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Atrial Septostomy Decreases Sympathetic Overactivity in Pulmonary Arterial Hypertension^*

^* From the Department of Cardiology (Drs. Ciarka, Vachièry, Gujic, Stoupel, Velez-Roa, and van de Borne, and Ms. Houssière), Erasme University Hospital, Brussels, Belgium; the Department of Pathophysiology (Dr. Naeije), Faculty of Medicine, Free University of Brussels, Brussels, Belgium.

Correspondence to: Agnieszka Ciarka, MD, Department of Cardiology, Erasme Hospital, 808, Lennik Rd, 1070 Brussels, Belgium; e-mail: Agnieszka.Ciarka{at}ulb.ac.be

Abstract

Background: We have reported previously that the sympathetic nervous system is activated in patients with pulmonary arterial hypertension (PAH), and that this is only partly explained by a decrease in arterial oxygenation. Possible causes for increased muscle sympathetic nerve activity (MSNA) in patients with PAH include right atrial distension and decreased cardiac output. Both may be improved by atrial septostomy, but this intervention also further decreases arterial oxygenation. In the present study, we wanted to investigate the effect of atrial septostomy on MSNA in patients with PAH.

Methods: We recorded BP, heart rate (HR), arterial O₂ saturation (SaO₂), and MSNA before and after atrial septostomy in PAH patients (mean [± SE] age, 48 ± 5 years) and in closely matched control subjects. Measurements were also performed after septostomy, while SaO₂ was brought to the preprocedure level by supplemental O₂ therapy.

Results: Compared to the control subjects (n = 10), the PAH patients (n = 11) had a lower mean BP (75 ± 2 vs 96 ± 3 mm Hg, respectively; p < 0.001), lower mean SaO₂ (92 ± 1% vs 97 ± 0%, respectively; p < 0.001), increased mean HR (84 ± 4 vs 68 ± 3 beats/min; p < 0.01), and markedly increased mean MSNA (76 ± 5 vs 29 ± 2 bursts per minute; p < 0.001). Atrial septostomy decreased mean SaO₂ (to 85 ± 2%; p < 0.001) and mean MSNA (to 69 ± 4 bursts per minute; p < 0.01), but did not affect HR or BP. Therapy with supplemental O₂ did not affect MSNA, BP, or HR. The decrease in MSNA was correlated to the decrease in right atrial pressure (r = 0.62; p < 0.05).

Conclusions: Atrial septostomy in PAH patients decreases sympathetic hyperactivity despite an associated decrease in arterial oxygenation, and this appears to be related to decreased right atrial distension.

Key Words: atrial septostomy • muscle sympathetic nerve activity • pulmonary arterial hypertension