Assessment of exercise tolerance of cardiac patients by bicycle, treadmill and treadmill plus isometric exercise with and without nifedipine.

Abstract

Seventeen post-myocardial infarction patients experiencing angina on effort performed 6 different exercise tests until they reached symptom-limited maximal level, 3 after placebo and 3 after oral administration of 10 mg of the Calcium antagonist, nifedipine, in a randomized, double blind, cross-over controlled study. Four of the tests were conventional bicycle and treadmill tests with stepwise increasing load. In 2 of the tests an isometric exercise of carrying a weight averaging 6 kg and corresponding to about 30% of maximal grip strength was added to the treadmill walking. When the exercise was stopped because of moderately severe angina, the product of heart rate and systolic blood pressure did not show any statistically significant difference between the tests. However, in the treadmill plus isometric test the work time was shorter and the slope of the treadmill was less than in the treadmill test. The difference was caused partly by non-cardiac factors, namely fatigue of the hand muscles. In routine exercise tests of coronary patients the addition of an isometric to a dynamic load did not give substantially more information than dynamic exercise alone. Nifedipine caused a modest increase of exercise tolerance in all tests, the increase being greatest in the treadmill plus isometric test. The increase in exercise tolerance was seen also in patients receiving beta-blocking agent.