Dobutamine stress echocardiography and thallium-201 SPECT for detecting ischaemic dilated cardiomyopathy in patients with heart failure.

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Abstract
Aims: A diagnosis of ischaemic aetiology of a dilated cardiomyopathy has important therapeutic and prognostic implications. In such patients, abnormal ECG and atypical symptoms limit the usefulness of standard ECG-ergometry in detecting myocardial ischaemia. To assess the values of high-dose dobutamine stress echocardiography and of Thallium-201 SPECT (exercise-reinjection-rest protocol) in differentiating between ischaemic and non-ischaemic dilated cardiomyopathy, 37 patients with suspected myocardial ischemia, low ventricular ejection fraction (23±5%) and heart failure were studied. Methods and Results: Coronary artery disease was defined as >50% coronary stenosis in at least one coronary artery. By dobutamine stress echocardiography, ischaemic dilated cardiomyopathy was considered present when either an ischaemic response (biphasic response or direct deterioration) or a scar (fixed dyssynergy) was documented in at least two segments. By Thallium-201 SPECT, severe perfusion defects, either reversible (ischaemia) or fixed (scar), in at least two segments were considered markers of ischaemic dilated cardiomyopathy. Twenty-three patients had ischaemic dilated cardiomyopathy, while 14 had normal coronary arteries. The presence of myocardial ischaemia and/or scar by dobutamine stress echocardiography identified patients with ischaemic dilated cardiomyopathy with a sensitivity of 100% and a specificity of 86%. The sensitivity of Thallium-201 SPECT was 92%, its specificity was 69%. Three of the four false positive results occurred in patients with left bundle branch block. Thirty-two patients were concordantly classified by the two techniques (agreement=86%, k=0·73). Conclusion: Both dobutamine stress echocardiography and Thallium-201 SPECT are sensitive techniques for detecting the ischaemic aetiology of dilated cardiomyopathy. The specificity is lower, particularly by SPECT, when left ventricular branch block is present.

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