TY - JOUR T1 - Clinical relevance of autonomic nervous system disturbances in pulmonary arterial hypertension JF - European Respiratory Journal JO - Eur Respir J SP - 792 LP - 794 DO - 10.1183/09031936.00091609 VL - 34 IS - 4 AU - R. Naeije AU - P. van de Borne Y1 - 2009/10/01 UR - http://erj.ersjournals.com/content/34/4/792.abstract N2 - Pulmonary arterial hypertension (PAH) is a rare dyspnoea-fatigue syndrome defined by an isolated increase in pulmonary vascular resistance (PVR) and eventual right ventricular failure 1. In spite of progress achieved during the last two decades, the condition remains severe, with a median survival limited to 5–6 yrs and persistent functional limitation in approximately half of the survivors 1. Further improvement is needed, and this involves a better physiopathological understanding of the PAH “phenotype”. In the present issue of the European Respiratory Journal, Wensel et al. 2 add argument to the notion of PAH as a right heart failure with associated autonomic nervous system disturbances. These authors investigated heart rate variability and baroreflex sensitivity using a spectral analysis of ECG and blood pressure recordings, and correlated the results to aerobic exercise capacity. The spectral power of heart rate variability in their patients was decreased at all frequencies and the baroreflex sensitivity was blunted. These changes were correlated with decreased peak oxygen uptake, very much as previously reported in severe congestive heart failure. Patients with PAH hyperventilate during exercise, at rest and even during sleep, and this is related to disease severity and survival 3–7. The cause of hyperventilation in PAH is often assumed to be an increased physiological dead space related to extensive vascular remodelling and obliteration decreasing perfusion with respect to ventilation 4, 6, 7. However, end-tidal and arterial carbon dioxide tensions (PET,CO2 and Pa,CO2, respectively) are consistently found to be lower than normal, suggesting an additional component of increased chemosensitivity 3–7. The respective contributions of physiological dead space and chemosensitivity to hyperventilation in PAH are difficult to assess from reported expired and arterial blood respiratory gases. … ER -