Pulmonary arterial hypertension with left to right shunts: When to treat and/or close?

Pulmonary arterial hypertension (PAH) is defined as increase in mean pulmonary arterial pressure and pulmonary vascular resistance (PVR). It can be associated with congenital heart disease (CHD) with the following subtypes: 1) uncorrected left-to-right (L-R) intracardiac shunt leading to overload of the pulmonary circulation and a progressive increase of PVR; 2) Eisenmenger syndrome, appearing when a large post-tricuspid shunt is left uncorrected and pulmonary vascular disease (PVD) is severe, so the shunt becomes bidirectional or right-to-left, causing cyanosis; 3) PAH after shunt closure, when PVR arises after a defect correction; and 4) PAH associated with small or coincidental defects. While the treatment of patients with Eisenmenger syndrome is well established, the treatment of patients with PAH in whom there is a L-R shunt (with no cyanosis) remains unclear and requires expertise. In such patients, correction of the defect may be contemplated if there is mild PVD and a significant L-R shunt. Others may benefit from a “treat and repair” strategy, which involves the use of PAH therapy to achieve a drop in PVR, with the aim of achieving operability criteria. Cardiac catheterization is at the center of the evaluation and follow-up of these patients, collecting “baseline” data and providing the opportunity to challenge the pulmonary circulation, manipulate the loading status, or temporarily occlude the defect. This article provides a detailed overview of the pathophysiology and treatment options for patients with PAH associated with a L-R congenital shunt, including current approaches to operability and the use of PAH therapies.