Can antiarrhythmic drugs survive survival trials?

Cardiac Channelopathies and Sudden Death: Recent Clinical and Genetic Advances

Sudden cardiac death poses a unique challenge to clinicians because it may be the only symptom of an inherited heart condition. Indeed, inherited heart diseases can cause sudden cardiac death in older and younger individuals. Two groups of familial diseases are responsible for sudden cardiac death: cardiomyopathies (mainly hypertrophic cardiomyopathy, dilated cardiomyopathy, and arrhythmogenic cardiomyopathy) and channelopathies (mainly long QT syndrome, Brugada syndrome, short QT syndrome, and catecholaminergic polymorphic ventricular tachycardia). This review focuses on cardiac channelopathies, which are characterized by lethal arrhythmias in the structurally normal heart, incomplete penetrance, and variable expressivity. Arrhythmias in these diseases result from pathogenic variants in genes encoding cardiac ion channels or associated proteins. Due to a lack of gross structural changes in the heart, channelopathies are often considered as potential causes of death in otherwise unexplained forensic autopsies. The asymptomatic nature of channelopathies is cause for concern in family members who may be carrying genetic risk factors, making the identification of these genetic factors of significant clinical importance.

Ventricular tachycardia and sudden cardiac death

Ventricular tachycardia (VT), which most commonly occurs in patients with structural heart disease, can be associated with an increased risk of sudden death. The most common cause of ventricular fibrillation is acute coronary ischemia, whereas a myocardial scar from prior infarct is the most common cause of sustained monomorphic VT in patients with structural heart disease. More benign forms of idiopathic VT can also occur in the absence of structural heart disease. Treatment of VT involves both emergent management and prevention of recurrence with medical and device therapy. Appropriately selected patients who have experienced VT or those who are at risk of VT may be candidates for an implantable cardioverter-defibrillator. The left ventricular ejection fraction is most frequently used to stratify patients with either ischemic or nonischemic cardiomyopathy who are at risk of sudden death and may be candidates for a prophylactic defibrillator. Catheter ablation may also be an option for appropriately selected patients with many forms of VT. This article discusses the etiologies and management of VT and its association with sudden death.

Ventricular tachycardia and sudden cardiac death

Ventricular tachycardia (VT), which most commonly occurs in patients with structural heart disease, can be associated with an increased risk of sudden death. The most common cause of ventricular fibrillation is acute coronary ischemia, whereas a myocardial scar from prior infarct is the most common cause of sustained monomorphic VT in patients with structural heart disease. More benign forms of idiopathic VT can also occur in the absence of structural heart disease. Treatment of VT involves both emergent management and prevention of recurrence with medical and device therapy. Appropriately selected patients who have experienced VT or those who are at risk of VT may be candidates for an implantable cardioverter-defibrillator. The left ventricular ejection fraction is most frequently used to stratify patients with either ischemic or nonischemic cardiomyopathy who are at risk of sudden death and may be candidates for a prophylactic defibrillator. Catheter ablation may also be an option for appropriately selected patients with many forms of VT. This article discusses the etiologies and management of VT and its association with sudden death.

Heart rate variability in myocardial infarction and heart failure

The need to refine the identification of patients who might benefit from implantation of an implantable cardioverter defibrillator has been risen by the results of many clinical trials on ICD therapy. Traditional parameters such as left ventricular ejection fraction and the presence of non-sustained ventricular tachycardia were not strong enough to achieve this goal with reasonable cost-effectiveness. Heart rate variability (HRV) is one of the most popular parameters used to assess the autonomic tone. HRV has been reported as a strong predictor of cardiovascular mortality. Currently, three different categories of methods in HRV analysis are being used; the time domain, frequency domain, and non-linear dynamic analysis. Both time domain and frequency domain analyses of HRV have been investigated extensively regarding their use as a prognostic marker for cardiovascular mortality. The non-linear dynamic analysis is the latest tool that has shown to have an even higher predictive value than any of the traditional parameters. However, standardized and supporting evidence on this new technique is still lacking. In this article, the current role of HRV in the prediction of cardiovascular mortality in myocardial infarction and heart failure patients has been reviewed.

Lipid-lowering therapy with statins, a new approach to antiarrhythmic therapy

Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (statins) are the most effective and best-tolerated drugs to treat elevated levels of low-density lipoprotein cholesterol (LDL-C). In addition, they exhibit other effects unrelated to their lipid lowering effects (pleiotropic actions). In recent years, experimental and clinical evidence demonstrates that statins exert antiarrhythmic properties, reducing the recurrences of supraventricular and life-threatening ventricular arrhythmias both in patients with and without coronary artery disease (CAD). Thus, statins may constitute a novel therapeutic approach to cardiac arrhythmias. This article reviews the antiarrhythmic properties of statins as well as the possible mechanisms involved, including the lowering of LDL-C levels, the improvement of endothelial dysfunction and autonomic function, the stabilization of the atherosclerotic plaques, the antioxidant, antiinflammatory, antithrombotic and cardioprotective properties and the modulation of transmembrane ion fluxes.

Implications for Nursing Care of Patients With Atrial Fibrillation

Atrial fibrillation is the most common sustained cardiac dysrhythmia treated in North America and Europe. As such, it is one of the current epidemics in cardiovascular disease. Findings from the AFFIRM (Atrial Fibrillation Follow-up: Investigation of Rhythm Management) and RACE (RAte Control versus Electrical cardioversion for persistent atrial fibrillation) clinical trials are presented and the current evidence for the management of atrial fibrillation using anticoagulation, rate-control, and rhythm-control strategies is outlined. Implications for nurses are discussed including physiologic and psychosocial interventions.

Mortality in patients after a recent myocardial infarction: a randomized, placebo-controlled trial of azimilide using heart rate variability for risk stratification

BACKGROUND

Depressed left ventricular function (LVF) and low heart rate variability (HRV) identify patients at risk of increased mortality after myocardial infarction (MI). Azimilide, a novel class III antiarrhythmic drug, was investigated for its effects on mortality in patients with depressed LVF after recent MI and in a subpopulation of patients with low HRV.

METHODS AND RESULTS

A total of 3717 post-MI patients with depressed LVF were enrolled in this randomized, placebo-controlled, double-blind study of azimilide 100 mg on all-cause mortality. Placebo patients with low HRV had a significantly higher 1-year mortality than those with high HRV (>20 U; 15% versus 9.5%, P<0.0005) despite nearly identical ejection fractions. No significant differences were observed between the 100-mg azimilide and placebo groups for all-cause mortality in either the "at-risk" patients identified by depressed LVF (12% versus 12%) or the subpopulation of "high-risk" patients identified by low HRV (14% versus 15%) or for total cardiac or arrhythmic mortality. Significantly fewer patients receiving azimilide developed atrial fibrillation than did patients receiving placebo (0.5% versus 1.2%, P<0.04). The incidences of torsade de pointes and severe neutropenia (absolute neutrophil count < or =500 cells/microL) were slightly higher in the azimilide group than in the placebo group (0.3% versus 0.1% for torsade de pointes and 0.9% versus 0.2% for severe neutropenia).

CONCLUSIONS

Azimilide did not improve or worsen the mortality of patients after MI. Low HRV independently identified a subpopulation at high risk of mortality.

ICD Therapy for the Prevention of Sudden Cardiac Death in Post-MI Patients

Implantable cardioverter-defibrillators (ICDs) are unequivocally the treatment of choice for patients who have already experienced a near-fatal tachyarrhythmic event. Recently, studies have conclusively demonstrated that extending the benefits of ICD therapy to postinfarction patients with resultant left ventricular dysfunction results in dramatic additional lifesaving without the need for complex risk- stratification procedures. The landmark Multicenter Automatic Defibrillator Implantation Trial II (MADIT II) shows that patients with reduced left ventricular function (ejection fraction < 30%) 1 month after a myocardial infarction should receive an ICD to prevent sudden cardiac death.

Long-term pharmacologic management of atrial fibrillation in the elderly

The first decision to be made in treating atrial fibrillation in the elderly is to determine whether to pursue a treatment strategy of rate control or rhythm control. Both strategies require use of anticoagulation therapy with warfarin (target international normalized ratio, 2.5; range 2-3). If a decision is made for rhythm control, the critical therapy is almost always with an antiarrhythmic drug. Before selecting an antiarrhythmic drug for use, it is first necessary to determine the presence or absence of underlying structural heart disease, as that will affect the available options for antiarrhythmic drug use. If there is no underlying structural heart disease, any of the available antiarrhythmic drugs may be used, although a clinically reasoned approach is suggested. If there is underlying structural heart disease, not all antiarrhythmic drugs are appropriate for use. A clinically reasoned approach is suggested in the presence of coronary artery disease, left ventricular dysfunction /congestive heart failure, or hypertension based largely on the risk/benefit profile of the drugs.

Effect of low-dose amiodarone on atrial fibrillation or flutter in Japanese patients with heart failure

The efficacy and safety of amiodarone in the management of atrial fibrillation (AF) or flutter in 108 Japanese patients with heart failure was retrospectively examined. Thirty-four (41%) of the 82 patients who were in sinus rhythm after 1 month of amiodarone administration had their first recurrence, 70% of cases occurring within 1 year of initiation. The cumulative rates of maintenance of sinus rhythm were 0.68, 0.55, and 0.47 at 1, 3, and 5 years, respectively. Amiodarone was more effective in maintaining sinus rhythm in patients with paroxysmal AF or flutter than in those with the persistent form (p<0.05). The cumulative rates for cases that remained in permanent AF were 0.04, 0.11, and 0.14 at 1, 3, and 5 years, respectively. Apart from suppressing AF, the mean heart rate during Holter monitoring was significantly decreased with amiodarone therapy in cases of permanent AF. Adverse effects requiring the discontinuation of amiodarone therapy occurred in 16% of patients. Low-dose amiodarone therapy may prevent AF or flutter in Japanese patients with heart failure.

Role of Antiarrhythmic Therapy in Patients at Risk for Sudden Cardiac Death: An Evidence-Based Review

Sudden cardiac death (SCD) accounts for more than half of all cardiac deaths occurring each year in the United States. Although it has several causes, patients at greatest risk are those with coronary artery disease and impaired left ventricular function, heart failure secondary to ischemia or idiopathic dilated cardiomyopathy, hypertrophic cardiomyopathy, documented sustained ventricular tachycardia or ventricular fibrillation, and survivors of cardiac arrest. The presence of asymptomatic ventricular arrhythmias, positive signal-averaged electrocardiogram (ECG), low heart rate variability index, or inducible ventricular tachycardia or ventricular fibrillation increases the risk. In primary prevention trials in patients with ischemic heart disease, beta-blockers reduced both total mortality and SCD, whereas class I antiarrhythmic drugs, especially class IC, increased mortality. Among class III agents, d,l-sotalol and dofetilide have a neutral effect on mortality, whereas d-sotalol increases mortality. Amiodarone has a neutral effect on total and cardiac mortality but does reduce the risk of arrhythmic death and cardiac arrest. Three primary prevention trials in patients with ischemic heart disease were conducted with implantable cardioverter-defibrillators (ICDs). Patients with low ejection fractions (EFs), asymptomatic ventricular arrhythmias, and inducible ventricular tachycardia or ventricular fibrillation had significant reductions in total, cardiac, and arrhythmic death with ICDs compared with either no drug therapy or conventional antiarrhythmic agents. The ICDs did not reduce mortality in patients with low EFs and a positive signal-averaged ECG undergoing coronary bypass graft. In those with heart failure, beta-blockers reduced total and SCD mortality, but dofetilide and amiodarone had a neutral effect on mortality. In the secondary prevention of SCD, antiarrhythmic drugs alone generally are not thought to improve survival. In three trials in patients with documented sustained ventricular tachycardia or ventricular fibrillation, or survivors of SCD, ICDs reduced cardiac and arrhythmic mortality. Total mortality, however, was significantly reduced in only one of these trials. The role of antiarrhythmic drugs in secondary prevention of SCD is limited to patients in whom ICD is inappropriate or in combination with ICD. Antiarrhythmics can be given selectively with ICDs to decrease episodes of ventricular tachycardia or fibrillation to reduce ICD discharges, to suppress episodes of nonsustained ventricular tachycardia that trigger ICD discharges, to slow the rate of ventricular tachycardia to increase hemodynamic stability, to allow effective antitachycardia pacing, or to suppress supraventricular arrhythmias.

Management of postinfarct ventricular tachycardias

The clinical profile of patients with postinfarct VT has changed in the past two decades. Along with these changes, existing treatments have improved, and entirely new therapeutic approaches have been developed. The expanded range of treatment options has made postinfarct VT a less imposing clinical problem than it once was. Emerging therapies promise to make an even greater beneficial impact. The challenge in treating patients with postinfarct VT has changed from merely keeping patients alive to keeping up with innovations in therapy that can provide them with a better quantity and quality of life.

Lessons from antiarrhythmic trials involving class III antiarrhythmic drugs

Beta-adrenergic blockers reduce mortality and sudden death in patients convalescing from myocardial infarction, and probably in patients with heart failure. However, the notion that class I antiarrhythmic drugs might save lives by suppressing the triggers of life-threatening ventricular arrhythmias was proved incorrect when the Cardiac Arrhythmia Suppression Trial (CAST) demonstrated that patients, whose ventricular ectopics were successfully suppressed by a number of class I antiarrhythmic drugs, died more readily than similar patients when treated with drugs rather than the placebo. Attention was diverted to class III antiarrhythmic drugs for patients with a poor ejection fraction who survived myocardial infarction and those with heart failure. A preliminary metaanalysis of 3 trials (Basel Antiarrhythmic Study of Infarct Survival [BASIS], Polish Amiodarone Trial [PAT], and the Canadian Amiodarone Myocardial Infarction Arrhythmia Trial [CAMIAT]) suggested that amiodarone might reduce arrhythmic and all-cause mortality in high-risk post-myocardial-infarction (MI) patients. BASIS suggested that this was only true for patients with preserved ventricular function. Nevertheless, 2 major trials were instituted: the European Myocardial Infarct Amiodarone Trial (EMIAT) and the CAMIAT. Both reported similar results except that patients recruited because of high-density ventricular ectopy seemed to benefit a little more from amiodarone than did patients with poor ventricular function. Detailed analysis of these trials revealed important insights into the value of amiodarone.

New primary prevention trials of sudden cardiac death in patients with left ventricular dysfunction: SCD-HEFT and MADIT-II

Primary prevention of sudden arrhythmic death in patients with organic heart disease with poor left ventricular function and/or heart failure is currently a major challenge in cardiology. Amiodarone (with or without beta blockers) and the implantable cardioverter defibrillator (ICD) are considered the 2 major therapeutic tools to prevent sudden arrhythmic death in these patients. Two large trials have been launched to define the prophylactic benefit of the ICD or amiodarone on total mortality in patients that receive optimal heart failure and anti-ischemic treatment but remain at high risk of dying suddenly. The Sudden Cardiac Death in Heart Failure Trial (SCD-Heft) is designed to determine whether amiodarone or the ICD will decrease overall mortality in patients with coronary artery disease or nonischemic cardiomyopathy who are in heart failure New York Heart Association (NYHA) class II or III and have a left ventricular ejection fraction < 35%. The primary endpoint is total mortality; secondary objectives are comparison of arrhythmic and nonarrhythmic mortality and morbidity in the 3 arms as well as quality of life, cost-effectiveness, and incidence of episodes of ventricular tachyarrhythmias. The Multicenter Automatic Defibrillator Implantation Trial (MADIT) II is a follow-up study to the MADIT trial. It examines the prophylactic benefit in coronary artery disease patients with a left ventricular ejection fraction of < 30%, who have had at least 1 myocardial infarction but require no further risk stratification. MADIT II is a sequential design trial that compares ICD versus no ICD therapy. Programmed electrical stimulation to test inducibility of ventricular tachycardia is performed during ICD implantation, and various noninvasive risk markers are tested after randomization. Primary endpoint is total mortality, and secondary objectives are quality-of-life issues as well as cost-effectiveness ratio.

What risk should justify implantable cardioverter defibrillator therapy?

Implantable cardioverter defibrillators (ICDs) were developed to prevent sudden cardiac death in patients with ventricular tachycardia (VT) or ventricular fibrillation (VF). Their safety and efficacy have been proved in multiple retrospective and prospective studies. Many of the published trials were directed at secondary prevention for patients who had already had a sudden cardiac death or a sustained VT. For primary prevention, the information available is limited, as only 2 trials have yet been published. Ongoing trials will probably allow us to broaden the indications for prophylactic ICD implantation. Justification of the risk will have to be evaluated against complexity of the implant, the latter including not only cost but quality of life and morbidity associated with an ICD. However, our efforts still have to be directed to improve risk stratification and to decrease the complexity of the procedure.

Which strategy is "best" after myocardial infarction? The Beta-blocker Strategy plus Implantable Cardioverter Defibrillator Trial: rationale and study design

The Beta-blocker Strategy plus Implantable Cardioverter Defibrillator (BEST-ICD) Trial is a multicenter prospective randomized trial that started in June 1998, in 95 centers in Italy and Germany. The trial will test the hypothesis whether, in high-risk post myocardial infarction (MI) patients already treated with beta blockers, electrophysiologic study (EPS)-guided therapy (including the prophylactic implantation of implantable cardioverter defibrillator [ICD] in inducible patients) will improve survival compared with conventional therapy. Patients eligible for the study are survivors of recent MI (> or = 5 and < or = 21 days), aged < or = 80 years, with left ventricular ejection fraction < or = 35% and > or = 1 of the following additional risk factors: (1) ventricular premature beats > or = 10/hour; (2) decreased heart rate variability (standard deviation of unusual RR intervals < 70 msec); and (3) presence of ventricular late potentials. Furthermore, all enrolled patients must be able to tolerate at least 25 mg of metoprolol per day. These patients constitute about 9% of all patients with recent MI and are expected to have a 2-year all-cause mortality > 25% of which 50% is anticipated to be from sudden death. The main criteria of exclusion from the study are (1) a history of sustained ventricular arrhythmia; (2) documentation of nonsustained ventricular tachycardia during the screening phase; and (3) the need for myocardial revascularization and contraindications or intolerance to beta-blocker therapy. Eligible patients will be randomized to 2 different therapeutic strategies: conventional strategy or EPS/ICD strategy. Patients allocated to the EPS/ICD strategy will undergo further risk stratification, and electrophysiologically inducible patients (approximately 35%) will receive prophylactic ICDs, in addition to the conventional therapy, whereas noninducible patients will be only conventionally treated. The primary endpoint of the study will be death from all causes. By hypothesizing a 30% reduction in the 2-year mortality (from 20% to 14%) in the EPS/ICD group compared with conventionally treated patients, 1,200 patients will have to be included. A triangular, 2-sided sequential design with preset boundaries, for a 5% significance level and 90% power to detect a reduction in 2-year mortality from 20% to 14%, will be used to permit early termination of the trial if the strategy is found to be efficacious, no difference, or inefficacious.