Beta-blocker therapy in patients with ventricular tachyarrhythmias in the setting of left ventricular dysfunction

Beta-Blockers and ACE Inhibitors Are Associated with Improved Survival Secondary to Ventricular Tachyarrhythmia

OBJECTIVE

The study sought to assess the impact of treatment with beta-blocker (BB) or ACE inhibitor/angiotensin receptor blocker (ACEi/ARB) on secondary survival in patients presenting with ventricular tachyarrhythmia.

BACKGROUND

Data regarding outcome of patients presenting with ventricular tachyarrhythmia treated with BB and ACEi/ARB is limited.

METHODS

A large retrospective registry was used including consecutive patients presenting with ventricular tachycardia and fibrillation from 2002 to 2016 on admission. Applying propensity-score matching for harmonization, the impact of "BB" and "ACEi/ARB" was comparatively evaluated. The primary prognostic outcome was long-term all-cause death at 3 years.

RESULTS

A total of 972 matched patients were included. Both patients with BB (long-term mortality rate 18 versus 27%; log rank p = 0.041; HR = 0.661; 95% CI = 0.443-0.986; p = 0.043) and with ACEi/ARB (long-term mortality rate 13 versus 23%; log rank p = 0.004; HR = 0.544; 95% CI = 0.359-0.824; p = 0.004) revealed better secondary survival compared to patients without after presenting with ventricular tachyarrhythmia on admission. The prognostic benefit of BB was comparable to ACEi/ARB (long-term mortality rate 21 versus 26%; log rank p = 0.539).

CONCLUSION

BB and ACEi/ARB were associated with improved secondary survival in patients surviving ventricular tachyarrhythmia on admission.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02982473.

Benefits of β blockers in patients with heart failure and reduced ejection fraction: network meta-analysis

OBJECTIVE

To clarify whether any particular β blocker is superior in patients with heart failure and reduced ejection fraction or whether the benefits of these agents are mainly due to a class effect.

DESIGN

Systematic review and network meta-analysis of efficacy of different β blockers in heart failure.

DATA SOURCES

CINAHL(1982-2011), Cochrane Collaboration Central Register of Controlled Trials (-2011), Embase (1980-2011), Medline/PubMed (1966-2011), and Web of Science (1965-2011).

STUDY SELECTION

Randomized trials comparing β blockers with other β blockers or other treatments.

DATA EXTRACTION

The primary endpoint was all cause death at the longest available follow-up, assessed with odds ratios and Bayesian random effect 95% credible intervals, with independent extraction by observers.

RESULTS

21 trials were included, focusing on atenolol, bisoprolol, bucindolol, carvedilol, metoprolol, and nebivolol. As expected, in the overall analysis, β blockers provided credible mortality benefits in comparison with placebo or standard treatment after a median of 12 months (odds ratio 0.69, 0.56 to 0.80). However, no obvious differences were found when comparing the different β blockers head to head for the risk of death, sudden cardiac death, death due to pump failure, or drug discontinuation. Accordingly, improvements in left ventricular ejection fraction were also similar irrespective of the individual study drug.

CONCLUSION

The benefits of β blockers in patients with heart failure with reduced ejection fraction seem to be mainly due to a class effect, as no statistical evidence from current trials supports the superiority of any single agent over the others.

Importance of beta blockade in the therapy of serious ventricular arrhythmias

Beta blockers have traditionally been considered relatively poor antiarrhythmic agents for patients with ventricular arrhythmias. This view is based on the observations that beta blockers are less effective in suppressing spontaneous ventricular ectopy or inducible ventricular arrhythmias than are the class I and class III agents. However, there are convincing data that beta blockers can have a clinically important antiarrhythmic effect and prevent arrhythmic and sudden death. Beta blockers have multiple potential effects that can contribute to a therapeutic antiarrhythmic action, including an antiadrenergic/vagomimetic effect, a decrease in ventricular fibrillation threshold, and prevention of a catecholamine reversal of concomitant class I/III antiarrhythmic drug effects. Postinfarction trials, recent congestive heart failure studies, and observations in patients who are at risk for sustained ventricular arrhythmias all suggest a potent antiarrhythmic effect of beta blockade.

Mechanisms and management of ventricular dysrhythmias in heart failure

Despite recent pharmacologic and surgical advances in the management of heart failure, the morbidity and mortality rates of this chronic illness remain high. Ventricular dysrhythmias are common in heart failure and may be independently associated with increased mortality rates. Although the risks of sudden cardiac death leading to the patient's death are increased by the presence of complex ventricular dysrhythmias, the management of dysrhythmias is subject to controversy. The purpose of this article is to review the normal electrophysiologic properties of the heart and to examine the likely mechanisms, diagnostic approaches, and proposed treatments for ventricular dysrhythmias in heart failure.

A review of why and how we may use beta-blockers in congestive heart failure

The history of the use of beta-blockers for congestive heart failure, beginning with the innovative seminal study by the Swedish group in 1975 to studies in 1995, is reviewed and shows that almost all trials favored the use of beta-blockers. They tended to demonstrate an increase in ejection fraction, a decrease in left ventricular mass, and in some studies, even a decrease in mortality. Even after the introduction of angiotensin-converting enzyme inhibitors, additional improvement in function and mortality was observed. Patients with nonischemic dilated cardiomyopathy derived more benefit from beta-blockers than did patients with ischemic cardiomyopathy. Least likely to benefit were patients treated for <2 months, patients with alcoholic cardiomyopathy, and those with marked intercellular fibrosis. Although the starting dose of metoprolol, the most common beta-blocker used, may have to be as low as 2.5 mg/d, mortality analysis failed to show a decrease in sudden death unless the dose was raised to about 300 mg/d, a dose at which beta-selectivity is generally not expected to be present. The non-beta-specific bucindolol or carvedilol may ultimately be preferred to metoprolol because they are better tolerated initially due to a slight vasodilatation effect. Initial studies with carvedilol showed remarkable promise in reducing mortality. However, these agents cannot yet be said to have been studied adequately.

Beta adrenergic blockade in the treatment of sustained ventricular tachycardia or ventricular fibrillation

The value of beta-blockers as antiarrhythmic drugs in patients with sustained VT or VF has received only little attention. This article summarizes the current state of knowledge regarding the identification of patients with sustained VT or VF with the highest benefit of beta-blockade. The antiarrhythmic mechanisms of beta-blockade and its efficacy as single or adjuvant therapy in patients with sustained VT or VF are reviewed. Current insights into the effects of beta-blockade in patients suffering from VT, in particular in the setting of heart failure, are discussed and future directions are considered.

Management of patients with life-threatening sustained ventricular tachyarrhythmias--the role of guided antiarrhythmic drug therapy

Two recent studies have evaluated the utility of electrophysiologic (EP) testing in the treatment of patients with serious ventricular arrhythmias. The first study compared electrophysiologically guided antiarrhythmic drug therapy with nonguided beta-blocker therapy. Patients without inducible arrhythmias were assigned to oral metoprolol; patients with inducible arrhythmias were randomly assigned to receive either oral metoprolol or EP-guided drug therapy with propafenone, flecainide, disopyramide, sotalol, or amiodarone. Antiarrhythmic drugs were tested in a random order, but amiodarone was always tested last. A total of 170 patients were evaluated; 115 patients had inducible arrhythmias, and 61 patients were randomly assigned to serial drug testing, 54 to metoprolol without invasive testing, and the remainder who were noninducible to empiric metoprolol. The best outcome was observed in patients without inducible arrhythmias, all of whom received metoprolol. There was no difference in outcome between the two groups with inducible arrhythmias, either treated with metoprolol or with EP-guided serial antiarrhythmic drug testing. The second study evaluated survivors of out-of-hospital ventricular fibrillation (VF) without new myocardial infarction. Patients received assessment of left ventricular ejection fraction, Holter monitoring (HM), and EP testing. Only patients with inducible sustained ventricular arrhythmias or with sufficient ambulatory ventricular ectopy were included in the study. Therapy was randomized either to empiric amiodarone or conventional drug therapy guided by EP testing and/or HM. A total of 228 patients were treated, 113 with amiodarone and 115 with conventional antiarrhythmic drug therapy. The composite primary end points were total mortality, documented out-of-hospital resuscitation from recurrent VF, or syncopal implantable cardioverter/defibrillator shock followed by return of consciousness. Patients treated with empiric amiodarone had a better outcome than did patients treated with guided conventional drug therapy. In those patients in whom an implantable cardioverter/defibrillator was used, patients treated with amiodarone had fewer total shocks and fewer syncopal shocks than did patients treated with conventional therapy. Patients with a history of out-of-hospital VF or sustained ventricular tachycardia without inducible ventricular arrhythmias at EP study have the best outcome. Empiric metoprolol is equivalent to conventional antiarrhythmic drug therapy guided by EP testing. Empiric amiodarone is superior to conventional antiarrhythmic drug therapy guided by HM and/or EP testing.

New evidence for improved survival in chronic heart failure

Chronic heart failure is a common clinical syndrome with high associated mortality and morbidity. Recent advances in therapy for the condition with vasodilators and, in particular, angiotensin-converting enzyme inhibitors, have led to hopes for improvement in survival. Several large scale studies examining the role of vasodilators have reported over the last few years, and the role of vasodilators in the treatment and prevention of chronic heart failure is being delineated. There is new hope for patients with symptomatic heart failure; symptoms can be alleviated and prognosis improved. Increasingly, it appears as if there is a role for drug therapy in preventing the onset of chronic heart failure. In this paper, we examine the results of these studies and of some smaller studies in order to discuss the implications for current therapy and future research.

A prospective study of the efficacy and safety of adjuvant metoprolol and xamoterol in combination with amiodarone for resistant ventricular tachycardia associated with impaired left ventricular function

Combination antiarrhythmic drug therapy may be more effective than treatment with a single agent for control of refractory cases of sustained ventricular tachycardia (VT). In a prospective randomized crossover study of 20 patients with impaired left ventricular function (ejection fraction of 28% +/- 8%) and recurrent VT in spite of treatment with amiodarone, we compared the efficacy and safety of adjuvant therapy with metoprolol, 50 mg two times daily and xamoterol, 200 mg two times daily. Metoprolol caused hemodynamic deterioration in five patients, and only one also experienced intolerance to xamoterol. Sustained VT was inducible in all 20 patients who were receiving amiodarone alone but was suppressed or rendered nonsustained in 8 of 20 patients during treatment with amiodarone plus xamoterol and in 6 of 17 patients during treatment with amiodarone plus metoprolol. Addition of xamoterol restored sinus rhythm in four patients who presented with incessant VT, and metoprolol was effective for three of them. Neither beta-blocker significantly altered tachycardia cycle length or any electrophysiologic parameter other than the slowing of the sinus rate. Both beta-blockers suppressed exercise-induced VT in 3 of 4 patients, and addition of xamoterol significantly increased treadmill exercise duration (7.1 +/- 1.8 min) compared with administration of amiodarone alone (3.8 +/- 1.5 min; p < 0.01). Fourteen patients were discharged with prescriptions for amiodarone-beta-blocker combinations. During a mean follow-up period of 13 months (range, 2 to 24 months), there were three cases of recurrent VT (in all patients VT remained inducible) and no sudden deaths.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of electrophysiologically guided antiarrhythmic drug therapy with beta-blocker therapy in patients with symptomatic, sustained ventricular tachyarrhythmias

BACKGROUND

Antiarrhythmic drug therapy guided by invasive electrophysiologic testing is now widely used in patients with symptomatic, sustained ventricular tachyarrhythmias.

METHODS

We conducted a prospective, randomized trial in 170 patients to investigate whether this approach would improve long-term outcome. Patients whose arrhythmia was inducible by programmed electrical stimulation were assigned to treatment with electrophysiologically guided drug therapy based on serial testing (61 patients) or with metoprolol (54 patients). Electrophysiologically guided therapy consisted of serial testing of antiarrhythmic agents to identify the first one that rendered the arrhythmia noninducible. The 55 patients whose arrhythmia was noninducible during the initial electrophysiologic test were also treated with metoprolol.

RESULTS

During a mean (+/- SD) follow-up period of 23 +/- 17 months, recurrent, nonfatal arrhythmia occurred in 44 patients and sudden death due to cardiac factors in 27. The incidence of symptomatic arrhythmia and sudden death combined was virtually the same in the two groups with inducible arrhythmia after two years of observation (electrophysiologically guided therapy vs. metoprolol therapy, 46 percent vs. 48 percent). The outcome was more favorable in the patients with noninducible arrhythmia at base line (75 percent had neither adverse event) than in those with inducible arrhythmia who were assigned to metoprolol therapy (P = 0.009 by log-rank test). Only 6 of the 29 patients (21 percent) with inducible arrhythmia that became noninducible during drug therapy had recurrent arrhythmia or sudden death, as compared with 21 of the 32 patients (66 percent) with arrhythmia that continued to be inducible (P less than 0.001). A multivariate regression analysis identified continued inducibility of the arrhythmia as an independent predictor of recurrent arrhythmia or sudden death (relative risk, 7.3; 95 percent confidence interval, 2.3 to 23.2; P less than 0.001).

CONCLUSIONS

As compared with metoprolol therapy, electrophysiologically guided antiarrhythmic drug therapy did not improve the overall outcome of patients with sustained ventricular tachyarrhythmias. However, effective suppression of inducible arrhythmia by antiarrhythmic drugs was associated with a better outcome than was lack of suppression.

Adjuvant metoprolol improves efficacy of class I antiarrhythmic drugs in patients with inducible sustained monomorphic ventricular tachycardia

Inducible ventricular tachycardia frequently persists despite solitary class I antiarrhythmic drug therapy. To determine the effect of metoprolol as adjuvant therapy, 19 patients with clinical ventricular tachycardia with baseline inducible sustained monomorphic ventricular tachycardia and persistently inducible ventricular tachycardia despite class I drugs were evaluated. Eight of 19 patients (42%) became noninducible when metoprolol was added to class I drug therapy. Sixteen of 19 patients (84%) were harder to induce or noninducible on a regimen of adjuvant metoprolol therapy. In evaluating the clinical characteristics of the 19 patients, no significant differences were found between patients who were persistently inducible and those rendered noninducible. In evaluating the electrophysiologic characteristics, the group eventually rendered noninducible had a significantly shorter baseline induced cycle length (259 +/- 27 vs 305 +/- 53 msec). Combination class I drug and metoprolol therapy significantly lengthened the ventricular effective refractory period in both groups compared with baseline. The long-term follow-up was excellent in all patients remaining on metoprolol in the noninducible group. Therefore adjuvant metoprolol therapy creates a significant improvement in a number of patients with persistently inducible ventricular tachycardia despite class I drug therapy.

Current issues in advanced heart failure

In the past 50 years, an increased understanding of the pathophysiologic mechanisms associated with the development of heart failure has produced a more precise treatment of this syndrome. The effects of the agents used for the treatment of patients with advanced heart failure have been summarized in this article and demonstrate the importance of vasodilatory drugs on the survival and progression of dilated cardiomyopathy.

Evidence of a selective increase in cardiac sympathetic activity in patients with sustained ventricular arrhythmias

BACKGROUND

Although enhanced efferent cardiac sympathetic nervous activity has been proposed as an important factor in the genesis of ventricular arrhythmias and sudden cardiac death, direct clinical evidence has been lacking.

METHODS

We measured the rates of total and cardiac norepinephrine spillover into the plasma, which reflect respectively overall and cardiac sympathetic nervous activity, in 12 patients who had recovered from a spontaneous, sustained episode of ventricular tachycardia or ventricular fibrillation outside the hospital 4 to 48 days earlier. The results were compared with those from three age-matched reference groups without a history of ventricular arrhythmias: 12 patients with coronary artery disease, 6 patients with chest pain but normal coronary arteries, and 12 healthy, normal subjects.

RESULTS

The patients who had had ventricular arrhythmias had reduced left ventricular ejection fractions, as compared with the patients with coronary artery disease or chest pain (mean [+/- SE], 46 +/- 3 percent vs. 58 +/- 4 percent and 69 +/- 5 percent, respectively; P less than 0.003). The rates of total norepinephrine spillover into the plasma were similar in the three reference groups, but 80 percent higher in the patients with ventricular arrhythmias (P less than 0.005). The rate of cardiac norepinephrine spillover was 450 percent higher in these patients (176 +/- 39 pmol per minute, as compared with 32 +/- 8 pmol per minute in the normal subjects; P less than 0.001), a disproportionate increase relative to the increase in total spillover, which indicated selective activation of the cardiac sympathetic outflow. This increase in cardiac norepinephrine spillover was probably caused by a reduction in left ventricular function.

CONCLUSIONS

These results suggest that in some patients major ventricular arrhythmias are associated with and perhaps caused by sustained and selective cardiac sympathetic activation. We speculate that depressed ventricular function was present before the ventricular arrhythmia occurred, and that this resulted in reflex cardiac sympathetic activation, which in turn contributed to the genesis of the arrhythmia.

Diagnostic value of ventricular stimulation in patients with idiopathic dilated cardiomyopathy

To assess the response to programmed ventricular stimulation and the clinical outcome, we performed a prospective study in 103 patients with idiopathic dilated cardiomyopathy. The protocol used up to three extrastimuli delivered at two right ventricular sites during sinus rhythm and ventricular pacing at 100 and 150 beats/min and was repeated during infusion of 1 to 4 micrograms/min of isoproterenol. Sustained monomorphic ventricular tachycardia (VT) was induced in 8 of 11 patients with spontaneous sustained VT, in none of 35 patients without significant ventricular arrhythmias during Holter monitoring, and in 9 of 56 patients with salvos of ventricular premature beats. Isoproterenol infusion facilitated the induction of two episodes of sustained VT in patients with spontaneous sustained VT; however, in all but one of the remaining patients, induction of ventricular tachyarrhythmias was not impaired. During the follow-up period there were eight sudden deaths among patients who initially had syncope, inducible sustained VT, or both and three episodes of sustained VT in patients who initially had nonsustained VT but inducible sustained VT. Isoproterenol infusion can be used to safely facilitate induction of ventricular tachyarrhythmias in patients with dilated cardiomyopathy. The induction of sustained VT was associated with a poor prognosis.

Relation between beta-adrenergic blocker use, various correlates of left ventricular function and the chance of developing congestive heart failure. The Multicenter Diltiazem Post-Infarction Research Group

This study examined the relations among beta-adrenergic blocker use, various correlates of left ventricular function and the chance of developing congestive heart failure in patients after myocardial infarction. The study was performed with the placebo group of the Multicenter Diltiazem Post-Infarction Trial. Ejection fraction data were available in 1,084 patients; of these, 557 were receiving a beta-blocker and 527 were not. In addition to ejection fraction, other correlates of left ventricular function included the presence or absence of pulmonary rales, chest X-ray film evidence of pulmonary congestion and the presence of an S3 gallop. Beta-blocker use was less frequent in patients with an ejection fraction less than 30%, rales, an S3 gallop and pulmonary congestion on chest X-ray film. Twenty-one percent of patients with an ejection fraction less than 30%, 42% of patients with rales, 28% of patients with an S3 gallop and 28% of patients with pulmonary congestion were receiving beta-blocker therapy. For every correlate of left ventricular function, the chance of developing congestive heart failure was greater in patients with diminished left ventricular function than in those without. For each level of left ventricular function, the chance of developing congestive heart failure requiring treatment was greater in patients not taking a beta-blocker.(ABSTRACT TRUNCATED AT 250 WORDS)

Effectiveness of propranolol added to a type I antiarrhythmic agent for sustained ventricular tachycardia secondary to coronary artery disease

The effect of adding propranolol to procainamide, quinidine, propafenone or disopyramide was prospectively evaluated in 37 patients, all with prior infarction and inducible ventricular tachycardia (VT). After showing that VT remained inducible during therapy with a type I drug, 23 patients received intravenous propranolol. The ventricular effective refractory period, prolonged by the type I agent, was further increased by propranolol. The cycle length of the VT also increased after the type I drug and propranolol exaggerated this effect. Seven of the 23 patients were rendered noninducible after propranolol and another 10 manifested a greater than 100 ms increase in induced VT cycle length. In the other 14 patients, propranolol was infused immediately after the basal study. If VT remained inducible, testing was repeated after a type I drug was added. The ventricular effective refractory period, as well as the VT cycle length, increased after propranolol and was further prolonged after the addition of a type I agent. Seven of these 14 patients were rendered noninducible, 3 with propranolol alone and 4 others with the combination, and in 4, the VT cycle length was prolonged by greater than 100 ms. A total of 17 patients were discharged on either propranolol alone (3 patients) or on an effective combination (14 patients). During a mean follow-up of 20 months, 1 patient died suddenly, 2 had recurrence of well-tolerated VT and 9 remain on therapy. Thus, propranolol has a demonstrable antiarrhythmic effect in the invasive laboratory and may supplement the antiarrhythmic efficacy of conventional type I antiarrhythmic drugs.

Efficacy of intravenous propranolol for suppression of inducibility of ventricular tachyarrhythmias with different electrophysiologic characteristics in coronary artery disease

The efficacy of intravenous propranolol for suppression of inducibility of sustained ventricular tachyarrhythmias (VT) was studied in 24 patients who had failed greater than or equal to 1 membrane-active antiarrhythmic drug (mean 2.2 +/- 1.2 drugs/patient). The response to propranolol was compared in 13 patients who had only stable monomorphic VTs inducible at baseline and another 11 patients who had greater than or equal to 1 episode of electrically unstable VTs (polymorphic VT, ventricular flutter or ventricular fibrillation) at baseline. Seven patients (29%) became noninducible (responders) and 17 patients (71%) remained inducible to sustained VT (nonresponders) after propranolol. The basal heart rate was faster in responders than in nonresponders (101 +/- 14 vs 86 +/- 11 beats/min, p less than 0.01). The magnitude of heart rate reduction was also greater after propranolol in responders (from 101 +/- 14 to 80 +/- 9 beats/min, p less than 0.001) than in nonresponders (from 86 +/- 11 to 74 +/- 9 beats/min, p less than 0.01) (p less than 0.05 between the groups), despite equal plasma propranolol concentrations (84 +/- 50 vs 88 +/- 43 ng/ml, difference not significant). Seven of 11 patients (64%) who had greater than or equal to 1 episode of unstable VTs inducible at baseline responded to intravenous propranolol, whereas none of the patients with only stable monomorphic VTs became noninducible after beta blockade (p less than 0.001). Responders had shorter cycle length of inducible VTs than nonresponders (225 +/- 38 vs 302 +/- 66 ms, p less than 0.001). Thus, intravenous propranolol appears to be efficacious in suppressing fast, electrically unstable VTs, compared to monomorphic VTs with slower rates.

The effect of beta-adrenergic blockade on vulnerability to ventricular fibrillation and inducibility of ventricular arrhythmia in short- and long-term feline infarction models

Previous investigation, predominantly in the short-term canine model, has documented a potent antifibrillatory effect of beta-adrenergic blockade. To determine whether the protection afforded by beta blockade is species- and model-specific, we studied 23 chloralose-anesthetized cats. Eight animals were studied over a short term and underwent serial determinations of the ventricular fibrillation (VF) threshold prior to and 1 minute after occlusion of the left anterior descending coronary artery (LAD) and immediately following reperfusion of a 10-minute occlusion. Beta-blocking doses of intravenous propranolol (P) (0.5 mg/kg) attenuated the fall in VF threshold during acute ischemia. Increasing the dose of P to 1 mg/kg did not provide further protection, nor did P protect against reperfusion VF. The other 15 animals underwent a preliminary surgical procedure during which the LAD was completely and irreversibly occluded (nine animals) or in which a sham procedure was performed (six animals). Two weeks later, we measured ventricular refractoriness at several left ventricular sites, ventricular inducibility using programmed electrical stimulation, and VF thresholds both before and after administration of intravenous P (1 mg/kg). Ventricular refractory periods in the infarcted zones were significantly increased compared with normal sites and with values obtained in sham-operated animals. In addition, VF thresholds in the infarcted animals were lower than those obtained in the sham-operated group. Before treatment, a reproducible sustained ventricular tachyarrhythmia was induced by means of programmed stimulation in seven of the nine chronically infarcted animals but in none of the sham-operated animals (p less the 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Antiarrhythmic efficacy of solitary beta-adrenergic blockade for patients with sustained ventricular tachyarrhythmias

To assess the efficacy and predictability of solitary beta-adrenergic blocker (BB) therapy for ventricular tachyarrhythmia (VT), 30 patients (16 men and 14 women) with a mean age of 55 years, who initially had sustained ventricular tachycardia (70%) or ventricular fibrillation (30%), were studied. Results of baseline arrhythmia tests showed VT on ECG monitoring in 57% of the patients, during exercise in 50%, induced by programmed stimulation in 69%, increasing to 86% during isoproterenol. BB therapy prevented inducible VT during programmed stimulation in 37% of the patients, prevented VT on ECG monitoring in 54%, and prevented VT during exercise in 83%. Long-term BB therapy was given to 24 of 30 patients, whereas six other patients with hemodynamically unstable VT during BB therapy received other long-term treatment. During a mean follow-up of 824 days, 6 of 24 patients had recurrent VT. BB therapy was discontinued in two patients because of side effects. Long-term success was predicted by left ventricular ejection fraction greater than 45%, absence of coronary disease, and age less than 60 years (all p less than 0.02). Neither suppression of arrhythmia during exercise testing, nor results of programmed stimulation or ECG monitoring were predictive of outcome. Thus beta-adrenergic blockers can be effective as solitary antiarrhythmic therapy in selected patients with VT.