Prognostic utility of exercise cardiovascular magnetic resonance in patients with systemic sclerosis-associated pulmonary arterial hypertension.

Aims: Systemic sclerosis complicated by pulmonary arterial hypertension (SSc-PAH) is a rare condition with poor prognosis. The majority of patients are categorized as intermediate risk of mortality. Cardiovascular magnetic resonance (CMR) is well placed to reproducibly assess right heart size and function, but most patients with SSc-PAH have less overtly abnormal right ventricles than other forms of PAH. The aim of this study was to assess if exercise CMR measures of cardiac size and function could better predict outcome in patients with intermediate risk SSc-PAH compared with resting CMR.

Methods and results: Fifty patients with SSc-PAH categorized as intermediate risk underwent CMR-augmented cardiopulmonary exercise testing. Most patients had normal CMR-defined resting measures of right ventricular (RV) size and function. Nine (18%) patients died during a median follow-up period of 2.1 years (range 0.1-4.6). Peak exercise RV indexed end-systolic volume (ESVi) was the only CMR metric to predict prognosis on stepwise Cox regression analysis, with an optimal threshold < 39 mL/m2 to predict favourable outcome. Intermediate-low risk patients with peak RVESVi < 39 mL/m2 had significantly better survival than all other combinations of intermediate-low/-high risk status and peak RVESVi< or ≥39 mL/m2. In our cohort, ventilatory efficiency and resting oxygen consumption (VO2) were predictive of mortality, but not peak VO2, peak cardiac output, or peak tissue oxygen extraction.

Conclusion: Exercise CMR assessment of RV size and function may help identify SSc-PAH patients with poorer prognosis amongst intermediate risk cohorts, even when resting CMR appears reassuring, and could offer added value to clinical PH risk stratification.