Pathological and OCT studies have indicated that ACS lesions have either ruptured-fibrous (RFC-ACS) or intact (IFC-ACS) fibrous caps. While CT-angiographic (CTA) characteristics of RFC-ACS include low-attenuation plaques (LAP) and positive plaque remodeling (PR), the prospective relation of PR and LAP to the future cardiac events has not been well described. Furthermore, CTA features associated with IFC-ACS have not been previously described.
Firstly, we prospectively examined 1,059 patients with CTA, lesions were classified for the presence and absence of PR and LAP. Of the 45 patients with PR and LAP (2-feature positive), ACS developed in 10 (22.2%), compared with 1 (3.7%) of the 27 patients with either feature (1-feature positive). Only 4 (0.5%) of the 820 patients with neither PR nor LAP (2-feature negative) did ACS develop. None of the 167 patients with normal CTA had ACS (p<0.001).
Secondarily, we prospectively performed multiple imagings including OCT, IVUS, angioscopy, CTA and QCA in 66 patients with ACS and stable angina. Of these, 57 culprit lesions were evaluated with sufficient image quality. Intraluminal thrombus was assessed by OCT/angioscopy. Of 35 ACS lesions, OCT revealed IFC with thrombus in 10 (29%) and RFC in the remaining 25 (71%); all 22 lesions with stable angina had intact-fibrous caps. However, none of the specific CT-angiography features clearly distinguished IFC-ACS from stable lesions.
Finally, we performed OCT imaging after aspiration thrombectomy and identified OCT–verified intact fibrous cap (IFC-ACS; plaque erosion) as the cause in 31 patients presenting with STEMI in four PCI centers.
Conclusions; Patients demonstrating PR and LAP on CT angiography were at a higher risk of ACS developing over time compared with patients without these characteristics. In contrast to the situation with RFC-ACS, distinct culprit lesion characteristics associated with IFC-ACS are not identified by CT-angiography. The identification between IFC-ACS (plaque erosion) and RFC-ACS (plaque rupture) might offer an alternative treatment strategy such as non-stenting policy in AMI.
