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Background: The structural correlates of 201Tl uptake in patients with advanced postischemic pump dysfunction are unclear. There are no good experimental models adequately reflecting the mixture of normal, dysfunctional but viable, and necrotic regions characteristic of chronic ischemic heart disease in human beings.Methods and Results: Four heart transplant candidates with idiopathic dilated cardiomyopathy and seven with ischemic heart disease underwent rest-injection 4-hour redistribution 201Tl single-photon emission computed tomography before surgery. Delayed tracer uptake was categorized into severely reduced (<50%), mildly or moderately reduced (50% to 74%), and normal (> or =75%) and related to echocardiographic wall motion and histologic findings in the hearts excised at transplantation. In idiopathic dilated cardiomyopathy, despite severe wall motion impairment, minimal or mild myocardial damage and homogeneously high 201Tl uptake were found. In ischemic heart disease, wall motion did not discriminate extensive from mild structural damage. 201Tl activity was inversely related to myocardial fibrosis (r = -0.50, p = 0.0001). Severe defects in 201Tl uptake (<50%) predicted extensive (>30%) fibrosis with 83% sensitivity and 63% specificity. Segmental akinesis and apical location resulted in loss of sensitivity (74% and 58%, respectively). No histologic or wall motion abnormality accounted for poor specificity. In the individual patient, more than nine segments determined viable by imaging criteria predicted left ventricular fibrosis of less than 15% with 86% accuracy.Conclusions: This histopathologic-clinical correlative study supports current evidence of good sensitivity but limited specificity of 201Tl rest-redistribution tomographic imaging in the evaluation of viable myocardium. In the individual patient, more than nine viable segments reliably predicted a limited extension of fibrosis. [ABSTRACT FROM AUTHOR]

The exact role and relative importance of the microvascular dysfunction in the pathophysiology and natural history of CAD is still to be defined. However, this disorder might affect imaging of both baseline and stress myocardial perfusion. A resting perfusion defect should not always be considered a marker of severe coronary stenosis not adequately counterbalanced by a maximal distal vasodilation. In fact, resting hypoperfusion does not necessarily imply exhaustion of vasodilator reserve and may be observed even in regions supplied by angiographically normal coronary arteries. Similarly, the absence of a perfusion defect during stress might indicate the presence of either a nonsignificant stenosis or a diffuse impairment in microcirculatory function. The possibility of obtaining absolute measurements of regional myocardial perfusion by positron emission tomography allows identification of mechanisms affecting myocardial blood flow regulation, providing a more precise characterization of CAD beyond simple agreement with the morphologic angiographic picture. [ABSTRACT FROM AUTHOR]

Background: The incremental diagnostic information of two noninvasive tests for the detection of coronary artery disease (CAD), dipyridamole echocardiography, and exercise 201Tl myocardial scintigraphy was assessed in a series of 102 patients with ordered logistic regression and receiver-operating characteristic curves.Methods and Results: Patients were selected from those referred to our cardiovascular centers with the clinical suspicion of CAD. After clinical evaluation, all patients underwent both noninvasive tests during hospitalization 2 weeks before coronary arteriography. The coronary arteriogram was used as a gold standard: CAD was defined as the presence of one or more vessels with 50% or greater narrowing of the luminal diameter. Clinical data were 73.0% +/- 5.7% accurate in the prediction of CAD. The addition of dipyridamole echocardiographic data to the clinical model yielded a diagnostic accuracy of 88.3% +/- 4.3% (p < 0.00001), whereas the addition of thallium scintigraphic parameters to the clinical model improved diagnostic accuracy to 93.8% +/- 2.6% (p < 0.00001). A significant increase in accuracy to 97.2% +/- 1.4% was achieved when thallium scintigraphic data were added to the clinical and dipyridamole-echocardiographic model (p < 0.00001).Conclusion: Both noninvasive methods for detection of CAD, DET, and ETS showed a good diagnostic accuracy especially when tests-derived parameters were combined with clinical data by means of relative logistic models; nevertheless the ETS model showed a higher sensitivity in comparison with the DET model, essentially in presence of a lower extent of CAD. [ABSTRACT FROM AUTHOR]