Selecting therapy for sustained ventricular tachycardias: importance of the sensitivity and specificity of programmed electrical stimulation for predicting arrhythmia recurrences

Comparison of epicardial and endocardial programmed stimulation in patients at risk for ventricular arrhythmias after cardiac surgery

Programmed ventricular stimulation was performed on 36 patients after recent cardiac surgery using implanted right ventricular epicardial temporary wires and with catheters positioned percutaneously at two right ventricular endocardial sites. Patients were followed for a mean of 18.5 months (range 3 to 36 months). Epicardial wires were nonfunctional in 10 patients (28%) due to excessively high pacing thresholds. Overall, 22 patients (61%) had inducible sustained ventricular tachycardia; epicardial wires were functional in 15 (68%) of these patients. Six patients without inducible ventricular tachycardia with epicardial stimulation were inducible using endocardial stimulation. Of the 24 patients in whom epicardial and endocardial ventricular stimulation could be performed, concordant results were obtained in only 17 (71%), despite similar epicardial and endocardial ventricular effective and functional refractory periods. A total of 14 arrhythmic events occurred during the follow-up period. Of the 22 patients with an inducible sustained ventricular tachycardia, 12 (64%) had subsequent arrhythmic events. Only 2 of the 14 noninducible patients had follow-up arrhythmic events, one of which was caused by medication proarrhythmia. Endocardial ventricular stimulation had a superior sensitivity (83% versus 30%, P < 0.0001) and an improved negative predictive value (86% versus 61%, P < 0.05) compared with epicardial ventricular stimulation. These results indicate that noninducibility using epicardial programmed ventricular stimulation does not reliably portend a low risk for recurrent ventricular tachyarrhythmias. Epicardial programmed stimulation, used alone, may be inadequate for postoperative electrophysiological evaluation of patients at risk for ventricular arrhythmias.

Prevention of sudden death in survivors of myocardial infarction: a decision analysis approach

During the first year after myocardial infarction, 5% to 15% of patients die, and the majority of deaths occur suddenly. Highly efficacious therapy, such as the implantable cardioverter-defibrillator, may reduce the chance of sudden death, but broad application is limited by associated risks. Hence, attempts to identify patients at high risk so they can receive therapy are desirable. Subgroups with high or low sudden death risks can be identified based on left ventricular function. Further risk stratification using programmed electrical stimulation and the signal-averaged ECG has been advocated, but the best strategy is unknown. Using a decision analysis model, we compared the 1-year survival rates in survivors of myocardial infarction treated with the implantable cardioverter-defibrillator either empirically or based on screening with the signal-averaged ECG and programmed electrical stimulation. The best strategy for selecting patients for therapy depended on the pre-therapy sudden death risk. For patients at low risk, such as those with well-preserved ventricular function, antiarrhythmic therapy selected with screening tests or given empirically increased both the mortality rate resulting from the adverse effects of therapy and the excellent survival rate without therapy. In the moderate-risk population, both empiric and stratified approaches reduced mortality, but stratification substantially limited the number of patients receiving unnecessary therapy. In the high-risk population, empiric treatment achieved the best survival rate, and screening resulted in only a small reduction in the number of patients treated unnecessarily.(ABSTRACT TRUNCATED AT 250 WORDS)

Routine programmed electrical stimulation in survivors of acute myocardial infarction for prediction of spontaneous ventricular tachyarrhythmias during follow-up: results, optimal stimulation protocol and cost-effective screening

Of 3,286 consecutive patients treated for acute myocardial infarction, electrophysiologic testing was performed in 1,209 survivors (37%) free of significant complications at the time of hospital discharge to determine their risk of spontaneous ventricular tachyarrhythmias during follow-up. Sustained monomorphic ventricular tachycardia was inducible by programmed electrical stimulation in 75 (6.2%). Antiarrhythmic therapy was not routinely prescribed regardless of the test results. During the 1st year of follow-up, 14 infarct survivors (19%) with inducible ventricular tachycardia experienced spontaneous ventricular tachycardia or fibrillation in the absence of new ischemia compared with 34 (2.9%) of those without inducible ventricular tachycardia (p less than 0.0005). During the extended follow-up period (median 28 months) of those with inducible ventricular tachycardia, 19 (25%) had a spontaneous electrical event; 37% of these first events were fatal. These results suggest that the most cost-effective strategy for predicting arrhythmia will be obtained by restricting electrophysiologic testing to infarct survivors whose left ventricular ejection fraction is less than 40% and using a stimulation protocol containing four extrastimuli. Electrophysiologic testing is the single best predictor of spontaneous ventricular tachyarrhythmias during follow-up in infarct survivors. The majority (94%) with a negative test benefit from the more reliable reassurance that all is well, whereas the 25% risk of electrical events in those with inducible ventricular tachycardia justifies a prospective trial of effective prophylactic antiarrhythmic interventions.