Electrophysiologic evaluation of antiarrhythmic therapy for ventricular tachyarrhythmias

Programmed ventricular stimulation after myocardial infarction does not help reduce the risk of ventricular events

Programmed ventricular stimulation could be a useful technique to detect patients at high risk for ventricular arrhythmias and sudden death after acute myocardial infarction. However, prevention of arrhythmic events using this technique has never been demonstrated. To determine whether prophylactic antiarrhythmic therapy influences prognosis after acute myocardial infarction, 196 patients without spontaneous ventricular tachycardia (VT) but with inducible sustained monomorphic VT were followed for 3 +/- 1 years. Ninety-seven patients were not treated (control group). In 99 patients (study group), the antiarrhythmic therapy was guided by electrophysiologic study: One to four trials using class I, II, and III antiarrhythmic drugs were performed until the VT was not inducible or the induced VT was slower and was associated with hemodynamic stability. An effective antiarrhythmic drug prevented VT induction in 34 patients (34%; group I). Sixty-five patients (group II) still had inducible VT with the antiarrhythmic drug. Group II differed from group I in having a higher incidence of an inferior myocardial infarction location (57% vs. 47%; NS), a lower left ventricular ejection fraction (36.5% vs. 41%; NS), a slower rate of induced VT in the control state (227 vs. 255 beats/min; p < 0.05), and a higher number of drug trials (1.9 vs 1.3; p < 0.001). During the follow-up in the control group and in groups I and II, the incidence of total cardiac events was 25%, 15%, and 16% (NS), respectively, and the incidence of total arrhythmic events (VT, sudden death) was 18.5%, 9%, and 12% (NS). Only the risk of VT was reduced (14%, 0%, and 4%; p < 0.05). In conclusion, guided-antiarrhythmic therapy, including class III agents after acute myocardial infarction, was successful in only 34% of patients, and the incidence of arrhythmic events was not significantly decreased. Therefore, programmed ventricular stimulation does not help in managing patients at risk of ventricular arrhythmia after myocardial infarction but could help indicate the need for nonmedical treatment, such as device therapy.

Efficacy of class 1C antiarrhythmic agents in patients with inducible ventricular tachycardia refractory to therapy with class 1A antiarrhythmic drugs

The efficacy of class 1C antiarrhythmic agents was determined in 36 patients with inducible sustained monomorphic ventricular tachycardia during baseline electrophysiology study (EPS), who continued to have inducible monomorphic ventricular tachycardia during EPS on class 1A antiarrhythmic therapy. Of 12 patients who partially responded to class 1A drugs, 11 (91.7%) continued to have a partial response during EPS on class 1C therapy, whereas one patient did not respond. Of 24 nonresponders to class 1A therapy, 2 (8.3%) responded during EPS on class 1C therapy, 7 (29.2%) partially responded, and 15 (62.5%) did not respond. In the 24 nonresponders to class 1A therapy, 9 of 17 patients (53%) with left ventricular ejection fraction (EF) > or = 30% responded or partially responded to class 1C therapy, compared with none of 7 patients with EF < 30% (P < .05). The EPS on class 1C agents in patients who fail to respond to class 1A therapy may be warranted only in those with EF > or = 30%.

Reproducibility of programmed electrical stimulation responses in patients with ventricular tachycardia or fibrillation associated with coronary artery disease

Invasive electrophysiologic studies were performed in 102 patients with sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) using an aggressive programmed electrical stimulation (PES) protocol. The study was repeated after 2.0 +/- 2.9 days in all patients with no intercurrent changes in antiarrhythmic therapy. Patients with coronary artery disease (n = 72) were identified and PES results of these patients were analyzed and compared with results of patients without coronary artery disease. Multiple clinical and electrophysiologic factors were analyzed to determine any association with concordance of PES responses. No significant difference in concordance of PES responses was found in the 2 groups of patients. PES responses were groups into 3 categories: (1) noninducible, (2) nonsustained VT, and (3) sustained VT. Kappa values of PES responses of noninducible and sustained VT in both groups were higher and therefore the PES responses were more reproducible than nonsustained VT. The induction of sustained monomorphic VT was more reproducible than a PES response of nonsustained or sustained polymorphic VT. Inducible sustained VT with a rate of greater than or equal to 250 beats/min was less reproducible than induction of sustained VT with a rate less than 250 beats/min. Induction of VT by 3 extrastimuli was less reproducible than with any other mode. This short-term variability may account for false negatives associated with PES-directed antiarrhythmic therapy. Because of these findings, it is recommended that nonsustained VT and sustained polymorphic or rapid polymorphic VT should not be used as PES end points to guide antiarrhythmic therapy.

Treatment of ventricular arrhythmias after CAST

OBJECTIVE

The primary objective of this article is to review the management of ventricular arrythmias in the light of the unfavourable results reported in the Cardiac Arrhythmia Suppression Trial (CAST).

STUDY SELECTION, DATA EXTRACTION AND SYNTHESIS

CAST tested the hypothesis that suppression of ventricular arrhythmias recorded on a Holter monitor in patients with myocardial infarction would lead to a decrease in subsequent mortality, presumably by preventing sudden death. In the trial, patients with a myocardial infarction which occurred six days to two years previously and with asymptomatic ventricular premature beats which could be suppressed by one of the antiarrhythmic agents flecainide, encainide or moricizine, were randomised to treatment with one of these agents or placebo. Over a mean follow-up period of 10 months, mortality was significantly higher in those patients receiving flecainide or encainide than in those receiving placebo. On the recommendation of the Data and Safety Monitoring Board the trial in these groups was terminated. More recently CAST II in which moricizine was compared to placebo was also terminated, again because of a higher mortality in the patients receiving active treatment. It is likely that much of the excess mortality can be attributed to proarrhythmic effects of the agents.

CONCLUSION

Current management of ventricular arrhythmias are considered in the light of these findings. CAST suggests that specific treatment should be dictated by the presence of associated symptoms and as much by associated structural heart disease as the arrhythmia per se. In particular, specific treatment of ventricular premature beats alone should be avoided. In those with potentially lethal ventricular arrhythmias, referral for appropriate investigation and consideration of non-pharmacological measures is necessary.

Evaluation of bepridil efficacy by electrophysiologic testing in patients with recurrent ventricular tachycardia: comparison of two regimens

The purpose of the study was to evaluate this effect of different doses of intravenous and oral bepridil on the induction of ventricular tachycardia. Thirty-eight patients underwent electrophysiologic evaluation for recurrent ventricular tachycardia (VT). Sustained monomorphic VT was induced by programmed ventricular stimulation, using up to three extrastimuli in all patients. The effects of intravenous bepridil (2 mg/kg) were evaluated during the initial study. Intravenous bepridil prevented the induction of sustained VT in eight patients (21%). Electrophysiologic study was repeated after oral bepridil. In six patients the study was stopped because of adverse effects or VT recurrence. Thirty-two patients underwent repeat study 7 days later, taking oral bepridil, 500 mg/day (n = 16) or 900/day (n = 16). A dose of 500 mg/day of bepridil prevented the induction of sustained VT in only one patient. A dose of 900 mg/day of bepridil prevented the induction of sustained VT in eight patients. There were no significant clinical adverse effects, except in one patient receiving intravenous bepridil. The response to intravenous bepridil did not predict the response to oral bepridil. The response to intravenous or oral bepridil was not related to the plasma level of bepridil but was related to a higher left ventricular ejection fraction. Eight patients (21%) in whom VTs were noninducible on oral bepridil were discharged on 300 mg/day of bepridil if their initial loading dose was 500 mg/day or on 600 mg/day if their initial loading dose was 900 mg/day. They remained free of VT during a follow-up of at least 6 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of ventricular tachycardia induced cardiogenic shock by percoronary chemical ablation

Incessant ventricular arrhythmias pose an especially challenging therapeutic dilemma. We describe the successful treatment and follow-up of a patient with refractory ventricular tachycardia-induced cardiogenic shock with percoronary chemical ablation. After endocardial mapping was used to identify the "tachycardia-related" coronary artery, temporary termination of the arrhythmia with balloon occlusion and subselective intracoronary installation of iced saline as previously advocated was unsuccessful. This was probably due to a dual arterial blood supply to the arrhythmogenic focus. However, infusion of 2 cc ethanol (99%) permanently terminated the arrhythmia. Contrary to previous experience, ethanol-induced arrhythmia termination did not result in arterial occlusion, further supporting a direct toxic effect on the myocardium as its mode of action. Use of standard angioplasty balloon inflation prevents "backwash" of distally infused ethanol and more generalized cell death. The only complication of this procedure was temporary third-degree AV block, requiring permanent pacemaker implantation.

Prolongation of ventricular refractoriness by class Ia antiarrhythmic drugs in the prevention of ventricular tachycardia induction

The effects of class la antiarrhythmic drugs (procainamide, quinidine) on the right ventricular effective refractory period (VERP) and intraventricular conduction time were assessed during serial invasive electrophysiologic studies for sustained monomorphic ventricular tachycardia (VT). In 47 patients with remote myocardial infarction, sustained VT was inducible by up to two extrastimuli after the basic drive at one of two basic cycle lengths at the right ventricular apex. With oral drug administration, sustained VT was no longer inducible (group I) in 27 patients but remained inducible (group II) in 20 with the same protocol. Class la drugs prolonged the VERP in both groups, but there was greater lengthening when drugs were effective (e.g., +32 +/- 14 msec in group I vs +12 +/- 19 msec in group II; p less than 0.005, basic cycle length 600 to 700 msec). Prolongation of the VERP by greater than 30 msec had an 88% positive predictive value for prevention of sustained VT induction. In all except one patient in group I, drugs prolonged the VERP such that the coupling intervals that had resulted in sustained VT induction under control conditions were no longer attainable. In contrast, conduction time through the ventricle (surface QRS duration) in sinus rhythm and during right ventricular pacing was prolonged similarly regardless of efficacy (e.g., +33 +/- 21 msec vs +27 +/- 27 msec at a cycle length of 400 msec). The presence of similar plasma levels of drug did not imply equivalent prolongation of the VERP in the two groups. These results suggest that greater prolongation of the VERP by oral procainamide or quinidine correlates with drug efficacy against VT induction and is a better predictor of drug effect than achievement of a "therapeutic plasma level."

Assessment and follow-up of pediatric survivors of sudden cardiac death

In the young patient resuscitated from sudden cardiac arrest, the risks of recurrence are uncertain and so are the criteria defining therapeutic efficacy for the presumed cause of the initial event. In this study, we analyzed the outcome of 15 consecutive young patients, who were resuscitated from pulseless ventricular tachycardia or ventricular fibrillation and who were evaluated by comprehensive hemodynamic and electrophysiological testing. Patients were 11.2 +/- 2.7 (mean +/- SD) years old at the time of their event, and each was known to have some form of heart disease before sudden cardiac arrest. Ventricular tachycardia or fibrillation was inducible by programmed electrical stimulation in eight patients. Accessory atrioventricular connections, with antegrade effective refractory periods less than 220 msec, were identified in three patients. Sustained atrial flutter was the only arrhythmia inducible in two patients, and no arrhythmias were inducible in two other patients. Surgical or electrophysiological-guided medical therapy resulted in noninducibility of the ventricular arrhythmias in six patients. Surgical division of the accessory atrioventricular connections was performed in three patients, and arrhythmias were not inducible after operation. The four patients with atrial flutter or without defined arrhythmia were treated with an empiric therapy. During 37 +/- 14 months of follow-up, the nine patients with documented noninducibility of a defined cause of sudden cardiac arrest were free of recurrent events. In contrast, during 18 +/- 10 months of follow-up, two of the six patients with empiric therapy or persistent inducibility of ventricular tachycardia died suddenly, and three others had recurrence of ventricular tachycardia or fibrillation.(ABSTRACT TRUNCATED AT 250 WORDS)

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.