SCMR 22nd Annual Scientific Sessions
Left Ventricular Flow Component Analysis (LV-FCA) by 4D-Flow MRI has been previously investigated in normal individuals and patients with dilated cardiomyopathy to evaluate alterations in LV flow distribution. We hypothesized that this technique could be of value to assess the influence of bicuspid aortic valve (BAV) disease and associated aortic regurgitation (AR) on LV hemodynamics.
Methods: 63 subjects, 48 with BAV and 15 healthy controls were prospectively enrolled and completed a standardized MRI protocol at 3T inclusive of whole heart 4D-Flow. Patients with mitral regurgitation were excluded. AR severity was graded by the regurgitant fraction (RFr) as mild, moderate or severe. Within the BAV group, 24 had no AR, 16 had mild, and 8 had moderate or severe AR. The LV was segmented and used to generate pathlines throughout the cardiac cycle (CC) (Fig. 1A-C). Pathlines were considered to represent the whole intraventricular blood volume. LV-FCA was performed by dividing the blood volume into four functional components: 1) Direct flow (DirF): enters LV during diastole and leaves during systole, 2) Retained flow (RetF): enters LV during diastole but does not leave during the first systole, 3) Delayed ejection flow (DelE): resides inside the LV from the former CC and leaves during systole of the following CC, 4) Residual volume (ResV): resides within the LV for at least two successive CCs. Flow analysis planes were prescribed at the aortic and mitral valves to quantify peak velocity (PV), net flow (NF) and regurgitant fraction (RFr) (Fig. 1B).
BAV subjects (age 46±16 years, 14 women) and healthy control subjects (age 32±13 years, 7 women) showed no significant difference in aortic NF (p=0.5). FCA showed significant differences between controls and BAV in DirF (p=0.002) and ResV (p=0.03), (figure 2). A progressive reduction in DirF and a corresponding rise in ResV were observed versus controls for patients with BAV with no AR, BAV with mild AR, followed by BAV with mod-severe AR (p=0.004 across groups), (figure3). Significant correlations were observed between RFr and both DirF (p=0.001) and ResV (p=0.015).
FCA by 4D-Flow MRI identifies significant alterations in LV hemodynamics related to BAV disease, with incremental change seen with superimposed AR. A reduction in DirF (and a rise in ResV) was observed in BAV with no AR, suggesting reduced ejection efficiency. This was exaggerated with increasing severity of AR. Expanded investigation of FCA analysis in BAV and among patients with AR is warranted.