Relation Between Superficial Calcifications and Plaque Rupture: An Optical Coherence Tomography Study.

BACKGROUND

There are several forms of calcium deposition, which play different roles in the stability of the coronary artery. It remains unknown whether certain calcification morphological characteristics determine rupture of lipid-rich lesions in the same plaque in acute coronary syndrome (ACS).

METHODS

We retrospectively analyzed 550 patients with ACS between May 2008 and October 2014, who had undergone preintervention optical coherence tomography (OCT) imaging examination. A total of 78 patients with 78 culprit lipid-rich lesions having superficial calcifications on OCT images were included in this study, among which 45 were ruptured lesions with calcium and 33 were nonruptured lipid-rich lesion with calcium. The smallest depth of calcium (CAL-DEP) was determined, and the morphology of the calcifications and plaques was analyzed during preintervention OCT imaging.

RESULTS

The CAL-DEP was significantly thinner in ruptured lesions with calcium than in nonruptured lipid-rich lesion with calcium (median, 50 [interquartile range (IQR), 33-63] μm vs 110 [73-208] μm; P < 0.001) and in myocardial infarction than in unstable angina pectoris patients (median, 57 [IQR, 36-78] μm vs median, 85 [IQR, 43-140] μm; P = 0.045). For lipid-rich calcified plaques, when CAL-DEP was < 63 μm, the lipid-rich lesion was most vulnerable and prone to rupture (sensitivity = 77.8%; specificity = 81.8%; area under the curve: 0.804; P < 0.0001).

CONCLUSIONS

Small CAL-DEP in lipid-rich calcified plaques is a morphological characteristic of a vulnerable plaque phenotype. A CAL-DEP ≤ 63 μm is the critical depth of calcification for lipid-rich calcified plaque rupture in patients with ACS.