Imaging of beta-oxidation by static PET with 14(R,S)-[18F]-fluoro-6-thiaheptadecanoic acid (FTHA) in patients with advanced coronary heart disease: a comparison with 18FDG-PET and 99Tcm-MIBI SPET.

14(R,S)-[18F]-fluoro-6-thiaheptadecanoic acid (FTHA) has been proposed as a PET tracer of the beta-oxidation pathway. The aim of this study was to investigate the diagnostic value of FTHA using static PET imaging in patients with ischaemically reduced left ventricular function. Twenty-one patients with angiographically proven advanced coronary heart disease were examined. All patients underwent SPET with 400 MBq [99Tcm]-2-methoxy-isobutyl-isonitrile (MIBI) for perfusion assessment and PET with 250 MBq FTHA under fasting conditions and with 150 MBq 2-[18F]-fluoro-2-deoxyglucose (FDG) following an oral glucose load. The uptake of FTHA and FDG was analysed quantitatively in 33 regions. Regional uptake was normalized to the region with highest MIBI uptake and expressed as a percentage. FTHA uptake paralleled MIBI uptake (r = 0.80) but not FDG uptake (r = 0.57). Mean FTHA uptake (38.1 +/- 16.3%) in 190 regions with severely reduced perfusion (MIBI uptake < 50%, mean uptake 36.8 +/- 9.4%) was significantly lower compared to FDG uptake (54.6 +/- 25.0%). FTHA uptake was preserved (> or = 70%) in 8 of 52 (13%) regions only with severely reduced perfusion but preserved glucose metabolism (FDG uptake > or = 70%). The similarity between FTHA and MIBI uptake suggests that static PET imaging with FTHA is of limited value when distinguishing between ischaemic or hibernating myocardium and scar. The underestimation of viability may be caused both by the dependence of uptake on flow and the suppression of beta-oxidation in regional chronic ischaemia under fasting conditions.