[Relaxation and regional myocardial stiffness in obstructive hypertrophic cardiopathy patients: effect of verapamil].

Diastolic stiffness of the septum and the posterior wall were determined in 6 patients with hypertrophic obstructive cardiomyopathy before and 10 to 15 min after the intravenous administration of verapamil, 0,1 mg/kg. Left ventricular high-fidelity pressure measurements and M-mode echocardiography were carried out in all patients before and after verapamil. Diastolic stiffness of the septum (beta S) and of the posterior wall (beta) were assessed from the slope of a viscoelastic stress-strain relationship: sigma = alpha (e beta epsilon -1) + eta epsilon where sigma = meridional wall stress (g/cm2) alpha = intercept (g/cm2), beta = constant of myocardial stiffness, epsilon = mid-wall strain, eta = constant of myocardial viscosity (g. sec/cm2), epsilon = strain rate (sec-1). Left ventricular relaxation was evaluated from the time constant of left ventricular pressure fall (T; msec) by plotting left ventricular pressure versus dP/dt during the isovolumic relaxation period. Heart rate (71 versus 74 beats/min), left ventricular end-diastolic pressure (17 versus 17 mmHg) and peak systolic pressure (152 versus 146 mmHg) were not significantly different before and after intravenous administration of verapamil. The constant of myocardial wall stiffness of the septum (17 versus 16) and the posterior wall (15 versus 13) remained unchanged after verapamil, however, myocardial stiffness of the septum was slightly higher than myocardial stiffness of the posterior wall. The time constant of left ventricular pressure fall decreased significantly (P less than 0.05) from 53 to 43 msec following administration of verapamil. It is concluded that in patients with hypertrophic, obstructive cardiomyopathy, diastolic myocardial stiffness of the septum is slightly higher than the stiffness of the posterior wall. Verapamil does not influence the regional passive diastolic properties but has a beneficial effect on ventricular relaxation.