Adenosine Tc-99m Tetrofosmin SPECT in Differentiation of Ischemic From Nonischemic Cardiomyopathy in Patients With LV Systolic Dysfunction

Background: The noninvasive differentiation of ischemic from nonischemic cardiomyopathy is clinically important. However, whether adenosine Tc-99m tetrofosmin SPECT can offer clear and accurate information was not known. The aim of this study is to investigate the usefulness of adenosine Tc-99m tetrofosmin SPECT in differentiation of ischemic from nonischemic etiology in patients with mild to severe LV systolic dysfunction and to compare the relationship between patients with mild LV systolic dysfunction and those with severe LV systolic dysfunction. Methods: Seventy-five patients with chronic heart failure (LV ejection fraction ≤50%) underwent adenosine Tc-99m tetrofosmin SPECT and coronary angiography to identify ischemia. The patients were divided into 2 groups based on the result of ejection fraction (EF); group I (44 patients) had mild LV dysfunction, LVEF >35%, group II (31 patients) had severe LV dysfunction, LVEF ≤35%. As the result of SPECT, percent abnormal myocardium was categorized into 3 groups: small defect, <10%; medium defect 10% to 20%; and large defects, ≥20%. Myocardial ischemia was defined by ≥70% stenosis in at least one vessel by coronary angiography. Results: In group I, 4 (30.8%) of 13 patients with small defects, 1 (25.0%) of 5 patients with a medium defect, and 22 (84.6%) of 26 patients with large defects demonstrated myocardial ischemia documented by coronary angiography. The relationship between the extent of the SPECT defect and myocardial ischemia was statistically significant in the group I population (P < 0.001). However, in group II, 1 (33.3%) of 3 patients with small defect, 3 (33.3%) of 9 patients with medium defects, and 7 (36.8%) of 19 patients with large defects demonstrated myocardial ischemia confirmed by coronary angiography. There was no statistical relationship between the extent of the SPECT defect and myocardial ischemia in group II. Conclusions: Adenosine Tc-99m tetrofosmin SPECT is a useful modality to differentiate ischemic from nonischemic etiology in patients with mild LV systolic dysfunction. However, other noninvasive approaches other this SPECT may be considered for confirming the etiology in patients with severe LV systolic dysfunction.