Pulmonary Hypertension: Intensification and Personalisation of Combination Rx

Inclusion Criteria: * Able to provide informed consent * Age 18-80 years * PAH which is idiopathic, heritable or associated with drugs, toxins or connective tissue disease * Stable PAH therapeutic regime comprising any combination of ERA and PDE5i for at least 1 month prior to screening (unless unable to tolerate therapy) * WHO functional class III * Resting mPAP ≥20 mmHg, pulmonary capillary wedge pressure ≤15 mmHg, pulmonary vascular resistance ≥2 Wood Units measured by right heart catheterisation at time of diagnosis * 6MWT \>50m at entry * Estimated glomerular filtration rate (eGFR)\>30 ml/min/1.73 m² at entry (Appendix C) * Inadequate treatment response (clinically determined) Exclusion Criteria: * Unable to provide informed consent * Pregnancy * Unprovoked pulmonary embolism (at any time) * Acute infection at time of screening (rescreening is permitted) * PAH due to human immunodeficiency virus, portal hypertension, schistosomiasis, congenital heart disease * Pulmonary hypertension due to left heart, lung, thromboembolic or unclear/multifactorial disease (Group II-V) * Unable to tolerate aspirin or P2Y12 inhibitor * Hypersensitivity to selexipag or riociguat * Clinically-significant renal disease (eGFR≤30 ml/min/1.73m2) * Anaemia (haemoglobin \<10 g/dl) * Left-sided heart disease and/or clinically significant cardiac disease, including but not limited to any of the following: aortic or mitral valve disease greater than mild aortic insufficiency; mild aortic stenosis;…