Despite plaque accumulation, expansion (positive remodeling) of early lesions maintains the lumen size. In contrast, shrinkage (negative remodeling) contributes to luminal stenosis independent of plaque accumulation [1].
In the present study, the most expansive non-obstructive atherosclerotic lesion was identified. The reference segment was identified as the most proximal segment without detectable plaque and as close as possible to the lesion. We found that positive arterial remodeling was present in both genders, and there was a change in the vessel size and substantial increase in the outer contour of the vessel wall. Patients who were presented with unstable angina had a significant association with lesions with higher remodeling index. The mean remodeling index was 1.4, and low-attenuation plaque area was found larger at the site of remodeling with a mean of 32.73 ± 11.04% of the whole plaque area compared to the reference segment.
Medium attenuation plaque component area was found larger at the reference segment compared to the remodeling site with a mean of (62.76 ± 9.24% vs 50.04 ± 14.53%).
All patients had normal LV systolic function. Among different cardiovascular risk factors, dyslipidemia was the most common (67.3%), diabetes was present in 52.7% patients mainly type 2 DM. Most of the lesions included in the study were exhibiting 40–50% luminal stenosis by visual assessment. A significant association was present between low-attenuation plaque in lesions with high remodeling index. Remodeling was found mainly in the LAD 83.6% affecting more the proximal segments. At remodeling site, the mean vessel area was 26.49 ± 10.63 mm2, mean wall area 17.49 ± 6.92 mm2, mean plaque burden 66.80 ± 8.29%, and mean area of the plaque 17.22 ± 6.64. At the reference site, the mean vessel area was 18.93 ± 6.98 mm2, mean wall area 8.40 ± 3.37 mm2, mean plaque burden 44.67 ± 5.84%, and total area of the plaque 8.44 ± 3.28 mm2.
These findings were similar to the results conducted by Schmid et al. [6]. In their study, they found that lipid rich plaques with low attenuation on CT were correlated with positive remodeling and subsequently increased risk for plaque rupture and clinical events. In contrast to our mean remodeling index of 1.4, their mean remodeling index was found 1.17 ± 0.30 and this could be attributed to the majority of their studied lesions which were located in the mid segments of the vessels. Forty-seven lesions (42%) were located in proximal segments and 65 (58%) in mid coronary segments. In both studies, the remodeling index was not significantly associated with any of the coronary risk factors, lesion location, or statin use. The mean cross-sectional vessel area in the lesion was 0.25 ± 0.08 cm2, and the mean reference vessel area was 0.22 ± 0.09 cm2. The mean CT attenuation of atherosclerotic plaque in the lesions was 71 ± 26 HU.
The mean attenuation measured in positively remodeled lesions was significantly lower than in lesions with no or negative remodeling.
The same results were found by Pflederer and his colleagues [7] that in patients with acute coronary syndrome, the incidence of positively remodeled culprit lesions was more than those with stable coronary artery disease. The remodeling index and the plaque and media complex area in the acute coronary syndrome group were also larger than those in the stable angina group.
Similarly, a study was done by Motoyama et al. [3], who studied the CT characteristics of coronary lesions in ACS. He compared between 38 patients with ACS and 33 patients with stable angina, and the coronary plaques were evaluated in both arms using CT plaque characteristics, including vessel remodeling and consistency of non-calcified plaque. They found that positive remodeling (87% vs. 12%), non-calcific plaques (NCP) less than 30 HU (79% vs. 9%), and spotty calcification (63% vs. 21%) were significantly more frequent in the ACS patients.
In our study, after 90-day follow-up, we found that majority of patients were just allocated to medical treatment with no adverse future cardiovascular events in 51.8% and those who developed clinical events were 48.2%. Duration of diabetes and higher degree of luminal stenosis by visual assessment > 60% in the studied lesions were more associated with future cardiovascular events. We identified each plaque similar to IVUS into 3 different color codes using automated software. We were able to identify plaque area instead of plaque volume. However, the duration of follow-up was short, but we ended with the same conclusion to Nadjiri et al. and Tesche et al. [8, 9] that high-risk plaque characteristics including positive remodeling and low-attenuation plaque area were associated with future cardiovascular clinical events.
Moreover, we found that the higher plaque burden and higher wall/lumen area percentage at site of positive remodeling were significantly associated with future adverse clinical events.
Nadjiri et al. [8] studied the prognostic value of quantitative plaque assessment in coronary CT angiography during 5 years follow-up of 1168 patients. MACE was present in 46 patients (3.9%). MACE was associated with all plaque characteristics, and the strongest association was observed for low-attenuation plaque volume (LAPV).
Tesche et al. [9] studied the prognostic implications of coronary CT angiography-derived quantitative markers for the prediction of major adverse cardiac event. He found that patients with MACE had significantly more obstructive coronary lesions with higher non-calcific plaque volume (NCPV) (67.3 mm3 vs. 56.1 mm3), plaque burden (66.3% vs. 44.9%), and greater lesion length.
Yamamoto et al. [10] concluded that identification of non-calcified atherosclerotic lesions (NCALs) with low-attenuation plaques (LAP) and positive remodeling (PR) characteristics by CT coronary angiography indicate additional prognostic information to coronary stenosis for the prediction of future coronary events.
The long duration of follow-up in the previous studies influenced the kind of clinical events occurred. Hard events like death and myocardial infarction occurred in their MACE groups were not found among our patients who were followed up for shorter duration.
Previous studies showed that positively remodeled lesions detected by CT coronary angiography were associated with increased levels of plaque vulnerability on VH IVUS images. Thus, evaluation of remodeling on CT coronary angiography may provide a valuable marker for plaque vulnerability. A head to head comparison of CT coronary angiography with IVUS confirms the diagnostic accuracy of CCTA in the quantitative assessment of coronary plaques as shown by Nakazato et al. [11] who observed a high correlation between total plaque volumes as quantified by CCTA in comparison to IVUS with no significant differences between the two methods. Furthermore, CCTA had high diagnostic accuracy for identification of adverse plaque characteristics (low-attenuation plaque, positive remodeling, and spotty calcification) with no statistical differences with IVUS. In summary, CCTA allows quantitative analysis of plaque vessel area, lumen area, and plaque burden in addition to accurate detection of coronary atherosclerotic plaques.