Coronary CT angiography derived pericoronary inflammation and bespoke cardiovascular risk prediction in the lipid clinic: beyond the calcium score

Background

Dyslipidaemia promotes atherosclerosis. Genetic dyslipidaemias, Familial Hypercholesterolaemia (FH) being the most common, are associated with heightened risk of coronary artery disease (CAD) and premature major adverse cardiovascular events (MACE). However, this risk is both heterogeneous and modifiable with treatment.

CT coronary imaging can identify subclinical atherosclerosis, enabling personalised risk stratification and treatment targets. Coronary artery calcium scoring (CACS) is current first-line in European guidelines for asymptomatic patients. However, calcification occurs late in CAD pathogenesis and CACS has low specificity in young patients with severe FH. CT coronary angiography (CTCA) assesses non-calcific plaque and high-risk plaque (HRP) features unappreciable with CACS. Additionally, the pericoronary fat attenuation index (FAI) measures inflammation on routine CTCA and is the strongest non-invasive imaging biomarker of risk of fatal MI.

Purpose

To quantify and compare the reclassification of subclinical atherosclerosis burden in Lipid Clinic patients assessed via CACS vs CTCA with FAI analysis.

Methods

Analysis of a prospectively maintained clinical database of asymptomatic Lipid Clinic patients with both CACS and CTCA imaging from May 2019 to December 2020. CACS was reported with the standardised Agastston criteria and compared with (i) the CTCA-derived Coronary Artery Disease – Reporting and Data System (CAD RADS) grading of anatomical stenosis, including a modifier for HRP features, and (ii) FAI analysis. Significance was defined as two-tailed p75th percentile vs age and sex matched controls) was seen in 6/27 (22%) patients with none to mild calcification on CACS and 6/28 (21%) patients with none to mild CAD on CTCA, of whom 3/7 (43%) had HRP. High FAI was seen in all groups of calcification severity and CAD RADS score (Figure 2). The proportion with high FAI was higher in CAD RADS 0 vs CAD RADS 4, and CACS severity was not associated with level of inflammation (p=0.94).

High FAI was observed in 16% of patients on treatment, suggesting treatment failure. This included patients with CACS ranging from 0 to severe (>400), and CAD RADS of minimal (1) to severe (4).

Conclusion

CTCA re-stratifies CAD presence and severity vs CACS in a high-risk, asymptomatic patient group and identified a high proportion of patients with HRP features. FAI provides incremental value in identification of patients at risk of future MACE regardless of CACS grade, including patients without evidence of overt CAD. Identifying high FAI on treatment may imply treatment failure.

Funding Acknowledgement

Type of funding sources: None.

Automated quantification of epicardial adipose tissue on CCTA via deep-learning detection of the pericardium: clinical implications

Background

Epicardial adipose tissue (EAT) is a visceral fat deposit within the pericardial sac which surrounds the heart myocardium and coronary arteries. EAT volume has been demonstrated to be strongly associated with the development and prognosis of cardiovascular diseases, but its measurement is subjective and challenging in practice.

Purpose

To develop a deep-learning approach for automated segmentation of EAT from routine CCTA scans, that could assist clinical interpretation of CCTA.

Methods

A deep-learning method using a 3D Residual-U-Net neural network architecture for 3D volumetric segmentation of CCTA data was created. The network was trained on a diverse sample of 1900 CCTAs, each manually segmented by a single expert, drawn from the UK sites of the Oxford Risk Factors And Non-invasive imaging (ORFAN) Study. Three iterations of feedback learning were used to fine tune the algorithm for the segmentation of the whole heart within the bounds of the pericardium. In each iteration, the machine analysed sets of 100–250 unannotated CCTAs unseen by the machine which were then corrected by experts. EAT volumes were calculated by automated thresholding of adipose tissue (−190HU through −30HU) from within the bound of the pericardial segment (Figure 1). The network was then applied to 817 unseen CCTAs from US sites of the ORFAN Study. These scans were also segmented for ground truth by two experts blind to all other data. Comparisons between machine vs expert total pericardial volume and EAT volume were made using Lin's concordance correlation coefficient (CCC). The algorithm was then applied externally in 1588 CCTAs from the SCOTHEART trial (UK), and the EAT volume was automatically calculated for each case. Cross-sectional associations between standardised EAT volumes and prevalent AF and CAD were performed.

Results

Within both the internal (UK ORFAN sites) and external (USA ORFAN sites) validation cohorts correlation between human and machine segmented total pericardium and EAT was excellent, with CCC of 0.97 for both volumes (external validation cohort shown in Figure 2A). Utilising SCOTHEART CCTAs with automatically segmented EAT volumes, a multivariable-adjusted logistic regression model accounting for risk factors of age, sex, BMI, hypertension, diabetes mellitus, valvular disease, and previous heart surgery found that EAT volumes were significantly associated with prevalent AF, with odds ratio (OR) per 1 SD increase of EAT volume of 1.20 (95% CI, 1.06 to 1.44; P=0.03). A similar model for prevalent CAD, adjusted for age, sex, BMI, hypertension, non-HDL cholesterol, diabetes mellitus, and coronary artery calcium score resulted in an OR per 1 SD increase of EAT volume of 1.26 (95% CI, 1.10 to 1.45; P=0.001) (Figure 2B).

Conclusion

Highly accurate, reproducible, and instantaneous EAT volume quantification is possible utilising deep-learning detection of the whole human heart within the pericardial sac.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): British Heart FoundationNational Institute for Health Research - Oxford University Hospitals Biomedical Research Centre Figure 1Figure 2

Long-term cardiac risk in individuals with low calcium score on coronary computed tomography angiography can be stratified by the pericoronary fat radiomic profile (FRP)

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): UKRI, British Heart Foundation

Background

Inflammation in the coronaries induces macroscopic changes in perivascular adipose tissue composition, detectable by the pericoronary Fat Radiomic Profile (FRP) on coronary computed tomography angiography (CCTA).

Purpose

To assess the ability of FRP to stratify cardiac risk in patients with Coronary Artery Calcium (CAC) score below 100 following routine CCTA.

Methods

1,575 participants from the CCTA arm of the SCOT-HEART trial (NCT01149590) eligible for image analysis were included. Pericoronary FRP mapping was performed in perivascular adipose tissue segmentations around the proximal sites of the right and left coronary arteries, as previously validated. We first tested the prognostic value of FRP in the sub-cohort of patients with CAC < 100. We further analysed a sub-group based on the absence of high risk plaque (HRP) features and obstructive coronary artery disease (CAD). The association with future incidence of major adverse cardiac events (MACE: cardiac mortality or non-fatal myocardial infarction) or a composite endpoint of MACE ± late revascularization (MACE-ReVasc) was assessed using adjusted Cox regression models [adjusted for age, sex, systolic blood pressure (SBP), diabetes mellitus (DM), body mass index (BMI), smoking, CAD (≥50% stenosis), total cholesterol, high-density lipoprotein (HDL), and HRP features].

Results

In total, 1,032 patients (53.9% female sex) were found with low CAC score (CAC < 100), with a median age of 55 years. Over a mean follow-up of 4.87 ± 1.06 years, 12 MACE and 47 MACE-ReVasc were recorded. High FRP was associated with a 14.4-fold (95% CI: 3.80-54.78, p < 0.001) higher adjusted risk of MACE and a 2.8-fold (95% CI: 1.49-5.36, p = 0.001) higher adjusted risk of MACE-ReVasc (A). Addition of high FRP to a baseline model consisting of traditional risk factors (age, sex, systolic blood pressure, diabetes mellitus, BMI, smoking, CAD (≥50% stenosis), total cholesterol, HDL, HRP) significantly enhanced (deltaAUC at 5 years:0.15, p = 0.03) the model’s performance and reclassified individuals (NRI = 0.59, p = 0.02, B). Interestingly, after more rigorous filtering of the population by absence of HRP features and obstructive CAD, high FRP remained an independent predictor of MACE (n = 756, Adj.HR = 28.1, p = 0.003).

Conclusion

In individuals with low CAC scores the Fat Radiomic Profile biormarker significantly improves risk prediction for adverse clinical events beyond the current state-of-the-art. Non-invasive profiling of pericoronary adipose tissue using CCTA-derived FRP captures irreversible changes in perivascular adipose tissue composition associated with chronic vascular inflammation and atherosclerotic disease, and can supplement the traditional anatomical assessment of the coronary vasculature with a functional marker of disease activity.

Direct effects of canagliflozin on human myocardial redox signalling: a novel role for SGLT1 inhibition

Background

Recent clinical trials have demonstrated a role for sodium glucose cotransporter 2 (SGLT2) inhibitors in improving cardiovascular outcomes in heart failure patients, but the underlying mechanisms remain unknown. We investigated the direct effects of canagliflozin, a non-selective SGLT1/SGLT2 inhibitor on myocardial redox signalling in humans.

Methods

Study 1 included 364 patients undergoing cardiac surgery. Human right atrial appendage biopsies, obtained during surgery, were used to quantify the sources of superoxide (O2.-) and the gene expression of inflammation, fibrosis and myocardial stretch markers. In Study 2, myocardial biopsies from 51 patients were used ex vivo to study the direct effects of canagliflozin on O2.- generation and understand its role in controlling the activity of NADPH-oxidases and uncoupled nitric oxide synthase (NOS). Finally, we used differentiated H9C2 and human primary cardiomyocytes (hCM) to further characterise the key regulatory mechanisms (Study 3).

Results

SGLT1 was abundantly expressed in the human myocardial biopsies and hCM whilst SGLT2 was barely detectable. SGLT1 expression levels were positively correlated with basal O2.- production and the expression of natriuretic peptides, proinflammatory cytokines and pro-fibrotic markers in human myocardial biopsies from study 1. Incubation of human myocardium with canagliflozin significantly reduced basal and NADPH-oxidase-derived O2.- via AMP kinase (AMPK)-mediated suppression of GTP-activation and consequent reduction of membrane translocation of Rac1, an NADPH-oxidase subunit. This resulted in reduced oxidation and increased bioavailability of tetrahydrobiopterin, the nitric oxide synthase (NOS) co-factor essential for enzymatic coupling, leading to improved NOS coupling. These findings were replicated in hCM, where canagliflozin was shown to regulate AMP/ATP ratio, which could be upstream of AMPK activation. The effects of canagliflozin were significantly attenuated by knocking-down SGLT1 in hCM. Transcriptional profiling of hCM treated with canagliflozin revealed that canagliflozin had striking effects on myocardial redox signalling, causing suppression of apoptotic and inflammatory pathways in the human heart.

Conclusions

We demonstrate for the first time in humans that canagliflozin suppresses myocardial NADPH-oxidase activity and improves NOS coupling through an SGLT1/AMPK/Rac1-mediated pathway, leading to global anti-inflammatory and anti-apoptotic effects in the human myocardium. These findings provide a mechanistic basis for the beneficial effects of SGLT1/2 inhibitors in patients with heart failure.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): 1. British Heart Foundation (FS/16/15/32047 and PG/13/56/30383 to CA, CH/16/1/32013 to KC, and Centre of Research Excellence award RG/13/1/30181), 2. The Japanese Heart Rhythm Society-European Heart Rhythm Association fellowship grant sponsored by Biotronik.

Pericoronary fat radiomic profile (FRP) predicts long-term cardiac risk in individuals with calcium score below 100 on coronary computed tomography angiography

Background

Coronary computed tomography angiography (CCTA) provides useful information regarding cardiovascular risk assessment. Key aspects of coronary biology induce changes in perivascular adipose tissue composition, detectable by the pericoronary Fat Radiomic Profile (FRP) index.

Purpose

We assessed the ability of FRP to further stratify cardiac risk in patients with Coronary Artery Calcium (CAC) scoring below 100 following routine CCTA.

Methods

The study population consisted of 1,575 participants from the CCTA arm of the SCOT-HEART trial (NCT01149590) with images available and eligible for analysis. Pericoronary FRP mapping was performed in perivascular adipose tissue segmentations around the proximal sites of the right and left coronary arteries, as previously validated. The prognostic potential of FRP was initially tested in a sub-cohort, consisting of patients with Coronary Artery Calcium (CAC) score lower than 100. Further analysis was performed after sub-grouping based on the absence of high risk plaque (HRP) features and obstructive coronary artery disease (CAD). The association with future incidence of major adverse cardiac events (MACE: cardiac mortality or non-fatal myocardial infarction) or a composite endpoint of MACE ± late revascularization (MACE-ReVasc) was assessed using adjusted Cox regression models [adjusted for age, sex, systolic blood pressure (SBP), diabetes mellitus (DM), body mass index (BMI), smoking, CAD (≥50% stenosis), total cholesterol, high-density lipoprotein (HDL), and HRP features].

Results

Two-thirds (66%) of the study population were at low-risk according to the CAC score (CAC<100). Over a mean follow-up of 4.87±1.06 years, 12 MACE and 47 MACE-ReVasc were recorded. In this sub-cohort, high FRP was associated with a 14.4-fold (95% CI: 3.80–54.78, p<0.001) higher adjusted risk of MACE and a 2.8-fold (95% CI: 1.49–5.36, p=0.001) higher adjusted risk of MACE-ReVasc. Adding high FRP to a baseline model consisting of traditional risk factors (age, sex, systolic blood pressure, diabetes mellitus, BMI, smoking, CAD (≥50% stenosis), total cholesterol, HDL, HRP) significantly enhanced (deltaAUC at 5 years:0.15, p=0.03) the model's performance (A) and reclassified individuals (NRI=0.59, p=0.02). Interestingly, following further filtering of the population by the absence of HRP features and obstructive CAD, high FRP remained an independent predictor of MACE (B).

Conclusion

The Fat Radiomic Profile biormarker significantly improves risk prediction for adverse clinical events beyond the current state-of-the-art in individuals with low CAC scores. Non-invasive profiling of pericoronary adipose tissue using CCTA-derived FRP captures irreversible changes in perivascular adipose tissue composition associated with chronic vascular inflammation and atherosclerotic disease, and can improve risk stratification and clinical decision making in low-risk populations.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): British Heart Foundation, National Institute of Health Research, Oxford Biomedical Research Centre

3258Perivascular fat attenuation index stratifies the cardiac risk associated with high-risk plaque features on coronary computed tomography angiography

Background

Qualitative high-risk plaque (HRP) features detected on coronary computed tomography angiography (CCTA) are associated with increased risk of adverse cardiac events. Coronary inflammation is a key determinant of plaque progression and instability and can now be captured on routine CCTA as inflammation-induced changes in perivascular adipose tissue composition, detectable by the perivascular Fat Attenuation Index (FAI).

Purpose

To explore the ability of perivascular FAI phenotyping to stratify the cardiac risk associated with the presence of adverse plaque morphology on routine CCTA.

Methods

This was a post-hoc analysis of the CRISP-CT (Cardiovascular RISk Prediction using Computed Tomography) study, which involved 3912 patients (mean age 55.7±13.7 years, 41.1% females) undergoing clinically-indicated CCTA in two centres (Erlangen, Germany & Cleveland, USA). Perivascular FAI mapping was performed around the proximal 10–50 mm of the right coronary artery and defined as the weighted mean attenuation of the perivascular adipose tissue, as previously validated. HRP features were defined as the presence of ≥1 of the following: positive remodelling, low-attenuation plaque, spotty calcification or napkin-ring sign (A). Cox regression models (adjusted for age, sex, epicardial fat volume and coronary artery disease [≥50% stenosis]) were used to explore the association between FAI, HRP, and future major adverse cardiac events (MACE: defined as the composite of cardiac mortality and non-fatal myocardial infarction).

Results

At baseline the prevalence of HRP and high FAI (≥-70.1 Hounsfield Units, as previously validated) was 23.6% (n=923) and 24.3% (n=952) respectively. Over a median follow-up period of 5.6 years (25th-75th percentile: 4.0–7.0 years) there were 91 confirmed MACE. Patients with both HRP features (HRP+) and high FAI (FAI+) had a 6.3-fold (P<0.001) higher adjusted risk of MACE compared to individuals with neither of these risk features (HRP-/FAI-) (B). Furthermore, patients without HRP features but with high FAI (HRP-/FAI+) had a 4.9-fold (P<0.001) higher adjusted risk of MACE compared to the reference (HRP-/FAI-) group. However, among patients with low FAI, there was no significant difference in the prospective risk of MACE between HRP+ and HRP- patients (P=0.87).

Conclusion

FAI is associated with an increased risk of adverse events in both patients with and without high-risk plaques, highlighting coronary inflammation as a major determinant of plaque vulnerability, independent of adverse plaque morphology. Non-invasive characterization of coronary inflammation using CCTA-derived FAI can improve risk stratification by supplementing the traditional anatomical assessment of the coronary vasculature with a functional marker of disease activity.

Acknowledgement/Funding

British Heart Foundation, National Institute of Health Research, Oxford Biomedical Research Centre

Assessment of left atrial volumes at 1.5 Tesla and 3 Tesla using FLASH and SSFP cine imaging

PURPOSE

To investigate left atrial volumes and function and their variability in healthy volunteers using steady state free precession (SSFP) and fast low angle shot (FLASH) sequences at both 1.5 and 3 T using both the short-axis and biplane area-length methods.

MATERIALS AND METHODS

Ten healthy volunteers underwent CMR at both 1.5 and 3 Tesla. The biplane area-length method utilized volumes from the horizontal and vertical long axis images.

RESULTS

There were no significant differences between left atrial short-axis volumes or function between 1.5 and 3 T assessed using either FLASH or SSFP sequences. The biplane area-length method underestimated maximal left atrial volume using FLASH by 12 mL at 3 T (18%) and by 10 mL (14%) at 1.5 T (p = 0.003 and p = 0.05 respectively). Variability was larger for left atrial measurements using the biplane area-length method.

CONCLUSION

Field strength had no effect on left atrial volume and function assessment using either FLASH or SSFP. The use of the short-axis method for the acquisition of left atrial parameters is more reproducible than the biplane area-length for serial measurements.

Semi-automatic boundary detection to improve reporting of regional left ventricular function

AIMS

The reporting of regional left ventricular function is based on subjective assessment of endocardial motion and thickening and has a significant learning curve. We hypothesized that the use of an semi-automatic boundary detection system generating images with superimposed moving endocardial borders and a fixed end-diastolic reference border could improve the reporting of regional function.

METHODS

We obtained 58 resting contrast images of 15 patients and using a new boundary detection system (Quamus), generated images with superimposed endocardial borders. The contrast images, images with additional Quamus borders and Quamus borders alone were assessed by two level 1 and two level 2 echocardiographers. They scored regional function and results were compared to two level 3 experienced stress echocardiography readers.

RESULTS

The addition of borders improved the agreement of level 1 echocardiographers (weighted Kappa increased from 0.55 to 0.64) but did not change for level 2 echocardiographers (0.63 to 0.64) and has the potential to be a useful training tool.

Inhibition of platelet aggregation with glyceryl trinitrate and xanthine oxidoreductase

Xanthine oxidoreductase (XOR) is a mammalian enzyme that possesses a series of redox centers, which use either NAD(+) or molecular oxygen for oxidation of the purines xanthine and hypoxanthine to uric acid. The ability of XOR to act as an NADH oxidase is a less well recognized function of the enzyme, and it is this function that we used to explore the metabolism of glyceryl trinitrate. The antiplatelet effect of nitric oxide (NO) on platelet aggregation was used as a bioassay to assess the bioconversion of glyceryl trinitrate to NO by XOR. The thromboxane mimetic U46619, 2 microM, was used to stimulate platelet aggregation in platelet-rich plasma prepared from healthy drug-free human volunteers. All incubations were carried out at 37 degrees C for 2 min after the addition of U46619. XOR produced a dose-dependent antiaggregant effect when incubated with glyceryl trinitrate (GTN), 220 microM. This did not occur when GTN or XOR was incubated with platelet-rich plasma independently. The antiaggregant effect of XOR plus GTN was dose dependently inhibited by allopurinol, with an IC(50) of 100 microM. The addition of superoxide dismutase (SOD), 100 U/ml produced a shift to the left in the antiaggregant dose-response curve for XOR. The IC(50) for XOR at 200 U/l without SOD was decreased to 80 U/l with SOD. Oxyhemoglobin, an extracellular NO scavenger, produced a dose-dependent, noncompetitive inhibition of the antiaggregant effect of XOR plus GTN. These findings suggest that GTN may be reduced to NO in vitro by the enzyme XOR in sufficient amounts to inhibit platelet aggregation.