The influence of decreased left-ventricular afterload on cardiac morphology in hypertrophied rat hearts.

The influence of afterload reduction on cardiac morphology was investigated in Goldblatt rats (hypertensive Wistar rats) with left-ventricular hypertrophy. The measurements were performed on a modified heart-lung preparation in which left-ventricular afterload was reduced either 0%, 15%-30% or 35%-50%. Goldblatt rats without heart-lung preparation served as control group. The aim of this study was to investigate the effects of decreased left-ventricular afterload on the myocardial morphology. The hearts were prepared for light and electron microscopy. For ultrastructural investigations, we developed a mitochondrial alteration score and graded the myocytes according to the degree of ischemic injury. The changes ranged from score 0 (normal) to score 4 (most severe). The mean score of the group with marked afterload reduction (35%-50%) was significantly increased compared to all other groups. Our data suggest that marked afterload reduction has a negative impact on the myocardial ultrastructure in hypertension-induced left-ventricular hypertrophy. Light microscopically, we found a correlation between myocardial cell diameter and blood pressure and a significant difference in arterial wall thickness between normotensive and hypertensive rats.