We evaluated the myocardial function of rats with sugar-induced hypertriglyceridemia (HTG) and hypertension, and the effect of serum on myocardial performance in the isolated heart preparation. Also, the response to reperfusion after 30 minutes of global ischemia was investigated. Hearts from HTG rats developed lower ventricular pressure (VP) and the conduction rate was higher than in hearts from control rats (CR). The recovery of VP after ischemia was significantly lower in HTG than in CR hearts (p < 0.05). The HTG sera produced a higher increase in the VP and in the perfusion pressure. During reperfusion, the incidence of premature beats, ventricular fibrillation and tachycardia in HTG hearts was increased so hypertriglyceridemia caused alterations in the mechanical and electrical conduction of the myocardium and exacerbated the injury produced by ischemia-reperfusion. Also a circulating factor in the HTG serum induced a vasoactive response of the heart which was reflected in its mechanical performance.