Effect of antiarrhythmic therapy on mortality in survivors of myocardial infarction with asymptomatic complex ventricular arrhythmias: Basel Antiarrhythmic Study of Infarct Survival (BASIS)

Critical review of the approaches to the prevention of sudden death

The types of cardiac rhythm in patients with sudden death may vary considerably, depending on the underlying cardiac disease. Although ventricular tachyarrhythmias are likely to be the most common causes, a significant proportion of patients may die suddenly due to asystole, electromechanical dissociation, or cardiac rupture. Therefore, the approaches to preventing sudden death may have to be multifactorial. The classic approach of arrhythmia suppression by empiric antiarrhythmic drugs has not resulted in a decrease in sudden death mortality. Although beta blockers have only a modest effect in suppressing arrhythmias, they have been clearly proven to prevent sudden death. Other promising approaches that require further evaluation include modulation of the autonomic balance between the sympathetic and parasympathetic nervous systems (perhaps by beta blockers, exercise training, or low-dose atropine or scopolamine), relief of ischemia by medical or surgical therapy, magnesium supplementation, and mechanical devices, such as the implantable defibrillator.

Secondary prevention after myocardial infarction with class III antiarrhythmic drugs

First-year mortality after myocardial infarction (MI) is high, amounting to 15%. It has been well documented that ventricular arrhythmias late after MI constitute a risk factor for sudden cardiac death. Consequently, several authors undertook attempts to decrease post-MI mortality with antiarrhythmic drugs. Unfortunately, the class I drugs most widely used in clinical practice proved to be ineffective or they even increased the risk of death, as occurred in the Cardiac Arrhythmia Suppression Trial (CAST). So far, only beta blockers, although not particularly effective in controlling ventricular ectopic beats, have been found to decrease first-year mortality after MI by 26-36%. Class III drugs appear to be promising in this clinical setting. Early study with sotalol showed a positive, although statistically nonsignificant, trend toward decreasing mortality. In a more recent trial with amiodarone (Basel Antiarrhythmic Study of Infarct Survival [BASIS]) done in Switzerland, total mortality was reduced (p < 0.05). It should be stressed that the drug was administered at a low dosage level (200 mg/day) to 98 patients and did not cause serious side effects. Similarly encouraging results have been provided by the Polish Amiodarone Study. Amiodarone given to 305 patients at a low dose (200-400 mg/day) reduced first-year cardiac mortality by 42% (p < 0.05). No serious side effects were noticed. Several ongoing trials should further substantiate the impact of this regimen on mortality after MI.

The European Myocardial Infarct Amiodarone Trial (EMIAT). EMIAT Investigators

The objective of the European Myocardial Infarct Amiodarone Trial (EMIAT) is to assess the efficacy of amiodarone on mortality of patients with depressed left ventricular (LV) function following myocardial infarction (MI). The rationale for the trial is as follows: patients with poor LV function after acute MI have a high sudden cardiac death (SCD) mortality; amiodarone is a successful prophylactic therapy against SCD in patients with ventricular arrhythmias; a number of small studies (Canadian Amiodarone Myocardial Infarction Arrhythmia Trial [CAMIAT] pilot study, Basel Antiarrhythmic Study & Infarct Survival [BASIS], and the Polish Amiodarone Trial [PAT]) of prophylactic amiodarone post AMI have shown a beneficial response attributable to amiodarone. Patients are enrolled between 5 and 21 days after acute MI if LV ejection fraction (assessed by multiple-gated image acquisition nuclear angiography) is < or = 40%. The study group is stratified according to ejection fraction (stratum 1, 31-40%; stratum 2, < 31%). Amiodarone or placebo treatment (blind, randomized) is initiated prior to the discharge of the patient from the hospital and each patient is followed up for the duration of the study, at least 1 year. Recruitment began on November 30, 1990, and will continue for 4 years; > 700 patients are enrolled from > 60 centers (13 countries). The total study mortality (10% at 500 days) and the differential mortality of both strata are as anticipated. Side effects have been infrequent and very few patients have been withdrawn from the study. Trial conclusion is forecast for October 1995.

Low-dose amiodarone for atrial fibrillation

Concerns about proarrhythmia risk and inefficacy associated with class I antiarrhythmic drugs have revived interest in low-dose amiodarone (maintenance dose 200-400 mg/day) for suppression of atrial fibrillation. In nonrandomized trials of amiodarone for atrial fibrillation refractory to conventional agents, amiodarone has been successful in maintaining sinus rhythm in 53-79% of patients during a mean follow-up of 15-27 months. Intolerable side effects, including pulmonary toxicity, are in the range of 1-12% per year and resolve following amiodarone withdrawal in the majority of cases. Proarrhythmia risk associated with amiodarone, even in the setting of left ventricular dysfunction, is extremely low. In patients with congestive heart failure, in whom other pharmacologic options are limited by proarrhythmia risk and negative inotropism, preliminary experience with amiodarone is especially promising. Randomized trials are needed, directly comparing amiodarone to conventional antiarrhythmic therapy for atrial fibrillation suppression and comparing amiodarone to warfarin for thromboembolism prevention in patients with atrial fibrillation refractory to conventional antiarrhythmic drugs.

Canadian Amiodarone Myocardial Infarction Arrhythmia Trial (CAMIAT): rationale and protocol. CAMIAT Investigators

The Canadian Amiodarone Myocardial Infarction Trial (CAMIAT) is a multicenter, triple-blind, randomized, placebo-controlled trial. Eligible patients are those found on 24-hour ambulatory electrocardiographic monitoring within 6-45 days of acute myocardial infarction to have ventricular premature depolarizations (VPDs) that are frequent (> or = 10/hr) or repetitive (> or = 1 three-beat run of ventricular tachycardia). Consenting patients are randomized to amiodarone or placebo with an oral loading dose of 10 mg/kg/day for 2 weeks; maintenance dose is 300-400 mg/day for 3.5 months, 200-300 mg/day for 4 months, and 200 mg/day for 5 or 7 days/week for 16 months. Patients are followed by alternate telephone and clinical visit at 2-month intervals for 24 months. The principal outcome is a composite of presumed arrhythmic death or resuscitated ventricular fibrillation. Outcomes are determined by an external validation committee. The anticipated rate of arrhythmic death is 7.5% over 2 years; the sample size is 1,200 patients. CAMIAT began in June 1990 and is anticipated to conclude enrollment by June 1994 and follow-up by June 1995. Recruitment rate is about 92% of projected.

Choice and chance in drug therapy of cardiac arrhythmias: technique versus drug-specific responses in evaluation of efficacy

Numerous recent advances in pharmacotherapy for arrhythmia have necessitated a reorientation in terms of choice of specific agents, techniques for predicting drug effects, and the endpoints for judging therapeutic efficacy. For the management of ventricular arrhythmias and preventing mortality, several trends are becoming clear. It is unlikely that sodium channel blockers will continue to play a major role, except in patients with structurally normal hearts. Emphasis is shifting way from class I agents to those that act by prolonging repolarization without effect on conduction. These latter agents have been termed pure class III agents and have been developed because of the clinical experience with sotalol and amiodarone. On the other hand, there is compelling evidence that sympathetic inhibition per se (as exemplified by beta blockers) or as an integral component of more complex molecules (e.g., sotalol, amiodarone) is a critical feature of desirable antifibrillatory agents. Thus, compared with D,L-sotalol or amiodarone, pure class III agents are likely to be much less effective and may need to be used in combination with antiadrenergic compounds. Compared with amiodarone, they are likely to induce a higher incidence of torsades de pointes, especially in the case of concomitant diuretic therapy. Therapy guided by programmed electrical stimulation or Holter monitoring is likely to play a diminishing role in the development of antiarrhythmic drug regimens, and thus an antiarrhythmic agent's effectiveness may need to be evaluated against the background of implantable cardioverter-defibrillators or against amiodarone therapy. There is increasing evidence that "guided" therapy may simply identify responders from nonresponders and objective endpoints of therapy may be influenced more by drug-specific responses than by the techniques used for their selection. The data raise the issue whether in the future, therapy for ventricular tachycardia or fibrillation might be chosen empirically but from a limited range of compounds, such as beta blockers, amiodarone, sotalol, and possibly certain pure class III agents that are presently under development. Although it is reasonably certain that there is a need to shift from delaying conduction as a means for treating arrhythmias to one that entails prolongation of repolarization, it remains to be determined what might be the characteristics of an ideal antifibrillatory compound. The greatest promise is the area of complex molecules with a diversity of electrophysiologic actions, as exemplified by amiodarone and similar compounds that have the property of blunting sympathetic excitation. The complexity of their electrophysiologic and pharmacodynamic properties might provide a more favorable match with the vulnerable substrate for reducing electrical instability, thereby preventing ventricular fibrillation.

Comparative mechanisms of action of antiarrhythmic drugs

The most widely used classification of antiarrhythmic drugs, formulated by Singh and Vaughan Williams, divides antiarrhythmic agents into 4 categories: (1) sodium channel blockers; (2) sympatholytic agents; (3) drugs that delay repolarization; and (4) calcium antagonists. Despite some controversy regarding its value, the available evidence indicates that this classification relates well to the most important clinically relevant mechanisms of antiarrhythmic drug action. Amiodarone is unique in that it possesses properties belonging to all 4 of the Singh and Vaughan Williams classes; moreover, all 4 properties contribute to the beneficial actions of the drug. Class 1 effects are responsible for amiodarone's ability to slow ventricular tachycardias, making them hemodynamically better tolerated, and are likely important in amiodarone's premature ventricular complex-suppressing properties. Class 2 effects may contribute to atrioventricular (AV) node-suppressing actions and may confer protection against sudden death in the postmyocardial infarction population. Class 3 actions contribute to amiodarone's ability to prevent reentrant atrial and ventricular arrhythmias, and may be responsible for a superior ability to maintain sinus rhythm after cardioversion of atrial fibrillation. Class 4 properties contribute to amiodarone's ability to slow the ventricular response in atrial fibrillation and to prevent AV node reentrant arrhythmias. Calcium channel antagonism may also suppress arrhythmias (such as torsades de pointes) caused by early after-depolarizations and contribute to the apparent infrequency of torsades, despite substantial QT prolongation, among patients treated with amiodarone. Consideration of the link between amiodarone's pharmacologic properties and clinical effects illustrates well the various mechanisms of antiarrhythmic drug action.

A comparison of seven antiarrhythmic drugs in patients with ventricular tachyarrhythmias. Electrophysiologic Study versus Electrocardiographic Monitoring Investigators

BACKGROUND

The relative efficacies of various antiarrhythmic drugs in the treatment of ventricular tachyarrhythmias are not well known. This study examined the effectiveness of imipramine, mexiletine, pirmenol, procainamide, propafenone, quinidine, and sotalol in patients with ventricular tachyarrhythmias who were enrolled in the Electrophysiologic Study versus Electrocardiographic Monitoring trial.

METHODS

Patients were randomly assigned to undergo serial testing of the efficacy of the seven antiarrhythmic drugs by one of two strategies: electrophysiologic study or Holter monitoring together with exercise testing. The seven drugs were then tested for efficacy in random order in patients who were eligible to receive them. The frequencies of predictions of drug efficacy and of adverse drug effects during the initial drug titration were tabulated for all 486 randomized subjects. Patients received long-term treatment with the first antiarrhythmic drug that was predicted to be effective on the basis of drug testing. Recurrences of arrhythmia, deaths, and adverse drug effects during long-term follow-up were recorded for the 296 patients in whom an antiarrhythmic drug was predicted to be effective.

RESULTS

In the electrophysiologic-study group, the percentage of patients who had predictions of drug efficacy was higher with sotalol (35 percent) than with the other drugs (16 percent, P < 0.001). There was no significant difference among the drugs in the Holter-monitoring group. The percentage of patients with adverse drug effects was lowest among those receiving sotalol. The actuarial probability of a recurrence of arrhythmia after a prediction of drug efficacy by either strategy was significantly lower for patients treated with sotalol than for patients treated with the other drugs (risk ratio, 0.43; 95 percent confidence interval, 0.29 to 0.62; P < 0.001). With sotalol, as compared with the other drugs combined, there were lower risks of death from any cause (risk ratio, 0.50; 95 percent confidence interval, 0.30 to 0.80; P = 0.004), death from cardiac causes, (0.50; P = 0.02), and death from arrhythmia (0.50; P = 0.04). The cumulative percentage of patients in whom a drug was predicted to be effective and in whom it remained effective and tolerated was higher for sotalol than for the other drugs (P < 0.001).

CONCLUSIONS

Sotalol was more effective than the other six antiarrhythmic drugs in preventing death and recurrences of arrhythmia. In patients similar to those in this study, if antiarrhythmic-drug therapy is to be used to prevent recurrences of ventricular tachyarrhythmias, treatment with sotalol and assessment of its potential efficacy by Holter monitoring are a reasonable initial strategy.

Effect of E-4031, a new class III antiarrhythmic drug, on reentrant ventricular arrhythmias: comparison with conventional class I drugs

We evaluated the antiarrhythmic efficacy of E-4031, a new class III drug, and compared it with that of conventional class I and II antiarrhythmic agents in terms of electrophysiological actions on refractoriness and conduction in a 7-day-old canine model of myocardial infarction. Sustained monomorphic VT was reproducibly induced in 26 dogs by a premature stimulation method from the right ventricle. Class I drugs (disopyramide, aprindine, flecainide) prevented VT induction in 5 of 13 dogs, and propranolol and E-4031 prevented it in 6 of 6 and 6 of 7 dogs, respectively. The effective refractory period (ERP) was determined at 47 epicardial sites overlying the infarct in each experiment by a S1S2 method. The standard deviation (SD) of the mean ERP of these sites was used as an index of ERP dispersion. The extent of ERP prolongation produced by class I drugs and E-4031 was significantly more marked than that produced by propranolol. However, the SD was increased by class I drugs and E-4031, but not by propranolol. Class I drugs increased the ERP dispersion mainly by an effect on the transmural infarct zone in which the control ERP was more prolonged than in the normal zone. E-4031 tended to prolong the ERP in both the normal and infarct zones, and had a minimal tendency to increase ERP dispersion. In contrast, propranolol decreased the ERP dispersion between zones. Conduction velocity calculated by epicardial mapping was significantly decreased by flecainide, but not by E-4031. We conclude that the antiarrhythmic effect of E-4031 depends largely on its ability to prolong refractoriness without suppressing conduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Amiodarone and post-MI patients

Amiodarone is a viable drug for preventing sudden cardiac death, particularly during the first year after MI. If larger trials confirm the aforementioned prospective trials of Ceremuzynski et al, Cairns et al, and the BASIS trial, the efficacy of amiodarone would outweigh the risk of its side effects during the first year after MI. Based on the long-term observation from the BASIS trial, the duration of amiodarone therapy need not be more than 1 year--which, as we have learned, is when these post-MI patients would benefit most from the drug. It is also likely that the effects of amiodarone would complement those of aspirin and angiotensin converting enzyme inhibitors. The SAVE, CONSENSUS II, and SOLVD trials demonstrated that captopril and enalapril did not reduce the mortality rate during the first year after MI, nor did they reduce the sudden cardiac death rate. Their beneficial effects became evident only during the second year and thereafter. Unlike other antiarrhythmic agents of various classes, amiodarone possesses antiarrhythmic properties but does not exert deleterious effects on ventricular function. More studies are needed to determine if the benefit of amiodarone could be enhanced by combination therapy (eg, angiotensin converting enzyme inhibitors, aspirin, or beta-blockers). Whether amiodarone will provide the same protection for patients who have poor left ventricular function or congestive heart failure is not known. The European and VA cooperative studies should help answer this question. If it turns out that amiodarone is beneficial, one must then determine whether higher doses of the drug will offer more protection, and, if so, if that greater protection would be offset by increased toxicity. How much amiodarone should be given to offer the most protection with the least risk? Another intriguing research question is this: If we treat patients with amiodarone for more than 1 year, would the drug continue to improve the mortality rate in subsequent years? Other studies are needed in patients at very high risk of sudden cardiac death (ie, those who have a low ejection fraction and high-density VPDs). A study comparing amiodarone and sotalol in high-risk patients for sudden cardiac death is also needed. These clinical studies should be carried out with basic science research investigating the actions of amiodarone at the molecular and cellular level in order to give us a better understanding of how the drug works.

Risk stratification and prognosis of patients treated with amiodarone for malignant ventricular tachyarrhythmias after myocardial infarction

Seventy-seven consecutive patients (mean age 62 years) with episodes of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) after acute myocardial infarction (AMI) were evaluated to assess the long-term efficacy of first-line amiodarone treatment and to identify clinical and laboratory factors associated with a high risk of death or arrhythmia recurrence. The presenting arrhythmia was VT in 41 cases (53%) and VF in 36 (47%). VT or VF occurred between the 4th and 90th day after AMI in 45 cases (58%) and later (more than 90 days) in the remaining 32 (42%). The mean number of arrhythmic episodes was 4.2. Forty patients (52%) were in New York Heart Association (NYHA) class I or II, and 37 (48%) were in class III or IV. Mean left ventricular ejection fraction was 32%; ventricular aneurysm was present in 41 subjects. Most patients had multivessel coronary artery disease. Amiodarone was administered as a first-choice drug in all patients, in combination with other antiarrhythmic drugs in 14. By ventricular stimulation after loading doses of amiodarone, sustained VT was inducible in 46 (62%) and noninducible in 28 (38%). During a mean follow-up of 28 months the incidence of cardiac mortality at 1, 3, and 5 years was 21%, 37%, and 47%; of sudden death was 7%, 19%, and 23%; of nonfatal VT recurrence was 13%, 13%, and 24%, respectively. The overall incidence of amiodarone side effects was 35%.2+ was a weak predictor only by univariate analysis (p = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Nonsustained ventricular tachycardia: identification and management of high-risk patients

NSVT is common in normal persons and in patients with a variety of heart diseases. When present in patients with coronary artery disease, particularly after a recent myocardial infarction, it is associated with an increased risk of sudden and nonsudden cardiac death. However, its prognostic significance in patients with nonischemic heart disease, with the possible exception of hypertrophic cardiomyopathy, remains controversial. In patients with coronary artery disease, certain diagnostic tools (e.g., determination of left ventricular function. PVS) help to identify low- and high-risk patients who may or may not benefit from antiarrhythmic treatment. There is no consensus at this point as to the best approach for identifying and treating high-risk patients. Ongoing clinical trials should provide important information on the roles of signal-averaged ECGs and PVS in the management of patients with NSVT and coronary artery disease. In the meantime, treatment should be individualized for each patient. beta-Blockers should probably be the first line of therapy to control symptoms. Asymptomatic potentially high-risk patients (i.e., those with LVEF < 40%) should be referred for enrollment in randomized controlled studies.

Long-term benefit of 1-year amiodarone treatment for persistent complex ventricular arrhythmias after myocardial infarction

BACKGROUND

In the Basel Antiarrhythmic Study of Infarct Survival trial, low-dose amiodarone improved 1-year survival in patients with asymptomatic complex ventricular arrhythmias persisting 2 weeks after myocardial infarction. To assess whether this beneficial effect persisted despite discontinuation of amiodarone after 1 year, the long-term outcomes of all patients of the amiodarone-treated group (initially n = 98) and those of the control group (n = 114) were assessed.

METHODS AND RESULTS

After a mean follow-up of 72 (55-125) months, information on 96% of patients (203 of 212) was obtained regarding survival or cause of death. The probability of death after 84 months according to actuarial life-table analysis (Kaplan-Meier) was 30% for the amiodarone-treated patients and 45% for control patients. For the total follow-up, mortality remained significantly lower in the amiodarone group versus the control group regarding all deaths (p = 0.03) as well as cardiac death (p = 0.047). This mortality reduction was entirely due to the first-year amiodarone effect, since there was no significant mortality difference between groups when considering survival after discontinuation of amiodarone only.

CONCLUSIONS

These data suggest that the beneficial effect of amiodarone on survival in this high-risk group of patients persists for several years. In addition, the results stress the importance of early treatment after myocardial infarction, whereas the rate of sudden death and all cardiac death is low (1.6% and 4.1% per year, respectively) during late follow-up and therefore may not warrant further therapy.

Syncope in advanced heart failure: high risk of sudden death regardless of origin of syncope

OBJECTIVES

The purpose of this study was to assess the importance of syncope as a warning sign for sudden death in advanced heart failure and to determine the relative importance of cardiac syncope and syncope from other causes.

BACKGROUND

Despite remarkable advances in the pharmacologic approach to advanced heart failure, 20% to 40% of patients with advanced heart failure will die each year. In such patients, the relation between sudden death and the etiology of syncope has not been evaluated.

METHODS

The relation of syncope to sudden death was evaluated in 491 consecutive patients with advanced heart failure (New York Heart Association functional class III or IV), no history of cardiac arrest and a mean left ventricular ejection fraction of 0.20 +/- 0.07. Patients were evaluated for the presence and origin of syncope. The severity of heart failure was assessed from serum sodium levels, ejection fraction, functional class and echocardiographic and hemodynamic variables.

RESULTS

Sixty patients (12%) had a history of syncope; the condition had a cardiac origin in 29 (48%) and was due to other causes in 31 (52%). The origin of heart failure was coronary artery disease in 234 patients (48%) and dilated cardiomyopathy in 253 (51%) and its severity was similar in patients with and without syncope. During a mean follow-up interval of 365 +/- 419 days, 69 patients (14%) died suddenly and 66 patients (13%) died of progressive heart failure. The actuarial incidence of sudden death by 1 year was significantly greater in patients with (45%) than in those without (12%, p < 0.00001) syncope. In the Cox proportional hazards model, syncope predicted sudden death independent of atrial fibrillation, serum sodium, cardiac index, angiotensin-converting enzyme inhibition and patient age. The actuarial risk of sudden death by 1 year was similarly high in patients with either cardiac syncope or syncope from other causes (49% vs. 39%, p = NS).

CONCLUSIONS

Patients with advanced heart failure are at especially high risk for sudden death regardless of the etiology of syncope.

Amiodarone therapy does not compromise subsequent heart transplantation

OBJECTIVES

The objective of this study was to determine the frequency of pulmonary complications, feasibility of early hospital discharge and requirements for postoperative inotropic and chronotropic support in patients receiving amiodarone therapy before heart transplantation.

BACKGROUND

Although many patients waiting for heart transplantation will die of arrhythmias before a donor heart is found, the use of amiodarone has been limited by concern about increased complications in the perioperative period.

METHODS

The 29 patients receiving amiodarone at the time of heart transplantation at University of California, Los Angeles Medical Center between October 1986 and September 1990 were compared with 29 control recipients to evaluate postoperative morbidity. Patients were receiving amiodarone for recurrent ventricular tachyarrhythmias (n = 11), atrial fibrillation (n = 2) or complex ventricular ectopic activity (n = 16). The average daily dose was 360 +/- 230 mg/day for an average of 11 +/- 22 months before transplantation. Amiodarone and control groups had a similar ejection fraction (0.18 +/- 0.07 vs. 0.20 +/- 0.08), frequency of coronary disease, age and gender. There were three more status I patients in the control group. OKT3 was given to only two patients receiving amiodarone and 12 control patients at high risk for renal dysfunction.

RESULTS

Postoperatively, the duration of assisted ventilation was 21 +/- 19 h after amiodarone therapy versus 26 +/- 2 h in the control group (20 +/- 18 h vs. 15 +/- 9 h after excluding patients receiving OKT3), discharge arterial oxygen saturation was > 95% in both groups. Two patients in the amiodarone group with a smoking history of > 100 pack-years developed bilateral pulmonary infiltrates of brief duration. Although patients receiving amiodarone required atrial pacing more frequently (eight vs. two patients) and had a lower heart rate at discharge (75 +/- 18 vs. 86 +/- 11 beats/min), the duration of inotropic support (2.1 +/- 1.5 vs. 3.5 +/- 2.5 days) and of hospital stay (10 +/- 3 vs. 15 +/- 10 days) was not higher in the amiodarone than in the control group. The mortality rate at 30 days was similar in the two groups (6.8% vs. 3.4%, p = NS).

CONCLUSIONS

Amiodarone therapy before heart transplantation may contribute to occasional pulmonary complications but does not significantly increase perioperative morbidity or mortality with the regimens used in this retrospective study.

Effect of amiodarone on mortality after myocardial infarction: a double-blind, placebo-controlled, pilot study

OBJECTIVES

The goal of this study was to evaluate the effect of amiodarone on mortality, ventricular arrhythmias and clinical complications in high risk postinfarction patients.

BACKGROUND

No therapy has been shown to reduce sudden death in patients ineligible to receive beta-adrenergic blocking agents after myocardial infarction.

METHODS

Patients who were not eligible to receive beta-blockers were randomized to receive amiodarone (n = 305) or placebo (n = 308) for 1 year.

RESULTS

There were 21 deaths in the amiodarone group compared with 33 in the placebo group (odds ratio 0.62, 95% confidence interval [CI] 0.35 to 1.08, p = 0.095). There were two noncardiac deaths in the amiodarone group and none in the placebo group; thus, the difference in cardiac mortality (19 vs. 33, respectively) was statistically significant (odds ratio 0.55, 95% CI 0.32 to 0.99, p = 0.048). There was a significant decrease in Lown class 4 ventricular arrhythmias (7.5% vs. 19.7%, respectively, p < 0.001). Adverse effects developed in 30% of amiodarone-treated patients and 10% of placebo-treated patients. Pulmonary toxicity, which was mild and reversible, occurred in only one patient in the amiodarone group but in no patient in the placebo group.

CONCLUSIONS

This trial demonstrated a significant reduction in cardiac mortality and ventricular arrhythmias with amiodarone treatment. However, given the wide confidence intervals and borderline statistical significance of our trial, larger trials are needed to confirm or refute this view.

Effects of ibutilide fumarate, a novel antiarrhythmic agent, and its enantiomers on isolated rabbit myocardium

Ibutilide fumarate is currently in Phase II clinical trials for the treatment of life-threatening cardiac arrhythmias. The cardiovascular effects of ibutilide and its d- and l-stereoisomers, U82208E and U82209E were tested in an isolated rabbit myocardium system. In a series of repeated measures experiments, threshold, effective refractory period, force of contraction, conduction time and rate were measured at various pacing frequencies in isolated papillary muscles, ventricular muscle strips and right atria exposed to 10(-7), 10(-6) and 10(-5) M drug. Although there were occasional instances where one form had a greater or lesser effect on a given parameter, overall there was little pharmacological difference between the racemic mixture and its constituent forms. At the highest dose, effective refractory periods at 1 and 3 Hz increased by 18-32 ms, conduction times measured at 3 Hz increased by 27-30% and atrial rate decreased by 19-32%, while threshold and force of contraction were generally unaffected. In this study there were no clear cut pharmacologic differences between the three forms of this class III antiarrhythmic agent. Parallel studies to determine pA2 values of ibutilide and sotalol demonstrated that ibutilide possesses weak beta-adrenoceptor blocking properties.

Subclassification of class I antiarrhythmic drugs: enhanced relevance after CAST

Class I antiarrhythmic drugs are traditionally divided into three subclasses--Ia, Ib, and Ic--on the grounds of differences in kinetics of interaction with the sodium channel and different effects on the duration of the action potential. The CAST study has highlighted our growing awareness of the proarrhythmic potential of this group of agents, particularly the Class Ic subgroup. Class I drugs can cause arrhythmias either by slowing conduction to critical levels, thus enhancing the possibility of reentrant arrhythmias, or in some cases by prolonging action potential duration, leading to early afterdepolarizations, which probably underlie triggered automaticity. Evidence is presented that the Class Ic compounds may be inherently more proarrhythmic than the Ib compounds, because of their lesser ability to depress ischemic myocardium selectively. Arguments are advanced for the continued use of a slightly modified subclassification of Class I antiarrhythmic drugs.

Use-dependent electrophysiologic effects of amiodarone in coronary artery disease and inducible ventricular tachycardia

Amiodarone produces use-dependent block of cardiac sodium channels in vitro. This study assessed whether similar use-dependent block occurred in 19 patients with coronary artery disease and inducible, sustained, monomorphic ventricular tachycardia treated with amiodarone. Beat-to-beat measurements of ventricular paced QRS durations during 12-beat trains at cycle lengths of 700, 600, 400 and 300 ms were analyzed at a baseline antiarrhythmic drug-free study and after 2 and 10 weeks of amiodarone therapy. At the drug-free study, there were no significant changes in paced QRS durations within the 12-beat trains at any pacing cycle lengths. After 2 and 10 weeks of amiodarone therapy, progressive prolongation of paced QRS durations occurred over the 12-beat trains at pacing cycle lengths of 600, 400 and 300 ms (p less than 0.05). Significant changes in QRS duration were not observed at a pacing cycle length of 700 ms. This progressive prolongation in QRS duration can be fitted as a function of beat number to a monoexponential equation and occurred with an onset time constant of 1.02 +/- 0.41 beats (306 +/- 122 ms) at a pacing cycle length of 300 ms. The magnitude of QRS prolongation increased as the pacing cycle length was shortened. The magnitudes of QRS prolongation were similar after 2 and 10 weeks of amiodarone therapy. In conclusion, use-dependent prolongation in QRS duration occurs at rapid pacing cycle lengths in humans receiving amiodarone.

Effect of the antiarrhythmic agent moricizine on survival after myocardial infarction

BACKGROUND

The Cardiac Arrhythmia Suppression Trial (CAST) tested the hypothesis that the suppression of asymptomatic or mildly symptomatic ventricular premature depolarizations in survivors of myocardial infarction would decrease the number of deaths from ventricular arrhythmias and improve overall survival. The second CAST study (CAST-II) tested this hypothesis with a comparison of moricizine and placebo.

METHODS

CAST-II was divided into two blinded, randomized phases: an early, 14-day exposure phase that evaluated the risk of starting treatment with moricizine after myocardial infarction (1325 patients), and a long-term phase that evaluated the effect of moricizine on survival after myocardial infarction in patients whose ventricular premature depolarizations were either adequately suppressed by moricizine (1155 patients) or only partially suppressed (219 patients).

RESULTS

CAST-II was stopped early because the first 14-day period of treatment with moricizine after a myocardial infarction was associated with excess mortality (17 of 665 patients died or had cardiac arrests), as compared with no treatment or placebo (3 of 660 patients died or had cardiac arrests); and estimates of conditional power indicated that it was highly unlikely (less than 8 percent chance) that a survival benefit from moricizine could be observed if the trial were completed. At the completion of the long-term phase, there were 49 deaths or cardiac arrests due to arrhythmias in patients assigned to moricizine, and 42 in patients assigned to placebo (adjusted P = 0.40).

CONCLUSIONS

As with the antiarrhythmic agents used in CAST-I (flecainide and encainide), the use of moricizine in CAST-II to suppress asymptomatic or mildly symptomatic ventricular premature depolarizations to try to reduce mortality after myocardial infarction is not only ineffective but also harmful.

Beneficial effect of amiodarone on cardiac mortality in patients with asymptomatic complex ventricular arrhythmias after acute myocardial infarction and preserved but not impaired left ventricular function

To determine whether the beneficial effect of low-dose amiodarone on survival in patients with complex ventricular arrhythmias after myocardial infarction was dependent on left ventricular (LV) function, results of the Basel Antiarrhythmic Study of Infarct Survival were analyzed. Two hundred twelve patients after acute myocardial infarction with asymptomatic complex arrhythmias were randomly assigned to receive amiodarone 200 mg/day or to a control group and followed up for 1 year. Results of mortality and arrhythmic events were related to baseline radionuclide LV ejection fraction. With preserved (greater than or equal to 40%) LV ejection fraction, there was a significantly lower 1-year cardiac mortality in patients treated with amiodarone (1 of 68 or 1.5%) versus control subjects (5 of 56 or 8.9%; p less than 0.03). This was not the case for patients with LV ejection fraction less than 40%. Similarly, arrhythmic events were significantly reduced only in patients with preserved LV function. These results suggest an interaction between the effects of amiodarone on survival and LV dysfunction in patients after acute myocardial infarction. Because of 2 other small studies with similar results, this finding may be of clinical relevance and should be addressed in ongoing and future research with this drug.

Amiodarone. An overview of its pharmacological properties, and review of its therapeutic use in cardiac arrhythmias

Amiodarone, originally developed over 20 years ago, is a potent antiarrhythmic drug with the actions of all antiarrhythmic drug classes. It has been successfully used in the treatment of symptomatic and life-threatening ventricular arrhythmias and symptomatic supraventricular arrhythmias. In patients with left ventricular dysfunction amiodarone does not usually produce any clinically significant cardiodepression and the drug has relatively high antiarrhythmic efficacy. Preliminary studies indicate that amiodarone may have a beneficial effect on mortality and survival in certain groups of patients with ventricular arrhythmias, an action probably related to both its antiarrhythmic and antifibrillatory effects. The adverse effect profile of amiodarone is diverse, involving the cardiac, thyroid, pulmonary, hepatic, gastrointestinal, ocular, neurological and dermatological systems. Interstitial pneumonitis and hepatitis are potentially fatal, but the vast majority of adverse events are less serious, and some may be dose dependent. Pretreatment monitoring, regular assessments and the use of minimum effective doses are, therefore, necessary. Thus, with appropriate monitoring to control its well recognised adverse effects amiodarone has an important place as an effective 'broad spectrum' antiarrhythmic drug which has, so far, been used when other treatments have proved ineffective. More recent preliminary data also suggest that it may also have a beneficial effect in the prevention of sudden death in some patients.

Prognostic features in patients with congestive heart failure and selection criteria for cardiac transplantation

Cardiac transplantation can be a highly successful therapeutic option for patients with end-stage congestive heart failure. Successful results, however, depend on the appropriate selection of patients for the procedure. Patients whose survival or quality of life would be compromised without cardiac transplantation and who are likely to benefit from this intensive type of treatment are potential candidates. Each patient should undergo a thorough assessment to identify any medical or psychologic contraindications to cardiac transplantation. In this review, we discuss the important predictors of survival in patients with congestive heart failure: the cause of heart failure, the patient's symptomatic and functional status, the hemodynamic and pathologic findings, the evaluation of neurohumoral activity, and the presence of cardiac arrhythmias. Once a patient with congestive heart failure has been identified as having a limited life expectancy and severely impaired quality of life, cardiac transplantation should be considered.

Sudden death in patients with congestive heart failure: future directions

Sudden, unexpected cardiac death continues to be a major clinical problem in patients with congestive heat failure. This review summarizes the current state of knowledge regarding the identification and management of these patients. The roles of ambulatory ECG monitoring, electrophysiological testing, signal-averaged ECG, and other methods of predicting increased risk of sudden death are discussed. The modes of sudden cardiac death and the potential mechanisms of ventricular arrhythmias in congestive heart failure are reviewed. Current therapeutic options including antiarrhythmic drugs, neurohormonal blockade, and automatic implantable cardioverter defibrillators are discussed. Finally, future directions and ongoing clinical investigations of the management of these complex patients are considered.

Comparison of one-, six- and 24-hour ambulatory electrocardiographic monitoring for ventricular arrhythmia as a predictor of mortality in survivors of acute myocardial infarction. CAMIAT Pilot Study Group. Canadian Amiodarone Myocardial Infarction Arrhythmia Trial

To compare 1-, 6- and 24-hour ambulatory electrocardiograms for prediction of mortality after acute myocardial infarction (AMI), all patients with AMI hospitalized in Hamilton, Ontario during 1 year were identified. There were 683 patients discharged alive after AMI. One-, 6- and 24-hour ambulatory electrocardiographic results were available in 565 patients, and follow-up mortality data at 1 year was available in 560. Mean age of the patients was 64 years; 160 (29%) had previous AMI and 105 (19%) had had congestive heart failure. One hundred and fifty-two patients (27%) were receiving beta blockers, and 31 (6%) were receiving antiarrhythmic drugs. Regression modeling of survival times up to 1 year showed that all 3 durations of recording were univariate predictors of mortality. Using greater than 10 ventricular premature complexes/hour as the criterion of a positive test, neither the 6- nor 24-hour data contained statistically significant residual explanatory power after the 1-hour data were accounted for by the model. The longer durations of recording increased sensitivity at a cost of decreased specificity. The positive and negative predictive values of the 3 durations of recording were virtually identical. The presence of ventricular tachycardia was not a significant predictor of mortality in this population. There appears to be no benefit to ambulatory electrocardiographic recordings greater than 1 hour when they are to be used for prediction of 1-year mortality after AMI.