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 Sā. 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 ā 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.