Increased left ventricular emptying at maximal exercise after reduction in afterload.
Twelve healthy men were studied by M mode echocardiography during exercise to investigate the effect of afterload reduction on left ventricular function at maximal exertion. They performed two maximal exercise bicycle tests 4 hr apart while in the semisupine position and were given 20 mg nifedipine sublingually 30 min before the second test. During the first test end-systolic dimension decreased (p less than .01) and fractional shortening increased from rest to peak exercise (p less than .01), while end-diastolic dimension did not change significantly. At maximal exercise systolic blood pressure was lower after nifedipine than in the preceding control test (202 +/- 10 [mean +/- SD] vs 212 +/- 14 mm Hg; p less than .01), while heart rate was not significantly changed (168 +/- 15 vs 162 +/- 13 beats/min). End-systolic dimension was lower (25.6 +/- 3.3 vs 28.8 +/- 4.2 mm; p less than .01) and fractional shortening higher (50.7 +/- 6.0% vs 45.3 +/- 7.0%; p less than .01) while end-diastolic dimension was unchanged (52.3 +/- 1.9 vs 52.4 +/- 2.6 mm). Our data indicate increased left ventricular emptying at maximal exercise after nifedipine, most probably due to reduction in afterload.
D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects*; D004452:Echocardiography; D005080:Exercise Test; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology*; D005082:Physical Exertion; D013318:Stroke Volume / Q000187:drug effects*; D013997:Time Factors
D009543:Nifedipine