Left ventricular myocardial tissue characteristics and function among healthy subjects with varying atherosclerotic cardiovascular disease risk

Abstract The Atherosclerotic Cardiovascular Disease Risk (ASCVD) score by pooled cohort equation is a reliable predictor for future ASCVD events and is used to guide primary prevention in asymptomatic aging subjects. ASCVD risk is associated with burden of coronary artery disease as measured from computed tomography angiography. Purpose We aim to investigate the association between ASCVD risk and cardiac magnetic resonance (CMR) derived left ventricular (LV) myocardial tissue characteristics (T1 values) and LV systolic and diastolic ventricular function in a large cohort of healthy subjects. Methods We selected all healthy subjects who underwent CMR from the UK-Biobank cohort study. We collected patient characteristics, cardiovascular risk factors, blood pressure at CMR, medication use and cholesterol levels. We used AI-CMRQC, our quality-controlled tool for analysis of cardiovascular function metrics from CMR using artificial intelligence [1,2], to automatically extract septal T1 values from native T1 maps and LV ejection fraction (EF), peak ejection and early filling rates (PER, PEFR), peak systolic longitudinal strain and diastolic strain-rate, mitral valve annular plane systolic excursion and diastolic peak velocity from cine long and short axis acquisitions. Subjects were stratified for low (<7.5%), intermediate (7.5–21%) and high (>21%) ASCVD risk. One-way repeated measures ANOVA was used to examine the association between cardiovascular metrics and ASCVD risk groups. Results 12,493 healthy subjects were included (females n=6,000). Mean age was 62.7±7.5 years, 3.2% had diabetes, 12.5% received treatment for hypertension and 23% smoked. ASCVD risk score could be calculated in 9,487 subjects. Mean ASCVD risk was 12.7±9%. 38% of subjects had low, 43% intermediate and 19% high ASCVD risk. T1 values fell across the incremental ASCVD groups (low: 943±51 ms, intermediate: 921±47 ms, high: 918±50 ms, P<0.001). Indexed LV PEFR (low: 188±45 ml/ms·m2, intermediate: 170±48 ml/ms·m2, high: 147±45 ml/ms·m2, P<0.001), diastolic longitudinal strain rate (low: 1.25±0.36, intermediate: 1.20±0.37, high: 1.17±0.36, P<0.001) also fell consistently with incremental risk. A statistically significant, but clinically less relevant decrease was seen for LVEF (low: 59±6%, intermediate 58±6%, high: 57±6% p<0.001) and longitudinal systolic strain (low: 21±3.5%, intermediate: 21±3.4%, high: 21±3.5%). Conclusion Increasing ASCVD risk was associated with lower native T1 values and decreasing metrics of diastolic and systolic LV function. The fall in T1 might suggest fibrofatty replacement in the LV myocardium in patients with incremental ASCVD risk that could contribute to the observed deterioration of LV function. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): NIHR MedTech cooperation awarded to Guy's and ST Thomas NHS Foundation Trust