Mechanism of prolongation of pre-ejection period in the hypertrophied left ventricle with normal systolic function in unanesthetized hypertensive dogs

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Abstract
To determine the mechanism for prolongation of pre‐ejection period (PEP) in the hypertensive heart with normal systolic function, cardiac catheterizations, echocardiograms, and electrocardiograms were performed at the baseline period (CS, control stage) and eight weeks (HS, hypertensive stage) after the induction of systemic hypertension by Page's method in unanesthetized dogs. Mean aortic blood pressure increased significantly (96 ± 12 to 137±26 mmHg) (p3 dynes/cm2, CS vs. HS). Heart rate, mean velocity of circumferential fiber shortening (VCF) and end‐systolic wall stress of HS did not change. That is, myocardial contractility in the hypertensive heart of HS most likely is not depressed. At autopsy, left ventricle to body weight ratio of HS was significantly (pet al. reported that the abnormalities in systolic time intervals (STI) were equivalent in patient subgroups with high and low diastolic arterial pressure within hypertensive groups. Therefore, we conclude that the main factor to prolong PEP in the hypertensive heart with normal systolic function is possibly the decrease of preload rather than the depressed myocardial contractility or elevated diastolic aortic pressure.