Study of the influence of left bundle branch block on the signal-averaged electrocardiogram: a qualitative and quantitative analysis.

UNLABELLED: To study the influence of left bundle branch block (LBBB) on the signal-averaged electrocardiogram (SAECG), quantitative and qualitative analyses of SAECG parameters were undertaken in 48 patients with electrocardiographic evidence of intrinsic LBBB and in 39 patients with a "normal" surface QRS duration (less than 120 msec) who underwent right ventricular pacing-induced LBBB. We assumed pacing of the right ventricular apex to be a suitable model of this conduction defect. Sustained monomorphic ventricular tachycardia (SMVT) was inducible in 16 of 48 patients with intrinsic LBBB and in 23 of 39 patients with pacing-induced LBBB. Utilizing a filter setting of 25 to 250 Hz, late potentials were defined as a total filtered QRS duration greater than or equal to 120 msec, a root mean square voltage in the terminal 40 msec (RMS 40) of less than or equal to 25 microV, and the duration of signals less than 40 microV (LAS 40) of greater than or equal to 38 msec. Only RMS 40 and LAS 40 criteria were used in patients with LBBB. Prolongation of LAS 40 and fragmentation of signals in the terminal portion of the filtered QRS were characteristic of all patients with LBBB aberration. Of those patients with intrinsic LBBB, the mean total filtered QRS duration, RMS 40, and LAS 40 for inducible and noninducible patients were significantly different (170 +/- 28, 16 +/- 10, 55 +/- 24, and 153 +/- 18 msec, 25 +/- 10 microV, 33 +/- 16.9 msec; p = 0.04, 0.009, and 0.007, respectively). Noninducible patients with a normal QRS duration demonstrated a 60% decrement in the mean RMS 40 value during pacing-induced LBBB. These changes resulted in a 59% false positive incidence of late potentials during pacing-induced LBBB. This correlated with a similarly low mean RMS 40 value in patients with intrinsic LBBB and no inducible SMVT, hence giving rise to a false positive incidence of late potentials of 63%. Since "standard" RMS 40 and LAS 40 criteria resulted in low specificity and positive predictive value, new parameters were selected and analyzed. The combination of RMS 40 less than or equal to 17 microV plus LAS 40 greater than or equal to 55 msec yielded the best overall statistical result, with a sensitivity, specificity, and total predictive accuracy of 69%, 81%, and 77%, respectively. IN CONCLUSION: (1) A reduction of RMS 40, prolongation of LAS 40, and fragmentation of signals in the terminal portion of the filtered QRS are characteristics of LBBB.(ABSTRACT TRUNCATED AT 400 WORDS)

Complete heart block complicating retrograde left heart catheterization.

Three cases of complete heart block complicating retrograde left heart catheterization are presented. In two of the three cases, electrophysiologic study documented block below the AV (atrial ventricular) node. In the third recurrent complete heart block was fatal. It appears that complete heart block complicating retrograde left sided cardiac catheterization is not simply a pericatheterization event; rather, it appears that there is high risk of recurrent complete heart block and that electrophysiologic study is mandatory.

Risk stratification and management of patients with organic heart disease and nonsustained ventricular tachycardia: role of programmed stimulation, left ventricular ejection fraction, and the signal-averaged electrocardiogram.

PURPOSE: Programmed stimulation, left ventricular ejection fraction, and signal-averaged electrocardiography were performed in patients with organic heart disease and spontaneous nonsustained ventricular tachycardia (VT) to determine the role of these techniques in risk stratification and management. PATIENTS AND METHODS: The study consisted of 90 patients: 63 had coronary artery disease and 27 had idiopathic dilated cardiomyopathy. Radionuclide ventriculography, signal-averaged electrocardiography, and programmed electrical stimulation were performed in all patients within 48 hours of index ambulatory electrocardiography. RESULTS: Fifty-three patients (59%) had an ejection fraction less than 40%. Programmed stimulation induced sustained monomorphic VT in 22 patients (24%), ventricular fibrillation (VF) in 10 patients (11%), and no sustained VT/VF in 58 patients (64%). The signal-averaged electrocardiogram (ECG) showed late potentials in 23 patients (26%). Sustained monomorphic VT could be induced in 65% of patients with late potentials and in 10% of those without late potentials. There was no case of inducible sustained monomorphic VT in 33 patients with no late potentials and an ejection fraction of 40% or greater. All patients with induced sustained monomorphic VT received antiarrhythmic therapy guided by the results of programmed stimulation. All 58 patients with no induced sustained ventricular tachyarrhythmias and eight patients with induced VF were discharged without receiving antiarrhythmic drugs. During a follow-up of 30 +/- 10 months, the three-year sudden death rate was 19% in patients with induced sustained VT, 0% in those with induced VF, and 9% in those with no induced sustained VT/VF. The three-year sudden death rate was the same (7%) in patients with no induced sustained VT/VF, both in those with an ejection fraction of 40% or greater or less than 40%. On the other hand, the three-year total cardiac mortality was significantly higher (27%) in those patients with ejection fractions less than 40% compared to those with ejection fractions of 40% or greater (7%). CONCLUSION: It is concluded that the signal-averaged ECG, ejection fraction, and programmed stimulation could be used for the risk stratification and management of patients with organic heart disease and nonsustained VT as follows: (1) Patients with no late potentials and with an ejection fraction of 40% or greater do not require invasive evaluation or antiarrhythmic therapy, since the incidences of induced VT and sudden death are very low. (2) Patients with late potentials as well as patients without late potentials but with an ejection fraction of less than 40% may be advised to undergo electrophysiologic evaluation.(ABSTRACT TRUNCATED AT 400 WORDS)

Prognostic significance of the signal-averaged ECG depends on the time of recording in the postinfarction period.

Serial recordings of the signal-averaged ECG and the 24-hour ambulatory ECG were obtained from 156 patients with acute myocardial infarction up to 5 days (phase 1), 6 to 30 days (phase 2), and 31 to 60 days (phase 3) after the infarction. Left ventricular ejection fraction by radionuclide ventriculography was also determined in phase 2. The signal-averaged ECG was abnormal during one or more of the three phases in 51 patients (31%). In 35 of these patients (69%) the recording changed category between normal and abnormal with the highest prevalence of abnormal recording occurring during phase 2. Eight patients had ventricular tachycardia/ventricular fibrillation in the first 48 hours after myocardial infarction. The signal-averaged ECG was abnormal in only one of these patients. Twelve patients had late arrhythmic events during the first year of follow-up (four sudden deaths and eight instances of documented ventricular tachycardia or ventricular fibrillation). Nine of the 12 patients had an abnormal signal-averaged ECG in phase 2 and four of these nine had a normal recording in phase 1. Five patients had a transient abnormal signal-averaged ECG in phase 1, whereas six patients had an abnormal recording only in phase 3. None of these 11 patients had an arrhythmic event. Stepwise logistic regression showed that an abnormal signal-averaged ECG in phase 2 has the most significant relation to late arrhythmic events. Both an abnormal signal-averaged ECG and a left ventricular ejection fraction less than 40%, but not complex ventricular arrhythmias, were independent significant risk factors for late arrhythmic events.(ABSTRACT TRUNCATED AT 250 WORDS)

Time course of ventricular arrhythmias and the signal averaged electrocardiogram in the post-infarction period: a prospective study of correlation.

The incidence and time course of complex ventricular arrhythmias and of the abnormal signal averaged electrocardiogram were studied prospectively in 90 patients in the first two months after acute myocardial infarction. Serial recordings of both 24 hour ambulatory and signal averaged electrocardiograms were obtained 0-5 days (phase 1), 6-30 days (phase 2), and 31-60 days (phase 3) after infarction. A total of 264 ambulatory electrocardiograms and 264 signal averaged electrocardiograms were available for analysis. Complex ventricular arrhythmias were seen in 31%, 17%, and 38% of patients during phases 1, 2, and 3 respectively, and abnormal signal averaged electrocardiogram in 13%, 24%, and 16%. The incidence of complex ventricular arrhythmias was not significantly different in patients with or without an abnormal signal averaged electrocardiogram in the entire study period nor in any of the three phases after infarction. During phase 2 when abnormal signal averaged electrocardiograms were most common complex ventricular arrhythmias were least common. This lack of correlation suggests that the abnormal signal averaged electrocardiogram and complex ventricular arrhythmias after infarction have different electrophysiological bases.

Value of the signal-averaged electrocardiogram as a predictor of the results of programmed stimulation in nonsustained ventricular tachycardia.

A prospective assessment of several clinical variables, left ventricular function indexes, Holter recording characteristics and signal-averaged electrocardiogram (ECG) for their value in predicting the inducibility of sustained ventricular tachyarrhythmias was carried out in a consecutive series of 105 patients with nonsustained ventricular tachycardia (VT). The patients were divided into 3 groups based on the results of programmed electrical stimulation: group 1, 22 patients with induced sustained monomorphic VT; group 2, 14 patients with induced ventricular fibrillation (VF) and group 3, 69 patients with no induced sustained VT/VF. Left ventricular ejection fraction less than 0.40, history of syncope/presyncope and abnormal signal-averaged ECG were significantly more common in group 1 than in group 3. No significant difference was found between groups 2 and 3. The sensitivity, specificity and predictive accuracy of the signal-averaged ECG for the induction of sustained monomorphic VT were 64, 89 and 84%, respectively. Using stepwise discriminant function analysis, the signal-averaged ECG was found to be the single most accurate screening test to predict the inducibility of sustained VT in patients with nonsustained VT and its value was independent of the etiology of heart disease and the length of spontaneous runs. Because of the very high specificity and negative predictive accuracy, patients with normal signal-averaged ECGs may not require invasive evaluation.

Antiarrhythmic effects of oral indecainide in patients with ventricular tachyarrhythmias.

In order to assess the efficacy and safety of oral indecainide in patients with serious ventricular arrhythmias we studied 11 patients with high-grade ventricular ectopy and ventricular tachycardia (VT) which were refractory to therapy with at least one standard antiarrhythmic drug. Spontaneous arrhythmias were quantitated by 24-h Holter monitor before and during therapy with indecainide. Spontaneous VT was sustained in 4 patients and nonsustained in 7. Ten patients underwent baseline electrophysiologic study (EPS) and VT was induced in 9. The mean ejection fraction was 25 +/- 14%. Indecainide was given orally at a dose of 211 +/- 118 mg/day. The frequency of ventricular premature beats (VPBs) was significantly (greater than 85%) decreased in 90% of patients, while ventricular couplets frequency decreased in 78%. Spontaneous VT was abolished in 5 of 11 (45%). Sustained VT was induced in 5 of 7 (71%) patients who underwent follow-up EPS. The QRS duration was significantly prolonged during therapy (0.13 +/- 0.04 s) compared to control (0.10 +/- 0.02 s). The PR, QTc, and JTc intervals were not significantly changed. Indecainide was well tolerated, but 2 patients died of ventricular tachyarrhythmias while receiving the drug. Indecainide suppressed VPBs in a high percentage of patients, but was much less successful in controlling VT. Caution is necessary when using this drug because of its potential for exacerbation of arrhythmia.