Impairment of Autonomic Nervous System Activity in Patients With Pulmonary Arterial Hypertension: A Case Control Study

BackgroundChronotropic response to exercise (CR) and heart rate recovery (HRR) immediately after exercise are indirect indices of sympathetic and parasympathetic activity, respectively. The aim of this study was to evaluate CR and HRR in patients with pulmonary arterial hypertension (PAH) in relation to disease severity.Methods and ResultsTen PAH patients (6 females/4 males, mean age: 48 ± 12 years) and 10 control subjects matched for age, gender, and body mass index (6 females/4 males, mean age: 46 ± 6 years) performed a ramp incremental symptom-limited cardiopulmonary exercise test on a cycle ergometer. Main measurements included heart rate at rest (HR), CR = [(peak HR-resting HR/220-age-resting HR) × 100, %], HRR1 = HR difference from peak exercise to 1 minute after, ventilatory efficiency during exercise (VE/VCO2 slope), peak oxygen uptake (VO2p), and the first-degree slope of VO2 for the first minute of the recovery period (VO2/t-slope). PAH patients had a significantly decreased CR (58 ± 31 vs 92 ± 13, %, P < .001) and HRR1 (10 ± 5 vs 29 ± 6, beats/min, P < .001) as well as VO2p (11.9 ± 3.5 vs 26.9 ± 6.6, mL·kg·min) and VO2/t-slope (0.2 ± 0.1 vs. 0.9 ± 0.2, mL·kg·min2) compared with controls. CR and HRR1 correlated well with VO2p (r = 0.7; P < .001 and r = 0.85; P < .001, respectively) and VO2/t-slope (r = 0.66; P < .001 and r = 0.85; P < .001, respectively) and had a significant inverse correlation with VE/VCO2 slope (r = –0.47; P < .01 and r = –0.77; P < .001, respectively).ConclusionsPAH patients present a significant impairment of CR and HRR1 in relation to disease severity, indicating profound autonomic nervous system abnormalities.