MRI shows increase in aortic regurgitation after TAVI

Using cardiac MRI, researchers found that aortic regurgitation (AR) after transcatheter aortic valve implantation (TAVI) did not decrease over time. Instead, the incidence and severity of paravalvular AR increased slightly at six-month follow-up.

The results were published online Aug. 13 in Circulation: Cardiovascular Interventions.

“In previous studies, patients were examined by using echocardiography,” wrote Constanze Merten, MD, of the Academic Teaching Hospital of the Universities of Kiel and Hamburg in Bad Segeberg, German, and colleagues. “Compared with TTE [transthoracic echocardiography], MRI has a lower intraobserver and interobserver variability in the assessment of regurgitant volumes and might therefore be more reliable for serial measurements.”

Merten et al enrolled 43 patients treated with TAVI between October 2008 and January 2012 for the study. Each patient receive a baseline MRI (median 11 days after TAVI) and a follow-up MRI at six months. They used cine MRI sequences to assess left ventricular (LV) volumes and function. With MRI data, they calculated aortic regurgitant fraction and categorized it as mild (grade I, 15 percent or less); moderate (16 percent to 30 percent); moderate to severe (31 percent to 50 percent); or severe (more than 50 percent).  

The study group had a mean age of 79.9 years, with 65 percent women. At baseline, AR was detected in 86 percent of the patients. The median regurgitant fraction for the whole group was 5.2 percent; median LV ejection fraction was 58.1 percent; mean LV end-diastolic volume was 149.7 mL; and mean myocardial mass was 156 g.

At a median six months after TAVI, AR was present in 91 percent of the patients; median regurgitant fraction was 7.8 percent; median LV ejection fraction was 63.4 percent; mean LV end-diastolic volume was 140 mL; and mean myocardial mass was 142.7 g.

Subgroup analysis showed significant changes in LV ejection fraction, volumes and mass occurred in patients with no or mild AR but “more than mild AR seems to prevent LV functional and structural recovery after TAVI,” they wrote.

Many of their findings were in line with results from other studies, but the small increase in the incidence and severity of paravalvular AR at follow-up differed from “the few follow-up data available” that pointed to a decrease or stabilizing after TAVI.

One reason for the difference may be the imaging protocol used. “TTE allows only semiquantitative estimation, and eccentric or multiple jets are possibly underestimated,” Merten and colleagues proposed. “In contrast, by using flow measurements by cardiac MRI, a quantitative assessment of AR is possible, which is independent of the number or eccentricity of the regurgitant jets.”

The study perforce excluded patients who could not undergo MRI scans, such as those with a pacemaker and included only clinically stable patients. In addition, the sample size was too small for robust subanalyses, they acknowledged.