1. Combined use of intracoronary near-infrared spectroscopy (NIRS) and intravascular ultrasound were effective at detecting untreated intracoronary lesions at high risk of major adverse cardiac event (MACE).
2. Highly lipidic lesions and large plaque burden were found to be independent predictors of non-culprit lesion-related MACEs.
Evidence Rating Level: 2 (Good)
Study Rundown: Cardiac disease remains one of the world’s leading causes of death. In particularly, acute coronary syndrome has significant mortality associated with it, and is primarily caused by a rupture of large, lipid-dense atherosclerotic plaques. Several factors associated with plaque rupture include size of the plaque and lipid content. The former can often be measured by intravascular ultrasound (IVUS), while the latter can most easily be obtained using near-infrared spectroscopy (NIRS). This prospective natural history study, PROSPECT II, assessed the utility of combined IVUS with NIRS for the identification of non-obstructive plaques that are suspected to cause major adverse cardiac events (MACEs). Amongst a total of 898 patients, 3629 untreated intracoronary lesions were identified using IVUS. Of those, 787 (22%) had an occlusion of greater than 70% (i.e., plaque burden). At 4-year follow-up, a total of 112 of 898 patients (13.2%) had experienced a MACE. Of those 112 patients experiencing a MACE, 66 (59%) were determined to have experienced the MACE related to a previously untreated lesion detected via IVUS+NIRS. Having at least one lesion with a plaque burden >70% was predictive of MACE; MACE rate also increased with increasing plaque lipid content. In a multivariable model constructed by the authors, high lipid content and large plaque burden were independently predictive of untreated lesion-related MACE. A major limitation of this study was the rate of untreated lesion-related MACEs, which were lower than anticipated. However, sufficient events occurred to have established several characteristics which make certain plaques high risk.
In-Depth [prospective cohort]: This multicenter, prospective natural history study took place at 16 centers across Denmark, Norway and Sweden. A total of 898 patients with a recent (<4 weeks ago) myocardial infarction and subsequent successful intervention comprised the full analysis population. The median age was 63 (IQR 55-70); 153 (15%) were women. The primary outcome of this study was the occurrence of MACEs, defined as either myocardial infarction, unstable angina or progressive angina requiring revascularization, or cardiac death. Events were either classified as caused by the original, treated lesion or by an untreated (non-culprit) lesion at the time of follow-up. At 4-year follow-up, 112 of 989 patients (13.2%, 95%CI 11.0-15.6) had experienced a MACE. Of those 112 patients, 66 of the events were non-culprit lesion-related (8.0% of all patients, 95% CI 6.2-10.0). A total of seven cardiac deaths and 54 myocardial infarctions occurred during follow-up; all cardiac deaths and 14/54 of the infarctions were of indeterminate origin. The average diameter of stenosis of non-culprit lesions was 46.9% (SD 15.9) at baseline and 68.4% (SD 17.7) at the time of MACE. A multivariable model constructed by the authors demonstrated high lipid content (adjusted OR 3.80, 95% CI 1.87-7.70; p=0.0002) and large plaque burden (adjusted OR 5.37, 95% CI 2.42-11.90; p<0.0001) to be independent predictors of untreated lesion-related MACE.
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