Effects of Pulmonary Vasodilator Therapy on Ventilatory Efficiency during Exercise in Adults with Eisenmenger Syndrome

Abstract

Eisenmenger syndrome, characterized by systemic-level pulmonary arterial resistance with resultant right-to-left shunt, is associated with low exercise capacity and hyperpnea at rest and exercise. Because ventilatory requirements are augmented by right-to-left shunting, we hypothesized that if pulmonary vasodilator treatment improved pulmonary perfusion in this condition, this would also improve ventilatory efficiency during exercise. To investigate this, data from incremental cardiopulmonary exercise tests performed by Eisenmenger patients before and after beginning therapy with pulmonary hypertension medications were retrospectively analyzed. Setting. Ahmanson/University of California, Los Angeles Adult Congenital Heart Disease Center. Ten adults with Eisenmenger syndrome treated with either bosentan or sildenafil. The primary analysis was comparison, before and after treatment, of the efficiency of exercise ventilation as reflected in the ratio of ventilation (.V(E)) to carbon dioxide output (.VCO₂) measured at the anaerobic threshold (AT), the slope of .V(E)/.VCO₂ during incremental exercise, and end tidal partial pressure of CO₂ (PETCO₂) at the AT. Secondary measures included peak oxygen uptake (.VO₂) and AT. Following treatment there were significant reductions in the slope .V(E)/.VCO₂ (59.5 ± 12.9 vs. 50.0 ± 7.2, P= .003), and significant decrease in .V(E)/.VCO₂ ratio (56.9 ± 6.2 vs. 50.2 ± 5.9, P= .00004) and increase in PETCO₂ (21.12 ± 2.43 vs. 23.9 ± 2.62 torr, P= .0092) measured at the AT. Increases in peak .VO₂ (0.73 ± 0.25 vs. 0.78 ± 0.32 L/min, P= .333) and AT (0.61 ± 0.20 vs. 0.68 ± 0.25 L/min, P= .154) were not significant. These findings are consistent with reduction in right-to-left shunt due to improved pulmonary blood flow, though attenuation of ventilatory drive is not excluded. Treatment of adult Eisenmenger patients with pulmonary the pulmonary vasodilators bosentan or sildenafil leads to improvement in parameters of ventilatory efficiency during exercise.