Discussion
We aimed to ascertain whether RV dysfunction was associated with CV events in patients with MR who underwent MitraClip therapy. The main findings of this study are as follows: first, RV dysfunction was independently associated with CV events following MitraClip therapy; second, TAPSE was the best RV functional parameter of conventional echocardiography for predicting adverse events; third, the cut-off value of TAPSE for predicting CV events was 11 mm.
RV function is an important parameter with prognostic value in predicting symptomatic limitation and outcome in different cardiovascular pathologies.(17-22) Several parameters have been developed for the evaluation of RV systolic function, including TAPSE, FAC, and S’. Among them, TAPSE is a commonly utilized single-dimension measure of global RV systolic function. It simply measures the distance of systolic excursion of the RV annular segment along its longitudinal axis. According to the ASE/EACVI guidelines, a TAPSE of <16 mm suggests impaired RV systolic function.(14) In patients with severe MR, RV dysfunction is associated with increased morbidity and mortality.(1,23,24) Our results are in agreement with those of previous studies(7,25,26) in determining the prognostic role of baseline RV function in patients with MR undergoing MitraClip therapy. Our study expands on these previous studies in demonstrating an 11-mm cut-off value of TAPSE for predicting CV events following MitraClip therapy. Atrial fibrillation (AF) could result in pulmonary hypertension, causing RV dysfunction and RA dilation or loss of atrial contraction, which reduces RV filling and could reduce TAPSE.(27) In the present cohort study, 80% of the event group had AF. This might have resulted in a low cut-off value for TAPSE.
Apart from RV dysfunction,(28) pulmonary hypertension is a common complication in HF and predicts the occurrence of adverse outcome.(29,30) Pulmonary hypertension has long been considered a serious complication in patients with significant MR. Elevation of LAP occurs in the transitional and decompensated phases of chronic MR(31) and leads to increased pulmonary arterial pressure, eventually resulting in RV dysfunction.(32)
A number of previous studies have described the impact of RV-PA coupling (TAPSE/PA systolic pressure).(33) Because RV systolic performance is highly dependent on RV afterload,(34) a combination of these coupling parameters would be more important than each parameter in isolation. Combined evaluation (i.e. RV-PA coupling) could be considering right heart hemodynamics.(35) RV-PA coupling ratio was impaired in patients with HF with preserved ejection fraction.(36) Sultan et al. demonstrated that RV-PA coupling is strongly associated with all-cause mortality and its evaluation may be superior to RV or PA alone in predicting worse outcomes in patients undergoing transcatheter aortic valve replacement.(37) In contrast, our study demonstrated that TAPSE had a larger AUC than RV-PA coupling (0.793 vs. 0.675) to predict CV events (Supplemental figure 1). On multivariate Cox regression sub-analysis, CV events were independently associated with lower TAPSE (HR: 0.873, 95%CI; 0.788 – 0.968, p = 0.010) after adjustment for PA pressure measured by transthoracic echocardiography. According to our results, RV dysfunction (by TAPSE) could independently predict worse outcomes regardless of hemodynamics.
In the present study, we found that residual MR>2+ was also an independent predictor of CV events. Similarly, a previous study reported that MitraClip therapy was effective in reducing MR.(38,39) Since residual MR after MitraClip therapy has been associated with suboptimal outcomes and increased mortality(40), the goal of the procedure is to reduce residual MR as much as possible.
Limitations
Previous studies demonstrated that RV function improved after MitraClip therapy.(41,42) However, there was no mention of periprocedural change of RV function in this study. This was a single-center study and the sample size was small, which limits its generalizability. Further, this study focused on short-term results. Properly designed trials with longer follow-up and more patients are required to confirm our results.