Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2000-08-30
2003-12-30
Evanisko, George R. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C600S518000
Reexamination Certificate
active
06671548
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to implantable cardiac stimulation devices, and in particular, a stimulation device capable of discriminating among various atrial and ventricular arrhythmias and delivering high voltage shocks to treat such arrhythmias.
BACKGROUND OF THE INVENTION
An ICD device is a particular type of cardiac stimulation device, which recognizes ventricular tachycardia (VT), ventricular fibrillation (VF) and other arrhythmias, and delivers high voltage electrical therapy to terminate such arrhythmias.
ICD devices have met with wide success in the detection of arrhythmias and in the administering of high voltage shocking therapy in response thereto, yet considerable room for improvement remains. In particular, many ICD recipients also suffer from supraventricular tachycardias (SVT), that is, an arrhythmia whose origin is above the ventricles and is conducted to the ventricles. The true underlying arrhythmia in these cases is often atrial fibrillation (AF), sinus tachycardia (ST), or other supraventricular tachycardias (SVTs), such as ectopic atrial tachycardia, atrial reentry, A/V nodal reentry, and paroxysmal atrial fibrillation or flutter. The SVT symptoms typically correspond to a heart rate, which is in a “low tachycardia rate” zone normally associated with VT.
These ICD patients may receive inappropriate therapy if the implanted device is not capable of reliably discriminating between VT and SVT and inappropriately classifies the rhythm as VT. It is unlikely that these arrhythmias would respond to ventricular therapy, and application of such therapy may accelerate an existing arrhythmia or induce additional arrhythmias.
ICD devices capable of dual-chamber sensing often provide better discrimination between the various types of arrhythmias than single-chamber ICD devices. However, even in dual-chamber ICD devices, it remains difficult to discriminate between VT's with 1:1 retrograde conduction (VT 1:1), and SVT's with 1:1 conduction (SVT 1:1), or ST's. Other arrhythmias that may need to be discriminated one from the other include VT's without 1:1 retrograde conduction (VT not 1:1), high rate VT's (VT
H
), SVT's without 1:1 conduction (SVT not 1:1) and atrial flutter (AFL).
Even in circumstances where the ICD ultimately administers the correct therapy, initial errors in discriminating between the various types of arrhythmias often results in one or more intervals lapsing before therapy is administered. For example, some ICD devices discriminate between different arrhythmias by making a preliminary classification as to the type of the arrhythmia, if any, associated with each individually detected event (e.g. P-waves, R-waves, etc.) and then counting each type of event using a set of running totals. A predetermined threshold is associated with each running total. The ICD device does not make a final decision as to the type of arrhythmia until the threshold of one of the running totals is exceeded. The ICD device administers therapy appropriate to that arrhythmia.
For example, if the threshold is programmed to twenty counts and the running total for events given a preliminary classification of VT reaches twenty counts, the stimulation device identifies the arrhythmia as being a VT arrhythmia and administers appropriate therapy at that time. Unfortunately, because of the difficulty in discriminating among events associated with different types of similar arrhythmias, the wrong running total may occasionally be incremented, thereby delivering inappropriate therapy for the true underlying rhythm or delaying appropriate therapy for the underlying rhythm.
Hence, there is a need for an improved ICD device which achieves a reduction in the occurrence of inappropriate VT therapy and which provides appropriate therapy more quickly. It is to these and other ends that the invention is primarily directed.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the invention, a method for use with an implantable stimulation device connected to heart tissue is provided for discriminating various arrhythmias of the heart. As used herein, the term “stimulation device” is used to cover all stimulation devices which may benefit from the use of the present invention for discriminating various arrhythmias, whether it is a pacemaker, cardioverter, defibrillator, a single-chamber or a dual chamber device, or a combination thereof.
In accordance with the method, a sequence of events are detected within the heart beginning at an initial point in time and a preliminary classification for each detected event is determined out of a plurality of heart rhythms. Running totals of the numbers of detected events within each of the predetermined classifications since the initial point in time are maintained along with sliding totals of the numbers of detected events within each of the predetermined classifications out of the most recent events. The arrhythmia of the heart is then determined based upon a combination of the running totals and the sliding totals.
In an exemplary embodiment, the implantable stimulation device is a combination ICD device which offers both atrial and ventricular pacing, and the plurality of heart rhythms includes normal sinus rhythm (NSR), ventricular fibrillation (VF), ventricular tachycardia without 1:1 retrograde conduction (VT not 1:1), ventricular tachycardia with 1:1 with retrograde conduction (VT 1:1), supraventricular tachycardias without 1:1 conduction (such as, atrial fibrillation (AF), atrial flutter (AFL), and other SVTs not 1:1) and supraventricular tachycardias with 1:1 conduction (either physiologic sinus tachycardia (ST) or a pathological SVT 1:1).
The determination of the patient's heart rhythm, based upon a combination of the running totals and the sliding totals, is performed by first determining whether the sliding total of any one of the predetermined classifications exceeds a corresponding sliding total threshold. If so, the running totals of the predetermined classifications are selectively modified. Then, a determination is made as to whether the modified running total of any one of the predetermined classifications exceeds a corresponding running total threshold and, if so, the current state of the heart is identified as being the heart state corresponding to that predetermined classification and appropriate therapy is administered.
In one specific example, the running total for VF is selectively modified as follows. If the sliding total of the number of events having a preliminary classification of VF exceeds a corresponding sliding total threshold (such as, six out of the last eight events), then the running totals for ST, VT 1:1 and VT not 1:1 are added to the running total for VF. The running totals for ST, VT 1:1, VT not 1:1 and AF are then cleared.
In the exemplary embodiment, by adding the running totals for various preliminary classifications to other preliminary classifications based upon the values of the sliding totals, the stimulation device thereby biases the running totals using the sliding totals. The specific manner by which the running totals are biased is selected to help overcome common discrimination problems occurring in stimulation devices to thereby permit the stimulation device to make a correct and final therapy decision more quickly. For example, VF events are sometimes erroneously classified as being ST events, VT 1:1 events or VT not 1:1 events. Hence, as set forth in the example, the running totals for ST, VT 1:1 and VT not 1:1 are added to the running total for VF whenever at least six of the last eight events were identified as being VF events. Thus, if such an erroneous classification occurred, it is compensated for by adding the erroneous counts to VF counts. If no such erroneous classification occurred, then even with the added counts the running total for VF will not likely exceed the corresponding threshold and erroneous therapy will not be administered.
In accordance with a second aspect of the invention, a method is provided for use
Badelt Steven W.
Mouchawar Gabriel A.
Street Anne M.
Evanisko George R.
Pacesetter Inc.
LandOfFree
Implantable stimulation device and method for discrimination... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Implantable stimulation device and method for discrimination..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Implantable stimulation device and method for discrimination... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3138319