The results of therapy with propafenone were evaluated in 45 patients with complex ventricular ectopic activity that had been refractory to a mean of 3.8 antiarrhythmic drugs. The cardiac diagnoses were ischemic heart disease (in 16 patients), cardiomyopathy (in 7), mitral valve prolapse (in 7), idiopathic ventricular ectopic beats (in 6), valvular heart disease (in 5), and hypertension (in 4). The frequency of ventricular ectopic beats was established after therapy with antiarrhythmic agents had been discontinued. Patients then received propafenone during a dose-ranging protocol. An effective response was defined as a reduction in total ventricular ectopic beats of 80% or more. During dose ranging, therapy failed in four patients because of side effects, in eight because of a reduction in ventricular ectopic beats of less than 80%, and in three because of an aggravation of the arrhythmia. Thirty patients had a reduction in total ventricular ectopic beats of 80% or more. During a mean follow-up of 12.4 months, therapy failed in 1 patient because of sustained ventricular tachycardia and in 7 because of intolerable side effects; 22 patients continued to receive propafenone. PR and QRS intervals were significantly prolonged (P = 0.001), but the corrected QT interval and the heart rate were unchanged. The mean trough plasma level of propafenone associated with an effective response was 756 ng/ml, and that associated with intolerable side effects was 920 ng/ml. Thus, in patients with refractory complex ventricular ectopic beats, propafenone was effective and well tolerated initially in 67% of patients and during long-term administration in 49%, and toxicity was minor in most patients.
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