Determinants of exercise tolerance and post-interventional right ventricular dysfunction in severe primary mitral regurgitation

Background Right ventricular (RV) dysfunction in severe primary mitral regurgitation (MR) reflects advanced disease and poor prognosis, yet resting echocardiography may fail to detect early RV impairment. Exercise stress echocardiography (SE) enables assessment of RV contractile reserve and RV–pulmonary arterial (RV–PA) coupling, potentially unmasking subclinical dysfunction. Purpose To identify echocardiographic determinants of exercise tolerance and predictors of RV dysfunction following mitral valve (MV) intervention in patients with severe primary MR. Methods Thirty-two patients with severe primary MR underwent symptom-limited bicycle SE. Exercise tolerance was classified according to median achieved workload. RV contractile reserve was assessed using exercise-induced changes in tricuspid annular plane systolic excursion (TAPSE), systolic annular velocity (S′), and fractional area change (Fig. 1). The ratio of TAPSE to pulmonary artery systolic pressure (PASP) was used as RV-PA coupling index. Logistic regression identified predictors of exercise tolerance and moderate-to-severe RV dysfunction after MV intervention. Results Mean age was 65 ± 16 years, and 72% of patients were male. RV contractile reserve was present in 66% and left ventricular (LV) contractile reserve in 78%. Median workload was 88 [50–125] Watts. In univariable analysis, age, NYHA class, resting LV global longitudinal strain, left atrium reservoir strain at rest, LV contractile reserve and stress RV-PA coupling index were associated with workload. After age adjustment, only stress RV-PA coupling index remained independently associated with workload (β = 11.61, 95% CI 1.29–21.93; p = 0.029). ROC analysis demonstrated good discrimination of high versus low workload (AUC 0.82, 95% CI 0.67–0.97), and a cut-off of 0.35 yielded 93% sensitivity and 60% specificity (Fig. 2). Six patients developed significant RV dysfunction post MV intervention. RV contractile reserve and higher resting TAPSE were protective, whereas higher resting pulmonary vascular resistance and stress RV–PA uncoupling increased risk of RV dysfunction. Multivariable modelling was limited by the small number of events. Among treated patients (surgery n = 15, TEER n = 7, NeoChord n = 1), SE altered management in three cases by prompting transcatheter rather than surgical intervention due to lack of RV contractile reserve. No in-hospital mortality was observed, and mechanical circulatory support was not required during hospital admission. Transcatheter treatment was associated with shorter hospital stay and minimal intensive care requirements. Conclusion In severe primary MR, stress-derived RV-PA coupling index is a robust marker of functional capacity and identifies patients at risk of post-interventional RV dysfunction. Dynamic RV–PA coupling assessment provides incremental information beyond resting parameters and may support individualized treatment decision-making.