Evaluation of Left Ventricular Contractile State in Children With a Chronic Left Heart Pressure Overload

Abstract

Recent animal investigations have indicated that myocardial hypertrophy may be accompanied by a depression of muscle function as analyzed in terms of length-tension and force-velocity relationships. Myocardial function was evaluated in these terms in 14 children with left ventricular hypertrophy (LVH) secondary to aortic stenosis or coarctation of the aorta and 10 children with normal left hearts who were undergoing diagnostic cardiac catherization. Serial left ventricular volumes were calculated from biplane cineanangiocardiograms exposed at 60/frames sec, and left ventricular pressure was recorded simultaneously using a catheter tip transducer. Left ventricular circurrferential stress (LVS), LV circumference at the equator (LVC), and LV contractile element velocity (VCE) were calculated. Mean values for VCE at isostress points during isovolumic contraction were not different from normal in 9 patients with moderate LVH (LV Mass 115±13 vs. normal 82±10 g/M2). In 5 patients with more severe LVH and LV Mass averaging 156±31 g/M2, VCE was significantly depressed from normal during isovolumic systole indicating a depressed force-velocity relationship. In addition 4 of the 5 patients with severe LVH had depressions of LV stress at isocircumference points at end-systole when compared with normal children suggesting a depressed length-tension relationship. These date indicate that severe left ventricular hypertrophy in children may be accompanied by impaired muscle function when expressed in terms of basic muscle mechanics.