Effects of
therapy with the
potassium-channel opener and
vasodilator nicorandil were studied in reperfused
infarction of hypertrophied hearts by using magnetic resonance imaging (MRI), hemodynamic measurements, and histochemical staining. Aortic banding was performed on 22 Sprague-Dawley rats to induce left ventricular (LV)
hypertrophy; 11 were the controls. Eight weeks later, the left coronary artery was occluded for 25 minutes in all 33 animals, followed by 3 hours of reperfusion. During occlusion, 11 rats with LV
hypertrophy received
nicorandil (0.1 mg/kg bolus and 1.5 mg/kg/h for 3 hours). The new
necrosis-specific
contrast agent Gadophrin-3 was administered to all animals to delineate
infarction on multislice T1-weighted spin-echo MRI.
Nicorandil increased ischemic tolerance of LV
hypertrophy as shown by the reduction of
infarction size from 19.3% +/- 1.3% to 10.0% +/- 2.5% LV (P = .005).
Infarction size in treated animals was identical to control (9.3% +/- 1.6%). Close correlation was found between MRI and postmortem findings. Functional MRI revealed an improvement in ejection fraction in
nicorandil-treated hearts (48.5% +/- 3.4% vs 38.1% +/- 3.2%, P = .04). LV end-diastolic volume and pressure, aortic pressure, and peripheral vascular resistance were highest in untreated hypertrophied hearts. Brief
ischemia caused severe injury in hypertrophied hearts. Infusing
nicorandil increased the tolerance of hypertrophied hearts to
ischemia. MRI is a suitable technique for the evaluation of new
therapies in LV
hypertrophy.