Cardiac Consequences of Prolonged Exposure to an Isolated Increase in Aortic Stiffness

Abstract

In elderly patients, aortic stiffness is a major determinant of increased end-systolic stress leading to left ventricular (LV) hypertrophy with impaired cardiac performance. However, in a rat model of aortic elastocalcinosis (induced by vitamin D(3)-nicotine [VDN] treatment), brief exposure (1 month) to increased aortic stiffness modified neither cardiac function nor cardiac structure. Here we report the impact of longer exposure (3 months) to aortic stiffness. Three months after induction of aortic stiffness, aortic characteristic impedance was measured in awake rats, 8 control and 10 VDN. Stroke volume was measured (electromagnetic probe) at baseline and after acute volume overload. LV weight/body weight ratio, collagen, and myosin heavy chain (MHC) contents were determined. Although aortic characteristic impedance increased (controls, 32+/-2; VDN rats, 50+/-8 10(3) dyne. s/cm(5); P=0.0248), stroke volume was maintained in VDN rats at baseline (controls, 223+/-18; VDN, 211+/-13 microL) and after volume overload (controls, 378+/-14; VDN, 338+/-15 microL). However, LV weight/body weight ratio (controls, 1.54+/-0.07; VDN, 1.73+/-0.05 g/kg; P=0.0397) and LV collagen content (controls, 31+/-4; VDN, 52+/-4 microgram/g dry wt; P=0.0192) increased. A shift from alpha-MHC (controls, 82+/-2%; VDN, 69+/-3%; P=0.0056) to beta-MHC (controls, 18+/-2%; VDN, 31+/-3%; P=0. 0056) was also observed. Three months' exposure to increased aortic stiffness in VDN rats induced LV hypertrophy with moderate interstitial fibrosis and a shift in the MHC-isoform pattern. Such structural adaptation maintains LV performance.