Role of nuclear cardiology in differentiating scar from ischemic myocardium

For 10 years, patients with abnormal ventricular function (sometimes with ejection fractions under 10%) have generally been offered surgery. Significant improvement in ejection fraction, or in wall motion in a specific segment, has often been observed postoperatively. In the past, simple and effective means to differentiate preoperatively which areas will improve (ischemic myocardium) from those which will not (scar tissue) have not been available. Several radionuclide techniques have been used to study the problems, including use of radio‐labeled particles, 201thallium, 133xenon, and first‐pass radionuclide angiography with and without nitroglycerin intervention. Only the last technique has proven reliable in predicting postoperative improvement in wall motion. Thirty patients have been studied with routine catheterization and first‐pass radionuclide angiography and all had significant wall motion abnormalities preoperatively. Preoperative radionuclide angiograms with nitroglycerin have been compared with postoperative radionuclide angiograms. The images of the RAO radionuclide angiogram were divided into six segments for analysis of wall motion by trisecting the long axis of the left ventricle. Results show that nitroglycerin accurately predicts improvement in ejection fraction with surgery. In terms of wall motion, approximately 50% of akinetic segments improve and 65% of hypokinetic segments improve both with nitroglycerin and revascularization. To summarize, nitroglycerin predicts wall motion improvement with 80% sensitivity and 90% specificity. These data suggest that nitroglycerin radionuclide angiography is a safe, noninvasive technique for differentiating ischemic viable muscle from scar tissue.