Asynchronous development of electrical remodeling and structural remodeling in rabbit left ventricle with chronic pressure-overload.

Objective To investigate asynchronous development and its significance in electrical remodeling and structural remodeling in rabbit left ventricle with chronic pressure-overload.Methods Sixty-four new Zealand rabbits were randomly divided into constriction group and sham group.The rabbit ventricle models with chronic pressure-overload were prepared by partial constriction of superrenal abdominal aorta.At 2 and 8 weeks after operation,the single myocytes were enzymatically isolated from the midmyocardium in the antelateral free wall of left ventricle.Whole cell patch clamp technique was used to record the membrane capacitance,action potential(AP) of the single midmycardial(M)cells.The volume and protein content of M cells were measured by confocal laser scanning microscope analysis.Results At 2 weeks after operation,compared with sham group,the volume,protein content and membrane capacitance of M cells from constriction group had no changes,however,at basic cycle length(BCL) of 2 s,the AP duration at 90% repolarization (APD90) of M cells in constriction group was 13.7% longer than that in sham group(P0.05).At 8 weeks after operation,compared with sham group,the volume,protein content and membrane capacitance of M cells from constriction group significantly increased by 28.0%,38.3%,34.0%(P0.05 or 0.01),respectively.At BCL of 2 s,APD90 of M cells in constriction group was 30.6% longer than that in sham group(P0.01).At 2 and 8 weeks after operation,compared with sham group,APD of M cells in constriction group presented more pronounced slow frequency-dependence and were easier to produce early afterdepolariztion(EAD). Conclusion During the chronic pressure-overload,electrical remodeling of M cells from left ventricle precedes structural remodeling,which could be a risk factor for the occurrence of arrhythmia.[Chinese Journal of Cardiac Pacing and Electrophysiology,2009,23(1):59-62]