Antiarrhythmic Effect of Nifekalant on Atrial Tachyarrhythmia in Four Patients With Severe Heart Failure

Atrial tachyarrhythmia such as atrial fibrillation and flutter often occur as complications of heart failure. Uncontrolled atrial fibrillation reduces the ventricular filling time, worsens the heart failure, and provokes“tachycardiomyopathy”. The absence of atrial contraction and irregularity of the ventricular rhythm also contribute to worsening of heart failure. Therefore, prevention or conversion of atrial tachyarrhythmia to sinus rhythm is important in the management of heart failure. Many class Iantiarrhythmic agents can convert atrial fibrillation and maintain sinus rhythm by slowing the conduction velocity. However, these agents may also worsen heart failure because they have significant negative inotropic effects. In contrast, classIII antiarrhythmic drugs prolong the action potential duration and increase the myocardial refractory period without negative inotropic effects, and are useful for the treatment of atrial fibrillation and flutter. Therefore, classIIIantiarrhythmic drugs are also expected to be useful for converting atrial fibrillation and flutter to sinus rhythm and maintaining the sinus rhythm in patients with heart failure.