodiment, a method provides for classification of a
tachyarrhythmia by its origin. An atrial activation sequence is
received. The atrial activation sequence indicates an order of
occurrence of an RA event, an atrial septal event, and an LA event
during an atrial depolarization. The tachyarrhythmia is classified
as a tachyarrhythmia of RA origin if the RA event occurs first in
the atrial activation sequence, as a tachyarrhythmia of LA origin
if the LA event occurs first in the atrial activation sequence, and
as a tachyarrhythmia of atrial septal or ventricular origin if the
atrial septal event occurs first in the atrial activation
sequence.
[0013] In one embodiment, a method provides for detection and
classification of tachyarrhythmias. A plurality of atrial
electrograms and at least one ventricular electrogram are sensed.
The atrial electrograms indicates regional depolarizations in
substantially different atrial locations. An atrial rate is
detected from at least one of the atrial electrograms. A
ventricular rate is detected from the ventricular electrogram. A
tachyarrhythmia is detected based on at least one of the atrial
rate and the ventricular rate. The detected tachyarrhythmia is
classified as a 1:1 tachyarrhythmia when the atrial rate and the
ventricular rate are substantially equal. Following the
classification of the detected tachyarrhythmia as the 1:1
tachyarrhythmia, an atrial activation sequence is mapped based on
the atrial electrograms. The atrial activation sequence indicates
an order of occurrence of the regional depolarizations in the
substantially different atrial locations. The 1:1 tachyarrhythmia
is classified based on the atrial activation sequence.
[0014] In one embodiment, a method provides for monitoring of a
heart. An RA electrogram is sensed using an electrode placed in the
RA or the superior vena cava near the SA node. An LA electrogram is
sensed using an electrode placed in the coronary sinus or coronary
vein near the LA. An RA event is detected from the RA electrogram,
and an LA event is detected from the LA electrogram, for each
atrial depolarization. An inter-atrial interval is measured as the
time interval between the RA event and the LA event.
[0015] This Summary is an overview of some of the teachings of the
present application and not intended to be an exclusive or
exhaustive treatment of the present subject matter. Further details
about the present subject matter are found in the detailed
description and appended claims. Other aspects of the invention
will be apparent to persons skilled in the art upon reading and
understanding the following detailed description and viewing the
drawings that form a part thereof, each of which are not to be
taken in a limiting sense. The scope of the present invention is
defined by the appended claims and their equivalents.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The drawings, which are not necessarily drawn to scale,
illustrate generally, by way of example, but not by way of
limitation, various embodiments discussed in the present
document.
[0017] FIG. 1 is an illustration a CRM system including an
arrhythmia detection and classification circuit and/or an
inter-atrial interval monitoring circuit and portions of an
environment in which the CRM system operates.
[0018] FIG. 2 is a graph illustrating an atrial activation sequence
indicating a tachyarrhythmia of RA origin.
[0019] FIG. 3 is a graph illustrating an atrial activation sequence
indicating a tachyarrhythmia of atrial septal or ventricular
origin.
[0020] FIG. 4 is a graph illustrating an atrial activation sequence
indicating a tachyarrhythmia of LA origin.
[0021] FIG. 5 is a block diagram illustrating an embodiment of
portions of a circuit of the CRM system.
[0022] FIG. 6 is a block diagram illustrating an embodiment of the
arrhythmia detection and classification circuit.
[0023] FIG. 7 is a block diagram illustrating a specific embodiment
of the arrhythmia detection and classification circuit.
[0024] FIG. 8 is a flow chart illustrating an embodiment of a
method for classifying tachyarrhythmia based on the atrial signal
mapping.
[0025] FIG. 9 is a flow chart illustrating an embodiment of a
method for detecting and classifying tachyarrhythmia.
[0026] FIG. 10 is a block diagram illustrating an embodiment of the
inter-atrial interval monitoring circuit.
[0027] FIG. 11 is a block diagram illustrating a specific
embodiment of the inter-atrial interval monitoring circuit.
[0028] FIG. 12 is a flow chart illustrating an embodiment of a
method for monitoring cardiac conditions based on an inter-atrial
interval.
DETAILED DESCRIPTION
[0029] In the following detailed description, reference is made to
the accompanying drawings which form a part hereof, and in which is
shown by way of illustration specific embodiments in which the
invention may be practiced. These embodiments are described in
sufficient detail to enable those skilled in the art to practice
the invention, and it is to be understood that the embodiments may
be combined, or that other embodiments may be utilized and that
structural, logical and electrical changes may be made without
departing from the scope of the present invention. The following
detailed description provides examples, and the scope of the
present invention is defined by the appended claims and their
equivalents.
[0030] It should be noted that references to "an", "one", or
"various" embodiments in this disclosure are not necessarily to the
same embodiment, and such references contemplate more than one
embodiment.
[0031] This document discusses, among other things, a CRM system
that detects and classifies tachyarrhythmias and/or monitors
inter-atrial conduction intervals. The origin of each
tachyarrhythmia classified as a 1:1 tachyarrhythmia is located by
atrial signal mapping. The 1:1 tachyarrhythmia, characterized by a
one-to-one association between atrial and ventricular
depolarizations, is indicated by substantially equal atrial and
ventricular rates. Electrograms are sensed from multiple atrial
sites and at least one ventricular site. The atrial signal mapping
results in an atrial activation sequence showing the order of
regional depolarization at the multiple atrial sites during an
atrial depolarization, thus allowing for localization of the origin
of the 1:1 tachyarrhythmia. For example, an RA electrogram, an
atrial septal electrogram, an LA electrogram, and a ventricular (RV
or LV) electrogram are sensed. A 1:1 tachyarrhythmia is classified
as a tachyarrhythmia of RA origin (or SVT of RA origin) if RA
depolarizes first during the atrial depolarization, a
tachyarrhythmia of LA origin (or SVT of LA origin) if LA
depolarizes first during the atrial depolarization, and a
tachyarrhythmia of atrial septal origin or ventricular origin with
one-to-one retrograde conduction via the atrioventricular (AV) node
if the atrial septum depolarizes first during the atrial
depolarization. Morphological analysis is applied to further
discriminate between a tachyarrhythmia of atrial septal origin (or
SVT of atrial septal origin) and a tachyarrhythmia of ventricular
origin with one-to-one retrograde conduction via the AV node (or
VT). The classification of the 1:1 tachyarrhythmia is used for
diagnostic and/or therapy control purposes. Electrograms sensed
from different atrial sites also provide for measurement of an
inter-atrial interval, which is a time interval between two
regional depolarizations at substantially different atrial location
during an atrial depolarization. Abnormalities in the inter-atrial
interval serve as factors prognosticating conditions such as heart
failure and AF.
[0032] FIG. 1 is an illustration a CRM system 100 and portions of
an environment in which system 100 operates. CRM system 100
includes an implantable medical device 105 that is electrically
coupled to a heart through leads 110, 115, and 125. An external
system 190 communicates with implantable medical device 105 via a
telemetry link 185.
[0033] Implantable medical device 105 includes a hermetically
sealed can housing an electronic circuit that senses physiological
signals and delivers therapeutic electrical pulses. The
hermetically sealed can also functions as an electrode for sensing
and/or pulse delivery purposes. In one embodiment, implantable
medical device 105 includes an arrhythmia detection and
classification circuit that detects and classifies
tachyarrhythmias. If a detected tachycardia is classified as a 1:1
tachyarrhythmia, it is further classified by determining its origin
based on at least an atrial signal mapping. Exemplary embodiments
of the arrhythmia detection and classification circuit and method
are described in detail below with reference to FIGS. 2-9. In one
embodiment, implantable medical device 105 includes an inter-atrial
interval monitoring circuit to measure an inter-atrial interval for
cardiac condition prognosis or therapy monitoring purposes.
Exemplary embodiments of the inter-atrial interval monitoring
circuit and method are described in detail below with reference to
FIGS. 10-12.
[0034] Lead 110 is a pacing lead. In one embodiment, as illustrated
in FIG. 1, lead 110 is an RA pacing lead that includes an elongate
lead body having a proximal end 111 and a distal end 113. Proximal
end 111 is coupled to a connector for connecting to implantable
medical device 105. Distal end 113 is configured for placement in
the RA in or near the atrial septum. Lead 110 includes a high RA
(HRA) electrode 112, an atrial septal tip electrode 114A, and an
atrial septal ring electrode 114B. HRA electrode 112 is a
pacing-sensing electrode incorporated into the lead body in a
location suitable for placement in the RA or the superior vena cava
near the SA node. Atrial septal electrodes 114A and 114B are
pacing-sensing electrodes incorporated into the lead body at or
near distal end 113 for placement in or near the atrial septum.
Electrodes 112, 114A, and 114B are each electrically coupled to
implantable medical device 105 through a conductor disposed within
the lead body. HRA electrode 112 allows for sensing an RA
electrogram indicative of depolarizations in an upper RA region
including the SA node and its vicinity and delivering pacing pulses
to that region. In one embodiment, HRA electrode 112 is a ring
electrode incorporated onto the elongate lead body. The distance
between distal end 113 and HRA electrode 112 is determined such
that when distal end 113 is placed in the atrial septum, electrode
112 is in a location suitable for sensing the RA electrogram
indicative of depolarizations in the upper RA region including the
SA node and its vicinity and delivering pacing pulses to that
region. Atrial septal electrodes 114A and/or 114B allow for sensing
an atrial septal electrogram indicative of depolarizations in the
atrial septal region and delivering pacing pulses to that
region.
[0035] Lead 115 is a defibrillation lead. In one embodiment, as
illustrated in FIG. 1, lead 115 includes an elongate lead body
having a proximal end 117 and a distal end 119. Proximal end 117 is
coupled to a connector for connecting to implantable medical device
105. Distal end 119 is configured for placement in the RV. Lead 115
includes a proximal defibrillation electrode 116, a distal
defibrillation electrode 118, and an RV electrode 120.
Defibrillation electrode 116 is incorporated into the lead body in
a location suitable for supraventricular placement in the RA and/or
the superior vena cava. Defibrillation electrode 118 is
incorporated into the lead body near distal end 119 for placement
in the RV. RV electrode 120 is a pacing-sensing electrode
incorporated into the lead body at distal end 119. Electrodes 116,
118, and 120 are each electrically coupled to implantable medical
device 105 through a conductor disposed within the lead body.
Proximal defibrillation electrode 116, distal defibrillation
electrode 118, and the can of implantable medical device 105 allow
for delivery of cardioversion/defibrillation pulses to the heart.
RV electrode 120 allows for sensing an RV electrogram and
delivering pacing pulses to the RV.
[0036] Lead 125 is a pacing lead that allows for the atrial signal
mapping, either by itself or in combination with leads 110 and/or
115. In one embodiment, as illustrated in FIG. 1, lead 125 is a
coronary pacing lead that includes an elongate lead body having a
proximal end 121 and a distal end 123. Proximal end 121 is coupled
to a connector for connecting to implantable medical device 105.
Distal end 123 is configured for placement in the coronary vein.
Lead 125 includes an HRA electrode 122, an atrial septal electrode
124, an LA electrode 126, and an LV electrode 128. HRA electrode
122 is a pacing-sensing electrode incorporated into the lead body
in a location suitable for placement in the RA or the superior vena
cava near the SA node. Atrial septal electrode 124 is incorporated
into the lead body in a location suitable for placement in the
coronary sinus near the atrial septum. LA electrode 126 is
incorporated into the lead body in a location suitable for
placement in the coronary sinus or coronary vein near the LA. LV
electrode 128 is incorporated into the lead body at the distal end
for placement in the coronary vein over the LV. Electrodes 122,
124, 126, and 128 are each electrically coupled to implantable
medical device 105 through a conductor disposed within the lead
body. HRA electrode 122 allows for sensing an RA electrogram
indicative of depolarizations in the upper RA region near the SA
node and delivering pacing pulses to that region. Atrial septal
electrode 124 allows for sensing an atrial septal electrogram
indicative of depolarizations in the atrial septal region and
delivering pacing pulses to that region. LA electrode 126 allows
for sensing an LA electrogram indicative of depolarizations in the
LA and delivering pacing pulses to the LA. LV electrode 128 allows
for sensing an LV electrogram indicative of depolarizations in the
LV and delivering pacing pulses to the LV. LV electrode 128 is at
or near distal end 123. At least a distal portion of the elongate
lead body that includes distal end 123 is made suitable for
insertion into the coronary vein through the coronary sinus. In one
embodiment, HRA electrode 122, atrial septal electrode 124, and LA
electrode 126 are each a ring electrode incorporated onto the
elongate lead body. The portion of the elongate lead body onto
which HRA electrode 122, atrial septal electrode 124, and LA
electrode 126 are incorporated has a diameter suitable for
insertion into the coronary sinus and a portion of the sinus vein
next to the coronary sinus. Atrial septal electrode 124 has an
outer diameter suitable for placement in the coronary sinus. LA
electrode 126 has an outer diameter suitable for placement in the
coronary sinus and the portion of the sinus vein next to the
coronary sinus.
[0037] In the exemplary embodiment illustrated in FIG. 1,
pacing-sensing electrodes 112, 114A, 114B, 120, 122, 124, 126, and
128 each allow for sensing by pairing with another pacing-sensing
electrode or the can of implantable medical device 105. In one
example, atrial septal electrodes 114A and 114B allow for bipolar
sensing of an atrial septal electrogram, while one or more of
electrodes 112, 120, 122, 124, 126, and 128 each allow for sensing
of an electrogram from wherein the electrode is placed by using a
different electrode selected from electrodes 112, 114A, 114B, 120,
122, 124, 126, and 128 as a reference electrode. In another
example, atrial septal electrodes 114A and 114B allow for bipolar
sensing of an atrial septal electrogram, while one or more of
electrodes 112, 120, 122, 124, 126, and 128 each allow for unipolar
sensing of an electrogram from wherein the electrode is placed by
using the can of implantable medical device 105 as a reference
electrode. In other embodiments, one or more of electrodes 112,
120, 122, 124, 126, and 128 are each replaceable by a pair of
electrodes allowing for bipolar sensing when preferred. After
reading and comprehending this document, those skilled in the art
will understand that the present subject matter does not require
the inclusion or use of all the electrodes illustrated in FIG. 1.
In one embodiment, for example, an HRA electrode, an atrial septal
electrode, an LA electrode, and a ventricular electrode are needed
for tachyarrhythmia detection and classification according to the
present subject matter. The HRA electrode can be either HRA
electrode 112 or HRA electrode 122. The atrial septal electrode can
include one or more of atrial septal electrodes 114A, 114B, and
124. The ventricular electrode can be either RV electrode 120 or LV
electrode 128. Thus, various combinations of leads and electrodes
are possible. For example, lead 125 alone, with electrodes 122,
124, 126, and 128, is sufficient for the tachyarrhythmia detection
and classification according to the present subject matter.
Alternatively, lead 110 with electrodes 112, 114A, and 114B and a
modified version of lead 125 with electrodes 126 and 128 are used.
Other combinations are suitable based on overall design and
implantation considerations as understood by those skilled in the
art.
[0038] External system 190 allows for programming of implantable
medical device 105 and receives signals acquired by implantable
medical device 105. In one embodiment, telemetry link 185 is an
inductive telemetry link. In an alternative embodiment, telemetry
link 185 is a far-field radio-frequency telemetry link. Telemetry
link 185 provides for data transmission from implantable medical
device 105 to external system 190. This may include, for example,
transmitting real-time physiological data acquired by implantable
medical device 105, extracting physiological data acquired by and
stored in implantable medical device 105, extracting therapy
history data stored in implantable medical device 105, and
extracting data indicating an operational status of implantable
medical device 105 (e.g., battery status and lead impedance). In
one embodiment, the classifications of detected tachyarrhythmias
and/or the measured inter-atrial interval are transmitted to
external system 190, for purposes such as cardiac condition
diagnosis and therapy adjustment. Telemetry link 185 also provides
for data transmission from external system 190 to implantable
medical device 105. This may include, for example, programming
implantable medical device 105 to acquire physiological data,
programming implantable medical device 105 to perform at least one
self-diagnostic test (such as for a device operational status),
programming implantable medical device 105 to run a signal analysis
algorithm (such as an algorithm implementing the tachyarrhythmia
detection and classification method discussed in this document),
and programming implantable medical device 105 to deliver pacing
and/or cardioversion/defibrillation therapies.
[0039] FIGS. 2-4 illustrate mapped atrial activation sequences
indicating tachyarrhythmias of substantially different origins. In
each of FIGS. 2-4, events markers representing regional
depolarizations detected from an RA electrogram (sensed by an HRA
electrode), an atrial septal electrogram, and an LA electrogram are
shown.
[0040] FIG. 2 is a graph illustrating an atrial activation sequence
indicating a tachyarrhythmia of RA origin (SVT of RA origin). RA
event 201, atrial septal event 202, and LA event 203 represent
regional depolarizations during an atrial depolarization. That is,
events 201, 202, and 203 result from the conduction of the same
electrical impulse across the atria. As illustrated in FIG. 2, the
atrial activation sequence shows that RA event 201 occurs first
during the atrial depolarization and is referred to as an "RA
pattern". This indicates that the origin of the electrical impulse
(ectopic focus) is most likely in the RA.
[0041] FIG. 3 is a graph illustrating an atrial activation sequence
indicating a tachyarrhythmia of atrial septal origin or ventricular
origin with one-to-one retrograde conduction (SVT of atrial septal
origin or VT). RA event 301, atrial septal event 302, and LA event
303 represent regional depolarizations during an atrial
depolarization. That is, events 301, 302, and 303 resulted from the
conduction of the same electrical impulse across the atria. As
illustrated in FIG. 3, the atrial activation sequence shows that
atrial septal event 302 occurs first during the atrial
depolarization and is referred to as an "atrial septal pattern".
This indicates that the origin of the electrical impulse (ectopic
focus) is in the atrial septal region in a ventricle. In the case
that the ectopic focus is in the ventricle, the electrical impulse,
by following a retrograde conduction path, is conducted from the
ventricle through the atrio-ventricular node to the atrial septum
and then to other regions of the atria. Thus, the atrial signal
mapping shows that the atrial septum depolarizes first.
[0042] FIG. 4 is a graph illustrating an atrial activation sequence
indicating a tachyarrhythmia of LA origin (SVT of LA origin). RA
event 401, atrial septal event 402, and LA event 403 represent
regional depolarizations during an atrial depolarization. That is,
events 401, 402, and 403 resulted from the conduction of the same
electrical impulse across the atria. As illustrated in FIG. 4, the
atrial activation sequence shows that LA event 403 occurs first
during the atrial depolarization and is referred to as an "LA
pattern". This indicates that the origin of the electrical impulse
(ectopic focus) is most likely in the LA.
[0043] Thus, depending on the location of the ectopic focus, each
1:1 tachyarrhythmia of atrial origin (SVT) is associated with one
of the RA, atrial septal, and LA patterns of the atrial activation
sequence. A 1:1 tachyarrhythmia of ventricular origin (VT) is
associated with the atrial septal pattern of atrial activation
sequence. Additional analysis, as discussed below, is needed to
discriminate between a tachyarrhythmia of ventricular origin and a
tachyarrhythmia of atrial septal origin when the atrial signal
mapping results on the atrial septal pattern of the atrial
activation sequence.
[0044] FIG. 5 is a block diagram illustrating an embodiment of
portions of a circuit of CRM system 100 including HRA electrode(s)
522, atrial septal electrode(s) 524, LA electrode(s) 526,
ventricular electrode(s) 528, defibrillation electrode(s) 516, an
implantable medical device 505, an external system 590, and
telemetry link 185.
[0045] HRA electrode(s) 522 allows for sensing of an RA electrogram
indicative of regional depolarizations in the region near the SA
node. Examples of HRA electrode(s) 522 include HRA electrode(s) 112
and 122 as illustrated in FIG. 1.
[0046] Atrial septal electrode(s) 524 allows for sensing of an
atrial septal electrogram indicative of regional depolarizations in
the atrial septal region. Examples of atrial septal electrode(s)
524 include atrial septal electrodes 114A, 114B, and 124 as
illustrated in FIG. 1.
[0047] LA electrode(s) 526 allows for sensing of an LA electrogram
indicative of regional depolarizations in the LA. Examples of LA
electrode(s) 526 include LA electrode 126 as illustrated in FIG.
1.
[0048] Ventricular electrode(s) 528 allows for sensing of a
ventricular electrogram indicative of regional depolarizations in
one of the ventricles. Examples of ventricular electrode(s) 526
include RV electrode 120 and LV electrode 128 as illustrated in
FIG. 1.
[0049] Defibrillation electrode(s) 516 allows for sensing of
electrograms from and delivery of cardioversion/defibrillation
pulses to the heart. Examples of defibrillation electrode(s) 528
include defibrillation electrodes 116 and 118 as illustrated in
FIG. 1.
[0050] In addition to sensing electrograms, HRA electrode(s) 522,
atrial septal electrode(s) 524, LA electrode(s) 526, and
ventricular electrode(s) 528 also allow for delivery of pacing
pulses to the region where they are placed. To sense electrograms
using electrode pairs each including two electrodes placed in
substantially different regions, HRA electrode(s) 522, atrial
septal electrode(s) 524, LA electrode(s) 526, and ventricular
electrode(s) 528 each includes one electrode. To sense electrograms
using bipolar electrode configurations, HRA electrode(s) 522,
atrial septal electrode(s) 524, LA electrode(s) 526, and
ventricular electrode(s) 528 each include a pair of electrodes
separated by a short distance. A combination of electrode
configurations (arrangement of pairs) may be used to achieve
desirable electrogram quality. In one embodiment, HRA electrode(s)
522, atrial septal electrode(s) 524, LA electrode(s) 526, and
ventricular electrode(s) 528, each include a pair of electrodes and
are individually or collectively programmable for electrogram
sensing with various electrode configurations. One or more leads
are used to connect the electrodes to implantable medical device
505.
[0051] Implantable medical device 505 is one embodiment of
implantable medical device 105 and includes a sensing circuit 530,
an implant controller 532, a therapy circuit 534, and an implant
telemetry module 536. Sensing circuit 530 senses electrograms.
Implant controller 532 controls the operation of implantable
medical device 505, including processing and analyzing the
electrograms and controlling delivery of pacing, cardioversion, and
defibrillation pulses. Therapy circuit 534 delivers the pacing,
cardioversion, and/or defibrillation pulses. Implantable telemetry
module 536 receives data from, and sends data to, external system
590 via telemetry link 185.
[0052] Implant controller 532 includes one or both of an arrhythmia
detection and classification circuit 540 and an inter-atrial
interval monitoring circuit 570. Arrhythmia detection and
classification circuit 540 detects and classifies tachyarrhythmias
based on the electrograms sensed through one or more of HRA
electrode(s) 522, atrial septal electrode(s) 524, LA electrode(s)
526, ventricular electrode(s) 528, defibrillation electrode(s) 516.
Based on the classification of each detected tachyarrhythmia,
implant controller 532 determines whether to deliver a therapy,
including the type of the therapy and the site to which the therapy
is delivered. Therapy circuit 534 delivers therapies in response to
command signals received from implant controller 532. Inter-atrial
interval monitoring circuit 570 measures an inter-atrial interval
from two atrial electrograms, such as an RA electrogram sensed by
HRA electrode(s) 522 and an LA electrogram sensed by LA
electrode(s) 526. The inter-atrial interval is used as a prognostic
factor for monitoring development of, or effect of a therapy on,
cardiac conditions such as AF or heart failure. Exemplary
embodiments illustrating details of arrhythmia detection and
classification circuit 540 and inter-atrial interval monitoring
circuit 570 are discussed below.
[0053] External system 590 is one embodiment of external system 190
and includes an external telemetry module 594 that receives data
from, and transmits data to, implantable medical device 505. In one
embodiment, external system 590 includes a programmer. In another
embodiment, as illustrated in FIG. 5, external system 590 is a
patient management system including an external device 592 in
proximity of implantable medical device 505, a remote device 598 in
a relatively distant location, and a telecommunication network 596
linking the external device and the remote device. The patient
management system allows access to implantable medical device 505
from a remote location, for purposes such as monitoring patient
status and adjusting therapies.
[0054] FIG. 6 is a block diagram illustrating an embodiment of
arrhythmia detection and classification circuit 540. Arrhythmia
detection and classification circuit 540 is coupled to sensing
circuit 530 and includes a rate detection circuit 644, an
arrhythmia detection circuit 646, and an arrhythmia classification
circuit 648.
[0055] Sensing circuit 530 senses a plurality of atrial
electrograms (including the RA, atrial septal, and LA electrograms
as discussed above) and at least one ventricular electrogram (the
RV or LV electrogram as discussed above) through electrodes 522,
524, 526, and 528. Rate detection circuit 644 detects an atrial
rate from at least one of the RA, atrial septal, and LA
electrograms and a ventricular rate from the RV or LV electrogram.
Arrhythmia detection circuit 646 detects a tachyarrhythmia based on
at least one of the atrial rate and the ventricular rate. In one
embodiment, arrhythmia detection circuit 646 indicates a detection
of tachyarrhythmia when the ventricular rate exceeds a
predetermined tachyarrhythmia threshold rate.
[0056] Arrhythmia classification circuit 648 includes a 1:1
tachyarrhythmia detector 650, an atrial signal mapping module 652,
and an atrial pattern analyzer 654. A detected tachyarrhythmia is
classified by 1:1 tachyarrhythmia detector 648 as a 1:1
tachyarrhythmia when the atrial rate and the ventricular rate are
substantially equal. In one embodiment, 1:1 tachyarrhythmia
detector 648 classifies the detected tachyarrhythmia as a 1:1
tachyarrhythmia when the difference between the atrial rate and the
ventricular rate is within 10 beats per minute. Atrial signal
mapping module 652 maps an atrial activation sequence based on the
RA, atrial septal, and LA electrograms. The atrial activation
sequence indicative of an order of regional depolarizations in the
RA region near the SA node, the atrial septal region, and the LA
during an atrial depolarization. Atrial pattern analyzer 654
classifies the 1:1 tachyarrhythmia by its origin based on the
atrial activation sequence.
[0057] Arrhythmia classification circuit 648 also includes a
circuit for classifying the detected tachyarrhythmia when the
atrial rate and the ventricular rate are not substantially equal.
In one embodiment, this circuit classifies the detected
tachyarrhythmia as a VT if the atrial rate is substantially lower
than the ventricular rate and as a SVT or a dual arrhythmia if the
atrial rate is substantially higher than the ventricular rate. A
further detection is performed to discriminate between SVT and dual
arrhythmia.
[0058] FIG. 7 is a block diagram illustrating an arrhythmia
detection and classification circuit 740, which is a specific
embodiment of arrhythmia detection and classification circuit 540.
Arrhythmia detection and classification circuit 740 is coupled to
sensing circuit 530 and includes rate detection circuit 644,
arrhythmia detection circuit 646, and an arrhythmia classification
circuit 748. Arrhythmia classification circuit 748 is one specific
embodiment of arrhythmia classification circuit 648 and includes
1:1 tachyarrhythmia detector 650, an atrial signal mapping module
652, an atrial pattern analyzer 754, and a morphology analyzer 762.
Atrial pattern analyzer 754 and morphology analyzer 762 classify
the 1:1 tachyarrhythmia by its origin.
[0059] Atrial pattern analyzer 754 includes an RA pattern matching
module 756, an LA pattern matching module 758, and an atrial septal
pattern matching module 760. RA pattern matching module 756 detects
an SVT of RA origin by comparing the atrial activation sequence to
a predetermined RA pattern template sequence. In one embodiment, RA
pattern matching module 756 detects an SVT of RA origin when the
first event in the atrial activation sequence is an RA event. LA
pattern matching module 758 detects an SVT of LA origin by
comparing the atrial activation sequence to a predetermined LA
pattern template sequence. In one embodiment, LA pattern matching
module 758 detects an SVT of LA origin when the first event in the
atrial activation sequence is an LA event. Atrial septal pattern
matching module 760 detects one of an SVT of atrial septal origin
and a VT by comparing the atrial activation sequence to a
predetermined atrial septal pattern template sequence. In one
embodiment, atrial septal pattern matching module 760 detects an
SVT of atrial septal origin or a VT when the first event in the
atrial activation sequence is an RA event. That is, if the atrial
activation sequence has the atrial septal pattern, the detected 1:1
tachyarrhythmia is either an SVT of atrial septal origin or a VT.
In an alternative embodiment, only two of the RA pattern matching
module 756, LA pattern matching module 758, and atrial septal
pattern matching module 760 are included because if the atrial
activation sequence matches the template sequence of neither
pattern, the remaining pattern is identified.
[0060] Morphology analyzer 762 further classifies the 1:1
tachyarrhythmia as either an SVT of atrial septal origin or a VT
based on morphological features of one or more signals selected
from the RA, atrial septal, LA, and ventricular electrograms. In
one embodiment, morphology analyzer 762 includes a VT detector 764
that discriminates a VT from an SVT of atrial septal origin by
comparing the morphological features to a set of predetermined VT
template morphological features. An example of a morphology-based
classification of VT and SVT is discussed in U.S. Pat. No.
6,728,572, "SYSTEM AND METHOD FOR CLASSIFYING CARDIAC COMPLEXES,"
assigned to Cardiac Pacemakers, Inc., which is hereby incorporated
by reference in its entirety.
[0061] FIG. 8 is a flow chart illustrating an embodiment of a
method for classifying tachyarrhythmia based on the atrial signal
mapping. The method is applied to classify a 1:1 tachyarrhythmia by
its origin. In one embodiment, the method is performed by atrial
pattern analyzer 754 and morphology analyzer 762.
[0062] A signal indicative of a detection of a 1:1 tachyarrhythmia
is received at 800. This starts the process of classifying the
detected 1:1 tachyarrhythmia. An atrial activation sequence is
received at 810. The atrial activations sequence is the result of
the atrial signal mapping and indicates an order of occurrence of
an RA event, an atrial septal event, and an LA event during an
atrial depolarization. The RA event (also referred to as the HRA
event) represents a depolarization indicated by an RA electrogram
sensed in the RA region near the SA node. The atrial septal event
represents a depolarization indicated by an atrial septal
electrogram sensed in the atrial septal region. The LA event
represents a depolarization indicated by an LA electrogram sensed
near the LA. If the RA event is found to occur first in the atrial
activation sequence at 815, the tachyarrhythmia is classified as an
SVT of RA origin at 820. If the LA event is found to occur first in
the atrial activation sequence at 825, the tachyarrhythmia is
classified as an SVT of LA origin at 830. If neither the RA event
nor the LA event is found to occur first in the atrial activation
sequence, the tachyarrhythmia is classified as an SVT of atrial
septal or a VT at 840.
[0063] Arrhythmic morphological parameters are received at 850 if
the tachyarrhythmia is classified as an SVT of atrial septal or a
VT. The arrhythmic morphological parameters the measured from one
or more cardiac signals selected from the RA, atrial septal, and LA
electrograms and one or more ventricular electrograms sensed during
the tachyarrhythmia. The tachyarrhythmia is classified by
discriminating a VT from an SVT of atrial septal origin at 860. In
one embodiment, the tachyarrhythmia is classified as a VT if the
arrhythmic morphological parameters match template VT morphological
parameters. The template VT morphological parameters are measured
from the one or more cardiac signals during a known VT episode. An
example of a method for classifying VT and SVT based on morphology
is discussed in U.S. Pat. No. 6,728,572.
[0064] FIG. 9 is a flow chart illustrating an embodiment of a
method for detecting and classifying tachyarrhythmia. In one
embodiment, the method is performed by arrhythmia detection and
classification circuit 540 or 740.
[0065] A plurality of atrial electrograms from substantially
different atrial locations and at least one ventricular electrogram
are sensed at 900. In one embodiment, the electrograms include the
RA, atrial septal, LA, and ventricular electrograms as discussed
above with reference to FIG. 8. An atrial rate and a ventricular
rate are detected at 910. The atrial rate is detected from one of
the RA, atrial septal, and LA electrograms. The ventricular rate is
detected from the ventricular electrogram. A tachyarrhythmia is
detected based on at least one of the atrial rate and the
ventricular rate at 920. In one embodiment, the tachyarrhythmia is
detected when the ventricular rate exceeds a predetermined
tachyarrhythmia threshold rate. In one specific embodiment, the
tachyarrhythmia threshold rate is programmable in the range between
90 beats per minute and 220 beats per minute.
[0066] After being detected, the tachyarrhythmia is classified
based on a comparison between the atrial rate and the ventricular
rate. If the atrial rate is substantially lower than the
ventricular rate at 925, the tachyarrhythmia is classified as a VT
at 935. In one embodiment, the tachyarrhythmia is classified as a
VT if the atrial rate is lower than the ventricular rate by at
least a predetermined margin. In one specific embodiment, the
predetermined margin is about 10 beats per minute. If the atrial
rate is substantially higher than the ventricular rate at 930, the
tachyarrhythmia is classified as a SVT or a dual arrhythmia at 945.
In one embodiment, the tachyarrhythmia is classified as a SVT or a
dual arrhythmia if the atrial rate is higher than the ventricular
rate by at least a predetermined margin. In one specific
embodiment, the predetermined margin is about 10 beats per minute.
In one embodiment, a further detection is performed to discriminate
between SVT and dual arrhythmia at 955. The result of this further
detection determines whether the tachycardia is classified as a SVT
or a VT. If the atrial rate is neither substantially lower nor
substantially higher than the ventricular rate, the tachyarrhythmia
is classified as a 1:1 tachyarrhythmia at 940. In one embodiment,
the tachyarrhythmia is classified as a 1:1 tachyarrhythmia if the
atrial rate is neither lower than the ventricular rate by a
predetermined margin nor higher than the ventricular rate by
another predetermined margin. That is, the tachyarrhythmia is
classified as a 1:1 tachyarrhythmia if the difference between the
atrial rate and the ventricular rate falls within a predetermined
window. In one specific embodiment, both predetermined margins are
about 10 beats per minute.
[0067] After the tachyarrhythmia is classified as a 1:1
tachyarrhythmia at 940, the atrial activation sequence is mapped at
950. As discussed above with reference to FIG. 8, the atrial
activation sequence indicates of an order of occurrence of the RA,
atrial septal, and LA electrograms during one cardiac cycle. The
1:1 tachyarrhythmia is classified by its origin based on the atrial
activation sequence at 960. In one embodiment, the classification
process includes steps 810 through 860 as discussed above with
reference to FIG. 8.
[0068] In one embodiment, the classification of the 1:1
tachyarrhythmia is used to determine whether a therapy is to be
delivered, the site to which the therapy is to be delivered, and/or
the type of the therapy to be delivered. In one specific
embodiment, a ventricular defibrillation pulse is delivered when
the 1:1 tachyarrhythmia is classified as a VT. In another
embodiment, the classification of the 1:1 tachyarrhythmia and the
atrial activation sequence are used for diagnosing and/or
monitoring a patient's cardiac conditions.
[0069] FIG. 10 is a block diagram illustrating an embodiment of
inter-atrial interval monitoring circuit 570. Inter-atrial interval
monitoring circuit 570 is coupled to sensing circuit 530 and
includes an event detection circuit 1074 and an inter-atrial
interval measurement circuit 1076. Sensing circuit 530 senses an RA
electrogram through electrode 1022 and an LA electrogram through
electrode 1026. In one embodiment, electrode 1022 is placed in the
RA or superior vena cava near the SA node, and electrode 1026 is
placed in the coronary sinus or coronary vein near the LA.
[0070] In one embodiment, electrodes 1022 and 1026 are incorporated
into a single lead coupled to sensing circuit 530. In another
embodiment, electrodes 1022 and 1026 are incorporated into separate
leads coupled to sensing circuit 530. Event detection circuit 1074
detects an RA event from the RA electrogram and an LA event from
the LA electrogram for each atrial depolarization. Inter-atrial
interval measurement circuit 1076 measures an inter-atrial
interval, which is a time interval between the RA event and the LA
event during one atrial depolarization.
[0071] FIG. 11 is a block diagram illustrating inter-atrial
interval monitoring circuit 1170, which is a specific embodiment of
the inter-atrial interval monitoring circuit. Inter-atrial interval
monitoring circuit 1170 is coupled to sensing circuit 530 and
includes event detection circuit 1074, inter-atrial interval
measurement circuit 1076, an atrial enlargement detection circuit
1178, an atrial conduction disturbance detection circuit 1180, and
a therapy monitoring circuit 1182. Sensing circuit 530 senses an RA
electrogram through an HRA electrode 1122 and an LA electrogram
through an LA electrode 1126. Examples of HRA electrode 1122
include HRA electrodes 112 and 122. Example of LA electrode
includes LA electrode 126.
[0072] The inter-atrial interval is reflected in the duration of
the P-wave in a surface ECG. A normal range of the P-wave duration
is known to be between 80-120 milliseconds. In one embodiment,
inter-atrial interval monitoring circuit 1170 eliminates the need
of measuring the P-wave duration using a surface ECG. This allows,
for example, the monitoring of development of AF and/or heart
failure from a distant location using external system 590 as
illustrated in FIG. 5. AF is known to be associated with atrial
enlargement and atrial conduction disturbance. Heart failure is
usually associated with enlargement of the LA.
[0073] Atrial enlargement detection circuit 1178 detects an
abnormal enlargement of at least one atrium based on the
inter-atrial interval. In one embodiment, atrial enlargement
detection circuit 1178 includes a comparator that has an input to
receive the inter-atrial interval, another input to receive a
predetermined threshold interval, and an output to indicate an
abnormal enlargement of at least one atrium when the inter-atrial
interval exceeds the predetermined threshold interval. In one
embodiment, implant controller 532 starts delivering a therapy in
response to the indication of the abnormal enlargement. In another
embodiment, implant controller 532 produces an alert signal in
response to the indication of the abnormal enlargement. The alert
signal is transmitted to external system 590 via telemetry link
185.
[0074] Atrial conduction disturbance detection circuit 1180 detects
a variance of the inter-atrial interval indicating the degree of
atrial conduction disturbance. In one embodiment, atrial conduction
disturbance detection circuit 1180 includes a variance calculation
module and a comparator. The variance calculation module calculates
a variance of the inter-atrial interval, which is the difference
between successive inter-atrial intervals averaged for a
predetermined period of time or predetermined number of heart
beats. The comparator includes an input to receive the variance of
the inter-atrial interval, another input to receive a predetermined
threshold variance, and an output to indicate an atrial conduction
disturbance when the variance of the inter-atrial interval exceeds
the predetermined threshold variance. In one embodiment, implant
controller 532 starts delivering a therapy in response to the
indication of the atrial conduction disturbance. In another
embodiment, implant controller 532 produces an alert signal in
response to the indication of the atrial conduction disturbance.
The alert signal is transmitted to external system 590 via
telemetry link 185.
[0075] Therapy monitoring circuit 1182 monitors the effect of one
or more therapies based on the inter-atrial interval. In one
embodiment, pacing and/or drug therapies are delivered to prevent
or treat AF and/or heart failure. The therapies are indicated as
being effective when the inter-atrial interval decreases toward its
normal range and/or when the degree of atrial conduction
disturbance is reduced or minimized. In one embodiment, therapy
monitoring circuit 1182 allows for adjustment or optimization of
therapy parameters based on the inter-atrial interval and/or the
variance in the inter-atrial interval. One or more therapy
parameters are selected for reduced or minimized inter-atrial
interval and/or reduced or minimized variance in the inter-atrial
interval.
[0076] FIG. 12 is a flow chart illustrating an embodiment of a
method for monitoring cardiac conditions based on an inter-atrial
interval. In one embodiment, the method is performed by
inter-atrial interval monitoring circuit 570 or 1170.
[0077] An RA electrogram is sensed using an electrode placed in the
RA or the superior vena cava near the SA node at 1200. An LA
electrogram is sensed using an electrode placed in the coronary
sinus or coronary vein near the LA at 1210. An RA event is detected
from the RA electrogram, and an LA event is detected from the LA
electrogram, for each atrial depolarization, at 1220. The
inter-atrial interval is measured as the time interval between the
RA event and the LA event during one atrial depolarization at
1230.
[0078] In one embodiment, the measured inter-atrial interval is
used to monitor the development of AF and/or heart failure. In one
embodiment, an abnormal enlargement of at least one atrium is
detected based on the inter-atrial interval. The abnormal
enlargement is detected when the inter-atrial interval exceeds a
predetermined threshold interval. The detection of the abnormal
enlargement is used to initiate and/or to monitor a therapy. In
another embodiment, atrial conduction disturbance is detected based
on the variance of the inter-atrial interval. A variance of the
inter-atrial interval is measured to indicate the degree of atrial
disturbance. The atrial conduction disturbance is detected when the
variance of the inter-atrial interval exceeds a predetermined
threshold variance. The detection of the atrial conduction
disturbance is used to initiate and/or to monitor a therapy.
[0079] It is to be understood that the above detailed description
is intended to be illustrative, and not restrictive. For example,
the atrial signal mapping-based tachyarrhythmia classification can
be combined with other methods of tachyarrhythmia classification
for enhance the accuracy of classification of 1:1 tachyarrhythmias.
Other embodiments will be apparent to those of skill in the art
upon reading and understanding the above description. The scope of
the invention should, therefore, be determined with reference to
the appended claims, along with the full scope of equivalents to
which such claims are entitled.
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