ICU · Cardiovascular

Pulmonary hypertension and right heart failure

Also known as Pulmonary arterial hypertension (PAH) · Right ventricular failure · Cor pulmonale · WHO Group 1-5 classification · Pulmonary vascular disease · Pre-capillary PH · Post-capillary PH · Isolated post-capillary PH · CTEPH · BMPR2 mutation · Inhaled nitric oxide · Prostacyclin therapy

Pulmonary hypertension (PH) = mean pulmonary artery pressure (mPAP) 20 mmHg (ESC/ERS 2022). Five WHO groups: Group 1 (pulmonary arterial hypertension, PAH — idiopathic, heritable [BMPR2], connective tissue disease [SSc], congenital heart disease, portal hypertension, drugs), Group 2 (left heart disease — the commonest cause overall, HFpEF/HFrEF/valvular), Group 3 (lung disease/hypoxia — COPD, ILD, OSA), Group 4 (chronic thromboembolic PH, CTEPH — potentially curable by pulmonary endarterectomy), Group 5 (multifactorial — haematological, systemic, metabolic). Haemodynamic phenotyping by right heart catheterisation: pre-capillary (mPAP 20, wedge <15, PVR 2 WU), isolated post-capillary (mPAP 20, wedge 15, PVR <2 WU), combined pre/post-capillary. Pathophysiology: vascular remodelling triad — (1) endothelial dysfunction (reduced NO and prostacyclin, excess endothelin-1), (2) smooth muscle proliferation and medial hypertrophy, (3) in situ thrombosis (procoagulant state) — producing a fixed, obliterative pulmonary vasculopathy and raised PVR. RV FAILURE CASCADE (the main cause of death): chronic pressure overload - RV hypertrophy - RV dilatation - tricuspid regurgitation - septal shift into the LV - reduced LV filling - low cardiac output - cardiogenic shock. RV is uniquely afterload-sensitive (thin-walled, crescent-shaped, adapted to a low-pressure, low-resistance circuit). ICU PRESENTATION: exertional syncope (a red flag of low fixed output), hypoxaemia (right-to-left shunt via PFO, V/Q mismatch), and overt right heart failure (raised JVP, peripheral oedema). ICU MANAGEMENT: (1) protect the RV — cautious preload only if hypovolaemic; the RV is volume-intolerant), reduce afterload (inhaled nitric oxide around 20 ppm in ICU cohorts, inhaled/IV prostacyclin, milrinone), support contractility (milrinone PREFERRED — inotropy + pulmonary vasodilation; dobutamine), maintain systemic BP with noradrenaline (preserve RV coronary perfusion — systemic pressure must be kept at least close to RV systolic pressure or the RV ischaemias). (2) Optimise the gas exchange and ventilation — avoid hypoxia, hypercapnia, and acidosis (all heighten pulmonary vascular tone); minimise PEEP and intrathoracic pressure. (3) PAH-specific therapy for confirmed Group 1 PAH — endothelin receptor antagonists (bosentan, macitentan), PDE5 inhibitors (sildenafil, tadalafil), prostacyclin analogues (epoprostenol, iloprost, treprostinil), soluble guanylate cyclase stimulators (riociguat — never combined with PDE5 inhibitors). (4) Treat the underlying group — pulmonary endarterectomy for Group 4, left heart disease for Group 2 (PAH drugs are HARMFUL in post-capillary PH). (5) Mechanical support (VA-ECMO) for refractory RV failure. Avoid systemic vasodilators, excessive fluids, and high intrathoracic pressure.