Comparison of thallium-201 scanning in idiopathic dilated cardiomyopathy and severe coronary artery disease.

To determine whether cardiomyopathy could be distinguished from coronary artery disease, we used thallium scanning to study 25 patients with severe left ventricular dysfunction and chronic heart failure. Ten patients had normal coronary arteries and idiopathic cardiomyopathy (ejection fraction 20 +/- 5%), and 15 patients had multivessel coronary disease and left ventricular dysfunction (ejection fraction 25 +/- 6%). The exercise time and maximal heart rate were similar in the two groups. Two patients with cardiomyopathy and 11 with coronary artery disease had a positive exercise ECG (p less than 0.05). Thallium scans showed perfusion defects in all 25 patients. The perfusion defects were complete in nine coronary artery disease patients (60%) and in one patient (10%) with cardiomyopathy (p less than 0.05). Extensive defects involving more than 40% of the left ventricular circumference, the number of segments involved, redistribution on the 4-hour scan, lung uptake and ventricular size were similar in the two groups. Perfusion defects on thallium scanning can occur in patients with idiopathic dilated cardiomyopathy and chronic heart failure. Thallium scanning cannot be reliably used in patients with chronic heart failure to distinguish coronary artery disease from cardiomyopathy unless complete defects are present.