Coronary Superficial and Spotty Calcium Deposits in Culprit Coronary Lesions of Acute Coronary Syndrome as Determined by Optical Coherence Tomography

The characteristics of coronary artery calcium responsible for vulnerable plaque remain incompletely elucidated. We used optical coherence tomography to investigate the characteristics of coronary calcium in acute myocardial infarction (AMI), unstable angina pectoris (UAP), and stable angina pectoris (SAP). We evaluated calcium deposits in the culprit lesions (30-mm segment) using optical coherence tomography in 187 patients with AMI (n = 44), UAP (n = 73), or SAP (n = 70). The arc, area, and length of calcium were significantly smaller in those with AMI and UAP than in those with SAP (p <0.001). The number of spotty calcium deposits (with an arc of <90°) per patient was significantly larger in the AMI and UAP groups than in the SAP group (p <0.001). The number of large calcium deposits (with an arc of >90°) per patient was significantly lower in the AMI and UAP groups than in the SAP group (p <0.001). The minimum distance between the inner edge of the calcium and the luminal surface was significantly shorter in the AMI and UAP groups than in the SAP group (p <0.001). Plaque rupture frequency correlated positively with the number of spotty calcium deposits (r = 0.479, p <0.001) and inversely with the number of large calcium deposits (r = −0.219, p = 0.003). In conclusion, calcium was very spotty and more superficial in the culprit lesions of AMI and UAP. These characteristics of calcium might play an important role in the pathogenesis of plaque vulnerability.