Beneficial effect of carvedilol on heart rate response to exercise in digitalised patients with heart failure in atrial fibrillation due to idiopathic dilated cardiomyopathy.

Fourteen digitalised patients diagnosed with heart failure (NYHA Functional class II) with idiopathic dilated cardiomyopathy in chronic established atrial fibrillation were administered carvedilol in addition to their anti-heart failure medications in an attempt to improve their heart rate control. Fourteen matched patients who did not receive carvedilol acted as control subjects. Patients treated with carvedilol showed significantly reduced resting heart rates (10-36%), maximal heart rates on exercise (5-20%) and an increased exercise time (2-30%) on treadmill stress tests (all P=0.001). Ventricular ectopic activity was also diminished. This was associated with symptomatic improvement in effort intolerance and palpitations. NYHA functional class, left ventricular dimensions and ejection fractions did not improve during the study period of 3 months. Thus, addition of carvedilol to digoxin had a beneficial effect on exercise tolerance in patients with idiopathic dilated cardiomyopathy in atrial fibrillation by virtue of an improved heart rate control both at rest and on exercise. Carvedilol was well tolerated despite impaired myocardial function.