The Diagnostic Challenge of Group 2 Pulmonary Hypertension

Pulmonary hypertension (PH) secondary to left heart diseases associated with an increased pulmonary venous pressure is the second of a total of five groups recognized in the classification of PH. Group 2 PH is the commonest form of PH, and is associated with high morbidity and mortality. The diagnosis of group 2 PH relies on a clinical probability assessment in which echocardiography plays a major role, eventually followed by the invasive measurements of a mean pulmonary artery pressure (mPAP) ≥ 25 mmHg and a wedged PAP (PAWP) > 15 mmHg. This combination of mPAP and PAWP defines “post-capillary PH” (pcPH). Post-capillary PH is most often associated with a diastolic pressure gradient (DPG) or gradient between diastolic PAP and PAWP < 7 mmHg and/or a pulmonary vascular resistance (PVR) ≤ 3 Wood units (WU), and is called isolated pcPH (IpcPH). Postcapillary PH with a DPG ≥ 7 mmHg and/or a PVR > 3 WU is then combined pre- and postcapillary PH (CpcPH). Post-capillary PH is associated with a decreased survival in proportion to increased PAP and decreased right ventricular (RV) ejection fraction. CpcPH occurs in 12-13% of patients with pcPH. CpcPH is associated with pulmonary vascular remodeling and altered RV-arterial coupling. The prognosis of CpcPH is poor.