value of myocardial perfusion imaging in differentiating between idiopathic dilated cardiomyopathy from the ischemic form

ABSTRACT

Differentiating between ischemic cardiomyopathy [ICM] and idiopathic dilated cardiomyopathy [IDCM] is important as coronary revascularization can improve prognosis in the ischemic subgroup. Due to inherent problems of coronary angiography in patients with depressed ejection fraction [EF] introducing a noninvasive tool to diagnose those who will benefit from angiography seems to be rewarding. We examined usefulness of myocardial perfusion scan in this group of patients. Study was performed on 64 patients [62 male and 2 female] aged 57.1 +/- 6.7y [mean +/- SD] all with dilation of the left ventricular [LV] cavity and ejection fraction less than 40% by echocardiography. Myocardial perfusion scan was performed in stress and rest phases. All the patients had coronary angiography which was used as the gold standard test. On each set of images, heart was arbitrary divided into 17 segments and perfusion abnormality in each segment was scored by a 5 grade scoring system [0-4]. Summed Stress Score was used as the scan criteria to differentiate dilated ischemic from idiopathic cardiomyopathy. Scores more than 17 were considered ischemic, and less than that, idiopathic. Results were compared with angiography. From total 40 cases of ischemic cardiomyopathy [proved by angiography] 39 were correctly diagnosed by scan and only one case was miscategorized as IDCM. All 24 cases of IDCM were correctly diagnosed by scintigraphy. Sensitivity, specificity, positive predictive value, and negative predictive value of myocardial perfusion imaging for discrimination between ischemic and idiopathic dilated cardiomyopathy were 97.5%, 100%, 100%, and 96% respectively. Considering excellent accuracy of myocardial perfusion scan with scoring system in discrimination of ischemic dilated cardiomyopathy from idiopathic dilated cardiomyopathy, this noninvasive test could be considered the main diagnostic test