Incremento del valore diagnostico della tomoscintigrafia miocardica sincronizzata nella valutazione della perfusione miocardica regionale

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.