Effects of adaptive or fixed thresholds and different platforms on the assessment of plaque characteristics using coronary computed tomography angiography

BACKGROUND

Coronary computed tomography angiography (CCTA) is used to evaluate components of atherosclerosis. Either adaptive or diverse, fixed Hounsfield Units (HU) are used to define components such as low attenuation (LAP), mixed (MP) and calcified plaque (CP). Comparisons of different platforms and different thresholding approaches have not been extensively evaluated. We compare two fixed threshold options to an adaptive threshold option within a specific platform and to fixed threshold options measured with another platform.

METHODS

Coronary segments (n ​= ​24) of good image quality, with well-defined boundaries and representing a broad range of atheroma were analyzed for LAP, MP and CP. Thresholds for LAP vs MP and MP vs CP were either Fixed30/350, Fixed75/350 or based on an automatically determined Adaptive option. Pearson correlation and Bland-Altman analyses were undertaken.

RESULTS

Within a single platform, measures were highly correlated irrespective of use of Adaptive or Fixed30/350 and Fixed75/350 thresholds (R ​≥ ​0.819, p ​< ​0.000001). The correlation slope for measures of LAP progressively diminished comparing the Adaptive versus Fixed30/350 and the Fixed75/350 versus the Fixed30/350 approaches but bias was small. Between-platform comparisons yielded less optimal results, particularly with respect to measures of LAP and with one platform yielding both very small LAP volumes and very small ranges of volumes.

CONCLUSION

Measures of plaque components are highly correlated irrespective of use of Adaptive or Fixed threshold approaches within a given platform. But measures are more affected by the specific proprietary algorithms employed than by specific thresholding options, especially for LAP.

No evidence of coronary plaque stabilization by allopurinol in patients with acute coronary syndrome

BACKGROUND

Allopurinol, a xanthine inhibitor that lowers uric acid concentration, has been proven to reduce inflammation and oxidative stress in patients with cardiovascular disease. However, it is unknown whether these beneficial effects translate into favorable plaque modification in acute coronary syndromes (ACS). This study aimed to investigate whether allopurinol could improve coronary plaque stabilization using coronary computed tomography angiography (CCTA).

METHODS

This was a prospective, single-center, randomized, double-blind clinical trial began in March 2019. A total of 162 ACS patients aged 18-80 years with a blood level of high-sensitivity C-reactive protein (hsCRP) ​> ​2 ​mg/L were included. The subjects were randomly assigned in a 1:1 ratio to receive either allopurinol sustained-release capsules (at a dose of 0.25 ​g once daily) or placebo for 12 months. The plaque analysis was performed at CCTA. The primary efficacy endpoint was the change in low-attenuation plaque volume (LAPV) from baseline to the 12-month follow-up.

RESULTS

Among 162 patients, 54 in allopurinol group and 51 in placebo group completed the study. The median follow-up duration was 14 months in both groups. Compared with placebo, allopurinol therapy did not significantly alter LAPV (-13.4 ​± ​3.7 ​% vs. -17.8 ​± ​3.6 ​%, p ​= ​0.390), intermediate attenuation plaque volume (-16.1 ​± ​3.0 ​% vs. -16.2 ​± ​2.9 ​%, p ​= ​0.992), dense calcified plaque volume (12.2 ​± ​13.7 ​% vs. 9.7 ​± ​13.0 ​%, p ​= ​0.894), total atheroma volume (-15.2 ​± ​3.2 ​% vs. -16.4 ​± ​3.1 ​%, p ​= ​0.785), remodeling index (2.0 ​± ​3.9 ​% vs. 5.4 ​± ​3.8 ​%, p ​= ​0.536) or hsCRP levels (-73.6 [-91.6-17.9] % vs. -81.2 [-95.4-47.7] %, p ​= ​0.286).

CONCLUSIONS

Our findings suggest that allopurinol does not improve atherosclerotic plaque stability or inflammation in ACS.

Myocardial Flow Reserve in Coronary Artery Disease with Low Attenuation Plaque: Coronary CTA and 13N-ammonia PET Assessments

RATIONALE AND OBJECTIVES

Physiological measurements from coronary angiography show that coronary stenosis with necrotic core plaque reduces coronary flow reserve (CFR). Myocardial flow reserve (MFR) estimated by ¹³N-ammonia PET (NH₃-PET) is a different index from CFR. Low attenuation plaque (LAP) on coronary CTA (CCTA) contains necrotic core, but the link between LAP and MFR has not been elucidated. We aimed to investigate the influence of LAP on MFR in coronary artery disease (CAD).

MATERIALS AND METHODS

The study included 105 consecutive patients who underwent NH₃-PET and CCTA within 3 months. Nonevaluable coronary arteries due to severe calcification and stent implants were excluded. Finally, 290 major vessels were retrospectively analyzed. Coronary arteries were divided into mild (1%-49%), moderate (50%-69% stenosis), and severe (≥70% stenosis) groups. Coronary plaques were classified either LAP (including soft tissue CT value <30 HU) or completely classified plaques. MFR for the major vessels were calculated and MFR <2.0 was considered a significant decrease. Comparison of MFR between territories with and without LAP, and the effect of plaque characteristics on MFR was analyzed.

RESULTS

MFR was significantly lower for territories with LAP than with calcified plaques or no plaque (2.1 ± 0.7, 2.4 ± 0.7, and 2.3 ± 0.7; p < 0.05). There was no difference between calcified plaque and no plaque territories (p = 0.79). Multivariate logistic analysis for plaque characteristics and stenosis severity revealed that LAP and severe stenosis were independent predictors for territories with MFR <2.0 with odds ratios of 3.1 (95% confidence interval, 1.2-8.1) and 3.0 (95% confidence interval, 1.7-5.3).

CONCLUSION

LAP reduced MFR compared with calcified plaque or no plaque in CAD. LAP is an independent predictor of the territory with MFR <2.0.

Characteristics Detected on Computed Tomography Angiography Predict Coronary Artery Plaque Progression in Non-Culprit Lesions

Objective

This study sought to determine whether variables detected on coronary computed tomography angiography (CCTA) would predict plaque progression in non-culprit lesions (NCL).

Materials and Methods

In this single-center trial, we analyzed 103 consecutive patients who were undergoing CCTA and percutaneous coronary intervention (PCI) for culprit lesions. Follow-up CCTA was scheduled 12 months after the PCI, and all patients were followed for 3 years after their second CCTA examination. High-risk plaque features and epicardial adipose tissue (EAT) volume were assessed by CCTA. Each NCL stenosis grade was compared visually between two CCTA scans to detect plaque progression, and patients were stratified into two groups based on this. Logistic regression analysis was used to evaluate the factors that were independently associated with plaque progression in NCLs. Time-to-event curves were compared using the log-rank statistic.

Results

Overall, 34 of 103 patients exhibited NCL plaque progression (33%). Logistic regression analyses showed that the NCL progression was associated with a history of ST-elevated myocardial infarction (odds ratio [OR] = 5.855, 95% confidence interval [CI] = 1.391–24.635, p = 0.016), follow-up low-density lipoprotein cholesterol level (OR = 6.832, 95% CI = 2.103–22.200, p = 0.001), baseline low-attenuation plaque (OR = 7.311, 95% CI = 1.242–43.028, p = 0.028) and EAT (OR = 1.015, 95% CI = 1.000–1.029, p = 0.044). Following the second CCTA examination, major adverse cardiac events (MACEs) were observed in 12 patients, and NCL plaque progression was significantly associated with future MACEs (log rank p = 0.006).

Conclusion

Noninvasive assessment of NCLs by CCTA has potential prognostic value.

Relationship between coronary calcium score and high-risk plaque/significant stenosis

AIM

To investigate the relationship between coronary calcium score (CCS) and vulnerable plaque/significant stenosis using coronary computed tomographic angiography (CCTA).

METHODS

CCTA was performed in 651 patients and these patients were divided into the four groups (CCS 0, 1-100, 101-400 and > 400). We studied the incidence of high-risk plaque, including positive remodeling, low attenuation plaque, spotty calcification, and napkin-ring sign, and significant stenosis in each group.

RESULTS

High-risk plaque was found in 1.3%, 10.1%, 13.3% and 13.4% of patients with CCS 0, 1-100, 101-400 and > 400, respectively (P < 0.001). The difference was only significant for patients with zero CCS. The incidence of significant stenosis was 0.6%, 7.6%, 13.3% and 26.9% for each patient group, respectively (P < 0.001), which represented a significant stepwise increase as CCS increased. The combined incidence of high-risk plaque and significant stenosis was 1.9%, 17.7%, 26.9% and 40.3% in each patient group, respectively (P < 0.001), again representing a significant stepwise increase with CCS. The rate of major coronary event was 0%, 4.0%, 7.9% and 17.2% in each patient group, respectively (P < 0.001), another significant stepwise increase as CCS increased.

CONCLUSION

Stepwise increased risk of coronary events associated with increasing CCS is caused by increasing incidence of significant stenosis, while that of high-risk plaque remains the same.