Evaluation of Aortic Valve Regurgitation by Cardiovascular Magnetic Resonance Using 2D and 4D Flow Analysis

Background: Aortic regurgitation (AR) is caused by incomplete closure of the aortic valve and leads to a volume shift from the aorta back into the left ventricle. This ongoing volume overload of the left ventricle is a risk for ventricular dilation, functional impairment, and provokes the development of heart failure. The backward flow through the aortic valve can be measured directly by cardiovascular magnetic resonance (CMR). Since several measurement methods as 2D or 4D phase-contrast CMR are available less is known about the most reliable level in the ascending aorta. The aim of this study was to evaluate the appropriate level for ROI placement for 2D and 4D flow for the most accurate measurement of aortic regurgitation.

Method: Thirty 2D and 4D flow datasets from patients with aortic valve regurgitation (median age = 31 years, range: 8–56) were analyzed. Flow measurements for gold-standard 2D CMR were performed at three different levels of the aorta, 4D flow was measured along the entire thoracic aorta and three ROIs were positioned at the same levels as in 2D in post processing. The three different levels were defined as aortic valve, aortic bulb, and the proximal aorta ascendens. The occurrence of interfering parameters, such as vortices and stenosis, was also recorded. Two experienced investigators analyzed all data.

Results: AR at all defined levels by 2D flow was median 31% (range: 1–79) and 18% (range: 1–70) by 4D acquisition. AR by 2D flow at the level of the aortic valve was median 26% (range: 1–40), at the level of the aortic bulb 33% (range: 4–51), and at the level of the ascending aorta 32% (range: 1–79), AR by 4D flow was median 18% (range: 1–46), 17% (range: 1–70), and 16% (range: 1–41), respectively. Linear regression for 2D and 4D showed the best correlation for the level of the aortic valve (r ² = 0.53). Furthermore, correlation of antegrade 2D and 4D flow was at the same level (r ² = 0.83). Pronounced vortices showed a marked negative influence on the acquisition of retrograde flow with most accurate measurements on the level of the aortic valve (65.2%).

Conclusion: AR was measured most reliable at the level of the aortic valve when comparing gold-standard 2D flow with 4D flow CMR. Patients with pronounced vortices were significantly more often underestimated compared with patients with “straight” flow.

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Artikel online veröffentlicht:
12. Februar 2022