Background - Several studies have shown that long-term right ventricular (RV) overload in animal models alters myocardial energy substrate metabolism. However, whether long-term RV volume overload alters this metabolism in the human is unclear. Methods and Results - We performed positron emission tomography with [18F]fluorodeoxyglucose (FDG) and single-photon emission tomography (SPECT) with [201Tl] (Tl) and [123I]15-(p-iodophenyl)-3-R,S- methylpentadecanoic acid (BMIPP) in 11 patients with atrial septal defect (ASD) and 11 control subjects. In the FDG study, we calculated myocardial metabolic rate of glucose (MMR) in interventricular septum (IVS) and left ventricular (LV) free wall. MMR was significantly increased in IVS compared with LV free wall in the ASD patients (420±35 versus 333±32 mol · kg-1 · min-1; P<0.05) but not in the control group (347±27 versus 357±25 mol · kg-1 · min-1). In both ASD and control groups, SPECT count was not significantly different between IVS and LV free wall in Tl (ASD, 160±1 versus 177±12; control, 141±12 versus 157±14 counts per 15 minutes) and BMIPP studies (ASD, 203±14 versus 212±18; control, 162±16 versus 176±16 counts per 15 minutes). MMR in the IVS/LV free wall ratio in the ASD group significantly correlated with indices related to RV volume overload. Conclusions - Given the assumption that long-term RV volume overload did not affect the lumped constant, the present study suggests that, unlike myocardial perfusion or fatty acid analogue uptake, myocardial glucose utilization in IVS relative to LV free wall is increased in relation to long- term RV volume overload in patients with ASD.
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