The effects of bretylium on experimental cardiac dysrhythmias

Bretylium in severe ventricular arrhythmias associated with digitalis intoxication

Bretylium has been well-recognized as an effective antiarrhythmic agent for acute ventricular arrhythmias, but its use is believed to be contraindicated in digitalis intoxication. We report of two patients in whom digitalis-induced malignant ventricular arrhythmias were refractory to lidocaine. One patient had had repeated episodes of ventricular fibrillation associated with digitoxin and quinidine intoxication, and one patient had had malignant premature ventricular beats associated with digoxin intoxication. Cardiac electrical activity was paced in both instances. In the two patients, ventricular arrhythmias rapidly resolved, and no side effect was encountered. These observations support the administration of bretylium for severe digitalis-induced ventricular arrhythmias.

Ventricular ectopy: etiology, evaluation, and therapy

Ventricular ectopy occurs commonly. Its significance is related to the degree of complexity and the associated cardiac substrate. Coronary artery disease is the most frequent underlying cause, followed by cardiomyopathy and valvular disease. Symptomatic ventricular arrhythmias require treatment, whereas benign simple ventricular ectopy does not; however, the treatment of asymptomatic high-grade ventricular ectopy remains controversial. Therapy first must be directed toward the cardiac disease. Evaluation of the patient includes Holter monitoring, echocardiography, radionuclide studies, exercise testing, cardiac catheterization, and electrophysiologic testing. Programmed stimulation is useful in the diagnosis and prognosis of ventricular tachycardia, as well as in the evaluation of drug regimen efficacy. After treatment of ischemia and/or failure, specific antiarrhythmic agents, conventional and investigational, alone or in combination, are systematically selected. Should medical therapy alone be insufficient, consideration is given to surgical procedures such as subendocardial resection or ventriculotomy, often in combination with bypass grafting, aneurysmectomy, or valvular replacement. Electronic devices, including pacemakers or automatic internal defibrillators, may also be useful in certain selected cases. Suggested guidelines are proposed for a standardized approach, although therapy for each patient must still be individualized.

Acute and chronic digitalis toxicity: presentation and treatment

Although digitalis toxicity is commonly encountered, it can easily be mistaken because of its many manifestations. Recognition of toxicity depends on an awareness of the difference between an acute digitalis overdose and chronic digitalis toxicity. The gastrointestinal, central nervous, and cardiac conduction systems are most commonly involved. Ventricular ectopy and arrhythmias are common with chronic toxicity, while disturbances of sinus impulse formation, A-V blocks, and nodal arrhythmias are seen with both acute and chronic digitalis toxicity. Treatment is mainly supportive, except in acute poisoning, in which case attempts must be made to clear as much drug as possible from the gastrointestinal tract.

Cardiac arrhythmias produced by bretylium in cats anesthetized with halothane

Bretylium given by rapid intravenous injection into cats anesthetized solely with halothane precipitates severe and unusually long-lasting ventricular arrhythmias. They are observed 20-70 sec following doses of bretylium ranging from 0.8 mg/kg to 15 mg/kg and last for 60 sec to just over half an hour. Bretylium also manifests signs of sympathetic involvement since it raises blood pressure and heart rate just prior to the onset of arrhythmias. Propranolol pretreatment prevents bretylium arrhythmias. From these results and from those of other investigations, it is concluded that bretylium arrhythmias are mediated through the release of endogenous noradrenaline stored in adrenergic neurons of the heart. These results call attention to the arrhythmogenic potential of bretylium in the presence of halothane anesthesia.

Response of resistant ventricular tachycardia to bretylium. Relation to site of ectopic focus and location of myocardial disease

Ventricular tachycardias were determined to be of either right-or left-sided origin in 25 patients whose arrhythmias were life-threatening and resistant to lidocaine and other antiarrhythmic drugs. All five patients with right ventricular tachycardia responded well to bretylium and survived. Eleven of 20 patients with left ventricular tachycardia did not do well. Four did not respond to bretylium but survived, five had no response and died, and two responded but died when hypotension prevented continued treatment. Eight of these 11 had acute anterior myocardial infarction or ischemia. Of nine patients with left ventricular tachycardia who responded well to bretylium and survived, only two had anterior infarction, and none had anterior ischemia. Because bretylium was efficacious in all patients with right ventricular tachycardia or inferior myocardial infarction in this study, it seems warranted to investigate further the relationship between drug responsiveness and the site of ectopic impulse formation and the location of myocardial disease.