Hemodynamic characteristics of hypertrophic and congestive cardiomyopathies

To elucidate the hemodynamics and mechanical properties of the myocardium in hypertrophic (HCM) and congestive cardiomyopathies (CCM), preload (end-diastolic stress), afterload (mid-systolic stress), contractility (peak positive dp/dt, (dp/dt)/DP40, ejection fraction), relaxation (peak negative dp/dt, time constant T), compliance (elastic stiffness constant, end-diastolic elastic stiffness), and performance (left ventricular minute work, left ventricular minute work/muscle mass) were determined in 19 patients with HCM, 11 with CCM, and 15 normal subjects. Preload was in the normal range in HCM even with elevated left ventricular end-diastolic pressure. In cases of CCM it was high only when congestive heart failure was present. Afterload was mildly elevated in CCM with heart failure, but only half the normal value in patients with HCM. The three indices of contractility were in the normal range in patients with HCM, and markedly reduced in those with CCM. Relaxation abnormalities were demonstrated in both HCM and CCM. The elastic stiffness constant was high in HCM and normal in CCM. End-diastolic stiffness was normal in HCM and high in CCM with heart failure. These observations suggest that chamber stiffness is markedly elevated in HCM, and stiffness of unit muscle is elevated in CCM when heart failure appears. Although left ventricular minute work was normal in HCM, minute work of unit muscle (left ventricular minute work/muscle mass) was markedly reduced. These observations indicate that the chief problem in CCM is contractile failure and that elevation of preload and muscle stiffness is associated with congestive heart failure in this disease. Although the conventional indices of contractility are in the normal range in HCM, the contractility of unit muscle is reduced, and hypertrophy seems to be a compensatory mechanism when the relations between afterload and ejection fraction and between preload and performance are considered.