Microvascular obstruction on delayed enhancement cardiac magnetic resonance imaging after acute myocardial infarction, compared with myocardial ²⁰¹Tl and ¹²³I-BMIPP dual SPECT findings

Background The hypo-enhanced regions within the hyper-enhanced infarct areas detected by cardiac magnetic resonance (CMR) imaging reflect microvascular obstruction (MO) after acute myocardial infarction (AMI). The combined myocardial thallium-201 (²⁰¹Tl)/iodine-123-15-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (¹²³I-BMIPP) dual single-photon emission computed tomography (SPECT) is a useful tool for detecting myocardial reversibility after AMI. We evaluated whether MO could be an early predictor of irreversible myocardial damage in comparison with ²⁰¹Tl and ¹²³I-BMIPP dual SPECT findings in AMI patients. Methods Sixty-two patients with initial AMI who successfully underwent coronary revascularization were enrolled. MO was defined by CMR imaging. Patients were divided into 2 groups as follows: MO group (n = 32) and non-MO group (n = 30). Scintigraphic defect scores were calculated using a 17-segment model with a 5-point scoring system. The mismatch score (MMS) was calculated as follows: the total sum of (Σ) ¹²³I-BMIPP defect score minus Σ²⁰¹Tl defect score. The percentage mismatch score (%MMS) was calculated as follows: MMS/(Σ¹²³I-BMIPP score) × 100 (%). Results The percentage infarct size (%IS) was significantly greater in the MO group than in the non-MO group (32.2 ± 13.8% vs. 18.3 ± 12.1%, p < 0.001). The %MMS significantly correlated with the %IS and the percentage MO (r = -0.26, p = 0.03; r = -0.45, p < 0.001, respectively). The %MMS was significantly greater in the non-MO group than in the MO group (45.4 ± 42.4% vs. 13.3 ± 28.0%, p = 0.001), and was an independent predictor for MO (OR 0.97, 95%CI 0.94-0.99, p = 0.02). Conclusions Our results reconfirm that, in comparison with myocardial dual scintigraphy, MO is an important structural abnormality. CMR imaging is useful for the early detection of irreversible myocardial damage after AMI.