[Adaptation of left ventricular performance to isometric stress]

The authors report the haemodynamic changes observed during isometric stress corresponding to 30% of the maximum isometric effort, sustained for 3 minutes, in 22 normal subjects and 12 patients with cardiomyopathy. Echocardiographic study of the left ventricular diameters of 10 cardiac patients completes the work. The heart rate in normal subjects during effort increases by 45 +/- 30%, and the flow by 30 +/- 24%. The blood pressure is raised by +/- 25 +/- 8 mmHg, without significant change in the left ventricular end-diastolic pressure (less than +4 mmHg), or in peripheral resistance. The external work of the left ventricle increases by 75 +/- 41%, demonstrating an increase in the inotropic state of the myocardium. Max. vec. and the various indices of contractility are increased on average by +8.29 +/- 4.55 28 c/s. Adaptation to the increased pressure brings into play only the contractile reserve of the myocardium.