Exercise-Induced Pulmonary Hypertension in Primary Mitral Regurgitation Assessed by the mPAP/CO Slope

Background Exercise-induced pulmonary hypertension (PH), defined by a mean pulmonary arterial pressure over cardiac output (mPAP/CO) slope >3mmHg/L/min has important diagnostic and prognostic implications. Aims The aim of this study is to investigate the value of the mPAP/CO slope in patients with at least moderate primary MR with preserved ejection fraction and no or discordant symptoms. Methods A total of 184 consecutive patients were evaluated with exercise echocardiography and cardiopulmonary testing. Clinical outcome was defined as the composite of mitral valve intervention, new-onset atrial fibrillation, cardiovascular hospitalization, and all-cause mortality. Results Mean age was 63 years, 59% male, and mean LVEF 67±6%. The mPAP/CO slope correlated with peak VO2 (r = -0.37, p<0.001), while peak sPAP did not (r = -0.05, p=0.517). Thirty-nine percent (n=73) had peak exercise sPAP ≥60 mmHg, and 32% (n=58) had mPAP/CO slope >3mmHg/L/min. Event-free survival was 71% at 1 year and 59% at 2 years, with more clinical events in patients with mPAP/CO slope >3mmHg/L/min (HR of 4.1 (95% CI 2.6–6.5). In 61 patients, mPAP/CO slope and peak sPAP were discordant. Patients with slope >3mmHg/L/mmHg and sPAP <60mmHg (n=23) had worse outcome versus peak sPAP ≥60mmHg and normal slope (n=38, log-rank p=0.037). The mPAP/CO slope improved predictive models for outcome, incremental to resting and exercise sPAP, and peak VO2. Conclusions Exercise PH defined by the mPAP/CO slope >3mmHg/L/min is associated with decreased exercise capacity and higher risk of adverse events in significant primary MR and no or discordant symptoms. The slope provides a greater prognostic value than single sPAP measures and peak VO2.