Quantitative analysis of post-TAVI aortic regurgitation with cardiovascular magnetic resonance and the relationship to transthoracic echocardiography

Background

Transcatheter Aortic Valve Implantation (TAVI) is increasingly used to treat patients with severe aortic stenosis at high surgical risk. The severity of post-implantation valvular or paravalvular regurgitation has been shown to adversely affect patient outcome. The aim of the study was to assess the prevalence and severity of aortic regurgitation (AR) at 6 months post-TAVI using cardiovascular magnetic resonance (CMR).

Methods

Twenty five severe aortic stenosis patients underwent a 1.5T CMR (Intera, Philips Healthcare) scan at baseline and 6 months after CoreValve™ TAVI. LV function was assessed using cine imaging with a steady state free precession pulse sequence. The LV outflow tract was imaged in two planes and through-plane phase contrast velocity imaging was performed perpendicular to the aortic valve and transverse to the aorta at the sinotubular junction. Post-processing was performed using QMass 7.2 and QFlow 5.2 (Medis, Netherlands). AR severity was defined using regurgitant fraction (RF) as: none to mild <8%, mild to moderate 8 to 19%, moderate to severe 20 to 29% and severe >30% [1].

Transthoracic echocardiography (iE33, Philips Healthcare) was performed at baseline and 6 months follow-up. Aortic regurgitation was graded using a comprehensive integrated approach following the recent Valve Academic Research Consortium (VARC) guidelines.

Results

Mean age was 80.6±6.6yrs, 44% were female, Logistic EuroSCORE 19.5±14.9 LV ejection fraction significantly improved post-TAVI (52.1±11.8% vs. 55.9±9.6%, p<0.0001) and reduction in indexed end-systolic LV volume (46±18 ml/m² vs. 41±17 ml/m², p = 0.02). The end-diastolic volume (95±18 ml/m² vs. 91±20 ml/m², p = ns) and stroke volume (48±10 ml/m² vs. 50±10 ml/m², p = ns) did not change.

There was a significant reduction in aortic RF 6 months post-TAVI (median RF 12.4%, IQR 5.6 to 16.8% vs. 6.2% IQR 3.6 to 13.2%,p=0.034 ) (Figure 1). There was no significant difference between the transthoracic echo grading and CMR grading of aortic regurgitation. (Chi-squared = 3.74 p = 0.159) (Figure 2).

Figure 1

Quantification of aortic regurgitation by CMR phase contrast velocity mapping before and 6 months after TAVI implantation.

Figure 2

Comparison of aortic regurgitation grading by CMR and transthoracic echocardiography at 6 month follow up.

Echocardiography showed there was also a statistically significant reductions in peak forward flow velocity (4.87±0.57 ms^-1 vs.1.98±0.35 ms^-1 p < 0.05), peak pressure gradient (96.1±24.3 mmHg vs.17±5.7 mmHg p < 0.05) and mean pressure gradient (54.8±15.9 mmHg vs.8±3 mmHg p < 0.05) compared to baseline; the effective orifice area (EOA) was significantly larger compared to the baseline state (0.57±0.03 cm² vs. 1.63±0. 3cm² p < 0.05).

Conclusions

There was an overall reduction in aortic regurgitant fraction post-TAVI even in the presence of pre-existing AR. CMR can be used in the TAVI population, pre- and post-procedure to quantify the degree of aortic regurgitation

Funding

SP is funded by a British Heart Foundation fellowship (FS/10/62/28409).

SP and JPG receive an educational research grant from Philips Healthcare.