Brain Natriuretic Peptide Response to Six-minute Walk Test in Pulmonary Arterial Hypertension

Abstract

Background: Brain Natriuretic Peptide (BNP) levels increase in response to exercise in congestive heart failure patients. However, the timing, degree, and clinical consequences of exercise-related BNP elevation in Pulmonary Arterial Hypertension (PAH) remain unexplored. Methods: A total of 38 consecutive PAH patients were enrolled in this study. BNP levels were drawn prior to, and 6, 14, 20, and 60 minutes following, the six-minute walk test. Subjects were divided based on BNP level cut off used in our laboratory: BNP ≤100pg/ml and BNP >100pg/ ml. Time to Clinical Worsening (TTCW) was defined as a composite end point of death, transplant, prostacyclin initiation, or hospitalization for worsening PAH. Results: Twenty-four patients were in the BNP ≤100pg/ml group (44±28pg/ml, mean ± SD) and fourteen patients in the BNP >100pg/ ml group (285±179pg/ml). Baseline six-minute walk distance in the ≤100pg/ml group was higher as compared to the other group (P=0.003). Pre- and post-walk BNP levels did not differ significantly in the two groups. No deaths occurred in the BNP ≤100pg/ml group, and none of these patients were started on prostacyclin therapy. TTCW was shorter in the >100pg/ml group (P=0.005) with three deaths and four prostacyclin starts. Higher baseline BNP levels were associated with poor survival (P=0.014). Conclusion: Our findings indicate that in PAH patients with elevated baseline BNP levels had a shorter time to clinical worsening, higher mortality, and more prostacyclin initiation. BNP values do not change significantly from baseline values in response to a six-minute walk test. Pre-walk elevated BNP levels are indicator of worse disease rather than post-walk BNP level changes.