MUSCLE-FIBER ORIENTATION AND CONNECTIVE-TISSUE CONTENT IN THE HYPERTROPHIED HUMAN-HEART

  • 1 January 1982
    • journal article
    • research article
    • Vol. 46  (2) , 158-164
Abstract
To elucidate the structural correlates of cardiac failure in myocardial tissue, muscle fiber alignment and connective tissue volume fraction were measured at multiple sites in the left ventricular free wall and in the interventricular septum of 14 human hearts. Group 1 (5 hearts; 280 .+-. 20 g) had no evidence of cardiac disease, group 2 (5 hearts; 380 .+-. 30 g) had a history of systemic hypertension without clinical heart failure, and group 3 (4 hearts; 590 .+-. 40 g) had both left ventricular overload and congestive failure. Fiber orientations were determined by measuring fiber angle relative to the circumferential direction (helix angle). The fraction of the myocardial volume occupied by connective tissue was determined by point counting. There is a smooth transition of helix angle from epi- to endocardial surface in the normal left ventricular free wall with nearly 55% of the wall occupied by circumferentially oriented fibers near the cardiac equator (latitude of largest ventricular diameter); morphologically the interventricular septum was nearly identical with the free wall. Fiber alignment was maintained in all 3 groups as was the fraction of wall occupied by circumferential fibers. Connective tissue volume fraction was significantly increased (P < 0.02) in hypertrophied hearts (groups 2 and 3) as compared with normal hearts, and at 2 of 6 sites in clinically failed hearts as compared with hypertrophied but functionally compensated hearts. Muscle fiber orientation is not altered in the hypertrophied pressure-overloaded left ventricle, while connective tissue content is increased with the increase being greatest in the failing heart.