Abstract Background Myocardial oxygenation changes observed with Oxygenation-Sensitive Cardiovascular Magnetic Resonance (OS-CMR) during vasoactive breathing manoeuvres are a validated marker for coronary vascular function across multiple cardiovascular pathologies. Previous literature has measured myocardial oxygenation markers derived from a prolonged breath-hold following paced hyperventilation. This study aimed to assess myocardial oxygenation responses during a brief breath-hold, without hyperventilation, as a marker for vascular function associated with cardiovascular risk factors. Purpose To assess the utility of OS-CMR with a brief breath-hold to identify markers of vascular function associated with cardiovascular risk factors. Methods This was a cross-sectional, single-centre study recruiting sex- and age-matched healthy controls and individuals with metabolic risk factors (≥3) but no overt cardiovascular disease. All subjects underwent an OS-CMR exam on a 3T Signa Premier scanner, including a brief breath hold (10s). Myocardial contours were generated using an automated algorithm of a certified software, while signal intensity parameters were extracted using a custom Python script. The script also calculated heterogeneity as defined by myocardial signal entropy, i.e. the inter-pixel standard deviation in images across the cardiac cycle. T tests with Bonferroni correction were used to evaluate between-group differences, and multiple linear regression analyses within each group were used to explore the association of risk factors with heterogeneity. Results 34 healthy controls (50% female, mean age 55±10 years) and 34 at-risk individuals (50% female, mean age 55±10 years) were studied. Myocardial signal entropy across the baseline breath-hold was significantly reduced in the at-risk group (124±7.49) compared to healthy controls (136±5.7, p0.0001). The multiple linear regression analysis showed a significant impact of known metabolic risk factors on baseline entropy within each group; the multivariable model included age, sex, systolic and diastolic blood pressure, HBA1C, triglycerides, HDL cholesterol, and waist circumference. In the at-risk group, waist circumference (β= -0.32±0.10, p=0.006) and sex (β= -5.6±2.1, p=0.01) were inversely associated with baseline entropy. In contrast, in the control group, no factors within the model were significantly associated to baseline entropy. Conclusion Visualized with OS-CMR across a brief baseline breath hold, heterogeneity of myocardial oxygenation is associated with presence of cardiovascular risk factors. In individuals with risk factors, this response was inversely associated to waist circumference, suggesting that abdominal obesity may moderate this response. The clinical utility of this novel marker for cardiovascular risk assessment should be further explored.Entropy and Waist Circumference
Lindsay et al. (2026) studied this question.