RESUMO
The aim of the study was to compare infarction size and left ventricular (LV) function in normal and hypertrophied hearts after brief ischemia using Gadophrin-enhancement and functional assessment by MRI. Rats (n = 20) were assigned to aortic banding to induce LV hypertrophy or control. Eight weeks later, rats were subjected to 25 min of regional myocardial ischemia followed by 3 hr of reperfusion. The necrosis-specific agent Gadophrin-3 was injected to delineate infarcted myocardium on MRI. Effects of aortic banding and ischemia on LV mass and function were determined. At postmortem, areas at risk and infarction were measured. Close correlation was found between LV mass measured with MRI and at postmortem (r = 0.98). LV mass measured with MRI was significantly greater (0.81 +/- 0.02 g) in animals with aortic banding compared to control (0.62 +/- 0.02 g; P < 0.001). Infarction size was larger in hypertrophied hearts (19.0 +/- 1.4% / 18.3 +/- 1.5%) than in control (9.8 +/- 1.7% / 9.2 +/- 2.0%) on Gadophrin-enhanced MRI and at postmortem, respectively. Similarly, greater impairment in ejection fraction was observed in hypertrophied hearts with MRI (39 +/- 4% vs. 49 +/- 2%; P = 0.02). Gadophrin-3 provides accurate estimation of infarct size in hypertrophied hearts. Hypertrophied hearts are more sensitive to ischemia than nonhypertrophied hearts. The complementary assessment of Gadophrin-enhancement and LV function with MRI provides unique information about myocardium sensitivity to ischemia.