Differential morphometric and ultrastructural remodelling in the left atrium and left ventricle in rapid ventricular pacing-induced heart failure.

摘要

BACKGROUND: Heart failure induced by rapid ventricular pacing (RVP) is associated with left atrial (LA) but not left ventricular (LV) hypertrophy. OBJECTIVE: To determine whether differences in wall tension correlate with the differential ultrastructural remodelling in the LA and LV chambers, changes in ultrastructure, systolic function and wall tension (an index of wall stress) were compared in dogs after RVP (n=7) and with no RVP (n=9). RESULTS: Compared with dogs with no RVP (controls), dogs with RVP had increased collagen volume fraction (5.3% versus 8.3%), myocyte cross-sectional area (245 versus 366 microm(2)) and hydroxyproline (222 versus 323 microg/mg protein) in the LA (all P<0.05), but not in the LV. The increase in systolic wall tension produced by RVP was greater in the LA (five versus 43 units, P<0.0004) than in the LV (227 versus 290 units, P<0.01) chambers and correlated closely with the collagen volume fraction (r=0.87), which in turn correlated with myocyte cross-sectional area (r=0.98). In the left atrium, wall tension correlated with wall stress (r=0.99). CONCLUSIONS: The results suggest that differential wall tension may provide the stimulus for differential ultrastructural remodelling (with more hypertrophy and collagen) between LA and LV chambers in RVP-induced cardiomyopathy.