The findings of this study demonstrate that assessment of perfusion data alone by visual or quantitative SPECT MPI analysis underestimates the magnitude of left main CAD. The combination of perfusion and nonperfusion abnormalities on gated MPI identifies high risk in most patients with left main CAD.

Background Current guidelines of Food and Drug Administration for the evaluation of SPECT myocardial perfusion imaging (MPI) in clinical trials recommend independent visual interpretation by multiple experts. Few studies have addressed whether quantitative SPECT MPI assessment would be more reproducible for this application. Methods and Results We studied 31 patients (age 68 ± 13, 25 male) with abnormal stress MPI who underwent repeat exercise (n = 11) or adenosine (n = 20) MPI within 9-22 months (mean 14.9 ± 3.8 months) and had no interval revascularization or myocardial infarction and no change in symptoms, stress type, rest or stress ECG, or clinical response to stress on the second study. Visual interpretation per FDA Guidance used 17-segment, 5-point scoring by two independent expert readers with overread of discordance by a third expert, and percent myocardium abnormal was derived from normalized summed scores. The quantitative magnitude of perfusion abnormality was assessed by the total perfusion deficit (TPD), expressing stress, rest, and ischemic perfusion abnormality. High linear correlations were observed between visual and quantitative size of stress, rest, and ischemic defects (R = 0.94, 0.92, 0.84). Correlations of two tests were higher by quantitative than by visual methods for stress (R = 0.97 vs R = 0.91, P = 0.03) and rest defects (R = 0.94 vs R = 0.82, P = 0.03), respectively, and statistically similar for ischemic defects (R = 0.84 vs R = 0.70, P = ns). Conclusions In stable patients having serial SPECT MPI, quantification is more reproducible than visual for magnitude of perfusion abnormality, suggesting its superiority for use in randomized clinical trials and monitoring the effects of therapy in an individual patient.

No abstract

Twenty-one patients were studied who underwent thallium-201 stress-redistribution single photon emission computed tomography (SPECT) both before and after coronary artery bypass grafting (n = 15) or transluminal coronary angioplasty (n = 6). All patients underwent thallium imaging 15 min, 4 h and late (18 to 72 h) after stress as part of the preintervention thallium-201 scintigram. In a total of 201 tomographic myocardial segments with definite post-stress thallium-201 perfusion defects in which the relevant coronary arteries were subsequently successfully reperfused, the 4 h redistribution images did not predict the postintervention scintigraphic improvement: 67 (85%) of the 79 4 h reversible as well as 88 (72%) of the 122 4 h nonreversible segments improved (p = NS). The 18 to 72 h late redistribution images effectively subcategorized the 4 h nonreversible segments with respect to postintervention scintigraphic improvement: 70 (95%) of the 74 late reversible segments improved after intervention, whereas only 18 (37%) of the 48 late nonreversible segments improved (p less than 0.0001). The frequency of late reversible defects and the frequency of postrevascularization improvement of late nonreversible defects are probably overestimated by this study because of referral biases. The cardiac counts and target to background ratios from late redistribution studies resulted in satisfactory cardiac images for visual interpretation. For optimal assessment of the extent of viable myocardium by thallium-201 scintigraphic studies, late redistribution imaging should be performed when nonreversible defects are observed on 4 h redistribution images.

Background-We have advocated the use of a 5-category "normal," "probably normal," "equivocal," "probably abnormal," and "definitely abnormal" approach to final interpretation of myocardial perfusion single-photon emission computed tomography (SPECT). The prognostic value of expressing levels of certainty compared with a dichotomous normal/abnormal classification or categories for summed stress scores is unclear. Methods and Results-Myocardial perfusion SPECT (MPS) was visually assessed using a standard semiquantitative approach, yielding summed scores that were used for preliminary interpretation using 5 levels of certainty. The interpreter was permitted to then shift the level of certainty in the final interpretation by 1 degree, based on nonperfusion MPS variables and available clinical information. To examine the prognostic value of expressing levels of clinical certainty, we evaluated 20 740 unique consecutive patients who underwent rest Tl-201/stress Tc-99m sestamibi MPS (34.3% vasodilator stress), of whom 845 (4.4%) were lost to follow-up and 1695 were excluded from prognostic analysis due to an early revascularization (Ͻ60 days after MPS). The remaining 18 200 patients (59.1% men; age, 65Ϯ13 years) were followed up for cardiac death for a mean of 2.7Ϯ1.7 years. During the follow-up, a total of 591 cardiac death events occurred. By univariable analysis, there were substantial differences in the distribution of follow-up cardiac death by the category of clinical MPS certainty. The clinical certainty was found to be an independent multivariable predictor of cardiac death in the study population and better identified patients at increased risk of cardiac death than the approaches based solely on the standard categories of summed perfusion scores or based solely on categories of segmental perfusion scores. Conclusions-The