Performance of the hypertrophied left ventricle in spontaneously hypertensive rat. Effects of changes in preload and afterload

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Abstract
Isolated hearts from adult spontaneously hypertensive rats (SHR), with established hypertension were investigated in an antegrade perfusion apparatus where preload and afterload were varied independently. Frank-Starling curves were constructed at constant afterloads ranging from 50-150 mmHg. The SHR hearts exhibited a rightward shift of their Frank-Starling relationships compared to those from the normotensive control hearts, though visible only at afterloads up to .apprx. 100 mmHg. At higher afterloads the SHR hearts performed significantly better then the NCR [normal control rats] as their maximal stroke volume was significantly greater compared to that of controls. Left ventricular hypertrophy obviously increases the work capacity of the heart, though at the cost of an altered Frank-Starling relation dependent on the reduced diastolic compliance. The myocardial hypertrophy in established SHR hypertension must be considered a physiologic adaptation and not a degenerative phenomenon, though naturally degenerative processes may later become superimposed.