Pulmonary Vascular Disease: Grading, Grouping, and Risk
Pulmonary hypertension defined
The current hemodynamic definition of precapillary pulmonary hypertension is mean pulmonary arterial pressure >20 mmHg with pulmonary vascular resistance >2 Wood units and pulmonary artery wedge pressure ≤15 mmHg. Group 1 (pulmonary arterial hypertension) is idiopathic, heritable, drug/toxin-associated, or related to connective tissue disease, congenital heart disease, portal hypertension, or HIV. Group 2 is left heart disease, group 3 is lung disease/hypoxia, group 4 is chronic thromboembolic disease, and group 5 is multifactorial. Group assignment dictates therapy, so the exam traps live here: giving PAH drugs to group 2 or 3 disease causes harm.
Testing and therapy
Echocardiography estimates right ventricular systolic pressure but cannot diagnose; right heart catheterization confirms. Vasoreactivity testing with inhaled nitric oxide identifies the roughly 10% of idiopathic PAH patients who may be treated with calcium channel blockers; testing is appropriate only in group 1. Endothelin receptor antagonists need liver monitoring, phosphodiesterase-5 inhibitors must not be combined with nitrates, and riociguat must not be combined with sildenafil. Group 4 is treated surgically with pulmonary endarterectomy after lifelong anticoagulation.
Acute PE
Risk-stratify with the sPESI and markers of right ventricular strain plus troponin. Hemodynamic instability means high-risk PE and systemic thrombolysis (or catheter embolectomy). Normotensive patients with RV strain fall into intermediate-risk categories and generally receive anticoagulation with close monitoring rather than routine lysis.
Worked rule
Young woman with exertional dyspnea, loud P2, RVSP 70 on echo, normal wedge pressure, no V/Q mismatches: proceed to right heart catheterization and vasoreactivity testing before naming therapy.