Amiodarone in chronic heart failure

Heart rate is a marker of amiodarone mortality reduction in severe heart failure. The GESICA-GEMA Investigators. Grupo de Estudio de la Sobrevida en la Insuficiencia Cardiaca en Argentina-Grupo de Estudios Multicéntricos en Argentina

OBJECTIVES

The impact of amiodarone on mortality in patients with severe congestive heart failure (CHF) (New York Heart Association functional classes II [advanced], III and IV; left ventricular ejection fraction < 35%) In the Grupo de Estudio de la Sobrevida en la Insuficiencia Cardiaca en Argentina (GESICA) trial was analyzed in relation to initial mean baseline heart rate (BHR) and its change after 6 months of follow-up.

BACKGROUND

Trials of amiodarone therapy in CHF have produced discordant results, suggesting that the effect is not uniform in all patient subgroups with regard to survival.

METHODS

The present analysis was carried out in 516 patients randomized to receive amiodarone, 300 mg/day (n = 260), or nonantiarrhythmic therapy (n = 256, control group) and followed up for 2 years. Survival was evaluated for patients with a BHR > or = 90 beats/min (control: n = 132; amiodarone: n = 122) and < 90 beats/min (control: n = 124; amiodarone: n = 138). Survival was also analyzed according to heart rate reduction at 6 months for 367 patients.

RESULTS

For patients with a BHR > or = 90 beats/min, amiodarone therapy reduced mortality to 38.4% compared with 62.4% in control patients (relative risk [RR] 0.55, 95% confidence interval [CI] 0.35 to 0.95, p < 0.002). Both sudden death (RR 0.46, 95% CI 0.24 to 0.90, p < 0.02) and progressive heart failure death (RR 0.60, 95% CI 0.30 to 1.03, p < 0.06) were reduced, and functional capacity was improved. In patients with a BHR < 90 beats/min, amiodarone did not alter survival. Among 367 patients who completed 6 months of follow-up, amiodarone reduced 2-year mortality only in those with a BHR > or = 90 beats/min, which was reduced at 6 months.

CONCLUSIONS

Elevated rest heart rates in severe CHF identify a subgroup of patients who benefit from treatment with amiodarone. Amiodarone-induced heart rate slowing may be an important benefit for patients.

Refractory Heart Failure: A Therapeutic Approach

Optimal “triple therapy” for patients with chronic congestive heart failure (CHF) includes diuretics, digoxin, and either angiotensin-converting enzyme inhibitors or hydralazine plus nitrates. Refractory CHF is defined as symptoms of CHF at rest or repeated exacerbations of CHF despite “optimal” triple-drug therapy. Most patients with refractory CHF require hemodynamic monitoring and treatment in the intensive care unit. If easily reversible causes of refractory CHF cannot be identified, then more aggressive medical and surgical interventions are necessary. The primary goal of intervention is to improve hemodynamics to palliate CHF symptoms and signs (i.e., dyspnea, fatigue, edema). Secondary goals include improved vital organ and tissue perfusion, discharge from the intensive care unit, and, in appropriate patients, bridge to cardiac transplantation. Medical interventions include inotropic resuscitation (e.g., adrenergic agents, phosphodiesterase inhibitors, allied nonglycoside inodilators), load resuscitation (e.g., afterload and preload reduction with nitroprusside or nitroglycerin; preload reduction with diuretics and diuretic facilitators, such as dopaminergic agents or ultrafiltration), and electrical resuscitation (e.g., prevention of sudden death, correction of new or rapid atrial fibrillation, or dual chamber pacing in the setting of relative prolongation of the PR interval and diastolic mitral/tricuspid regurgitation). Surgical interventions are temporizing (e.g., intra-aortic balloon pump and other mechanical assist devices) or definitive (e.g., coronary artery revascularization, valvular surgery, and cardiac transplantation). Although these interventions may improve immediate survival in the short term, only coronary artery revascularization and cardiac transplantation have been shown to improve long-term survival.

Effect of amiodarone therapy on mortality in patients with left ventricular dysfunction and asymptomatic complex ventricular arrhythmias: Argentine Pilot Study of Sudden Death and Amiodarone (EPAMSA)

The efficiency of prophylactic antiarrhythmic treatment with amiodarone in reducing 1-year mortality in patients with reduced left ventricular ejection fraction ( < 35%) and asymptomatic ventricular arrhythmias (Lown classes 2 and 4) was investigated in a prospective, multicenter, randomized, controlled study. Among 127 patients who entered the study, 61 were assigned to no antiarrhythmic therapy (control group [CG] and 66 to amiodarone treatment (amiodarone group [AG]). Amiodarone was administered at a dosage of 800 mg/day for 2 weeks followed by 400 mg/day thereafter. A 12-month follow-up was completed for 106 patients (57 in the AG and 49 in the CG). Amiodarone reduced the overall mortality rate, which was 10.5% in the AG versus 28.6% in the CG (odds ratio [OR] 0.29; 95% confidence interval [CI] 0.10 to 0.84; log-rank test 0.02) and sudden death rate, which was 7.0% in the AG versus 20.4% in the CG (OR 0.29; 95% CI 0.08 to 1.00; log-rank test 0.04). Side effects were rare, and in only three patients did amiodarone treatment have to be discontinued.

Amiodarone in patients with congestive heart failure and asymptomatic ventricular arrhythmia. Survival Trial of Antiarrhythmic Therapy in Congestive Heart Failure

BACKGROUND

Asymptomatic ventricular arrhythmias in patients with congestive heart failure are associated with increased rates of overall mortality and sudden death. Amiodarone is now used widely to prevent ventricular tachycardia and fibrillation. We conducted a trial to determine whether amiodarone can reduce overall mortality in patients with congestive heart failure and asymptomatic ventricular arrhythmias.

METHODS

We used a double-blind, placebo-controlled protocol in which 674 patients with symptoms of congestive heart failure, cardiac enlargement, 10 or more premature ventricular contractions per hour, and a left ventricular ejection fraction of 40 percent or less were randomly assigned to receive amiodarone (336 patients) or placebo (338 patients). The primary end point was overall mortality, and the median follow-up was 45 months (range, 0 to 54).

RESULTS

There was no significant difference in overall mortality between the two treatment groups (P = 0.6). The two-year actuarial survival rate was 69.4 percent (95 percent confidence interval, 64.2 to 74.6) for the patients in the amiodarone group and 70.8 percent (95 percent confidence interval, 65.7 to 75.9) for those in the placebo group. At two years, the rate of sudden death was 15 percent in the amiodarone group and 19 percent in the placebo group (P = 0.43). There was a trend toward a reduction in overall mortality among the patients with nonischemic cardiomyopathy who received amiodarone (P = 0.07). Amiodarone was significantly more effective in suppressing ventricular arrhythmias and increased the left ventricular ejection fraction by 42 percent at two years.

CONCLUSIONS

Although amiodarone was effective in suppressing ventricular arrhythmias and improving ventricular function, it did not reduce the incidence of sudden death or prolong survival among patients with heart failure, except for a trend toward reduced mortality among those with nonischemic cardiomyopathy.

Usefulness of L-thyroxine to improve cardiac and exercise performance in idiopathic dilated cardiomyopathy

The short-term effects of L-thyroxine (100 micrograms/day, 10 patients) and placebo (10 patients) on idiopathic dilated cardiomyopathy were compared. Before and at the end of the treatment, a hemodynamic study was performed in the control state and during dobutamine infusion. A cardiopulmonary exercise test was also performed with hemodynamic monitoring. An echocardiogram was recorded in the control state and during acute changes of left ventricular afterload. Plasma levels of triiodothyronine, thyroxine, thyroid-stimulating hormone and norepinephrine were measured. Placebo was ineffective. After administration of L-thyroxine all patients had normal thyroid function. The increase in left ventricular ejection fraction and the rightward shift of the slope of left ventricular ejection fraction/end-systolic stress relation (p < 0.05) indicated an improvement in the cardiac inotropic state. This proved to be independent of adrenergic influences by the unchanged beta 1 response to dobutamine. A decrease in resting systemic vascular resistances and an increase in cardiac output (p < 0.05) were also observed. Cardiopulmonary effort parameters improved (p < 0.05) without hemodynamic changes at peak exercise. It is concluded that L-thyroxine short-term administration improves cardiac and exercise performance in patients with chronic heart failure, without modifying the adrenergic support to the heart and the circulatory parameters at peak exercise.

Are antiarrhythmic drugs safe?

The indications for antiarrhythmic therapy are far from clearly defined and the choice of treatment is usually based on empiric strategies. Antiarrhythmic agents can have serious side effects. Systemic adverse effects are usually use-related and reversible with withdrawal of the drug. Impairment of left ventricular function is considerable in patients with heart failure. The most important, life-threatening side effect of antiarrhythmic drugs is their proarrhythmic tendency which gives rise to certain concern about their clinical use. Aggravation of arrhythmia often occurs without symptoms, goes unrecognized by the patient, and is exposed only by monitoring, exercise testing, or invasive electrophysiological testing. Patient monitoring with electrolyte measurement, Holter recording, and electrophysiological reassessment can reveal or reduce the proarrhythmic risk but cannot eliminate the problem completely. The institution of antiarrhythmic therapy should be considered in highly symptomatic or life-threatening arrhythmias after careful consideration of the benefit-risk ratio.