FATTY-ACID UPTAKE IS PRESERVED IN CHRONICALLY DYSFUNCTIONAL BUT VIABLE MYOCARDIUM

Glucose uptake appears preserved or even enhanced in the chronically d ysfunctional but viable myocardium. However, the use of other fuels su ch as free fatty acids (FFA) remains unknown. We studied FFA uptake in the chronically dysfunctional but viable myocardium in seven patients with an occluded major coronary artery and a corresponding chronic wa ll motion abnormality but no previous infarction. Myocardial FFA uptak e kinetics in the fasting state were measured with positron emission t omography (PET) and 14(R,S)-[F-18]fluoro-6-thia-heptadecanoic acid ([F -18]FTHA). The FFA uptake index was calculated by multiplying the frac tional [F-18]FTHA uptake with serum FFA concentration. Myocardial bloo d flow (MBF) was measured with [O-15]H2O and PET. Myocardial viability was confirmed with a static F-18-labeled 2-fluoro-2-deoxy-D-glucose P ET imaging and a follow-up echocardiography in the revascularized pati ents. Regional MBF was slightly but not significantly lower in the dys functional compared with normal myocardial segments (0.76 +/- 0.18 vs. 0.81 +/- 0.14 ml.min(-1).g(-1), means +/- SD; P = 0.16). The fraction al [F-18]FTHA uptake rates [0.11 +/- 0.03 vs. 0.11 +/- 0.04 ml.g(-1).m in(-1); not significant (NS)], and the FFA uptake indexes (5.8 +/- 1.7 vs. 5.8 +/- 2.1 mu mol.100.g(-1).min(-1); NS) were similar in the dys functional but viable and in the normal myocardial regions. Thus, in t he chronically dysfunctional but viable (collateral-dependent) myocard ium, the fatty acid uptake probed by [F-18]FTHA appears preserved. Tak en together with preserved glucose uptake, the results indicate that t here is uncoupling of substrate uptake and mechanical function in the chronically dysfunctional but viable myocardium.