Heart rate slopes during 6‐min walk test in pulmonary arterial hypertension, other lung diseases, and healthy controls

Abstract

Six‐minute walk test (6MWT) continues to be a useful tool to determine the functional capacity in patients with vascular and other lung diseases; nevertheless, it has a limited ability to predict prognosis in this context. We tested whether the heart rate (HR) acceleration and decay slopes during the 6‐m walk test are different in patients with pulmonary arterial hypertension (PAH), other lung diseases, and healthy controls. In addition, we assessed whether the HR slopes are associated with clinical worsening. Using a portable, signal‐morphology‐based, impedance cardiograph (PhysioFlow Enduro, Paris, France) with real‐time wireless monitoring via a Bluetooth USB adapter we determined beat‐by‐beat HR. We included 50 subjects in this pilot study, 20 with PAH (all on PAH‐specific treatment), 17 with other lung diseases (obstructive [ n = 12, 71%] or restrictive lung diseases [5, 29%]), and 13 healthy controls. The beat‐by‐beat HR curves were significantly different among all three groups of subjects either during the activity or recovery of the 6MWT. HR curves were less steep in PAH than the other two groups ( P < 0.001). HR acceleration rates were slower in patients with PAH or other lung diseases with progression of their disease ( P < 0.001). In conclusion, the acceleration and decay slopes during 6MWT are different among patients with PAH, other lung diseases, and healthy controls. The HR slopes during 6MWT were steeper in patients without clinical worsening.

Abstract

For the first time, we studied study the heart rate (HR) acceleration and decay slopes during the 6‐min walk test (6MWT) in patients with pulmonary arterial hypertension (PAH) and compared them to subjects with parenchymal lung diseases and healthy controls. We analyzed a large number (>600) of standardized HR determinations in each patient and applied modern statistical analysis (nonlinear mixed models) to construct the slopes during the activity and recovery phases of the 6MWT. We found that the slopes are less steeper in PAH patients when compared with controls. The slopes of patients with parenchymal lung disease fell in‐between individuals with PAH and healthy controls. More importantly, patients with PAH or parenchymal lung disease has a lower acceleration or deceleration slope if their disease progressed during the follow‐up.