VALUE OF DIPYRIDAMOLE TL-201 IMAGING IN NONINVASIVE DIFFERENTIATION OF IDIOPATHIC DILATED CARDIOMYOPATHY FROM CORONARY-ARTERY DISEASE WITH LEFT-VENTRICULAR DYSFUNCTION

The purpose of this study was to noninvasively differentiate in patients with reduced global left ventricular function between those with idiopathic dilated cardiomyopathy (IDC) and coronary artery disease (CAD). Clinical features and findings of dipyridamole thallium-201 imaging in 55 consecutive patients with IDC were compared with those in 77 with CAD. Left ventricular ejection fraction was similar between the 2 groups (34 +/- 16% vs 39 +/- 7%). Patients with IDC had lower incidences of ischemic chest pain (11 vs 79%; p < 0.0001), electrocardiographic evidence of myocardial infarction (24 vs 82%; p < 0.0001), and reversible defects (4 vs 57%; p < 0.0001) than did those with CAD. The lowest percent thallium uptake in the initial imaging was less with CAD than IDC (30 +/- 15% vs 59 +/- 10%; p < 0.001). Patterns of perfusion defects were classified as: no defects, multiple small defects and large defects. Of patients with IDC, 15 had no defects, 19 had multiple small defects, and 21 had large defects, whereas all those with CAD had large defects (p < 0.0001). Stepwise discriminant analysis, using chest pain and electrocardiography, revealed sensitivity of 89%, specificity of 87%, accuracy of 88%, and positive predictive value of 83% in the identification of patients with IDC. After including the findings of dipyridamole thallium imaging, analysis revealed that the combination of the lowest percent thallium uptake in the initial imaging, the chest pain, reversible defects, blood pressure at rest, pattern of perfusion defects and electrocardiography best identified (p < 0.0001) patients with IDC (sensitivity 95%, specificity 96%, accuracy 95% and positive predictive value 95%). These results indicate that the addition of dipyridamole thallium-201 imaging data to known clinical and electrocardiographic variables can help differentiate patients with cardiac dysfunction between IDC and CAD with a high degree of certainty.