Pulmonary hypertension

Pulmonary arterial hypertension (PAH) in the setting of HIV infection recently acquired its own specific category in the Updated Classification of Pulmonary Hypertension (1). It consistently has been found in 0.5% of HIV-infected people, a figure unchanged by the widespread use of effective ART (2) and represents a rate about a thousand times greater than that of idiopathic pulmonary hypertension as reported in the general population. Hospital discharge data suggests that PAH is under-recognised in comparison to known prevalence rates (3).  Pathological features are similar to idiopathic PAH. Viral particles from HIV are not found in affected tissues suggesting that the pathogenesis is likely a consequence of HIV-induced inflammation or other systemic changes. There may also be a contribution from other viral infections. High HIV viral load and low CD4+ T cell count appear to be predictive of HIV-associated PAH (4). Findings on gender differences have been variable but male intravenous drug users seem to be particularly at risk. There is experimental evidence for an additive effect of cocaine. Recent evidence has suggested a particular pathogenic role for Endothelin-1 (5). HIV infection may first be recognized in patients admitted with an initial diagnosis of idiopathic PAH (6).  As in the general community, PAH often presents late (NYHA Class II or IV).

Published guidelines do not recommend routine screening for PAH in the HIV-infected population but do highlight the need for consideration of PAH in patients with unexplained dyspnea. Initial investigations should include transthoracic echocardiography (which may also identify other cardiac causes of dyspnea). Definitive diagnosis of PAH requires right heart catheterization to demonstrate elevated pulmonary artery pressures in the presence of normal ‘wedge’ (left atrial) pressure. Whilst echocardiographic derived pulmonary systolic pressures of > 40mmHg have been used to identify patients with potential PAH, others have suggested that a lower cut off of 20mmHg may be prudent in order to avoid underdiagnosis.  Patients with suspected PAH should be referred for specialist evaluation.

Management of HIV patients with PAH broadly follows the guidelines for PAH management in the general population (1). In the HIV population with PAH, anticoagulation is not recommended. Calcium channel blockers appear to be less effective in PAH due to HIV infection. Treatment with phosphodiesterase inhibitors may require dose adjustment due to drug-drug interactions. In a particular study of HIV-infected patients with PAH, a long-term benefit was demonstrated with bosentan (7). Lung transplantation has been successfully undertaken in cases with otherwise uncontrolled PAH.