Objective To determine the clinical and prognostic value of identifying metabolic abnormalities of myocardial fatty acid metabolism in idiopathic dilated cardiomyopathy using iodine-123 β-methyl-iodophenyl pentadecanoic acid (¹²³I BMIPP).

Setting Cardiac care division in national hospital.

Patients 32 consecutive patients with idiopathic dilated cardiomyopathy in whom both ¹²³I BMIPP and thallium-201 myocardial single photon emission computed tomography were performed.

Results The¹²³I BMIPP total score was correlated with pulmonary capillary wedge pressure (r = 0.68, p < 0.001), left ventricular end diastolic pressure (r = 0.65, p < 0.001), percentage fractional shortening at six months’ follow up (r = -0.58, p = 0.001), myocyte diameter (r = 0.66, p < 0.001), and percentage area of interstitial fibrosis (r = 0.69, p < 0.001) measured by morphometry in the biopsy specimens. During a mean (SD) follow up of 20 (11) months, deterioration of the New York Heart Association functional class was observed in 11 of the 32 patients; four of these died. Segments with a greater decrease in¹²³I BMIPP than thallium-201 uptake (type B mismatching) were often observed in patients with deterioration (88/187, 29%v 58/357, 16%; p < 0.001).

Conclusions The extent of the abnormality of myocardial fatty acid metabolism in idiopathic dilated cardiomyopathy reflects the severity of haemodynamic deterioration and histopathological changes. Type B mismatching is one of the important prognostic indicators in idiopathic dilated cardiomyopathy.