Temporal changes in left ventricular function and paravalvular aortic regurgitation after transcatheter aortic valve implantation: a cardiac magnetic resonance imaging study

Abstract

Background: Transcatheter aortic valve implantation (TAVI) has become a common procedure for high-risk patients with severe aortic stenosis. Aortic regurgitation (AR) is commonly seen after TAVI, but little is known about how it evolves over time. Similarly, the impact of TAVI on left ventricular (LV) function, LV volumes and mass is not well defined. Methods: Patients successfully treated with transfemoral TAVI using the Medtronic CoreValve bioprosthesis without contraindications for magnetic resonance imaging (MRI) underwent cardiac MRI 20+12 days after TAVI. Fourteen patients underwent follow-up MRI 11.3+7.1 months later and represent the population of the current study. LV volumes and function were assessed using standard cine MRI sequences. Additionally, phase-contrast imaging was conducted to quantify the degree of AR, for which the slice was positioned in the ascending aorta at the upper margin of the stent holding the CoreValve prosthesis. A calculated regurgitant fraction (RF) of 0-15% was graded as I (mild), 16-30% as II (moderate), 31-50% as III (moderate to severe) and >50% as grade IV (severe) AR. Results: The mean age of the evaluated patients was 81+5 years and 50% were women. At baseline MRI, the median LV ejection fraction was 54.9% (range 29.0 to 67.8%), which improved significantly at follow-up to 60.8% (range 24.0 to 71.9%, p=0.0017). LV end-diastolic volume (EDV) and myocardial mass did not significantly change. This was mainly due to one outlier with severely impaired LV function at baseline with further deterioration over time. Excluding this patient, a significant reduction of LV EDV (139.7+29.5 ml vs. 121.6+22.4 ml, p=0.017) and LV mass (139.3+21.0 g vs. 124.8+23.4 g, p=0.041) was observed. This was associated with a significant reduction of NT-pro-BNP levels at follow-up (1933+779 pg/ml vs. 621+470 pg/ml, p=0.008). Baseline MRI identified mild AR in 11 patients and moderate AR in 3 patients. Over time, aortic RF increased significantly from 8.08% (range 0.11 to 26.84%) to 11.99% (range 1.94 to 40.01%, p=0.004), resulting in 10 patients with mild, 3 patients with moderate and one patient with moderate to severe AR at follow-up MRI. At both time points, we observed a significant negative correlation between myocardial mass and LV ejection fraction, with r = -0.66 at baseline MRI and r = -0.85 at follow-up. Conclusion: Using cardiac MRI, mild to moderate AR is commonly seen in patients treated with TAVI. AR mildly increases over time. Nevertheless, a significant improvement of left ventricular function at follow-up MRI can be observed.