Radioiodinated beta-methyl phenyl fatty acids as potential tracers for myocardial imaging and metabolism.

Since fatty acids provide the majority of myocardial energy requirements under basal conditions, an alteration in the global or regional utilization of these substrates may be an early indicator of myocardial disease. To determine areas of potential clinical utility of fatty acid imaging, we synthesized a radioiodinated modified fatty acid 14-(p-iodophenyl) beta methyltetradecanoic acid IPBMTA, which cannot undergo beta-oxidation. Preliminary biodistribution and imaging studies were performed in animals and man. These studies suggest that radioiodinated beta-methyl phenyl fatty acids localized rapidly in the myocardium and had prolonged myocardial retention time. The long residence time permits the recording of high quality planar and SPECT images.

Rest and exercise right and left ventricular function late after the Mustard operation: assessment by radionuclide ventriculography.

To evaluate ventricular function late after atrial repair of transposition of the great arteries (TGA), 26 asymptomatic patients had rest and exercise radionuclide ventriculography performed a mean of 9 years (range 5 to 15) after undergoing the Mustard operation. The mean resting right (systemic) ventricular (RV) ejection fraction (EF) was 0.50 +/- 0.10 (+/- 1 standard deviation); the RVEF was less than 0.45 in 8 patients. With exercise the RVEF increased in 9 patients and either failed to increase or decreased in 15 (including all 8 patients with resting values less than 0.45). The weight-adjusted work load performed was a first predictor of RV exercise response (sensitivity 87%, specificity 92%); patients whose RVEF increased did more work. The mean resting left (pulmonary) ventricular (LV) EF was 0.58 +/- 0.09; the LVEF was less than 0.50 in 3 patients. With exercise the LVEF increased in 14 patients and did not increase in 10 (including all 3 with resting values less than 0.50). The presence of complex ventricular arrhythmia documented on Holter monitoring was a first predictor of failure of the LVEF to increase with exercise (sensitivity 84%, specificity 71%). The patient's age, operative age, postoperative interval, residual arterial desaturation, preoperative large ventricular septal defect or pulmonary stenosis, postoperative pulmonary stenosis or superior vena caval obstruction, or performance of a second open-heart procedure was predictive of the rest or exercise EF of either ventricle.