Real World Difference After Changing Medication From Nonselective to Selective Endothelin Receptor Antagonist in Stable Eisenmenger Syndrome: Observational Study

Endothelin receptor antagonist is an established class of targeted therapy for pulmonary arterial hypertension (PAH). Nonselective ERA, Bosentan was the first approved ERA for PAH. Selective ERA, Ambrisentan was also approved for PAH treatment consequently. Although non-selective and selective ERA are both effective in clinical trials, there is no direct comparison for non-selective and selective ERA. Furthermore, approval study for both non-selective and selective ERA did not include the PAH associated with congenital heart disease (PAH-CHD) with significant shunt including Eisenmenger syndrome. Approval study for Ambrisentan;ARIES-1 and ARIES-2 trials also did not include the PAH-CHD In Korea, Bosentan was approved in 2003 and Ambrisentan was approved in 2009 for idiopathic PAH. Bosentan was also approved for PAH-CHD, however, Amrisentan was not because of limited data for PAH-CHD. Therefore, Bosentan was the only ERA covered by public health insurance since 2018 for PAH-CHD. Recently, Amrisentan was also approved for PAH associated with congenital heart disease including Eisenmger syndrome. And, there is a need for changing medication from double pill medication to once-daily dose medication because of patient's compliance.

PAH associated with CHD includes the group with significant shunt vs without shunt (s/p corrected state). When there is a shunt flow, change in pulmonary vascular resistance (PVR) and cardiac output can be a modulator of shunt flow, thus impact of pulmonary vasodilator on hemodynamics can be different from PAH without shunt. However, there is a limited data for changing ERA from non-selective to selective ERA. Our patients population can be interesting study group to understand the clinical response to changing between ERA because they are uniformly treated with non-selective ERA to selective ERA, Bosentan to Ambrisentan.

In this study, the investigators will evaluate the treatment effects and safety, patient compliance of Ambrisentan in Eisenmenger syndrome in PAH patients who have been previously treated with Bosentan.