[Kinetics of myocardial isometric relaxation in patients with congenital and acquired heart defects].

The kinetics of isometric relaxation was examined in an isolated myocardium of patients undergoing surgical correction of mitral stenosis (MS), congenital septal heart defects (SHD) and on papillary muscles (PM) of patients suffering from mitral valvular insufficiency. The relaxation of MS preparations is slower than that of SHD that manifests in the decrease of the characteristic constants K and alpha. PM relaxation is slower than that of the rabbit ventricular muscle. Adrenaline and the increased stimulation rate accelerate the relaxation of the preparations of all groups (the greatest increase is seen in MS). Verapamil and paired stimulation slow down the constants. It is suggested that the action potential duration influences the relaxation constants in PM and MS preparations but not SHD. The constants in question seem likely to be independent of the myocardial inotropic state.