DYNAMICS OF LEFT-VENTRICULAR HYPERTROPHY AND FUNCTION IN SPONTANEOUS HYPERTENSION OF RATS

Left ventricular dynamics and papillary muscle mechanics were examined in 44 spontaneously hypertensive rats (SHR) (Okamoto, 9-21 weeks old), in 38 normotensive Wistar Kyoto inbred rats and in 31 control rats. In spite of marked pressure overload, SHR had normal peak systolic wall stress and reduced (21%) diastolic wall stress due to an increased proportion between left ventricular wall thickness and radius. Left ventricular function was normal (isovolumic contractility indices before and after aortic clamping) or augmented (pressure development per gramm of left ventricular weight before and after clamping). Papillary muscle mechanics showed decreases of contraction velocities (isometric and isotonic), whereas shortening and maximum tension development were nearly unaffected. Left ventricular hypertrophy in proportion to pressure overload, the increase in wall thickness/radius ratio and hence the normalisation or decrease of wall stress, provides normal left ventricular function even at extreme pressure overload. © 1978 Springer-Verlag.