"Treat-to-target" in pulmonary arterial hypertension and the use of extracorporeal membrane oxygenation as a bridge to transplantation

Abstract

To the Editor: A 30-yr-old female was referred to the Hanover Medical School (Hanover, Germany) in July 2007 following a diagnosis of idiopathic pulmonary arterial hypertension (PAH). She had no other comorbidities. At the time of diagnosis she was in World Health Organization functional class (WHO FC) III with a 6-min walk distance (6MWD) of 402 m. Cardiopulmonary exercise testing (CPET) showed that her peak oxygen uptake ( V ′O2) was markedly impaired (11.6 mL·min−1·kg−1; target range >15 mL·min−1·kg−1) [1]. Echocardiography revealed a tricuspid annular systolic plane excursion (TAPSE) of 1.6 cm (normal value >2 cm) indicating serious impairment of right ventricular function. The results of right heart catheterisation (RHC) are shown in table 1. Haemodynamics were compatible with diagnosis; a low cardiac output and high pulmonary vascular resistance. In accordance with guideline recommendations [1], treatment was initiated with sildenafil 20 mg three times daily. This was well tolerated and 3 months later her functional status had improved to WHO FC II and her 6MWD had increased to 465 m. Although her TAPSE had improved to 1.8 cm, it was still below normal, suggesting her right ventricular (RV) function remained impaired. To further investigate this CPET was repeated, which revealed that her peak V ′O2 had only slightly improved from baseline (12.5 mL·min−1·kg−1) and that her oxygen pulse ( V ′O2/heart rate), an indirect measure of stroke volume, was only approximately half of that predicted. Taken together these data indicated the patient's response to sildenafil was suboptimal, particularly with respect to RV function. The decision was then made to initiate treatment with bosentan in addition to her existing sildenafil regimen. Combination therapy was well tolerated, and there was no …