PMC10265674_01
Initial 12-lead electrocardiogram: A 12-lead electrocardiogram showed abnormal ST-segment elevation with pathologic Q-waves in precordial leads.
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During the transportation via ambulance, the patient had received electrical defibrillation for documented ventricular fibrillation (Supplementary Figure S1). A 12-lead electrocardiogram showed abnormal ST-segment elevation with pathologic Q-waves in precordial leads (Figure 1). After intracoronary nitroglycerin (I-NTG) administration, however, this stenosis was dramatically relieved (Figure 2B), but there was found systolic compression at the same site, suggestive of MB (Figures 2C,D, Supplementary Video S1).
Initial CAG finding: initial CAG demonstrated near-total occlusion (yellowish arrow) at the middle portion of LAD with reduced antegrade coronary flow. (A) This stenosis was dramatically relieved (yellowish arrow), after I-NTG administration (B) After I-NTG administration, systolic compression was seen at the middle portion of LAD, which means MB. (C,D) IVUS was further examined with a guidance system (Eagle Eye  Platinum RX Digital IVUS Catheter, Volcano Corporation, Rancho Cordova, CA, USA), demonstrating eccentric compression with a half-moon-like echo-lucent space between the MB segment and epicardial tissue. (E,F) Multiple-slice CCTA imaging showed a bridged coronary segment surrounded by myocardium at the middle portion of LAD (yellowish arrow). (G) CAG, coronary angiogram; CCTA, coronary computed tomography angiography; I-NTG, intracoronary nitroglycerin; LAD, left anterior descending coronary artery; MB, myocardial bridge.
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It revealed near-total occlusion at the middle portion of left anterior descending coronary artery (LAD) with reduced antegrade coronary flow (Figure 2A). After intracoronary nitroglycerin (I-NTG) administration, however, this stenosis was dramatically relieved (Figure 2B), but there was found systolic compression at the same site, suggestive of MB (Figures 2C,D, Supplementary Video S1). Figure S2). For the further evaluation, intravascular ultrasound (IVUS) study was examined with a guidance system (Eagle Eye  Platinum RX Digital IVUS Catheter, Volcano Corporation, Rancho Cordova, CA, USA). In IVUS, eccentric compression was seen in the MB segment with a half-moon-like echo-lucent space between the MB segment and epicardial tissue (Figures 2E,F, Supplementary Video S2). In multiple-slice coronary computed tomography angiography (CCTA), there was seen a coronary segment surrounded by myocardium at the middle portion of LAD (Figure 2G).
Myocardial perfusion SPECT imaging: SPECT scan showed medium-sized, non-transmural infarction around the apex (whitish arrow). This defect correlates to the downstream myocardium to the bridging segment of the mid-LAD, as marked by arrows. LAD, left anterior descending coronary artery; SPECT, single photon emission computed tomography.
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The cross-sectional area at this segment was 4.99 mm2 during the diastole, and 3.42 mm2 during the systole (Supplementary Figure S3). It demonstrated a medium-sized, moderate fixed perfusion defect around the apex, downstream to the bridging segment of the LAD, suggesting MI (Figure 3).
The cardiac SPECT/CCTA hybrid imaging also confirmed excellent correlation between the extent of perfusion defects and the anatomical location of MB, which was well correlated with CAG finding (whitish arrow and yellowish arrow) (A,B). CCTA, coronary computed tomography angiography; MB, myocardial bridge; SPECT, single photon emission computed tomography.
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The cardiac SPECT/CCTA hybrid imaging also confirmed excellent correlation between the extent of perfusion defects and the anatomical location of MB (Figure 4A), which was also correlated with CAG finding (Figure 4B).