Myocardial blood flow and mechanics in volume overload-induced left ventricular hypertrophy in dogs.

ABSTRACT

Chronic volume overload and subsequent left ventricular hypertrophy (LVH) were produced by a surgical shunt between the left subclavian artery and the left atrial appendage in eight dogs. A sham operation was performed on six control dogs. Analysis of biplane ventriculograms showed no significant differences in ejection fraction, mean wall stress, tension-time index, or stress-time index. A significant increase was found in stroke work per gram of left ventricle (P less than 0.005). Myocardial blood flow (MBF) was measured using 9 micrometers, radioactive microspheres at rest, at a constant treadmill workload (CWL) of 2 mph, 2% grade, and at a constant heart rate (CHR) of 175 beats.min-1. Total LVMBF (cm3.min-1) in the shunt dogs was increased at rest (P less than 0.05) with CWL (P less than 0.05) and a CHR (P less than 0.05). However, no differences were found between the groups in the LVMBF.g-1 of myocardium (cm3.g-1.min-1) at rest or during exercise, or in the endocardial to epicardial blood flow ration. Volume overload hypertrophy, without the presence of heart failure, is associated with normal haemodynamic and mechanical function at rest, normal LVMBF.g-1 of myocardium and normal flow distribution at rest and during exercise.