Diltiazem as adjunctive oral therapy in patients with chronic atrial fibrillation

Digoxin frequently fails to control the heart rate in patients of chronic atrial fibrillation particularly during exertion. We have studied in 20 such patients the effect of adding diltiazem (180 mg/day) on resting and peak exercise heart rates. An attempt was also made to determine its effects on exercise tolerance by using treadmill and 6 minute walk test. Addition of diltiazem resulted in significant attenuation of heart rate both at rest and at peak exercise. The resting and exercise mean heart rates on digoxin alone were 98.9 +/- 21.5 b.p.m. and 160.2 +/- 35.68 b.p.m. respectively. After diltiazem this reduced to 78.7 +/- 12.30 b.p.m. at rest and 132.4 +/- 40.4 b.p.m. at peak exercise (p < 0.01). There was no significant effect on exercise tolerance. In conclusion, the addition of diltiazem substantially reduced the excessive heart rate response to exercise in digitalised patients of chronic atrial fibrillation.