Gated stress-only 99mTc myocardial perfusion SPECT imaging accurately assesses coronary artery disease.

In today's cost containment environment it is important to consider changes to standard protocols which would reduce cost, particularly if there is no significant loss of diagnostic accuracy. The aim of the present study was to assess the usefulness of a gated stress-only Tc sestamibi protocol in comparison to conventional gated dual isotope rest-stress myocardial perfusion single photon emission computed tomography (SPECT) in the detection and localization of coronary artery disease (CAD). Sixty-five consecutive patients (65+/-10 years, 22 women) who had undergone conventional gated perfusion SPECT were chosen retrospectively. Fifty-three of these 65 patients had previous coronary arteriography, 45 with at least one stenosis, eight without stenosis, and 12 of these 65 patients had <5% likelihood of CAD. Three readers interpreted the gated stress-only and dual isotope studies in separate sessions blinded to (1). their previous readings, (2). the interpretation by others, and (3). the angiographic results. Readers used a five-point scale to score their visual and quantitative assessment of perfusion, function and compromised vascular territory. Their average score was used for determination of the accuracy by using receiver operating characteristic (ROC) analysis of the techniques. The areas under ROC curves were determined for the detection of CAD and localization of vascular territories. Fifty-four of these patients had 97 significant stress induced perfusion defects as determined by the CEqual quantitative program. The agreement between protocols for the assessment of reversibility in these 97 defects was analysed. There were no statistically significant differences between dual isotope rest/stress and gated stress-only studies for the detection and localization of CAD. The area under the dual isotope rest/stress ROC curve was 0.78+/-0.07 compared to the area under the gated stress-only ROC curve of 0.80+/-0.06, resulting in P=0.30. For the combined vessels comparison of the area under the dual isotope rest/stress ROC curve was 0.73+/-0.04 versus the area under the gated stress-only ROC curve of 0.74+/-0.04, resulting in P=0.27. Similar non-significant differences were obtained when comparing the area under the dual isotope versus gated stress-only ROC curves for the left anterior descending vascular territory (LAD, 0.61+/-0.08 vs 0.660.08, P=0.14), the left circumflex vascular territory (LCX, 0.82+/-0.07 vs 0.81+/-0.06, P =0.47) or the right coronary vascular territory (RCA, 0.80+/-0.06 vs 0.78+/-0.06, P=0.28). The analysis of the reversibility of stress induced perfusion defects yielded a global agreement between protocols of 93% (kappa=0.42). The differences were due to the expert readers, using the gated stress-only protocol, misinterpreting some patients with attenuation artefacts, subendocardial infarction and functional stunning. These results show that the lower cost gated stress-only myocardial Tc myocardial perfusion SPECT studies are comparable to the conventional dual isotope studies when the clinical question is the detection and localization of coronary artery disease. Nevertheless, we also showed that this approach is limited when attempting to interpret the reversibility of stress induced perfusion defects in patients who exhibit attenuation artefacts, subendocardial infarction and functional stunning.

Diagnostic performance of an expert system for the interpretation of myocardial perfusion SPECT studies.

UNLABELLED: An expert system (PERFEX) developed for the computer-assisted interpretation of myocardial perfusion SPECT studies is now becoming widely available. To date, a systematic validation of the diagnostic performance of this expert system for the interpretation of myocardial perfusion SPECT studies has not been reported. METHODS: To validate PERFEX's ability to detect and locate coronary artery disease (CAD), we analyzed 655 stress/rest myocardial perfusion prospective SPECT studies in patients who also underwent coronary angiography. The patient population comprised CAD patients (n = 480) and healthy volunteers (n = 175) (449 men, 206 women). Data from 461 other patient studies were used to implement and refine 253 heuristic rules that best correlated the presence and location of left ventricular myocardial perfusion defects on SPECT studies with angiographically detected CAD and with human expert visual interpretations. Myocardial perfusion defects were automatically identified as segments with counts below sex-matched normal limits. PERFEX uses the certainty of the location, size, shape, and reversibility of the perfusion defects to infer the certainty of the presence and location of CAD. The visual interpretations of tomograms and polar maps, vessel stenosis from coronary angiography, and PERFEX interpretations were all accessed automatically from databases and were used to automatically generate comparisons between diagnostic approaches. RESULTS: Using the physician's reading as a gold standard, PERFEX's sensitivity and specificity levels for detection and localization of disease were, respectively, 83% and 73% for CAD, 76% and 66% for the left anterior descending artery, 90% and 70% for the left circumflex artery, and 74% and 79% for the right coronary artery. These results were extracted from a receiver operating characteristic curve using the average optimal input certainty factor. CONCLUSION: This study shows that the diagnostic performance of PERFEX for interpreting myocardial perfusion SPECT studies is comparable with that of nuclear medicine experts in detecting and locating CAD.

Three-dimensional color-modulated display of myocardial SPECT perfusion distributions accurately assesses coronary artery disease.

UNLABELLED: The objective of this study was to compare visual assessment of 3-dimensional color-modulated (to counts) surface displays with visual assessment of oblique tomographic slices of myocardial SPECT perfusion distributions in the detection and localization of coronary artery disease (CAD). METHODS: Sixty-two consecutive patients (41 men, 21 women; mean age, 61 +/- 11 y) who had undergone conventional dual-isotope perfusion SPECT were retrospectively chosen; 50 had undergone coronary arteriography previously, and 12 had less than a 5% likelihood of CAD. Four readers interpreted the 3-dimensional displays and slices in separate sessions while unaware of the findings of previous readings, the interpretations of others, and the angiographic results. The readers used a 5-point scoring system. Their average score was used for receiver operating characteristic (ROC) analysis. The area under the ROC curves was determined so that the ability of the 2 methods to detect and localize CAD could be compared. RESULTS: No significant differences were found between visual interpretation of 3-dimensional displays and visual interpretation of slices. CONCLUSION: These preliminary results indicate that visual interpretation of 3-dimensional displays of myocardial perfusion SPECT distributions may someday replace visual assessment of conventional slices without loss of diagnostic accuracy.

Prognostic value of thallium-201 single-photon emission computed tomography for patients with multivessel coronary artery disease after revascularization (the Emory Angioplasty versus Surgery Trial [EAST]).

The aim of this study was to investigate the relation between reversible thallium single-photon emission computed tomography (SPECT) myocardial perfusion defects at 1-year after revascularization and quantitative indexes in Emory Angioplasty versus Surgery Trial (EAST) and outcomes 3 years after revascularization in 336 patients. EAST was a randomized controlled trial assessing cardiac outcomes for angioplasty versus bypass surgery for patients with multivessel coronary artery disease. During this prospective trial, a substudy included the evaluation of the prognostic value of reversible defects on quantitative thallium SPECT. At 1-year after revascularization, 336 patients underwent SPECT thallium-201 stress myocardial perfusion and 3-hour delayed imaging. Subsequent events, percutaneous transluminal coronary angioplasty, coronary artery bypass graft surgery, myocardial infarction, and death, were recorded at 3 years. A stress-induced reversible thallium-201 defect was defined using a quantitative index of a reversibility score >30% and severity score >500. Reversible defects were observed more frequently in the percutaneous transluminal coronary angioplasty than in the coronary artery bypass graft surgery treatment groups (46% vs 27%, p <0.001). A total of 123 patients had stress-induced, reversible thallium defects and more events than patients with other perfusion results (freedom from all events was 81.3% vs 94% [p <0.001], and freedom from myocardial infarction and death 88.3% vs 95.5% [p = 0.031]). Quantitative thallium SPECT at 1 year after revascularization risk stratifies patients as to their likelihood of major cardiac outcomes.

Clinical validation of three-dimensional color-modulated displays of myocardial perfusion.

BACKGROUND: Two-dimensional polar maps have been validated previously with coronary arteriography for determining vascular involvement of defects from a patient's myocardial perfusion distributions with and without quantification. The purpose of this study was to validate previously developed three-dimensional color-modulated surface displays representing myocardial perfusion. METHODS AND RESULTS: The validation consisted of comparing the agreement between the three-dimensional displays and two-dimensional polar maps in localizing perfusion defects to vascular territories in 30 patients (16 men/14 women) who underwent both a 1-day rest/stress exercise 99mTc-labeled sestamibi study and coronary arteriography. Reading by two experts was used to identify the size and location of quantified defects and corresponding areas of reversibility seen in the polar maps and, on a separate day, in the three-dimensional displays. Agreement between the two-dimensional polar maps and the three-dimensional displays resulted in identical percentages for the localization of both defects and reversibilities: left anterior descending coronary artery, 87% (26/30); left circumflex coronary artery, 97% (29/30); right coronary artery, 97% (29/30); and coronary artery disease, 97% (29/30). CONCLUSIONS: These results show that the color-modulated three-dimensional displays are at least as good as the CEqual polar maps in localizing a perfusion defect and its reversibility to angiographically defined vascular territories and thus could be used in the routine clinical evaluation of myocardial perfusion.

Prognosis in patients with left ventricular apical aneurysm diagnosed by thallium-201 or Tc-99m sestamibi SPECT images.

The prognosis of patients with left ventricular (LV) aneurysm diagnosed by thallium single-photon emission computed tomography (Tl-SPECT) or technetium-99m sestamibi SPECT (MIBI) has not previously been defined. Of 9,505 Tl or MIBI patients, 139 with apical infarct and probable LV aneurysm on tomographic images were identified. Patients were grouped by the presence of divergent versus parallel LV walls. Divergent walls show increasing separation of the walls as they approach the apex on vertical or horizontal long-axis slices. The degree of the deformation at the apex (divergent vs parallel walls), extent of impaired myocardium (total number of pixels in the defect/total number of pixels in the myocardium x 100%), percentage of reversibility, and segmental and total severity of standard deviations of perfusion defects were calculated. Seventy-six patients underwent contrast ventriculography. Patients with divergent walls (n = 57) were older (p = 0.05), had lower ejection fractions (p = 0.012), higher lung uptake (only Tl patients (p = 0.06), and more frequent ST elevation on the resting electrocardiogram (p = 0.009) than patients with nondivergent (parallel) walls. For both groups, the percent impaired myocardium was comparably high (44 +/- 9% vs 46 +/- 10%). Analysis of asynergic segments in 76 patients who underwent contrast ventriculography showed more akinetic, paradoxical, or aneurysmal segments in the apical region of the left ventricle in the group with SPECT divergent walls. Cox model analysis showed divergence as the significant correlate of death. At 5 years, survival for the group with divergent walls was 52% compared with 75% for those with nondivergent walls (p = 0.008). Despite significant apical LV impairment in both groups, mortality was almost twice as high in the group with divergent walls compared with patients with parallel walls. Thus, patients with LV aneurysm diagnosed by radionuclide SPECT perfusion imaging have a higher mortality when displaying a divergent wall pattern than patients with lesser deformity.

Thallium imaging in management of post-revascularization patients.

The role of myocardial perfusion imaging in the evaluation of post revascularization patients has not been well defined. Published data with special emphasis on the results from the Emory Angioplasty versus Surgery Trial (EAST) indicate that the frequency of adverse cardiac events (death, MI, repeat revascularization) following PTCA or CABG is equal in symptomatic and asymptomatic patients with ischemic thallium defects. Current American Heart Association Guidelines recommend radionuclide studies only in symptomatic patients. Recently reported data support the need for non invasive testing in asymptomatic as well as symptomatic patients at 1 year post-revascularization. Prognostic variables including transient and permanent left ventricular dilatation and thallium lung uptake in addition to stress perfusion defect reversibility on myocardial thallium SPECT scans are important prognostic indicators in post revascularization patients.

Left ventricular dilatation and multivessel coronary artery disease on thallium-201 SPECT are important prognostic indicators in patients with large defects in the left anterior descending distribution.

This study examines the importance of left ventricular (LV) dilatation, and evidence of multivessel coronary artery disease identified on thallium-201 (TI-201) single-photon emission computed tomographic (SPECT) scintigrams, for predicting long-term outcome in patients with an extensive left anterior descending (LAD) perfusion deficit. Impaired contractility of the left ventricle determined by low ejection fraction, elevated LV end-systolic volume, and dilatation of the left ventricle are known as major predictors of mortality after myocardial infarction. TI-201 single-photon emission computed tomography primarily reveals status of perfusion/redistribution, but also contains indirect information on LV function. To date, there are no TI-201 SPECT data on impaired function of the left ventricle (LV dilatation) and extent of perfusion deficits, discussed together as correlates of survival. Patient data were prospectively collected in the computer data base at Emory University. A large perfusion defect involving more than one third of the LAD territory was identified in 291 of 2,652 consecutive patients examined with TI-201 SPECT initial and 3-hour redistribution studies. Follow-up data were obtained for 284 patients (98%) at 38 +/- 14 months. Of the 291 patients, 58 died. The most powerful multivariate correlates of death were LV dilatation, multivessel disease, and the ratio of the LAD severity stress score to total severity of SDs stress score. Cox model analysis was used to determine correlates of survival. Three-year survival for patients with LV dilatation was 73% versus 89% without LV dilatation (p < 0.001). Three-year survival in patients with 1-vessel disease ("LAD only") was 94% versus 78% for multivessel disease (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Reproducibility of thallium-201 exercise SPECT studies.

UNLABELLED: A detailed analysis of intrapatient reproducibility of exercise SPECT thallium studies is presented. METHODS: Twenty patients in stable condition were re-examined with exercise-redistribution SPECT201 Tl within 3-9 days without intervening procedures. At peak stress, 3.5 mCi 201Tl were given intravenously 1 min prior to exercise termination. SPECT imaging started at 5 and 180 min. Acquisition and processing protocols were the same for all studies. Coronary angiography was performed on 19 patients and showed coronary artery disease (CAD) in 18, and no CAD in one; one patient did not have coronary arteriography. RESULTS: For 16 of 20 patients, exercise levels and ECG were comparable for both studies. Ten patients reproduced ST-segment depression; two reproduced angina; one had left bundle branch block (LBBB) on both studies after 1 min of exercise. The remaining seven patients had no ECG changes or symptoms during exercise. Four of 20 (20%) thallium scans differed: three in degree of redistribution and one (5%) in presence of a second stress defect. In three of four patients whose thallium studies showed some nonreproducibility, there were differences in exercise. Thallium results were identical in 15 of 16 patients whose ECG/exercise tests were reproducible (94%). Interobserver agreement was 95%. CONCLUSION: There was excellent reproducibility of 201Tl SPECT scintigraphy in patients who reproduced exercise test performance and symptoms.