The aim of this study was to determine the diagnostic accuracy of early/delayed ¹²³I-β-methyl-iodophenyl pentadecanoic acid (¹²³I-BMIPP) planar images to detect disrupted fatty acid metabolism in patients with vasospastic angina (VSA). Heart-to-mediastinum (H/M) ratios and washout rates were calculated from early and late (15 minutes and 4 hours after tracer injection, respectively) planar ¹²³I-BMIPP images from 13 hypertensive control individuals (mean age, 69.5 years) and 37 patients with VSA (mean age, 62.8 years) 10.5 (mean) days after administering the intracoronary acetylcholine provocation test. Patients with VSA had significantly lower early H/M and delayed H/M ratios (early; 2.2 ± 0.3 versus 2.7 ± 0.5, P = 0.007; delayed: 1.8 ± 0.3 versus 2.4 ± 0.4, P < 0.001) and significantly greater washout rates (39.8 ± 11.8% versus 29.3 ± 11.7%, P = 0.011) than controls. The overall area under the curve defi ning the accuracy of diagnostic performance was 0.76 (95% confidence interval (CI): 0.59-0.92) and 0.85 (95% CI, 0.73-0.98) for the early and delayed H/M ratios and 0.74 (95% CI, 0.73-0.90) for washout rates. Planar ¹²³I-BMIPP imaging can diagnose coronary artery spasm with acceptable diagnostic performance and indicates that the delayed H/M ratio has a powerful ability to assess recent ischemia. This technique might be useful in the face of apparently normal coronary angiographic fi ndings during the subacute and chronic phases after ischemic events.