Combined study with FDG PET and Tl SPECT in patients with idiopathic dilated cardiomyopathy

This study aimed to determine whether combined examinations of myocardial 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) and stress-redistribution 201Tl single-photon emission computed tomography (Tl SPECT) were useful in clarifying myocardial ischaemia and evaluating the prognosis in patients with idiopathic dilated cardiomyopathy (IDCM). Twenty-two patients with IDCM underwent echocardiography, cardiac catheterization, FDG PET, and Tl SPECT. In scintigraphic analysis, the total defect score (TDS) was semiquantitatively determined as the sum of scores of the 17 left ventricular (LV) segments with a 5-point scale (0 as normal to 4 as absent). Patients were classified according to the scintigraphic findings as follows: eight patients with small defects on Tl and FDG (TDS < or = 20) (group I), eight patients with small defects on FDG (TDS < or = 20) with FDG uptake increased relative to Tl or 'mismatch' (group II), and six patients with large defects on FDG and Tl (TDS >20) (group III). Eleven patients (50%) showed reversible defects on Tl and all showed preserved FDG uptake. The patients in group III had significantly lower LV ejection fraction (LVEF) (P<0.05, respectively) and a poorer prognosis as shown by the Kaplan-Meier event-free curve compared with those in groups I and II (P<0.01, respectively). Although patients in group II had significantly greater TDS on Tl compared with those in group I (P<0.01), no significant differences in LVEF and prognosis were found between patients in groups I and II. In multivariate analysis, a TDS on FDG revealed an independent predictor of subsequent cardiac events. In conclusion, such mismatched areas can be assumed to consist of impaired but viable myocardium, and may be associated with ischaemia of the microvasculature. Impaired myocardial glucose metabolism is a more powerful predictor of future cardiac events than perfusion abnormality in patients with IDCM.