Transverse shape characteristics of cardiac myocytes from rats and humans

The shape of the cardiac myocyte is complex; but, in general, it resembles that of an elliptical cylinder. Quantitative data, however, are lacking and adaptive changes in cross-sectional shape are unknown. The major and minor transverse diameters of myocytes from adult rats were measured using three independent methods: profile tracings of intact isolated myocytes, sectioned isolated myocytes, and whole-sectioned tissue. Values for major and minor diameters were virtually identical with all three methods. Using profile tracings of intact isolated myocytes, major and minor diameters were examined in isolated myocytes from freshly explanted human hearts. Five were non-failing donor hearts regarded as unsuitable for transplantation, of which 2 were normal hearts and 3 had concentric hypertrophy. Six were dilated, failing human hearts with ischemic cardiomyopathy. Major and minor diameters from the normal hearts were similar to those from normal rats. Although the number of patients was limited, the minor diameter was largest in myocytes from patients with concentric hypertrophy while the major diameter was greatest in cells from patients with ischemic cardiomyopathy. We conclude that the cross-sectional shape of structurally-intact myocytes is not altered by cell isolation. The data suggest that the transverse shape of normal human cardiac myocytes is similar to that found in rats, and that it may be altered in hypertrophy and failure.