Acute and chronic effects of surgical thromboendarterectomy on exercise capacity and ventilatory efficiency in patients with chronic thromboembolic pulmonary hypertension

Objective-To assess acute and chronic effects of surgical thromboendarterectomy on exercise capacity and ventilatory efficiency in patients with chronic thromboembolic pulmonary hypertension (CTEPH). Design-Cardiopulmonary exercise testing was performed in 20 patients with CTEPH before thromboendarterectomy (baseline), one month after (early phase), and four months after (late phase). Peak oxygen uptake (peak Vo(2)) and the ventilatory response to carbon dioxide production (VE-Vco(2) slope) were measured for assessment of exercise capacity and ventilatory efficiency. Right heart catheterisation was performed in all patients before and one month after surgery. Results-Baseline peak Vo(2) decreased and Ve-Vco(2) slope increased along with the increase in pulmonary vascular resistance in patients with CTEPH. After thromboendarterectomy, the Ve-Vco(2) slope decreased greatly from baseline to the early phase (mean (SD), 50 (9) to 37 (7), p < 0.05) and reached a steady level thereafter. In contrast, a continued increase in peak Vo(2) was noted from the early to the late phase (16.9 (4.1) to 21.1 (5.0) ml/kg/min, p < 0.05). The decrease in the Ve-Vco(2) slope from baseline to the early phase, but not the increase in peak Vo(2) correlated strongly with the decrease in pulmonary vascular resistance after surgery (r = 0.75, p < 0.01). Conclusions-Thromboendarterectomy may cause an immediate improvement in ventilatory efficiency, possibly through its beneficial haemodynamic effects. In contrast, exercise capacity may continue to improve towards the late phase, reflecting peripheral adaptation to exercise.