Introduction Mechanical energy losses are thought to be associated with aberrant aortic flow patterns in the presence of valvular disease that lead to increased afterload. The aim of this study was to compare viscous energy losses in the aortas of subjects with bicuspid aortic valves (BAV) and tricuspid aortic valves (TAV) with severe aortic stenosis (AS), both before and after aortic valve replacement (AVR). Methods Viscous energy losses were measured in the thoracic aorta of prospectively recruited patients using four-dimensional flow cardiac magnetic resonance imaging (4DF-CMR). Peak systolic and diastolic viscous energy losses were measured between the aortic root reference plane and the mid-ascending aorta (MAAo) and proximal aortic arch (PAA) anatomical planes using Circle Cardiovascular Imaging (Cvi42) (figures 1 and 2). Analysis of covariance was adjusted for confounding variables, age and diastolic blood pressure. Results We recruited 27 subjects with severe AS (BAV-AS n=10, age= 62 ± 12 years; TAV-AS n=17, age= 72 ± 5 years) and 9 healthy TAV controls (age= 58 ± 4 years). Twenty-four patients (BAV n=6, TAV n = 18) returned for 4DF-CMR an average 423 ± 52 days post-AVR. There were no statistically significant differences in viscous energy losses between the pre-AVR BAV-AS and TAV-AS patients (table 1). In post-AVR TAV patients, significant reductions were demonstrated at peak systole and diastole at the MAAo and PAA, which were normalised towards the TAV control values (table 2). However, no significant reduction occurred in the post-AVR BAV patients, and viscous energy losses remained significantly higher compared to the TAV control values (table 2). Conclusion Viscous energy losses are similarly elevated in BAV and TAV patients with concurrent severe AS. AVR results in reduction in these parameters, but this was only significant in TAV subjects and remained significantly higher in BAV patients compared to TAV controls. 4DF-CMR-derived viscous energy losses may be a sensitive biomarker for increased ventricular afterload when monitoring BAV phenotype for post-AVR complications.
Nourolahi-Oskoui et al. (Wed,) studied this question.