論文ID: CJ-21-0666
To prevent acute coronary syndrome (ACS), it is important to detect rupture-prone vulnerable plaques, which are likely to induce ACS in the future. In this issue of the Journal, Hiraya et al1 investigate the association between high-intensity plaque (HIP) on cardiac magnetic resonance angiography (MRA),2,3 which is considered to be vulnerable plaque, and circulating malondialdehyde-modified low-density lipoprotein (MDA-LDL), which has been reported as a marker of cardiovascular disease severity and plaque vulnerability, and a predictor of ACS.4 Their study showed that evaluating the combination of HIP and MDA-LDL improves the prediction of future cardiac events after percutaneous coronary intervention (PCI). No other study has evaluated the association between coronary HIP, circulating MDA-LDL, and future cardiac events after PCI; therefore, this is considered to be a very interesting study.
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Potential of Cardiac MRA for Detecting Vulnerable PlaquesThe morphological features of vulnerable plaques include: (1) vessel remodeling with a large, soft plaque, (2) large necrotic core >25% of plaque area, (3) intraplaque hemorrhage, (4) neovascularization, (5) thin fibrous cap (<65 μm), etc.5 Using magnetic resonance imaging to identify vulnerable plaques is a long-established method. On non-contrast T1-weighted (T1W) MRA, the necrotic core and intraplaque hemorrhage are known to show high-intensity signals, which are thought to represent vulnerable plaque.6,7 My group successfully depicted coronary artery plaques using this method and reported those with high-intensity signals as HIP (Figure 1). The HIPs detected by non-contrast T1W MRA had a high percentage of the characteristics of vulnerable plaques according to coronary computed tomography angiography (CTA).2 In addition, a coronary plaque to cardiac muscle ratio (PMR), as a quantitative measure of HIP, of ≥1.4 was found to be highly predictive of future coronary events (Figure 2).3 Thus, using non-contrast T1W MRA to detect HIP holds great promise in locating vulnerable plaques. However, recognition of the usefulness of cardiac MRA for the detection of vulnerable plaques and the penetration rate of this diagnostic method are still quite low.
Representative case of high-intensity plaque (HIP) on non-contrast T1-weighted magnetic resonance angiography (MRA). HIP with coronary plaque to cardiac muscle ratio (PMR) of 1.94 can be seen at the site corresponding to the plaque on computed tomography angiography (CTA). LAD, left anterior descending artery; IVUS, intravascular ultrasound.
Comparisons of event rates between coronary segments with and without plaques with plaque to cardiac muscle ratio (PMR) ≥1.4. ACS, acute coronary syndrome; cTnT, cardiac troponin-T; PCI, percutaneous coronary intervention; STEMI, ST-segment elevation myocardial infarction; UAP, unstable angina pectoris. Reproduced with permission from Noguchi T et al.3
LDL that undergoes oxidative modification by the action of free radicals such as reactive oxygen species is called oxidized LDL, a major factor in inducing atherosclerosis. MDA-LDL is representative of ox-LDL, and is used for risk assessment of atherosclerosis because its concentration is often elevated in patients with dyslipidemia and diabetes, although in trace amounts. It is usually measured as a predictive marker for the development of coronary artery disease (CAD) in diabetic patients with a history of CAD, or as a predictive marker for restenosis after percutaneous coronary angioplasty in diabetic patients. Recently, there have been some reports on the usefulness of MDA-LDL measurements in detecting the presence of unstable plaques in patients. In addition, there are reports on the association between MDA-LDL and the severity of CAD, plaque vulnerability as a predictor of ACS and the presence of thin cap fibroatheroma assessed by optical coherence tomography.4,8
The present study by Hiraya et al is of great interest because it is the first to investigate the association between coronary HIP and MDA-LDL level and, moreover, the prediction of cardiovascular events by both. The present study showed that the circulating level of MDA-LDL significantly correlated with PMR, and that the incidence of major adverse cardiac event (MACE) in patients with HIP was significantly higher in than those without HIP. In addition, most patients with MACE had non-culprit moderate coronary stenosis, in which HIP was detected by non-contrast T1W MRA. Furthermore, the MDA-LDL levels and PMR were significantly associated with MACE. Compared with MDA-LDL alone, the addition of PMR to MDA-LDL resulted in a statistically significant increase in net reclassification improvement.
The present study reiterates that coronary HIP is significantly associated with the occurrence of MACE. However, as mentioned previously, the prevalence of cardiac MRA is still quite low, so it is not practical to perform both tests simultaneously to evaluate patients with vulnerable plaques. Therefore, based on the results of this study, MDA-LDL should be evaluated first in patients with suspected CAD, and then HIP should be evaluated by non-contrast T1W MRA in patients with MDA-LDL >90 U/L. If the patient has a HIP with PMR ≥1.4, there is a high risk of future cardiovascular events, and aggressive medical treatment with statins or other drugs can be administered to reduce that risk. Thus, the combination of circulating MDA-LDL measurement and HIP detection by non-contrast T1W cardiac MRA has great potential for the identification of patients with a high risk of future cardiovascular events. Aggressive medical intervention in such patients may be preventive.
