Abstract
BackgroundPhase contrast (PC) cardiovascular magnetic resonance (CMR) in the ascending aorta (AAo) is widely used to calculate left ventricular (LV) stroke volume (SV). The accuracy of PC CMR may be altered by turbulent flow. Measurement of SV at another site is suggested in the presence of aortic stenosis, but very few data validates the accuracy or inaccuracy of PC in that setting. Our objective is to compare flow measurements obtained in the AAo and LV outflow tract (LVOT) in patients with aortic stenosis.MethodsRetrospective analysis of patients with aortic stenosis who had CMR and echocardiography. Patients with mitral regurgitation were excluded. PC in the AAo and LVOT were acquired to derive SV. LV SV from end-systolic and end-diastolic tracings was used as the reference measure. A difference ≥ 10% between the volumetric method and PC derived SVs was considered discordant. Metrics of turbulence and jet eccentricity were assessed to explore the predictors of discordant measurements.ResultsWe included 88 patients, 41% with bicuspid aortic valve. LVOT SV was concordant with the volumetric method in 79 (90%) patients vs 52 (59%) patients for AAo SV (p = 0.015). In multivariate analysis, aortic stenosis flow jet angle was a strong predictor of discordant measurement in the AAo (p = 0.003). Mathematical correction for the jet angle improved the concordance from 59 to 91%. Concordance was comparable in patients with bicuspid and trileaflet valves (57% and 62% concordance respectively; p = 0.11). Accuracy of SV measured in the LVOT was not influenced by jet eccentricity. For aortic regurgitation quantification, PC in the AAo had better correlation to volumetric assessments than LVOT PC.ConclusionLVOT PC SV in patients with aortic stenosis and eccentric jet might be more accurate compared to the AAo SV. Mathematical correction for the jet angle in the AAo might be another alternative to improve accuracy.
Highlights
Phase contrast (PC) cardiovascular magnetic resonance (CMR) in the ascending aorta (AAo) is widely used to calculate left ventricular (LV) stroke volume (SV)
Our objectives are to compare flow measurements obtained by PC in the ascending aorta (SVAAo) and the LV outflow tract (LVOT) (SVLVOT) in patients with various degrees of aortic stenosis
The main findings of this study are: (1) in patients with aortic stenosis, Stroke volume measured at the LVOT (SVLVOT) has better overall agreement to volumetric measurements than Stroke volume measured at the ascending aorta (SVAAo); (2) jet eccentricity is the main factor associated with discordant S VAAo; (3) mathematical correction using measured SV and eccentricity angle corrected the discordance in our population and (4) consistent with previous studies and current recommendation, aortic regurgitant volume is likely underestimated when assessed in the LVOT
Summary
Phase contrast (PC) cardiovascular magnetic resonance (CMR) in the ascending aorta (AAo) is widely used to calculate left ventricular (LV) stroke volume (SV). The accuracy of PC CMR may be altered by turbulent flow. Phase-contrast (PC) is the main approach to quantify blood flow parameters with cardiovascular magnetic resonance (CMR). The Guzzetti et al J Cardiovasc Magn Reson (2021) 23:124 accuracy of PC may be altered by the presence of turbulent flow. Such turbulence typically occurs in patients with heart valve diseases and stenotic or regurgitant jets, which are associated with flow acceleration/deceleration and intravoxel dephasing [4,5,6]. Regurgitant or stenotic valves are associated with flow eccentricity, increasing the difficulty to optimize the correct imaging plane
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