Analysis of the paced electrocardiogram (ECG) is important to the follow-up evaluation of patients with implanted pacemakers. Because of the complexity and variability of pacemaker algorithms, diagnosis of paced ECGs is often considerably more difficult than the interpretation of usual ECGs. Automated interpretation of the paced ECG can provide great clinical benefit because few clinicians are adequately trained in the diagnosis of such ECGs for the interpretation of pacemaker functionality. However, comparatively little work has been done in this area, mainly because the diversity and complexity of pacemaker logic makes interpretation, automated or manual, a difficult task. The following paper reviews research in computer interpretation of the pacemaker ECG and presents a new automated method which yields more detailed and accurate results than any previous technique.

Algorithms↗

PubMed1992

Separation of ventricular tachycardia from sinus rhythm using a practical, real-time template matching computer system.

Template matching morphology analysis of the intraventricular electrogram (IVEG) has been proposed for inclusion in implantable cardioverter defibrillators (ICDs) to reduce the number of false ventricular tachyarrhythmia detections caused by rate overlap between ventricular tachycardia (VT) and sinus tachycardia and/or supraventricular tachycardia. Template matching techniques have been developed that reduce the computational complexity while preserving the perceived important aspects of electrogram amplitude and baseline independence found in such computationally unsolved methods as correlation waveform analysis (CWA). These methods have been shown to work as well as CWA for separation of VT, however, they have not been proven in real-time on a system that incorporates many of the constraints of present day ICDs. The present study was undertaken with two purposes: (1) to determine if real-time IVEG template matching analysis on an ICD sensing emulator was accurate in separating VT from sinus rhythm (SR) electrograms; and (2) to compare amplitude normalized area of difference (NAD) with signature analysis (SIG), a new, computationally less expensive technique that normalizes for amplitude variation within the expected physiological level of variability. In this study, IVEGs, obtained from 16 patients who underwent electrophysiological study (EPS) for evaluation of sustained ventricular arrhythmia, were digitized to 250 Hz with 6-bit quantization after filtering (16-44 Hz) and differentiation. After an SR template was selected and periodically updated, it was compared to subsequent IVEGs using NAD and SIG. In general, SIG calculates the fraction of samples occurring outside template window boundaries. Eleven-beat running medians from beat-by-beat NAD and SIG results were determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1992

Ventricular tachycardia detection using bipolar electrogram analysis is site specific.

While algorithms for bipolar intraventricular electrogram analysis have potential use in complementing rate criteria for ventricular tachycardia (VT) detection by implantable antitachycardia devices, the sensitivity of such algorithms to the intracavitary site of electrogram detection has not been determined. In this study, unfiltered (1-500 Hz) electrograms were recorded from a bipolar electrode catheter initially positioned at the right ventricular (RV) apex (site 1) of 12 patients during sinus rhythm (SR1) and during induced monomorphic VT (VT1). Sinus rhythm (SR2) and the identical VT (VT2) were recorded a second time after repositioning the same electrode catheter within the RV apex (site 2) 7-44 mm (mean +/- SD = 15 +/- 10) from its original site. The data were digitized at 1,000 Hz. Templates from SR1 and SR2, respectively, were compared subsequently with individual intraventricular electrograms from 15-25 sec passages of SR1 and VT1 and SR2 and VT2, respectively, using correlation waveform analysis. At site 1, the mean patient correlation coefficient ranged from 0.982-0.998 during SR1 and 0.062-0.975 during VT1. At site 2, the mean patient correlation coefficient ranged from 0.995-0.998 during SR2 and 0.113-0.983 during VT2. Using a correlation threshold of 0.9, VT was differentiated from SR in 11/12 patients (91%) overall: 8/12 patients (67%) at site 1, 9/12 patients (75%) at site 2, and 6/12 patients (50%) at both sites. Thus, while discrimination of VT from SR is feasible with morphological analysis of bipolar right ventricular intracavitary electrograms, the accuracy of bipolar intraventricular electrogram analysis may depend upon intracavitary electrode location in selected patients.

Algorithms↗

PubMed1992

Driving restrictions advised by midwestern cardiologists implanting cardioverter defibrillators: present practices, criteria utilized, and compatibility with existing state laws.

Although some patients remain at risk of losing physical control or collapsing after implantation of a cardioverter defibrillator for sustained ventricular arrhythmias, little is known about restrictions advised by arrhythmia specialists to patients with implanted devices concerning physical activities such as driving. In this study, all of the 58 cardiologists implanting cardioverter defibrillators in three contiguous midwestern states were surveyed to determine present practices and the compatibility of these practices with existing state law. Of the 51 respondents (88%), 27 cardiologists (53%) advised only those implanted patients who had had arrhythmia-induced presyncope or physical collapse to cease driving. Twenty two of the remaining cardiologists (43%) advised all implanted patients to cease driving, whereas two cardiologists (4%) never advised any implanted patient to restrict driving. Permanent driving abstinence was advised by seven of the responding cardiologists (14%), while temporary driving abstinence for periods of 2-12 months (mean 6 +/- 3 months) was recommended by the remaining 42 respondents (82%) who advised against driving. The criteria utilized, driving restrictions advised, and durations advised for driving restrictions were not uniform in any of the 13 surveyed university and nonaffiliated cardiology practices with greater than or equal to 2 implanting cardiologists. Overall, 38 cardiologists (74%) advised against driving and recommended durations that equaled or exceed their state's minimum legal requirements, although only 27 of the 51 cardiologists (53%) based their practice upon knowledge of their state's driving laws. The results of this survey suggest that the majority of cardiologists who implant cardioverter defibrillators advise their patients against driving postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Automobile Driving↗

PubMed1991

Effects of increased heart rate and sympathetic tone on intraventricular electrogram morphology.

Electrogram pattern recognition by way of morphologic analysis has been proposed as a technique that may improve discrimination of ventricular tachycardia from sinus rhythm by antitachycardia devices. The potential impact that increases in heart rate and sympathetic tone could have on such techniques, however, has not been previously determined. A comparative study was undertaken to quantify possible changes in ventricular electrogram morphology using correlation waveform, area of difference, and amplitude analyses in 6 patients during atrial overdrive pacing at cycle lengths of 600 and 400 ms (group A), in 13 patients during infusions of physiologic doses of epinephrine (group B), and in 20 patients undergoing infusions of isoproterenol (group C). Four patients were in both groups A and B. A bipolar intraventricular template of cardiac depolarization during sinus rhythm at rest was compared with depolarization during subsequent passages of sinus rhythm at rest and subsequently increased heart rate. In 36 of 39 patients, waveform configuration as assessed by correlation waveform analysis remained relatively stable during atrial overdrive pacing, epinephrine infusion, and isoproterenol infusion when compared with sinus rhythm at rest. The correlation value did not fall below 0.950 in any patient. Area of difference values for the same 36 patients changed by an average of 6 and 37% during atrial overdrive pacing at cycle lengths of 600 and 400 ms intervals, respectively, by 3% during epinephrine infusion, and by 17% during isoproterenol infusion. In these same patients, there was an average change in electrogram amplitude of -1% during atrial overdrive pacing at 600 ms, 26% during pacing at 400 ms, -1% during epinephrine infusion, and 12% during isoproterenol infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

A comparison of four new time-domain techniques for discriminating monomorphic ventricular tachycardia from sinus rhythm using ventricular waveform morphology.

Electrical management of intractable tachycardia via implantable antitachycardia devices has become a major form of therapy. Newly advanced methods of ventricular tachycardia detection propose examination of changes in intraventricular electrogram morphology in addition to or in combination with earlier rate-based detection algorithms. Unfortunately, most of the proposed morphology analysis techniques have computational demands beyond the capabilities of present devices or may be adversely affected by amplitude and baseline fluctuations of the intraventricular electrogram. We have designed four new computationally efficient time-domain algorithms for distinguishing ventricular electrograms during monomorphic ventricular tachycardia (VT) from those during sinus rhythm using direct analysis of the ventricular electrogram morphology. All four techniques are independent of amplitude fluctuations and three of the four are independent of baseline changes. These new techniques were compared to correlation waveform analysis, a previously proposed method for distinction of VT from sinus rhythm. Evaluation of these four new algorithms was performed on data from 19 consecutive patients with 31 distinct monomorphic ventricular tachycardia morphologies. Three of the algorithms performed as well or better than correlation waveform analysis but with one-tenth to one-half the computational demands.

Aged↗

PubMed1991

Impact of filtering upon ventricular tachycardia identification by correlation waveform analysis.

Signal analysis of digitized waveforms has been postulated as a method for improving sensitivity and specificity of ventricular tachycardia (VT) detection in implantable antitachycardia devices. Such improvement may alleviate the problem of unwarranted delivery of therapy by adding precision to the identification of the pathological VT. Morphological analysis could also allow distinct therapies to be initialized for multiple VTs in the same patient. Correlation waveform analysis (CWA) has been demonstrated to be effective in separating benign rhythms from VT in wideband recordings (1-500 Hz) but the effect of filtering has not been previously examined. Bipolar (1 cm) intraventricular recordings (1-500 Hz) of sinus rhythm (SR) and 25 distinct VTs in 18 patients were analyzed by CWA using a signal-averaged SR template. Passages contained 65.9 +/- 19.8 VT depolarizations (range 45-108). Digital filtering was performed on all data passages with varying passbands. Results for passages with a bandwidth of 1-250 Hz were equivalent to wideband results, i.e., greater than or equal to 92% paired sets of SR and VT were separable at a 95% confidence level. A bandwidth of 1-100 Hz decreased discrimination to 84%. At a bandwidth of 1-80 Hz, 80% of cases were successfully separated, but at 10-80 Hz these results improved to 88%. Bandwidths of 20-80 and 30-80 Hz reduced reliability of CWA performance to 72% and 60%, respectively. Filtering at typical pacemaker/defibrillator passbands produced morphological analysis results equivalent to those yielded at wideband settings. Differences in the range between SR versus VT decreased in filtered recordings but overall detection of VT was not degraded.

Algorithms↗

PubMed1991

A time-domain analysis of intracardiac electrograms for arrhythmia detection.

The analysis of intracardiac electrogram morphology has been proposed as a complementary method for accurate discrimination between sinus rhythm (SR), supraventricular dysrhythmias, and ventricular dysrhythmias by automatic antitachycardia and cardioverter defibrillator devices. In this study, the performance of a traditional time-domain method for surface electrocardiogram interpretation--Correlation Waveform Analysis (CWA) and a newly developed technique--Bin Area Method (BAM) were used to analyze unfiltered intraatrial and intraventricular electrograms obtained from 47 patients during routine cardiac electrophysiology studies. Nineteen patients had 31 distinct, sustained, monomorphic ventricular tachycardias (VTs) induced; 13 patients had paroxysmal bundle branch block of supraventricular origin (BBB) induced; 19 patients had retrograde atrial activation during ventricular overdrive pacing. Three patients were common to two or more groups. Using a best fit electrogram alignment, both CWA and BAM distinguished VT from SR in 28/31 cases (90%), BBB from SR in 15/15 patients (100%), and anterograde from retrograde atrial activation in 19/19 patients (100%). We conclude that the use of time-domain techniques that are independent of amplitude and baseline fluctuations appear to be reliable for discrimination of retrograde atrial activation, paroxysmal BBB, and VT from SR using intracardiac electrograms. Reduction of computational time and power constraints, without sacrificing reliable dysrhythmia discrimination, is possible. These features may make real-time morphology analysis of intracardiac electrograms feasible for automatic antitachycardia and cardioverter-defibrillator devices.

Algorithms↗

PubMed1990

The role of beta-blockade therapy for ventricular tachycardia induced with isoproterenol: a prospective analysis.

Isoproterenol is sometimes required for ventricular tachycardia (VT) induction. However, the role of beta-blockade for treatment of such VT has not been critically assessed. The use of beta-blockade was evaluated prospectively in 14 consecutive patients who required isoproterenol 2.4 +/- 1.3 (+/- S.D.) micrograms/min to induce sustained monomorphic VT (greater than 30 seconds, or requiring termination due to hemodynamic collapse) after a negative baseline study. The VT mechanisms were enhanced automaticity (group A, six patients), triggered automaticity (group B, three patients), and reentry (group C, five patients). Groups A and B had serial intravenous electropharmacologic tests with propranolol alone (0.2 mg/kg), verapamil alone (0.15 mg/kg), and propranolol plus verapamil, and group C had serial tests with propranolol alone, procainamide or quinidine (class Ia drug) alone, and propranolol plus a class Ia drug until VT could no longer be induced. All six patients in group A responded to propranolol alone. In group B, one patient responded to verapamil alone, and two patients responded to propranolol plus verapamil. In group C, three patients responded to propranolol alone, one patient responded to a class Ia drug alone, and one patient responded to propranolol plus a class Ia drug. During a follow-up of 7 to 37 (17.9 +/- 10.7) (+/- S.D.) months, VT has not recurred in any patient. Three patients treated initially with propranolol alone have required substitution of amiodarone due to refractory congestive heart failure. In patients requiring isoproterenol for VT induction, beta-blockade alone appears to be effective in preventing reinduction of VT caused by enhanced automaticity. A heterogeneous response occurs when the VT mechanisms are triggered automaticity or reentry.

Adolescent↗

PubMed1990

Statistical validation of new ventricular tachycardia detection schemes.

Explore the source record for details and available documents.

Electrocardiography↗

PubMed1990

Impact of increased heart rate alone and heart rate plus contractility upon intraventricular ECG morphology.

Explore the source record for details and available documents.

Cardiac Pacing, Artificial↗

PubMed1990

The Bin Area Method: a computationally efficient technique for analysis of ventricular and atrial intracardiac electrograms.

Recent studies have reported a significant false positive rate in delivery of therapy by implantable antitachycardia devices utilizing detection algorithms based on sustained high rate. More selective decision schemes for the recognition of life-threatening arrhythmias have been recently proposed that use analysis of the intrinsic electrogram rather than rate alone. Morphological discrimination of abnormal electrograms using correlation waveform analysis (CWA) has been proposed as an effective method of intracardiac electrogram analysis, but its computational demands limit its use in implantable devices. A new method for intracardiac electrogram analysis, the bin area method (BAM), was created to detect abnormal cardiac conduction with computational requirements of one-half to one-tenth those of CWA. Like CWA, BAM is a template matching method that is sensitive to conduction changes revealed in the electrogram morphology and is independent of amplitude and baseline fluctuations. Performance of BAM and CWA were compared using bipolar right ventricular and right atrial electrode recordings from 47 patients undergoing clinical cardiac electrophysiology studies. Nineteen patients had 31 distinct monomorphic ventricular tachycardias (VTs) induced (group I), thirteen patients had paroxysmal bundle branch block of supraventricular origin (BBB) induced (group II), and 19 patients had retrograde atrial activation during right ventricular overdrive pacing (group III). (One patient was common to all three groups, and two patients were common to groups II and III.) Using the ventricular electrogram, both BAM and CWA distinguished VT from sinus rhythm in 28/31 (90%) cases, and BBB from Normal Sinus Rhythm (NSR) in 13/13 (100%) patients. Using the atrial electrogram, both BAM and CWA distinguished anterograde from retrograde atrial activation in 19/19 (100%) patients. BAM achieves similar performance to CWA with significantly reduced computational demands, and may make real-time analysis of intracardiac electrograms feasible for implantable pacemakers and antitachycardia devices.

Algorithms↗

PubMed1990

Paroxysmal bundle branch block of supraventricular origin: a possible source of misdiagnosis in detecting ventricular tachycardia using time domain analyses of intraventricular electrograms.

Current implantable antitachycardia devices use several methods for differentiating sinus rhythm (SR) from supraventricular tachycardia (SVT) or ventricular tachycardia (VT). These methods include sustained high rate, the rate of onset, changes in cycle length, and sudden onset. Additional methods for detecting VT include techniques based upon ventricular electrogram morphology. The morphological approach is based on the assumption that the direction of cardiac activation, as sensed by a bipolar electrode in the ventricle, is different when the patient is in SR as compared to VT. Whether paroxysmal bundle branch block of supraventricular origin (BBB) can be differentiated from VT has not been determined. In this study, we compared the morphology of the ventricular electrogram during sinus rhythm with a normal QRS (SRNIQRS) or SVT with a normal QRS (SVTNIQRS) with the morphologies of BBB and VT in 30 patients undergoing cardiac electrophysiology studies. Changes in ventricular electrogram morphology were determined using three previously proposed time domain methods for VT detection: Correlation Waveform Analysis (CWA), Area of Difference (AD), and Amplitude Distribution Analysis (ADA). CWA, AD, and ADA distinguished VT from SRNIQRS or SVTNIQRS in 16/17 (94%), 14/17 (82%), and 12/17 (71%) patients, and BBB from SRNIQRS or SVTNIQRS in 15/15 (100%), 13/15 (87%), and 6/15 (40%) patients, respectively. However, the ranges of values during BBB using these methods overlapped with ranges of values during VT in all cases for CWA, AD, and ADA. Hence, BBB may be a source of misdiagnosis in detecting VT when these time domain methods are used for ventricular electrogram analysis.

Adolescent↗

PubMed1990

Intraventricular electrogram analysis for ventricular tachycardia detection: statistical validation.

Time-domain analysis of intraventricular electrogram morphology during ventricular tachycardia (VT) and sinus rhythm or atrial fibrillation (SR/AF) has been proposed as a method for increasing the specificity of pathological tachycardia detection by antitachycardia devices. However, few studies have validated the use of such analysis with statistical methods. When statistical methods have been utilized, it has been assumed that the distribution of the values derived from analysis of the intracardiac electrograms have had a normal (gaussian) distribution. In this study, we sought to determine whether: (1) the distribution of values derived from analysis of intracardiac electrogram during SR/AF and VT is gaussian or nongaussian; and (2) the discrimination of monomorphic VT from SR/AF using SR/AF templates can be validated statistically. Two previously proposed time-domain methods--correlation waveform analysis (CWA) and area of difference (AD)--were selected for evaluation of 29 patients with 33 distinct, sustained monomorphic VTs. An initial SR/AF template was used to analyze subsequent SR/AF and VT passages with a minimum of 50 consecutive depolarizations using a "best-fit" alignment. The values derived from each analysis were examined subsequently for skewness (asymmetry) and kurtosis (shape) using two-tailed tests (P less than 0.02). For passages of SR/AF, a normal (gaussian) distribution was present in only 24% (CWA), and 45% (AD); for passages of VT, normal distribution was present in only 58% for both CWA and AD. Using appropriate statistical testing with nonparametric tolerance intervals, CWA and AD discriminated VT from SR/AF in 29 out of 33 (88%), and 30 out of 33 (91%) instances, respectively, with 95% confidence.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Fibrillation↗