Efficacy and safety ofdigoxin alone and in combination with low-dosediltiazem orbetaxolol to control ventricular rate in chronic atrial fibrillation

C hronic atria1 fibrillation (AF) is characterized by a rapid increase in the ventricular rate during exercise. Digoxin alone, acting primarily by causing an increase in vagal tone, often fails to control exercise-induced tachycardia in patients with AF.’ Beta-adrenergic blockade and calcium antagonists tend to act preferentially on exercise heart rate,2,3 but both can induce adverse effects2,4-7 that detract from their beneficial effects on control of heart rate, and are known to be dose-dependent.@ Few studies on the combination of digitalis and P-adrenergic blockade or calcium antagonists in chronic AF have taken into account the adequacy of digitalization as judged from serum leve1.2,6,9 Such determination seems mandatory in order to prove the true contribution of the added P-adrenergic blockade or calcium antagonist. The purpose of this study was therefore threefold: (1) to reevaluate the role of digitalis in maintaining adequate heart rates in patients with chronic AF, (2) to compare the effects and safety of digoxin in combination with low-dose diltiazem and betaxolol on ventricular rate response, blood pressure, rate-pressure products, and maximal exercise tolerance during exercise in patients with chronic AF; and (3) to study the frequency of adverse effects when using low-dose diltiazem and betaxolol. . . . Forty-five patients (22 men and 23 women, mean age 59 f 2 years, range 29 to 82) with AF for >I month (defined in this study as chronic AF) were included after providing informed consent. Three patients (2 in group III and 1 in group IV) did not complete the study protocol; thus, the results are obtained from 42 patients. On