The incidence and significance of contraction bands in endomyocardial biopsies from normal human hearts

With increasing use of myocardial biopsy as a diagnostic tool, different criteria of pathology have evolved from tissues obtained from biopsy and postmorten specimens. We reported that contraction bands may be produced artifactually by the biopsy procedure in the fresh, but not the postmorten or perfused fixed normal rat and dog hearts. Contraction bands have been used as a morphological index of pathology. From 12 normal human transplant donors endomyocardial biopsy samples were obtained from the right ventricle, were fixed immediately and then processed for light and electron microscopy. Contraction bands were quantitated by assigning 0, 1, 2, and 3 to represent 0, 1 to 5, 6 to 10, and 11 or more cells per square millimeter with contraction bands. A large number of contraction bands were present in 11 out of 12 hearts; 3rd, 2nd, 1st, and zero degrees of contraction bands were present in 11, 0, 1, and 0 samples, respectively. We conclude that contraction bands may be produced artifactually in normally human hearts, and based upon the rat and dog study, that the determinants of contraction band formation are activation of the contractile machinery by the biopsy procedure, together with sarcomeres capable of hypercontraction because their shortening is unopposed. Furthermore, contraction bands may be considered a morphological index of pathology in tissue obtained postmortem and after perfusion fixation, but not in tissue obtained from biopsies.