Assessment of Left Ventricular Stiffness in Primary Myocardial Disease and Coronary Artery Disease

Abstract

Stress-strain relations (σ-ε) were obtained in the form dσ/dε = kσ + c, where k is a stiffness constant. Utilizing the pressure-volume relation dP/dV = αP, the elastic stiffness (dσ/dε) and k were evaluated at end diastole in ten patients with normal ventricles (N), in 34 patients with coronary artery disease (CAD), and in 22 patients with primary myocardial disease. This latter group was classified into Type I (normal contraction patterns and elevated end-diastolic pressure), Type II (hypertrophy without obstruction), and Type III (hypokinetic and/or asynergic). The mean values and standard error of the means (sem) of k and elastic stiffness were 14.8 ± 0.7, 329 ± 54 gm/cm² (N); 17.8 ± 0.3, 684 ± 80 gm/cm² (CAD); 18.2 ± 0.5, 1133 ± 127 gm/cm² (Type I); 22.4 ± 1.2, 833 ± 150 gm/cm² (Type II); 18.7 ± 0.6, 1623 ± 348 gm/cm² (Type III). These studies indicate that 1) dP/dV, wall stress, and volume-mass ratio are the important determinants of stiffness, 2) normal stiffness levels can be recorded from hypertrophied ventricles, 3) CAD patients with end-diastolic pressure ≦ 12 mm Hg have normal stiffness levels, 4) normal contraction patterns and normal stiffness levels are not necessarily related.