Coronary computed tomography angiography based endothelial wall shear stress in normal coronary arteries

Background

Endothelial wall shear stress (ESS) is a biomechanical force which plays a key role in the formation and evolution of atherosclerotic lesions.

Purpose

This study aims to evaluate ESS in coronary arteries without atherosclerosis, and to assess various factors affecting ESS values.

Methods

Coronary computed tomography angiography (CCTA) images from patients with suspected coronary artery disease were analyzed to identify coronary arteries without atherosclerosis. Minimal and maximal ESS values were calculated for 3-mm segments with dedicated software. Segments were categorized according to lumen diameter tertiles into small (<2.6 mm), intermediate (2.6–3.2 mm) or large (≥3.2 mm) size classes. Normal ranges of minimal and maximal ESS values were calculated per vessel and vessel size.

Results

A total of 349 normal vessels from 168 patients (mean age 59.4±9.2 years, 39% men) were included. ESS was highest in the left anterior descending artery compared to the left circumflex and the right coronary arteries (2.3 Pa vs. 1.9 Pa vs. 1.6 Pa for minimal ESS, p<0.001 and 3.7 Pa vs. 3.0 Pa vs. 2.5 Pa for maximal ESS, p<0.001). ESS values were highest in small vessel segments compared to intermediate or large segments (3.8 Pa vs. 1.7 Pa vs. 1.2 Pa for minimal ESS, p<0.001 and 6.0 Pa vs. 2.6 Pa vs. 2.0 Pa for maximal ESS, p<0.001). Weak to moderate correlation was found between ESS and the distance from the ostium (ρ values ranging from 0.22 to 0.62 for different vessels).

Conclusion

We derived ESS values from the CCTA images for visually normal coronary arteries. ESS values depend strongly on the lumen diameter of the coronary vessel. The normal ranges of minimal and maximal ESS can be used in future studies, where ESS values in stenotic lesions are compared to the normal values derived in the present analysis.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Finnish Foundation for Cardiovascular Research

Calcified versus non-calcified plaque volume fraction in patients with coronary artery disease and their association with outcome

Background

The amount of coronary artery calcification is a general marker of coronary atherosclerosis and has been associated with increased risk of adverse cardiac events. On the other hand, calcification of coronary artery plaques has also been considered as a marker of plaque stabilization.

Purpose

We hypothesized that the fraction of the non-calcified volume of the total plaque volume in patients with coronary artery disease (CAD) is associated with abnormal myocardial perfusion and increased risk of future cardiac events.

Methods

Consecutive patients with suspected CAD undergoing sequential coronary computed tomography angiography (CCTA) with selective positron emission tomography (PET) perfusion imaging between 2007 and 2011 were selected. The total, calcified and non-calcified plaque volume (PV) were defined at patient-level. The non-calcified plaque volume fraction was calculated by dividing the non-calcified PV by the total PV, and expressed as percentage. Patients were divided into three groups: patients with 1) non-obstructive CAD (<50% diameter stenosis), 2) suspected coronary stenosis but normal PET perfusion and 3) suspected stenosis and abnormal regional PET perfusion. Difference between high vs. low PV was based on the median value. Clinical outcomes including all-cause mortality and myocardial infarction were recorded for 6.1 [SD 5.3–7.5] years.

Results

In total, 494 patients (age 63±9 years, 55% male) with documented atherosclerosis on CCTA were included. Total PV, calcified PV and non-calcified PV were all significantly larger in patients with abnormal myocardial perfusion compared to patients with non-obstructive CAD (370 [197–739] mm3 vs. 108 [59–177] mm3, 84 [23–220] mm3 vs. 9 [1–34] mm3 and 274 [157–500] mm3 vs. 94 [53–140] mm3, respectively, p<0.001 for all). However, the non-calcified fraction was smaller in patients with reduced myocardial perfusion (75 [63–86]% vs. 89 [76–98]%, p<0.001, Figure 1). During follow-up 35 events occurred. Patients with higher total PV, calcified PV and non-calcified PV showed worse outcome compared to patients with lower PV (log-rank p<0.001, Figure 2). In contrast, patients with a lower non-calcified plaque volume fraction showed poorer outcome (log-rank χ2=5.54; p=0.019) even after adjusting for statin therapy or revascularization.

Conclusion

We observed that higher volumes of any plaque component in general are associated with abnormal perfusion and increased risk of future cardiac events. In contrast, patients with a lower non-calcified plaque volume fraction showed poorer outcome.

Funding Acknowledgement

Type of funding sources: None. Non-calcified plaque volume fractionKaplan-Meier survival analysis

P861A quantitative CCTA evaluation in non-obstructive coronary artery disease for the diagnosis of vessel-specific ischemia: results from the prospective, multicenter, international CREDENCE trial

Aim

To improve the diagnosis of coronary vessel-specific ischemia in non-obstructive coronary artery disease (CAD) using a quantitative whole-heart coronary computed tomography angiography (CCTA) evaluation. To date, predictors of ischemia in non-obstructive CAD remain underexplored.

Methods

Within the CREDENCE trial, 612 patients with suspected CAD at 13 sites (64±10 years, 70% men) underwent coronary computed tomography angiography (CCTA) and invasive coronary angiography with 3-vessel fractional flow reserve (FFR) measurements. For this specific analysis, only vessels with non-obstructive plaque (1–49% maximal diameter stenosis) by CCTA were included. The primary endpoint was coronary vessel-specific ischemia which was defined as FFR ≤0.80 (or ≥90% stenosis). Multivariable logistic regression modeling was performed to evaluate the effect of quantitative CCTA features beyond coronary stenosis on the prevalence of vessel-specific ischemia.

Results

FFR ≤0.80 (or ≥90% stenosis) was prevalent in 22.8% of 1,102 vessels with non-obstructive plaque. Using a step-wise approach, in addition to diameter stenosis (χ2=72), non-calcified PAV (χ2=126, P<0.001), lumen volume (χ2=175, P<0.001) and number of lesions with >30% stenosis (χ2=187, P=0.001) were independent CCTA-predictors of coronary vessel-specific ischemia (Figure 1). In the final model, diameter stenosis was no longer significantly associated with ischemia (P=0.236).

Figure 1

Conclusion

In vessels with non-obstructive plaque on CCTA, ischemia was present in approximately 20%. Measures of overall non-calcified plaque burden and smaller lumen volume were more important determinants of vessel-specific ischemia than maximal diameter stenosis.

Acknowledgement/Funding

NIH R01-HLL118019; Dalio Foundation and Michael J. Wolk Foundation

P868Temporal remodeling of coronary arteries during progression of atherosclerosis with serial coronary CT angiography using 3D metrics: results from the PARADIGM study

Aim

To determine compensatory enlargement and luminal reduction of coronary arteries during the progression of atherosclerosis with serial coronary computed tomography angiography (CCTA) by using volumetric measurements. To date, the impact of coronary plaque progression on temporal remodeling, as opposed to the static remodeling, has only been studied with invasive imaging modalities and primarily two-dimensional areas rather than three-dimensional volumes.

Methods

In total, 1,245 patients with suspected coronary artery disease (CAD) at 13 sites (61±9 years, 39% women) underwent serial CCTA with interscan interval of ≥2 years. The primary objective was to assess volumetric temporal remodeling, defined as the linear association between the change in coronary plaque, lumen and vessel volume at follow-up CCTA on a per-segment level. Temporal remodeling was determined in strata of low and high baseline plaque burden as well as different coronary segments at baseline. Linear regression analysis and Pearson's correlation coefficients were calculated to assess associations.

Results

Amongst 1,245 patients with 19,920 segments, the median interscan interval was 3.3 (IQR 2.6–4.8) years. For each 1 mm3 increase in plaque volume, the increase in vessel volume was 0.72 mm3 and the decrease in lumen volume was 0.28 mm3 (Figure 1, both p<0.001). Volumetric temporal remodeling was similar in low versus high PAV [0.70 mm3 vs 0.73 mm3 (p for interaction=0.491)] and left-main arteries versus all other segments [0.78 mm3 vs. 0.72 mm3 (p for interaction=0.336)], but not in proximal versus distal segments at baseline [0.75 mm3 vs. 0.61 mm3 (p for interaction=0.020)].

Figure 1. Volumetric temporal remodeling

Conclusion

In general, coronary plaque grows approximately 70% outward and 30% into the coronary lumen during the progression of atherosclerosis. Volumetric temporal remodeling is not limited by baseline plaque burden, but is potentially dependent on its location within the coronary artery tree.

Acknowledgement/Funding

NRF of Korea (Grant No. 2012027176); Dalio Institute of Cardiovascular Imaging and Michael J. Wolk Foundation

4182Sex specific patterns in the onset and manifestation of coronary atherosclerotic plaque; insights from the multi-center CCTA CONFIRM registry

Background

Pathobiologic data support varied atherosclerotic plaque characteristics which uniquely define risk in women as compared to men (i.e., plaque erosion versus rupture). The advent of noninvasive coronary computed tomographic angiography (CCTA) allows for further exploration as to a sex-specific signature of atherosclerotic plaque features unique to women and different from that of men. In this analysis, we compared sex differences in the age of onset of coronary atherosclerosis and varied plaque findings between women and men.

Methods

From the multicenter CONFIRM registry, the Leiden CCTA score (based on segmental plaque extent, location, severity, and composition) was calculated in women and men without prior CAD, with imputation for missing plaque data. First, women and men were matched on the Leiden CCTA score to allow assessment of differences in atherosclerotic profile. Second, the earliest age of women and men to display a median Leiden CCTA score >0, >2, >6, >8 was evaluated. Third, the prognostic value of previously established thresholds of the Leiden CCTA score was examined for all-cause mortality with Cox-proportional hazard analysis, and specifically a sex interaction.

Results

In total, 11,678 women (age 58.5±12.4 years) and 13,272 men (age 55.6±12.5 years) were included. Of the patient subset matched on Leiden CCTA score (10,266 women, score 4.1±6.0 and 10,266 men, Leiden score 4.1±6.0, P=0.589), women were characterized by less obstructive CAD (≥50% stenosis) (17.5% vs 19.1%, P=0.003), more frequent non-obstructive left main plaque (10.1% vs 8.9%, P=0.004) and a lower number of segments with non-calcified or mixed plaque, but an equal number of calcified plaques. The earliest age when women and men have a median Leiden CCTA score above 0, 2, 4, 6, or 8 was consistently 14 to 16 years later for women. A visual representation of the CAD development delay is shown in Figure 1. Adjusted for age, the hazard ratio for death (827 events) for a score 6–20, and >20 (compared with 0–6) was 1.95 (95% CI 1.56–2.42), and 3.44 (95% CI 2.40–4.93) for women, respectively, and 1.63 (95% CI 1.31–2.03), 2.22 (95% CI 1.64–3.00) for men, respectively (P-interaction 0.006). Despite the low number of events, women <50 years with a score >20 were at 12.8 (95% CI 3.58–45.73) times increased risk.

Conclusion

There is an approximate 15-year delay in onset of coronary atherosclerosis for women compared to men. The burden of atherosclerotic plaque is associated with a higher relative hazard for death among women than men. The pattern of more nonobstructive CAD, especially in the left main coronary artery, but also less non-calcified plaque supports a sex-specific plaque signature which may uniquely define risk among women as compared to men.

Acknowledgement/Funding

The research reported in this manuscript was funded, in part, by the National Institute of Health (Bethesda, MD, USA) under award number R01 HL115150.