Reduced 123I-BMIPP uptake implies decreased myocardial flow reserve in patients with chronic stable angina

Purpose Long-chain fatty acid (LCFA) is the main energy source for normal myocardium at rest, but in ischemic myocardium, the main energy substrate shifts from LCFA to glucose. ¹²³I-BMIPP is a radiolabeled LCFA analog. In chronic stable angina without previous infarction, we suppose that reduced ¹²³I-BMIPP uptake is related to the substrate shift in myocardium with decreased myocardial flow reserve (MFR). The purpose of this study was to relate ¹²³I-BMIPP uptake to rest myocardial blood flow (MBF), hyperemic MBF, and MFR assessed with ¹⁵O-water positron emission tomography (PET).Methods We enrolled 21 patients with chronic stable angina without previous infarction, all of whom underwent ¹²³I-BMIPP single-photon emission computed tomography (SPECT) and ¹⁵O-water PET. The left ventricle was divided into 13 segments. In each segment, rest MBF and hyperemic MBF were measured by PET. ¹²³I-BMIPP uptake was evaluated as follows: score 0=normal, 1=slightly decreased uptake, 2=moderately decreased uptake, 3=severely decreased uptake, and 4=complete defect. ¹²³I-BMIPP uptake was compared with rest MBF, hyperemic MBF, and MFR.Results The numbers of segments with ¹²³I-BMIPP scores 0, 1, 2, 3, and 4 were 178, 40, 25, 24, and 0, respectively. The rest MBFs for scores 0, 1, 2, and 3 were 0.93±0.25, 0.86±0.21, 0.97±0.30, and 0.99±0.37 ml/min/g, respectively. The hyperemic MBFs for scores 0, 1, 2, and 3 were 2.76±1.29, 1.84±0.74, 1.37±0.39, and 1.08±0.40 ml/min/g, respectively. The MFRs for scores 0, 1, 2, and 3 were 3.01±1.38, 2.20±0.95, 1.44±0.22, and 1.10±0.26, respectively. As ¹²³I-BMIPP uptake declined, hyperemic MBF and MFR decreased.Conclusion In chronic stable angina without previous infarction, reduced ¹²³I-BMIPP uptake implies decreased MFR.