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Effect of Six-Minute Walk Test on Pro-BNP Levels in Patients with Pulmonary Arterial Hypertension

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Conference: 2014 International PHA Conference and Scientific Sessions

Release Date: 06.21.2014

Presentation Type: Abstracts

File Download: 2014 Conference Abstracts - Vikas Pathak

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Background: Plasma pro-BNP levels are often elevated in response to right ventricular (RV) volume and pressure overload, parameters potentially affected by exercise. Plasma pro-BNP levels change in association with long-term changes in pulmonary hemodynamics, thereby serving as a potential biomarker in pulmonary arterial hypertension (PAH). The 6 Minute Walk Test (6MWT) and Pro-BNP level are often checked in a single office visit. There is no universal standard for measuring Pro-BNP levels relative to the timing of the 6MWT. Based on the studies in normal subjects indicating that pro-BNP levels changes after exercise; we hypothesized that the pro-BNP might rise after the 6MWT, potentially impacting clinical decisions.

Methods: This is an interim analysis of a single-center study. Patients with WHO Group 1 PAH on active therapy at a stable dose for 30 days or more were enrolled.  After resting the patient for 30 minutes, blood was drawn for baseline pro-BNP and a 6MWT was performed.   Pro-BNP levels were drawn immediately after the 6MWT and 1 and 2 hours later. Pro-BNP was measured using a commercially available ELISA kit. The levels before exercise and after exercise were compared using student’s paired t tests.

Results: There were 11 female and 3 male subjects. The mean age was 51.5 years +/- 10. Six patients had SLE related PAH, 4 had idiopathic PAH, 3 had portopulmonary hypertension, and 1 had HIV-related PAH.  The mean PA pressure was 52 mmHg +/- 16 with a mean pulmonary vascular resistance of 10 wood units +/- 4. The majority of the patients were on multimodality PAH therapy, including parenteral prostacyclins. Mean 6MWT distance was 409 meters +/- 128. In 10/14 patients the pro-BNP level increased immediately after the 6MWT; in 12/14 patients the pro-BNP level was elevated at 1hour post exercise. In the majority of the patients the pro-BNP fell to baseline 2 hours post 6MWT. 

Conclusion: There appears to be a trend of pro-BNP level increasing immediately after exercise and continuing to be elevated at one hour. Pro-BNP levels then return to baseline at 2 hours post 6MWT. We are continuing to enroll patients in this study and hope to be able to draw more definitive conclusions as we continue beyond this small interim analysis.

Type: Clinical science