Impaired Cardiac Performance in Rats with Long-Term Spontaneous Hypertension
Cardiac performance was assessed during the progression from moderate to severe left ventricular hypertrophy in ether-anesthetized 6- and 18-month-old female spontaneously hypertensive rats (SHR), in 18-month-old male SHR, and in sex- and age-matched normotensive rats (NORM). Peak pumping ability during volume loading, maximum pressure generation during an aortic occlusion, and passive pressure-volume relationships were determined. Ejection phase indexes of young female SHR were comparable to those of age-matched NORM, i.e., both groups ejected the same peak stroke volumes from similar end-diastolic volumes, so that their indexes of ejection fraction were identical. However, a reduced peak stroke volume was ejected from a normal end-diastolic volume in old female SHR and from a significantly larger end-diastolic volume in old male SHR, so that ejection fraction indexes were moderately and substantially reduced, respectively. Maximum pressure developed during an aortic occlusion was always significantly greater in SHR. Despite elevated systemic arterial blood pressures and moderate cardiac hypertrophy, young female SHR ejected a normal stroke volume from a normal end-diastolic volume. Even though the severity of hypertension did not progress with age, cardiac mass increased markedly in old female and male SHR, and yet systolic function decreased. Therefore, hypertrophic growth of the left ventricle of the SHR is associated with both a compensated and a depressed phase of cardiac performance.
KeywordsCardiac Mass Aortic Occlusion Aortic Blood Flow Ventricular Weight Impaired Cardiac Performance
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