Management of pulmonary arterial hypertension associated with congenital systemic-to-pulmonary shunts and Eisenmenger's syndrome

Abstract

A large proportion of patients with congenital heart disease (CHD), in particular those with relevant systemic-to-pulmonary shunts, will develop pulmonary arterial hypertension (PAH) if left untreated. Persistent exposure of the pulmonary vasculature to increased blood flow, as well as increased pressure, may result in pulmonary obstructive arteriopathy, which leads to increased pulmonary vascular resistance that, if it approaches or exceeds systemic resistance, will result in shunt reversal. Eisenmenger's syndrome, the most advanced form of PAH associated with CHD, is defined as CHD with an initial large systemic-to-pulmonary shunt that induces severe pulmonary vascular disease and PAH, with resultant reversal of the shunt and central cyanosis. The histopathological and pathobiological changes seen in patients with PAH associated with congenital systemic-to-pulmonary shunts, such as endothelial dysfunction of the pulmonary vasculature, are considered similar to those observed in idiopathic or other associated forms of PAH. A pathological and pathophysiological classification of CHD with systemic-to-pulmonary shunt leading to PAH has been developed that includes specific characteristics, such as the type, dimensions and direction of the shunt, extracardiac abnormalities and repair status. A clinically oriented classification has also been proposed. The prevalence of PAH associated with congenital systemic-to-pulmonary shunts in Western countries has been estimated to range between 1.6 and 12.5 cases per million adults, with 25-50% of this population affected by Eisenmenger's syndrome. Clinically, Eisenmenger's syndrome presents with multiple organ involvement, with progressive deterioration of function over time. The signs and symptoms of Eisenmenger's syndrome in the advanced stages include central cyanosis, dyspnoea, fatigue, haemoptysis, syncope and right-sided heart failure. Survival of patients with Eisenmenger's syndrome is clearly less than that of the general population, but appears to be better than that of patients with idiopathic PAH in a comparable functional class. The treatment strategy for patients with PAH associated with congenital systemic-to-pulmonary shunts and, in particular, those with Eisenmenger's syndrome is based mainly on clinical experience rather than being evidence based. General measures include recommendations for physical activity, pregnancy, infections, air travel, exposure to high altitudes and elective surgery, and that psychological assistance be provided as necessary. Phlebotomies are required only when hyperviscosity of the blood is evident, usually when the haematocrit is >65%. The use of supplemental oxygen therapy is controversial and it should be used only in patients in whom it produces a consistent increase in arterial oxygen saturation. Oral anticoagulant treatment with warfarin can be initiated in patients with pulmonary artery thrombosis and absent, or only mild, haemoptysis. The following three classes of drugs targeting the correction of abnormalities in endothelial dysfunction have been approved recently for the treatment of PAH: (i) prostanoids; (ii) endothelin receptor antagonists; and (iii) phosphodiesterase-5 inhibitors. The efficacy and safety of these compounds have been confirmed in uncontrolled studies in patients with PAH associated with corrected and uncorrected congenital systemic-to-pulmonary shunts, as well as in patients with Eisenmenger's syndrome. One randomized controlled trial reported favourable short- and long-term outcomes of treatment with the orally active dual endothelin receptor antagonist bosentan in patients with Eisenmenger's syndrome. Lung transplantation with repair of the cardiac defect or combined heart-lung transplantation are options for Eisenmenger's syndrome patients with a poor prognosis. A treatment algorithm based on the one used in the treatment of PAH patients is proposed for patients with PAH associated with corrected and uncorrected congenital systemic-to-pulmonary shunts and Eisenmenger's syndrome.