Copyright © 1987 by the European Society of Cardiology.
© 1987 The European Society of Cardiology
Captopril versus placebo in congestive heart failure: effects on oxygen delivery to exercising skeletal muscle
Departments of Cardiology and Radiological Science, Guy's Hospital London, U.K.
Received 29 April 1987; revised 16 June 1987; .
Adam D. Timmis, Department of Cardiology, Guy's Hospital, St Thomas' Street, London SE1 9RT, U.K.
The effects of captopril versus placebo on oxygen consumption in the exercising leg have been examined Doppler measurements of femoral flow and arteriovenous oxygen difference. Twenty patients with heart failure were randomized to captopril 25 mg (N =10) or placebo (N =10). Maximal supine exercise of one was performed before treatment and again 1 h and 4 h afterwards. Systemic haemodynamic variables were unaffected by placebo, but captopril increased stroke index at peak exercise from 26±3 to 34±3 ml beat-1 m-2 and reduced pulmonary artery wedge pressure from 26±3 to 16±3 mmHg (P<0.05). Despite captopril-induced improvement in left ventricular function, exercise duration did not increase significantly peak values for femoral flow (1059±178 to 938±134 ml min -1, P = NS), and oxygen consumption (134±26 to 111±18 ml min-1, P = NS) in the exercising leg were unaffected. Cutaneous flow, as reflected skin temperature (27.5±0.4 to 27.6±0.4°C, P = NS), was also unaffected. In the patients randomized captopril, the acute improvement in left ventricular function was abbreviated and, after 4 h, all variables had returned towards baseline. Moreover, when the invasive studies were repeated after four weeks chronic treatment responsiveness to converting enzyme inhibition had attenuated and there were no detectable differences between the captopril and placebo groups.These data have demonstrated an acute captopril-induced improvement in left ventricular function patients with congestive heart failure. Nevertheless the beneficial acute response was abbreviated predicting the development of early tolerance. Oxygen delivery to the exercising leg showed no tendency to increase acutely when left ventricular function was significantly improved, or chronically when systemic responsiveness had attenuated. Thus irrespective of its effects on left ventricular function, captopril does not increase nutritive flow to exercising skeletal muscle in congestive heart failure.
Key Words: Captopril congestive heart failure exercise physiology