Abstract Body (Do not enter title and authors here): Background: M-TEER is an option for patients with severe mitral regurgitation (MR). Long-standing severe MR may lead to RVH; however, the clinical significance of RVH on ECG in patients undergoing M-TEER in relation to mortality is not known.

Methods:
A single-center, observational, prospective cohort of 443 adults with severe MR and a representative ECG from within 12 months prior to procedure date who underwent M-TEER between January 2018 and July 2020 was analyzed. Patients were assessed for paced rhythm (n=109), RAD only (n=28), and RVH (n=23) diagnosed by expert consensus. The rest of patients (n=283) served as control group. All-cause in-hospital mortality was evaluated as the primary outcome using log binomial regression models. The secondary outcome was one-year mortality calculated with multivariate Cox regression models.

Results
The prevalence of electrocardiographic RVH is low (5.2%). RVH was associated with increased in-hospital mortality (RR 6.15, 95% CI 1.64-23.01, p 0.007, Table 1). A total of 71 (16%) patients experienced a one-year mortality (Figure). Several variables including RVH, RAD, a history of smoking, and prior cardiogenic shock were identified as each having association with one-year mortality. A multivariable analysis adjusting for these covariates demonstrated that RVH still was associated with increased one-year mortality (HR 2.53, 95% CI 1.06-6.03, p 0.036, Table 2). Paced rhythm on ECG was not associated with in-hospital mortality or at one-year.

Conclusions:
Electrocardiographic RVH is associated with an increased risk of in-hospital and 365-day mortality in patients with severe MR undergoing M-TEER.