Abstract Body (Do not enter title and authors here): Introduction:
Right ventricular (RV) dysfunction is associated with poor outcomes following mitral transcatheter edge-to-edge repair (M-TEER) in patients with severe mitral regurgitation (MR), yet the prognostic value of surface electrocardiogram (ECG) markers of RV hypertrophy (RVH) remains unclear. Given ECG’s availability and low cost, we investigated whether RVH on ECG independently predicts clinical outcomes following M-TEER in patients with severe MR, as well as whether its addition augments Society of Thoracic Surgeons (STS) risk score in predicting mortality.

Methods:
A single-center, observational, retrospective cohort of 911 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=234), right axis deviation without RVH (n=46), and RVH (n=42). All other patients served as a control group (n=589). Adjusted Kaplan-Meier (KM) survival analyses and Cox regression analyses were performed to evaluate all-cause mortality, adjusted for clinical co-morbidities, hemodynamic parameters, and variables found to be independently associated with outcome by univariable analysis. Cohort was also stratified based on STS risk score into low (<4%), intermediate (4-8%), and high (>8%) surgical risk categories. KM and Cox regression were repeated both with and without RVH included to assess interaction effects and additive prognostic value.

Results:
ECG RVH prevalence was low (4.6%). We previously showed that in a multivariate Cox proportional hazard model that RVH is independently associated with 90-day mortality (HR 3.35, CI 1.48-7.60 p=0.004). When stratified by STS risk, the addition of RVH conferred significantly increased mortality across all risk categories compared to STS score alone (Figure 1). In patients with both high STS score and RVH, 90-day and 1-year survival estimates dropped precipitously compared to high STS alone (33.3% versus 77.3% at 1 year, log rank p-value <0.001). Cox models incorporating both RVH and STS risk category showed synergistically elevated hazard ratios in three different models (Table 1), significantly outperforming STS score alone.

Conclusion:
In patients with severe MR, electrocardiographic RVH is a readily available marker associated with increased all-cause mortality following M-TEER. ECG RVH may aid in risk stratification to identify high-risk patients and guide management strategies.