Aortic diastolic flow displacement from phase-contrast CMR is associated with exercise capacity in healthy adults

Abstract

Abstract Background Blood flow eccentricity, as determined by phase contrast (PC) CMR-assessed peak systolic flow displacement, has been linked to future aortic enlargement in patients with bicuspid aortic valve and thoracic aortic aneurysm. Its presence, extent and functional consequence in healthy adults are unknown. Purpose We quantified aortic flow eccentricity and studied its association with exercise capacity in a cohort of healthy Asian subjects using 2-dimensional (2D) PC-CMR and cardiopulmonary exercise testing (CPET), respectively. Method 169 community healthy volunteers (age 44±13 years, M:F 96:73) without cardiovascular diseases (the control group in a prospective observational study NCT03217240) underwent CMR, including 2D PC at an orthogonal plane just above the sinotubular junction, and CPET within one week. From 2D PC-CMR, we obtained the average flow displacements (FD) during systole (avFDSys), late systole (avFDLateSys) and diastole (avFDDias), as well as flow reversal ratios (FRR) during systole (FRRSys) and the whole cardiac cycle (FFRRR) (see Figure). Exercise capacity was determined by peak VO2 (PVO2) from CPET. Univariate analysis and multivariable regression using a model that included FD and FRR parameters as well as standard cine CMR-assessed left ventricular (LV) volumes and ejection fraction were performed to investigate the determinants of PVO2. Results Mean values of average flow displacements (avFDSys, avFDLateSys, avFDDias), and flow reverse ratios (FRRSys and FRRRR) were 17±6%, 19±8%, 29±7%, 5.9±5.1%, and 13.7±8.0%, respectively, which were positively correlated with age (R values of 0.623, 0.628, 0.353, 0.649, 0.708, respectively; all P <0.0001) and negatively correlated with PVO2 (R values of -0.302, -0.270, -0.253, -0.219, -0.205, respectively, all P <0.01). Women had higher avFDSys (18±7 vs. 15±6%, P=0.003) and avFDLateSys (21±9 vs. 18±8%, P=0.007), and lower PVO2 (median 21 vs. 26ml/kg/min, P <0.001) compared with men. On multivariable analysis, avFDDias (=-0.234, P=0.002) and LV end-diastolic volume (=0.116, P <0.001) were significantly associated with PVO2 after adjustment for age. For every 10-year increase in age, avFDDias increased by 1.4% in men and 2.6% in women; and for every 1% increase in avFDDias, PVO2 decreased by 0.2 ml/kg/min in men and 0.3 ml/kg/min in women. Conclusion Compared with men, women had more eccentric and less efficient aortic flow, and exhibited a higher ageing-related increase in avFDDias. The latter was independently associated with reduced PVO2, which lends support to its functional significance and potential application as a marker of cardiovascular health.Figure 1