Nonsustained ventricular tachycardia during programmed ventricular stimulation: criteria for a positive test

Analytic Reviews: Electrophysiologic Testing in the Intensive Care Unit

The role of electrophysiologic concepts and procedures in managing patients with potentially life-threatening ar rhythmias in the intensive care unit is discussed. These patients may be survivors of sudden cardiac arrest or myocardial infarction or may be admitted for syncope or sustained or nonsustained ventricular tachycardia. The value of electrophysiologic testing is discussed in terms of the distinction between wide QRS complex tachycardias that are supraventricular or ventricular in origin and those in which preexcitation syndromes may be important. Drug-induced ventricular arrhythmias are discussed, with specific emphasis on torsades de pointes. Finally, the use of His bundle recordings in pa tients with atrioventricular conduction disturbances is discussed. The methodology of electrophysiologic test ing, including stimulation protocols and interpretation of results, is described.

Clinical and electrophysiological characteristics of ventricular tachycardia in children with normal hearts

Characteristics of 18 patients with clinical ventricular tachycardia (VT) and normal hearts documented by physical examination, echocardiography, and angiocardiography were analyzed. There were 13 males and 5 females, aged 1 to 16 years (mean +/- SD, 9.7 +/- 4.8 years). Six patients had hemodynamic instability during VT and the other 12 patients were hemodynamically stable. Two patients (11%) presented with sustained VT and 16 (89%) with episodes of nonsustained VT at varying intervals (3 of 16 with repetitive monomorphic VT). Among 14 patients on whom exercise tests were performed, seven had exercise-induced VT. During electrophysiologic studies, VT was induced in 16 of 18 (89%) (in 13 patients with morphology identical to clinical VT). VT was induced by programmed stimulation (single, double, and burst stimulation of the right atrium or right ventricular apex during sinus rhythm or during pacind for eight beats) in 5 of 18 (28%) patients; with isoproterenol, VT was aggravated spontaneously in 6 of 15 (40%) patients; and during stimulation VT was induced in 8 of 15 (53%) patients. Among patients whose VT was not induced during programmed stimulation, VT was induced with the addition of isoproterenol in 11 of 12 (92%). All 14 patients in follow-up are in stable condition, seven patients with medication and seven without medication. Pediatric patients with normal hearts and clinically detected VT usually have VT induced by programmed stimulation, either with or without isoproterenol stimulation.

Therapy assessment for sustained ventricular tachyarrhythmias: how many electropharmacological tests are appropriate?

Surgery, implantable devices or catheter ablations offer therapeutic choices for the treatment of malignant ventricular tachyarrhythmias (VT) resistant to antiarrhythmic drugs. The number of electropharmacological (EP) tests that should precede consideration of a nonpharmacological therapy has not been defined. We performed serial EP tests in 94 patients with inducible sustained VT until an effective drug was identified or all available drugs had failed to suppress VT induction. With up to 11 tests in individual patients, suppression of VT inducibility was finally achieved in 66 patients (70%). In 47 of these 66 patients (70%), only one or two tests were necessary to identify an effective regimen. However, in 40%, 28%, 18%, and 9% of the patients still inducible after 2, 3, 4, and 5 drug tests, respectively, an effective agent could be identified during subsequent tests. No critical number of unsuccessful EP tests clearly separated responders and nonresponders to medical therapy. During follow-up (34 +/- 11 months), 14 patients placed on antiarrhythmic drugs predicted to be effective had symptomatic VT recurrence. VT recurrence was unrelated to the type or the number of unsuccessful EP tests preceding identification of the prescribed drug. Extensive EP testing with all available agents might therefore be worthwhile in selected patients. An "appropriate" number of EP studies has to be determined individually for each patient, based on the chance of finding an effective drug during subsequent studies and the risk and benefit of the therapeutic choices.

Conversion of sustained into nonsustained ventricular tachycardia during therapy assessment by programmed ventricular stimulation: criterion for a positive drug effect?

Serial electropharmacologic testing using up to 11 different antiarrhythmic drugs was performed in 130 consecutive patients (107 men, 23 women, ages 56 +/- 12) with inducible sustained ventricular tachycardia (VT). After 4 +/- 2.3 drug tests, complete suppression of VT inducibility (defined as less than 6 consecutive beats, mean 1.4 +/- 1.6) was achieved in 86 patients (66%), whereas in 44 patients (34%) nonsustained VTs (greater than or equal to 6 consecutive beats, less than 30 seconds in duration) were still inducible. There was no statistical difference between both groups regarding age, sex, underlying heart disease, ejection fraction or entry arrhythmia. After a mean follow-up period of 19 +/- 17 months, 24 patients (18%) had died, 8 (6%) suddenly. Eight patients (6%) experienced recurrent sustained VT. Symptomatic recurrences (sudden death or VT) occurred in 10 (11%) and 6 patients (13%, difference not significant), respectively. Probability of arrhythmia-free survival was comparable for patients with 0 to 5, 6 to 10, 11 to 15 and 16 to 32 inducible ventricular complexes with discharge medication. The negative predictive value of electropharmacologic drug testing was about 89%, irrespective of the maximal number of inducible complexes used for the definition of a negative test result. It is therefore concluded that conversion of sustained into nonsustained VT during therapy assessment by programmed ventricular stimulation indicates a positive drug effect.

Rapid self-terminating ventricular tachycardia induced during electrophysiologic study: a prospective evaluation

The clinical significance of rapid self-terminating ventricular tachycardia induced during electrophysiologic study was prospectively evaluated in three patient groups with clinical ventricular arrhythmias. Group A (11 patients) had inducible rapid self-terminating ventricular tachycardia only (mean cycle length less than or equal to 250 ms and greater than or equal to 10 beats in duration). In Group B (22 patients) induction of this arrhythmia was followed by the induction of sustained ventricular tachycardia. In Group C (82 patients) sustained ventricular tachycardia was induced without preceding rapid self-terminating ventricular tachycardia. All clinical characteristics of Group B patients were similar to those of Group C patients but differed markedly from those of Group A patients. Compared with Group A patients, Group B patients had a lower left ventricular ejection fraction (32 +/- 13% versus 52 +/- 17%, p = 0.004) and a greater prevalence of coronary artery disease (82% versus 0%, p less than 0.0001), structural heart disease and a history of clinical sustained ventrical arrhythmias. Similarly, the induced self-terminating ventricular tachycardia differed in Group A and Group B patients. The arrhythmias in Group B patients were more often monomorphic, were more often induced with one or two extrastimuli and had a longer cycle length than those in Group A patients. In Group B patients, the electrophysiologic characteristics of the self-terminating and the sustained induced ventricular tachycardias were similar. Cardioversion was required in 50% of Group B patients compared with 27% of Group C patients (p = 0.038).(ABSTRACT TRUNCATED AT 250 WORDS)

Electrophysiologic evaluation of antiarrhythmic therapy for ventricular tachyarrhythmias

The use of electrophysiologic studies has contributed significantly to our understanding of the mechanisms of ventricular tachyarrhythmias and enhanced our ability to assess objectively the efficacy of various therapeutic interventions in modifying or preventing their recurrence. The basis on which electrophysiologic testing techniques is founded is the ability reproducibility to initiate ventricular arrhythmias by programmed electrical stimulation in patients with a history of recurrent ventricular tachycardia or fibrillation. Ventricular tachycardia can be initiated by electrophysiologic studies in approximately 90% of patients with clinically documented recurrent, sustained ventricular tachycardia related to coronary artery disease and in 60% of patients with nonsustained ventricular tachycardia. Reports indicate that electrophysiologic testing is highly specific as well (99% for sustained monomorphic ventricular tachycardia). Studies in patients with recurrent ventricular tachycardia demonstrate that prevention by antiarrhythmic drugs of the ability to initiate tachycardias that were previously inducible by comparable stimulation techniques in the absence of therapy is highly predictive of freedom from recurrent episodes of spontaneous ventricular tachycardia and ventricular fibrillation. This end point can be achieved in 35 to 75% of patients. This wide range of success rates results from differences in the patient populations studied, as well as major differences in the programmed stimulation and antiarrhythmic drug protocols used among laboratories. The positive predictive value of this technique (defined as the percentage of patients in whom complete suppression of inducible ventricular tachycardia or ventricular fibrillation is achieved during electrophysiologic testing with antiarrhythmic drugs and in whom no spontaneous arrhythmia occurs at 1- to 2-year follow-up) ranges between 80 and 95%.

Induction of ventricular arrhythmias by programmed ventricular stimulation: a prospective study on the effects of stimulation current on arrhythmia induction

A protocol for programmed ventricular stimulation is described in which the effect of increasing stimulation current on ventricular refractoriness and arrhythmia induction was specifically examined. The protocol was evaluated prospectively in 70 patients undergoing electrophysiological study for documented or suspected ventricular arrhythmias. Programmed electrical stimulation was performed at the right ventricular apex and outflow tract using single and double extrastimuli and burst pacing. Stimulation currents of 2, 5, 10, and 20 mA were used in ascending order. The initial (lowest) current was never less than twice diastolic threshold and was maintained during each stimulation run until refractoriness was reached. The current was then increased to the next level to facilitate premature capture until refractoriness was encountered at 20 mA or a sustained arrhythmia occurred. Ventricular arrhythmias were induced in 34 patients, 31 of whom had presented with a sustained ventricular arrhythmia. The incidence of induced arrhythmias was low in those patients who had presented with symptoms alone, a non-sustained arrhythmia, or a sustained arrhythmia in association with a predisposing clinical event. Only one patient with a negative result had further ventricular arrhythmias during the mean follow up period of 15 months. Although each increase in stimulation current caused a decrease in measured ventricular refractoriness, this resulted in only four arrhythmias. Only one arrhythmia was induced above 5 mA. These results suggest that this simple protocol using two extrastimuli and a single stimulation current of 5 mA will reliably identify most patients who have symptomatic ventricular arrhythmias.

Electrophysiologic study in the management of cardiac arrest survivors: a critical review

This review discusses the value and limitations of EPS in the management of cardiac arrest survivors. Uncertainties associated with EPS include a lack of consensus with respect to stimulation protocol, end points for VT suppression during drug testing, significance of induced polymorphic VT or VF, and timing of EPS after myocardial infarction. Despite methodologic shortcomings in most clinical studies, a useful body of knowledge has emerged. In cardiac arrest survivors, incidence of inducible sustained VT ranged from 35% to 75%. Where induced VT (sustained or nonsustained) was successfully suppressed, recurrent arrhythmic events occurred in 0% to 33% of patients over a 1- to 5-year follow-up period. Failed regimens correlated with a high risk of arrhythmic recurrence. EPS also helps to select patients for the implantable defibrillator or electrocardiac surgery. In conclusion, EPS appears empirically useful in the management of cardiac arrest survivors with coronary artery disease; its value in other disease entities is uncertain.