STRUCTURAL REMODELING OF CARDIAC MYOCYTES IN PATIENTS WITH ISCHEMIC CARDIOMYOPATHY

Background. Chronic ischemic heart disease may lead to ventricular dilation and congestive heart failure (ischemic cardiomyopathy [ICM]). The changes in cardiac myocyte shape associated with this dilation, however, are not known. Methods and Results. Left ventricular myocyte dimensions were assessed in cells isolated from explanted human hearts obtained from patients with ICM (n=6) who were undergoing heart transplantation. Cells were also examined from three nonfailing donor hearts with normal coronary arteries (NCA). Compared with cells from patients with NCA, myocyte length was 40% longer in hearts from patients with ICM (197+/-8 versus 141+/-9-mu-m, p<0.01), cell width was not significantly different, and cell length/width ratio was 49% greater (11.2+/-0.9 versus 7.5+/-0.6, p<0.01). Sarcomere length was the same in myocytes from both groups. The extent of myocyte lengthening is comparable to the increase in end-diastolic diameter commonly reported in patients with ICM. Conclusions. These data suggest that increased myocyte length (an intracellular event), instead of myocyte slippage (an extracellular event), is largely responsible for the chamber dilation in ICM. Furthermore, maladaptive remodeling of myocyte shape (e.g., increased myocyte length/width ratio) may contribute to the elevated wall stress (e.g., increased chamber radius/wall thickness) in ICM.