Cardiac Arrest in Seattle: Conventional Versus Amiodarone Drug Evaluation (CASCADE)

BACKGROUND:

Sudden cardiac death can usually be attributed to the occurrence of the cardiac arrhythmia, ventricular fibrillation. Although a significant proportion of patients experiencing sudden cardiac death may be successfully resuscitated without disabling sequelae, this event tends to recur. Recurrent sudden cardiac death is more common among patients demonstrating certain clinical characteristics such as: ventricular fibrillation occurring in a setting of a remote prior transmural infarction; the presence of abnormal left ventricular function; male gender; concurrent complex ventricular arrhythmias identified by electrocardiographic monitoring; extensive coronary artery disease; and the ability to induce ventricular arrhythmias following electrical stimulation.

Multiple therapeutic approaches are offered to patients surviving primary ventricular fibrillation. In those with evidence of myocardial ischemia, coronary revascularization procedures may be employed. Pharmacological therapy with anti-arrhythmic agents either alone or in combination with selection guided by the results of continuous electrocardiographic monitoring or electrophysiologic studies is often the initial step. For those patients refractory to medical therapy, ventricular resection or implantation of pacemakers has been employed.

Amiodarone, a unique antiarrhythmic agent with complex pharmacokinetics and substantial potential toxicity, has been utilized when other antiarrhythmic agents failed. The agent was released as an oral agent for the treatment of ventricular fibrillation in the United States by the FDA. Several investigations suggested that amiodarone was efficacious in the treatment of ventricular fibrillation when other available agents had failed.

DESIGN NARRATIVE:

Patients were stratified by presence or absence of coronary artery disease, left ventricular function, and presence or absence of drug failure prior to randomization. All patients underwent an evaluation of left ventricular ejection fraction, usually by radionuclide ventriculography, and baseline drug-free Holter recording or electrophysiologic study, or both. A total of 113 patients were randomized to amiodarone and 115 patients to conventional therapy with other antiarrhythmic agents which included procainamide, quinidine, disopyramide, tocainide, mexiletine, encainide, flecainide, propafenone, moricizine, or combination therapy in that order. Holter exams were given at one, three, six, twelve, twenty-four, and thirty-six months. Patients were followed for one to five years, with an average of three years overall. Primary endpoints for the study included in the term 'cardiac survival' were cardiac mortality, resuscitated cardiac arrest due to documented ventricular fibrillation, and complete syncope followed by a shock from an automated implanted defibrillator. These endpoints included sudden arrhythmic cardiac death, resuscitated out-of-hospital ventricular fibrillation, and nonarrhythmic cardiac death. A patient death due to amiodarone pulmonary toxicity was also considered a primary endpoint.

Men and women with ventricular fibrillation who had survived an out-of-hospital cardiac arrest not associated with a Q-wave acute myocardial infarction.