Abstract
This study aimed to investigate if and how complex flow influences the assessment of aortic regurgitation (AR) using phase contrast MRI in patients with chronic AR. Patients with moderate (n = 15) and severe (n = 28) chronic AR were categorized into non-complex flow (NCF) or complex flow (CF) based on the presence of systolic backward flow volume. Phase contrast MRI was performed repeatedly at the level of the sinotubular junction (Ao1) and 1 cm distal to the sinotubular junction (Ao2). All AR patients were assessed to have non-severe AR or severe AR (cut-off values: regurgitation volume (RVol) ≥ 60 ml and regurgitation fraction (RF) ≥ 50%) in both measurement positions. The repeatability was significantly lower, i.e. variation was larger, for patients with CF than for NCF (≥ 12 ± 12% versus ≥ 6 ± 4%, P ≤ 0.03). For patients with CF, the repeatability was significantly lower at Ao2 compared to Ao1 (≥ 21 ± 20% versus ≥ 12 ± 12%, P ≤ 0.02), as well as the assessment of regurgitation (RVol: 42 ± 34 ml versus 54 ± 42 ml, P < 0.001; RF: 30 ± 18% versus 34 ± 16%, P = 0.01). This was not the case for patients with NCF. The frequency of patients that changed in AR grade from severe to non-severe when the position of the measurement changed from Ao1 to Ao2 was higher for patients with CF compared to NCF (RVol: 5/26 (19%) versus 1/17 (6%), P = 0.2; RF: 4/26 (15%) versus 0/17 (0%), P = 0.09). Our study shows that complex flow influences the quantification of chronic AR, which can lead to underestimation of AR severity when using PC-MRI.
Highlights
Aortic regurgitation (AR) is characterized by the diastolic backward flow of blood from the aorta into the left ventricle
The frequency of patients that changed in AR grade from non-severe to severe, and vice versa, when the position of the measurement changed from Ao1 to Ao2 was higher for patients with complex flow (CF) compared to non-complex flow (NCF) (RVol: 5/26 (19%) versus 1/17 (6%), P = 0.2; regurgitation fraction (RF): 4/26 (15%) versus 0/17 (0%), P = 0.09); Fig. 5)
No significant influence of measurement position, neither regarding regurgitation values nor regarding repeatability of regurgitation values, was found for patients with NCF (RVol: P = 0.3; RF: P = 0.7; Repeatability of regurgitation volume (RVol): P = 0.9; Repeatability of RF: P = 0.5; the P values are corrected for multiple testing [22]; Tables 1 and 3)
Summary
Aortic regurgitation (AR) is characterized by the diastolic backward flow of blood from the aorta into the left ventricle. Two-dimensional echocardiography is currently the first-line diagnostic tool and uses a combination of qualitative, semi-quantitative and quantitative parameters for the assessment of AR severity [3, 4]. Cardiovascular magnetic resonance imaging (MRI), currently used as a second-line diagnostic tool, can provide a. The assessment can be performed directly using phase contrast MRI (PC-MRI) measurements in an image plane orthogonal to the blood flow in the ascending aorta [7]. The diastolic blood flow in such complex flow regions displays regurgitant flow and forward flow from swirling blood
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