[Effectiveness of diltiazem in controlling ventricular response and improving exercise capacity in chronic atrial fibrillation. Double-blind, cross-over study].
Although digoxin is often the drug of choice to control the ventricular response in chronic atrial fibrillation, it fails to control exercise-induced increase in heart rate. The efficacy of diltiazem to control ventricular response and to improve cardiovascular performance during maximal exercise was investigated in 13 digitalized patients with chronic atrial fibrillation. A placebo controlled prospective randomized double-blind study, was preceded by open titration phase. During the diltiazem treatment phase, mean ventricular response diminished at rest (85 +/- 12 versus 107 +/- 19 during digoxin therapy and versus 101 +/- 18 during digoxin and placebo therapy; p less than 0.001), as well as during maximal exercise (142 +/- 13 versus 159 +/- 17 during digoxin treatment and versus 160 +/- 14 during digoxin plus placebo treatment; p less than 0.001). During exercise (50 W), in a subgroup of 7 patients, mean ventricular rate dropped: 109 +/- 19 versus 142 +/- 21 during digoxin treatment and versus 143 +/- 17 during digoxin plus placebo treatment; p less than 0.001). In all patients, the mean rate at rest decreased about 19.3 +/- 6.9% and at maximal exercise about 10.3 +/- 4.9%. In the subgroup of the 7 patients ventricular mean rate at a load of 50 W decreased about 23.6 +/- 7.9%. In all the patients, maximal exercise capacity improved: the MET mean value increased from 3.59 +/- 1.3 to 4.52 +/- 1.18 (p less than 0.001); the mean value of the maximum exercise (MEC), according to the Redfords formula, increased from 65 +/- 48 to 132 +/- 70 (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)