Value of impedance cardiography during 6-minute walk test in pulmonary hypertension

Abstract

Background: Methods that predict prognosis and response to therapy in pulmonary hypertension (PH) are lacking. We tested whether the noninvasive estimation of hemodynamic parameters during 6-minute walk test (6MWT) in PH patients provides information that can improve the value of the test.

Methods: We estimated hemodynamic parameters during the 6MWT using a portable, signal-morphology-based, impedance cardiograph (PhysioFlow Enduro) with real-time wireless monitoring via a bluetooth USB adapter.

Results: We recruited 48 subjects in the study (30 with PH and 18 healthy controls). PH patients had significantly lower maximum stroke volume (SV) and CI and slower cardiac output (CO) acceleration and decelerations slopes during the test when compared with healthy controls. In PH patients, CI change was associated with total distance walked (R = 0.62; P < 0.001) and percentage of predicted (R = 0.4, P = 0.03), HR recovery at 1 minute (0.57, P < 0.001), 2 minutes (0.65, P < 0.001), and 3 minutes (0.66, P < 0.001). Interestingly, in PH patients CO change during the test was predominantly related to an increase in SV instead of HR.

Conclusions: Estimation of hemodynamic parameters such as cardiac index during 6-minute walk test is feasible and may provide useful information in patients with PH. Clin Trans Sci 2013; Volume #: 1-7.

Keywords: 6-minute walk test; cardiac output; pulmonary hypertension.