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Background: High-rate short-duration ventricular pacing induces myocardial hypokinesis that persists once the hemodynamic conditions have been recovered. The aim was to study the factors that determine the persistence of myocardial dysfunction when ventricular tachycardia has ceased and hemodynamic conditions have been restored., Material/methods: An in vivo experimental pig model was used consisting of a ventricular pacing series (n=10), a ventricular pacing and aldosterone blockade (eplerenon) series (n=6), and a control series without ventricular pacing (n=6). Electrical stimulation was performed from the epicardial base of the left ventricle at a frequency 60% above the basal rate for 2 hours followed by a recovery period of 60 minutes. Cardiac and myocardial function parameters were studied. Plasma levels of aldosterone, renin activity, and glutathione were measured., Results: Electrically induced tachycardia produced hemodynamic and myocardial changes that persisted after stimulation had ceased, accompanied by an increase in aldosterone and a coronary flow decrease. These changes were not seen when aldosterone activity was blocked by eplerenon. There was a non-significant elevation in glutathione levels., Conclusions: These data show that although participation of other neurohormones cannot be ruled out, aldosterone blockade (eplerenon) ameliorates myocardial dysfunction persisting after ventricular tachycardia by preventing coronary endothelial dysfunction.

Background: The aim was to assess the effect of trimetazidine (TMZ) on mitochondrial alterations induced in a canine model of brief, repeated episodes of ischemia., Material/methods: Twelve crossbred dogs were analyzed, after double-blind randomization, to a 7-day treatment with either TMZ or placebo. Twenty brief, complete occlusions of the left anterior descending coronary artery were performed. Mitochondrial analysis entailed a qualitative (percentage of mitochondrial damage, merging, pairing, vacuoles, and lipofucsin granules) and a quantitative size analysis (major and minor axes, perimeter, and area) of the mitochondria in the ischemic and control zones., Results: Comparative study of the control zones revealed an increase in lipofucsin granules in the TMZ series and a greater percentage of damaged mitochondria and vacuoles. The control-zone mitochondria treated with TMZ presented a significant increase in the perimeter and major axis and a decrease in the minor axis (p<0.005). No significant differences were found between the series in the qualitative analysis of mitochondrial damage in the ischemic zone. The mitochondria in the TMZ series presented a greater major axis and perimeter than those in the placebo series (p<0.05), which presented a smaller minor axis., Conclusions: TMZ made the mitochondria adopt an elongated, "rod-like" morphology in both the control and ischemic zones. This is interpreted as an increase in the membrane surface. In the non-ischemic zone, TMZ produced an increase in mitochondrial turnover. There were no differences in the myocardium subjected to ischemia in both series in terms of observable mitochondrial damage.