Variability of spontaneous and exercise-induced ventricular arrhythmias in the absence and presence of treatment with acebutolol or quinidine

Reproducibility of drug efficacy predictions by Holter monitoring in the electrophysiologic study versus electrocardiographic monitoring (ESVEM) trial. ESVEM Investigators

Selection of antiarrhythmic therapy may be based on suppression of spontaneous ventricular arrhythmias assessed by Holter monitoring, but the implications of discordant Holter results on repeat 24-hour monitoring has not been defined. This study examines the frequency and significance of reproducible Holter suppression on two 24-hour recordings in the Electrophysiologic Study Versus Electrocardiographic Monitoring (ESVEM) trial. Repeat 24-hour Holter monitoring was obtained in patients randomized to the Holter monitor limb of the ESVEM trial, during the same hospitalization, after a drug efficacy prediction. These Holters were not used to define drug efficacy but were subsequently analyzed to determine the reproducibility of drug efficacy predictions by Holter monitoring. A repeat 24-hour Holter monitor, following the one that predicted drug efficacy, was available in 119 patients. Ninety-nine patients (83%) also had suppression that met efficacy criteria on the second Holter monitor. There were no significant differences in arrhythmia recurrence (p = 0.612) or mortality (p = 0.638) in patients with concordant Holter results (n = 99; 1-year arrhythmia recurrence = 45%; 1-year mortality = 10%) compared with those with discordant Holter results (n = 20; 1-year arrhythmia recurrence = 45%; 1-year mortality = 16%). We conclude that (1) there is discordance between the first effective Holter monitor and a repeat Holter monitor in 17% of patients, and (2) suppression of ventricular ectopic activity on 2 separate 24-hour Holter monitors does not identify a group with a better outcome, nor does failure of suppression on the second Holter monitor identify a group with a worse prognosis.

Review of nonparametric methods for the analysis of crossover studies

This paper reviews nonparametric methods for the analysis of crossover studies. Primary attention is given to crossover studies to compare two treatments for a response variable that has a metric measurement level. For this situation, one can often test hypotheses or obtain confidence intervals for parameters of interest by applying well known univariate nonparametric rank methods (e.g., the Wilcoxon rank sum test, or the Wilcoxon signed rank test) to appropriately specified functions of the data. Related extensions are also available, to some degree, for crossover studies to compare more than two treatments or those for which the measurement level of the response variable is ordinal or has a censored time-to-event nature. Methods for several specific situations along these lines are discussed in terms of principles with potentially broader applicability. Several examples are provided to illustrate the performance of some of the methods.

Do partial agonist beta-blockers have improved clinical utility?

Although beta-blockers were introduced into clinical medicine 30 thirty years ago, controversy continues as to the optimal pharmacodynamic profile of such agents. This commentary reviews the development of beta-blockers with partial agonist properties in the context of a recent study on epanolol. The influence of partial agonism on the efficacy and tolerability of beta-blockers is summarized, and it is concluded that, in general, there is little convincing evidence from controlled clinical studies that partial agonism confers significant clinical benefit over full antagonists.

Quinidine-related mortality in the short-to-medium-term treatment of ventricular arrhythmias. A meta-analysis

BACKGROUND

The interim results of the Cardiac Arrhythmia Suppression Trial requires physicians to use a higher threshold for employing antiarrhythmic agents in the treatment of benign or potentially lethal ventricular arrhythmias. Many have managed patients by switching to the traditional class I quinidine despite its known proarrhythmic tendency.

METHODS AND RESULTS

To evaluate the relation between quinidine therapy and mortality in patients with benign or potentially lethal ventricular arrhythmias, we performed a meta-analysis on four randomized double-blind active controlled parallel trials evaluating 1,009 patients in which quinidine (n = 502) was compared to flecainide (n = 141), mexiletine (n = 246), tocainide (n = 67), and propafenone (n = 53). All four trials had similar patient selection, protocols, and methodology (e.g., placebo lead-in and Holter monitoring) but varying lengths of drug exposure. A total of 12 deaths were reported on quinidine and four deaths on the other drugs: two on mexiletine, one on flecainide, and one on tocainide. The statistical analysis of the mortality rates was based on techniques for combining data across separate strata. Based on maximum likelihood estimation, the combined risk of dying on quinidine was statistically significantly higher compared to the other four drugs with a risk difference of 1.6%. The 95% confidence interval was 0-3.1% (p = 0.05). The likelihood ratio test for uniformity of the risk difference across strata showed the trials to be homogeneous (p = 0.88). There was one death recorded for the placebo lead-in period (2 weeks' exposure for 624 patients and 1 week for 385 patients), and seven deaths were reported within 2 weeks on active drug treatment--six on quinidine and one on mexiletine. Furthermore, proarrhythmia was reported in 20 patients on quinidine versus 11 patients on the four other drugs (p = 0.09).

CONCLUSIONS

These data suggest that quinidine may have an adverse effect on mortality as compared to other class I antiarrhythmic agents and that individualized patient selection for the use of this agent be carefully weighed relative to its potential for harm and benefit.

Mexiletine versus quinidine as first-line antiarrhythmia therapy: results from consecutive trials

The efficacy of mexiletine and quinidine in controlling ventricular couplets (VC) and ventricular tachycardia (VT) was compared in 156 trials (78 for each drug) in 114 consecutive patients. Forty-two patients received both drugs, whereas 36 patients were given mexiletine, and 36 patients received quinidine only. During acute drug testing, mexiletine was more effective than quinidine in controlling VC and VT (54 vs. 32 patients, respectively, P less than .001) and resulted in fewer proarrhythmic events (4 vs. 13, respectively, P less than .05). Mean duration of follow-up for mexiletine (27 +/- 14 mo) and quinidine (21 +/- 14 mo) did not differ. Long-term success was more frequent with mexiletine administration than quinidine administration (33/47 vs. 10/30 patients, respectively, P less than .01). The incidence of sudden death during follow-up with the two drugs did not differ overall, but more patients with ejection fraction greater than or equal to 40% died suddenly while taking quinidine than while receiving mexiletine (4/17 vs. 0/24, P less than .02). Mexiletine is as effective as quinidine for treating VC and VT and appears to be less proarrhythmic. It should be considered as an initial choice in the management of VC and VT.

A comparison of antiarrhythmic drugs for the suppression of ventricular ectopic depolarizations: a meta-analysis

This article reports the results of a meta-analysis of the effectiveness of antiarrhythmic drugs for the suppression of ventricular ectopic depolarizations. We analyzed 97 published articles that referred to a total of 27 drugs and contained data from 2989 patient-treatment trials; our goal was to determine the number of patients responding to therapy, defined as greater than or equal to 80% suppression of ventricular ectopic depolarizations. By means of logistic regression we tested the effect of 10 clinical and experimental variables on the likelihood of response to therapy. The likelihood of a drug response was significantly affected by the following six variables: increased by the use of dose titration (t = 3.59, p less than 0.0001), increased by the use of a higher daily dose (t = 3.21, p less than 0.0001), decreased by older age (t-2.67, p = 0.004), decreased by the use of blinding (t = -2.28, p = 0.011), increased by treating more male patients (t = 1.72, p = 0.043), and decreased by the presence of cardiovascular disease (t = -1.52, p = 0.064). Incorporating these six variables into our logistic regression model, we adjusted the response rate in each published study and calculated the mean response and standard error for each drug. Of the drugs tested in at least 100 patients, the most effective were amiodarone (estimated response rate 90%), encainide (80%), flecainide (79%), and propafenone (74%). Class IC drugs were significantly more effective than class IB and II drugs (p less than 0.05). With the exception of lorcainide and moricizine, class IC drugs were also more effective than class IA drugs (p less than 0.05). Amiodarone was significantly more effective than all drugs except encainide and flecainide (p less than 0.05). We found no significant differences among the response rates to class IA, IB, and II drugs. Whereas several patient and study characteristics affect the likelihood of response to antiarrhythmic drugs, class IC drugs and amiodarone are significantly more effective than other drugs in suppressing ventricular ectopic depolarizations.

Chronic ventricular arrhythmias: which drug for which patient?

Many agents, including a number of drugs recently approved by the Food and Drug Administration, are now available for the treatment of chronic ventricular arrhythmias. The so-called first-generation agents--quinidine, procainamide and disopyramide--have been used in large numbers of patients for many years, and the safety and efficacy profiles of these drugs are well established. The "second-generation" antiarrhythmic agents recently approved by the Food and Drug Administration offer promising new alternatives; however, their safety and efficacy profiles have yet to be confirmed for broad populations over extended periods of time. Although it is recognized that the choice of agent for treatment of a particular patient is a "therapeutic trial," with an unpredictable outcome of efficacy and adverse effects, certain "descriptors," such as patient age or co-existing medical conditions, are often helpful in determining which agent is most likely to be clinically effective, and which agents are most likely to produce adverse effects. When other medical conditions such as hepatic or renal failure are present, the appropriate choice of drug and dosage is required for optimal management of the arrhythmia and for prevention of overdosage, exacerbation of other medical problems and deleterious interactions. Combination therapy with multiple antiarrhythmic agents is often quite effective for increasing arrhythmia control without increasing adverse effects. However dosage modifications are often necessary when an antiarrhythmic drug is given in conjunction with another such agent, or with agents that also have electrophysiologic activity or modify metabolic or elimination functions. The following report is one clinician's approach for optimizing efficacy and minimizing toxicity while using the difficult class of drugs called antiarrhythmic agents. It will encourage the use of certain drugs before others, based on considerations of efficacy, safety, ease of administration, follow-up, and other factors.

Beta-adrenergic blockers

beta-Adrenergic blocking drugs have been available for several years to treat ischemic heart disease and other cardiovascular and noncardiovascular disorders. There are multiple drugs in this class with various pharmacodynamic and pharmacokinetic properties that may be important in specific clinical situations and in avoiding certain adverse reactions. These drugs have been shown to be efficacious in relieving anginal symptoms and prolonging exercise tolerance, in reducing high blood pressure, for treating various arrhythmias, in therapy of hypertrophic cardiomyopathy, and for prolonging life in many survivors of acute myocardial infarction.

Role of cardioselectivity and intrinsic sympathomimetic activity in beta-blocking drugs in chronic coronary artery disease

Beta-adrenergic blocking agents with various ancillary properties have been found valuable in the management of patients with hypertension, angina pectoris and atrial and ventricular arrhythmias. They are also used to reduce the risk of a subsequent coronary event after a myocardial infarction. In approximately 2 decades, the role of these agents in the patient with angina pectoris has expanded from one primarily involving the adjunctive treatment of the patient refractory to other drugs, to the present, in which beta-adrenergic blockers are the most common prophylactic agent prescribed for this indication.

Acebutolol: a review of its pharmacology, pharmacokinetics, clinical uses, and adverse effects

Acebutolol is a new hydrophilic, cardioselective beta-adrenergic-blocking agent that possesses partial agonist and membrane-stabilizing activities. In the treatment of mild to moderate essential hypertension, once-daily acebutolol as monotherapy provides effective control in a large majority of patients and produces a further reduction in blood pressure when used concomitantly with diuretics. Acebutolol is as effective as other beta-blocking agents, and in a large, double-blind, parallel study against propranolol was found to cause less reduction in heart rate, and fewer neurologic side effects and patient withdrawals due to adverse effects. Oral acebutolol is also effective in suppressing premature ventricular contractions, and in small numbers of patients generally beneficial results were obtained in supraventricular and ventricular arrhythmias with intravenous administration. These salutary effects are attributable to beta blockade. Controlled clinical trials documented the antianginal actions of oral acebutolol in chronic stable angina pectoris; its efficacy in this regard is comparable to that of other beta-blocking agents. The drug produces smaller decreases in heart rate and cardiac output and alterations in peripheral vascular hemodynamics than beta-blocking drugs without partial agonist activity, and because of its cardioselectivity, it may be used cautiously in patients with bronchospastic disease. Acebutolol has minimal metabolic effects and does not elevate levels of blood lipids during long-term therapy; high-density-lipoprotein cholesterol increased with acebutolol in a small number of patients.

Beta-blocking potency and electrophysiologic effects of acebutolol

The beta-blocking potency of three doses of acebutolol (100, 200, and 600 mg three times a day) has been compared to that of propranolol (30, 60, and 180 mg three times a day) in a double-blind crossover study in 10 healthy volunteers (seven men, three women). On the basis of reduction in resting and exercise heart rates, propranolol was three to four times more potent than acebutolol on a milligram-for-milligram basis. Plasma levels showed large interindividual variation for both agents. Plasma levels were weakly correlated with the degree of beta blockade for both acebutolol (r = 0.333, p less than 0.001) and propranolol (r = 0.381, p less than 0.01). Dose and percent beta blockade were more strongly correlated (propranolol, r = 0.503, p less than 0.001; acebutolol, r = 0.574, p less than 0.001). In 11 patients (10 men, one woman) with coronary artery disease, acebutolol at 1 mg/kg infused over 15 minutes decreased heart rate and slowed conduction, increased the refractoriness of the atrioventricular node without a significant change in the atrial refractoriness, and at plasma levels greater than or equal to 1000 ng/ml slowed His-Purkinje conduction. The comparative potency data suggest that the magnitude of the decrease in the resting and exercise-induced changes in heart rate and double product, in relation to dose of acebutolol, provides quantitative indices for judging adequacy by beta blockade in clinical therapeutics. The use of plasma drug levels, however, does not appear to be helpful in judging the adequacy of beta blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

Acebutolol: ten years of experience

During 10 years of clinical use involving almost 3 million patient-years, acebutolol has become established as a remarkably safe and well-tolerated beta-blocking agent, effective in treating essential hypertension and cardiac arrhythmias. The existence of a long-lived active metabolite (diacetolol) confers a 24-hour duration of action, which permits effective use of a once-daily regimen, particularly for hypertension. Acebutolol has low lipid solubility and low protein binding; the former property reduces the risk of central side effects, and the latter means that displacement interactions with other drugs are unlikely. Because acebutolol and its metabolite normally have both renal and hepatic excretion pathways, an alternative pathway is available should either be compromised through disease. Acebutolol is cardioselective, and clinical use has borne out the low incidence of bronchospasm in patients with impaired lung function. The possession of intrinsic sympathomimetic activity (ISA) leads to only modest reductions in cardiac output, which in turn reduces the chance of excessive bradycardia and the likelihood of precipitating heart failure. A combination of selectivity and ISA may be responsible for the low incidence of tiredness and cold extremities observed with acebutolol compared with other beta blockers. The unique pharmacologic and pharmacokinetic profile of acebutolol confers several therapeutic advantages and may be responsible for the generally low level of side effects experienced in clinical use.

Comparison of acebutolol and propranolol therapy for ventricular arrhythmias

The effects of acebutolol, a new investigational cardioselective beta blocker, and propranolol on ventricular arrhythmias were compared in 14 patients with more than 30 premature ventricular contractions (PVCs) per hour. Each patient served as their own control, receiving both drugs and placebo in random sequence and in double-blind fashion, with an intervening one-week, drug-free period. Each drug was given for a two-month period, the maximum acebutolol dosage reaching 600 mg tid and the maximum propranolol dosage 80 mg tid. Seventy-two-hour ambulatory electrocardiographic monitoring assessed arrhythmia frequency for each study period. Mean PVC counts did not significantly differ during the two control periods. Acebutolol decreased mean PVC count by 65% (P less than .02), with eight patients exhibiting a 70% or greater decrease. Only three patients exhibited a similar decline with propranolol. The incidence of PVCs was not significantly decreased by propranolol. Acebutolol reduced the number of couplets by 70% (P less than .04), whereas propranolol did not significantly affect couplets. At the dosage of 600 mg tid, acebutolol was well tolerated, effectively suppressed total PVCs and couplets, and appeared to be more effective than propranolol administered at 80 mg tid.