Abstract 18083: Does 6-Minute-Walk Distance Correlate With Right Ventricular Function in Patients With Pulmonary Arterial Hypertension?
Background: The majority of treatments available for pulmonary arterial hypertension (PAH) have been approved based on improvement in 6-minute walk distance (6MWD), shown to be an independent predictor of prognosis in these patients. Meanwhile, right ventricular (RV) size and function are also important prognosticators in these patients. We sought to determine whether RV indices on cardiovascular magnetic resonance imaging (CMR) correlated with 6MWD in patients with PAH.
Methods: Same-day CMR and 6MWD were performed in 35 PAH patients (51±14 yrs, 32 females, BSA=1.8±0.3/m2). 22 patients had repeat testing at 7±1 months. Consecutive short-axis cines spanning the entire RV were used to measure ejection fraction (RVEF) and indexed end-diastolic volume (EDVI). Patients who declined to perform the 6MWD test claiming inability were assigned 6MWD=0.
Results: Mean RVEF, EDVI and 6MWD at baseline were 36±14%, 134±47mL and 349±152m. Four patients were unable to perform 6MWD at baseline and 3 at follow-up. Poor correlation was observed between baseline RV indices and 6MWD (r=0.10 for EDVI and r=0.14 for RVEF; p<0.0001). Patients classified as WHO class III showed significantly worsened mean 6MWD than those classified as WHO class I (296m vs.469m; p<0.01). However, WHO class did not correlate with RVEF or EDVI. Even when 6MWD was categorized into recommended thresholds for predicting prognosis, namely ≤250m (n=7) and >440m (n=8), there was no significant difference in mean RVEF and EDVI between these 2 groups. Finally, when comparing changes in RVEF and 6MWD from baseline to follow-up, 10/24 patients showed concordant changes, while the remaining 12/24 patients showed discordant changes (p=0.59, Figure).
Conclusions: Since 6MWD does not appear to correlate with RV function in this patient population, further studies are needed to determine the optimal parameters to study disease progression in these patients.
- © 2013 by American Heart Association, Inc.