Six-minute walk test distance and resting oxygen saturations but not functional class predict outcome in adult patients with Eisenmenger syndrome

BackgroundEisenmenger syndrome (ES) represents the extreme manifestation of pulmonary arterial hypertension in patients with congenital heart disease, associated with significant exercise intolerance and mortality. Even though of six-minute-walk-test (6MWT) is routinely used in these patients, little is known about its prognostic value in comparison to functional class.Methods and resultsWe included 210 adult patients with ES who underwent a total of 822 6MWTs. Median walking distance (6MWD) was 330 m [IQR 260-395], oxygen saturation (SO2) at baseline 86% [IQR 82-91%] and SO2 at peak-exercise 69% [IQR 60-80%]. In patients commenced on advanced therapy for pulmonary hypertension, but not in the reminder, there was a significant improvement in walking distance (297 ± 97 m vs. 325 ± 87 m,P = 0.0019), SO2 at rest (84.9 ± 7.1 vs. 86.8 ± 5.9%,P = 0.003), SO2 at peak exercise (69.1 ± 12.7 vs. 72.3 ± 12.2%,P = 0.04) and NYHA functional class (P = 0.0047).During a follow up of 3.3 years, 29 patients died. On time-dependent Cox analysis, 6MWD (HR 0.94 per 10 m, 95%CI: 0.91-0.97,P < 0.001) and baseline SO2 (HR 0.90, 95%CI:0.86-0.94,P < 0.0001) were predictors of death. In contrast, age, functional class, peak-exercise SO2 and SO2 change were not related to mortality. A three-fold increased risk of death was identified in patients not reaching a 6MWD of 350 m or with baseline SO2 below 85%.ConclusionsThe 6MWD and resting SO2, but not functional class were predictive of outcome in this contemporary cohort of Eisenmenger patients and should be incorporated in both risk stratification and management algorithms for these patients.