Renal resistive index for risk stratification and functional evaluation after transcatheter mitral valve repair: the...

The renal resistive index (RRI) is increasingly used as a non-invasive marker of cardiorenal interaction. We aimed to determine (i) whether baseline RRI predicts survival after mitral transcatheter edge-to-edge repair (M-TEER) and (ii) whether RRI changes in response to the procedure.

In this prospective, single-center cohort we enrolled consecutive patients with severe mitral regurgitation who underwent M-TEER between October 2020 and December 2021 (trial registration number 412/20, date of registration 02.09.2020). Baseline demographics, estimated laboratory parameters, comprehensive echocardiography, and Doppler-derived RRI were collected before and 3 months after intervention. The primary endpoint was all-cause mortality. Associations were analyzed with multivariable Cox regression. Renal endpoints were not systematically collected and were therefore not included as clinical outcome measures.

Among 109 patients (53.2% women), the median baseline RRI was 0.71 (IQR 0.67-0.75) and showed no correlation with eGFR, left-ventricular ejection fraction, or echocardiographic measurements of mitral regurgitation at baseline. Higher RRI was associated with all-cause mortality, and in exploratory post hoc analyses an RRI cutoff > 0.70 remained predictive independent of baseline renal function (HR 5.37, p 0.07). RRI improved significantly 3 months after M-TEER (0.67; IQR 0.63-0.70; p < 0.001), particularly in patients with a post-procedural MR reduction of at least 1 grade. However, the change in RRI showed no correlation with mortality or changes in renal function.

A baseline RRI above 0.70 was independently associated with mortality following M-TEER, underscoring its potential prognostic relevance. The marked post-procedural decline in RRI, especially in patients with relevant MR improvement, suggests that RRI reflects hemodynamic rather than renal filtration changes. Given the limited sample size and number of events, these findings should be considered exploratory and hypothesis-generating, requiring validation in larger multicenter cohorts.