Improvement of the diagnostic value of synchronous myocardial tomoscintigraphy in the assessment of regional myocardial perfusion

INTRODUCTION: Gated SPECT using 99mTc-labeled flow tracers provides simultaneous assessment of global and regional myocardial function. PURPOSE: To investigate whether studying regional wall thickening after stress and at rest provides additional diagnostic information in coronary artery disease patients. METHODS: We examined 61 consecutive patients (40 men) who underwent conventional diagnostic dual day stress/rest Gated SPECT using a dual head SPECT camera, following injection of 925 MBq of 99mTc-Tetrofosmin. The mean age of these patients was 61 years (range: 23-73); 28 patients had a history of myocardial infarction. Perfusion was analyzed on both ungated and end-diastolic images using 20 segments scored on a 5-point scale (0 = normal, 4 = no uptake), while wall thickening and motion were assessed visually on stress/rest end-systolic images using a 4-point score (0 = normal, 3 = no wall thickening/motion). Twenty eight patients underwent coronary angiography. RESULTS AND DISCUSSION: 14/61 (23%) patients showed no segmental defects, while fixed equivocal defects, with preserved wall thickening, in 10/61 (16%) patients were considered artifactual. 11/61 (18%) showed true fixed defects. The remaining 26 patients showed al least one reversible defect. 14/61 (23%) patients with post-stress wall thinning and normal rest wall thickness, were considered stunned. The stunned subgroup showed a significant post-stress reduction in left ventricular ejection fraction. Finally, analyzing 1220 segments, we found an excellent agreement (k = .697) between the segmental score obtained by end-diastolic and ungated post-stress images: in fact, comparing the two sets of images, diagnostic accuracy was not significantly different. However the number of segments with fixed defects and normal wall thickening was lower with end-diastolic perfusion images than with ungated images, probably due to attenuation artifacts. This suggests a better accuracy of the former in the evaluation of regional myocardial perfusion. CONCLUSIONS: Although stress end-diastolic images do not seem to significantly improve diagnostic perfusion accuracy compared to ungated acquisitions, the simultaneous assessment of stress-rest wall thickening permits better characterization of a coronary artery disease population.