PURPOSE: Cardiopulmonary exercise testing (CPET) can evaluate physiology and predict survival in patients with pulmonary arterial hypertension (PAH). We hypothesized that adding follow-up CPET measurements would improve prognostic ability. We examined which CPET parameters provided optimal prognostic ability in our patient population.
METHODS: To evaluate the prognostic ability of CPET in predicting death or freedom from lung transplantation, we evaluated 103 PAH patients seen in our clinic who had prospective serial CPET performed. We measured peak VO2 and evaluated receiver operating characteristics (ROC) to determine the optimal cutoff value for separating survivors from non-survivors; we then evaluated Kaplan-Meier survival curves for various survival models.
RESULTS: Patients had baseline CPET and repeat testing after 12±12 months; patients were followed for a mean of 55±29 months. Based upon ROC analysis, we selected peak VO2 <0.75 L/min as the threshold value for increased risk of death or transplantation at baseline (P=0.04). Adding follow-up peak VO2 values increased prognostic significance: the best predictor of outcome was the combination of baseline peak VO2 <0.75 L/min and worsening over time, as compared to either a baseline peak VO2 >0.75 L/min or a peak VO2 <0.75 L/min, but no worsening (P<0.0001, Figure).
CONCLUSION: Repeated CPET measurements of peak VO2 adds incremental prognostic benefit to that of single CPET measurements in patients with PAH.
CLINICAL IMPLICATIONS: In patients with PAH, presence of severe gas exchange impairment at baseline combined with worsening over time identifies patients at highest risk for poor outcome.
DISCLOSURE: Raghu Midde, Grant monies (from industry related sources) Actelion, Encysive, Gilead, Pfizer, United Therapeutics; Consultant fee, speaker bureau, advisory committee, etc. Actelion, Encysive, Gilead, Pfizer, United Therapeutics; Product/procedure/technique that is considered research and is NOT yet approved for any purpose. ambrisentan