Comprehensive 4D-flow cardiac magnetic resonance evaluation of the descending thoracic aorta in aortic regurgitation

Abstract

Aims: To assess the reproducibility of 4D-Flow cardiac magnetic resonance (CMR) parameters in the descending thoracic aorta-DTAo-(regurgitant fraction [RF], end-diastolic reverse flow [EDRF], and holodiastolic flow reversal [HDR]), and the relationship with RF in the sinotubular junction (STJ), and the left ventricular end-diastolic volume index (LVEDVI) in patients with chronic aortic regurgitation (AR).

Methods and results: A descriptive study of these variables was conducted. A receiver operating characteristic curve was used to determine the optimal cut-off point. Thirty patients had severe AR (RF ≥ 30%, STJ) and 60 mild-to-moderate (RF < 30%). The mean age was 59 ± 17 years. Left ventricular ejection fraction (LVEF) was 56% (53-61%) and LVEDVI was 94 (76-128) mL/m². Flow in the DTAo at the left inferior pulmonary vein (LIPV) was easily identifiable and measurements were highly reproducible. The intraclass correlation coefficient was 0.969 (95% CI: 0.954-0.980) for RF and 0.929 (95% CI: 0.893-0.952) for EDRF. Flow parameters measured at the LIPV were all significantly greater in the severe AR group: RF (21% vs. 6%, P < 0.001), EDRF (20 vs. 4 mL/s; P < 0.001), and HDR (20% vs. 8%; P < 0.001). Three parameters-presence of HDR, RF ≥ 17%, and EDRF ≥ 7 mL/s at the LIPV-were associated with RF ≥ 30% in the STJ and elevated LVEDVI.

Conclusion: 4D-flow CMR can reproducibly assess flow in the DTAo in patients with chronic AR. An RF ≥ 17%, EDRF ≥ 7 mL/s, and/or the presence of HDR in the DTAo (LIPV) were associated with an RF ≥ 30% in STJ and elevated LVEDVI.

Keywords: 4D-flow; aortic regurgitation; cardiac magnetic resonance; descending thoracic aorta; holodiastolic flow reversal.

Graphical abstract

Figure 1

ROC curves. AUC for RF (left) and (EDRF) (right) measured in the DTAo at the LIPV to identify patients with severe AR (RF ≥ 30% at the sinotubular junction).

Figure 2

4D-flow CMR evaluation of the DTAo in patients with AR. (A) Severe AR: Significant regurgitant flow through the aortic valve, with an RF of 35% at the STJ (thin arrow). Qualitative evidence of HDR in the DTAo is observed using streamlines in 3D volumetric reconstruction (thick arrow) and in the derived curve (upper right, HDR compared with baseline). RF is 32%, and EDRF is 29 mL/s at the LIPV. (B) Non-severe AR: Significant regurgitant flow through the aortic valve, with an RF of 30% at the STJ (thin arrow). Qualitative evidence of non-significant flow reversal in the DTAo is observed using streamlines in 3D volumetric reconstruction (thick arrow) and in the derived curve (lower right, without HDR). This is in a patient with AR and complex blood flow patterns (BAV and dilated ascending aorta). RF is 4%, and EDRF is 4 mL/s in the DTAo (LIPV). Abbreviations: Ao, Aorta; AR, aortic regurgitation; DTAo, descending thoracic aorta; EDRF, end-diastolic reverse flow; HDR, holodiastolic flow reversal; IVC, inferior vena cava; LA, left atrium; LIPV, left inferior pulmonary vein; LV, left ventricle; RA, right atrium; RF, regurgitant fraction; STJ, sinotubular junction; SVC, superior vena cava.