Congenital Heart Disease part 10

RIGHT VENTRICLE TO PULMONARY CONDUIT

Conduit establish the continuity between the right ventricle and pulmonary artery in the complex defects when the native outflow tract is not amenable to reconstruction, including  pulmonary atresia, common arterial trunk, tetralogi of fallot, absent pulmonary valve syndrome, Rastelli procedure and Ross operation.

Types of conduits include valved (pulmonary or aortic homograft, bioprosthetic valves, bovine jugular vein conduit) and non-valved conduits.

There is no ideal conduit. Limited durability implicates early reoperation. Predictors for conduit failure are sterilization/preservation process, smaller conduit, conduit type, younger age at implantation, pulmonary stenosis, and diagnosis of transposition.

Complication include outgrowth, progressive obstruction with or wihout regurgitation, endocarditis, and aneurysm or pseudoaneurysms.

Clinical presentation may include exertional dyspnoea, palpitation, syncope and sudden cardiac death.


EISENMENGER SYNDROME AND SEVERE PULMONARY HYPERTENSION

A large proportion of patients with congenital heart disease, in particular those with relevant systemic to pulmonary shunts, if left untreated, develop pulmonary arterial hypertension. Eisenmenger syndrome is defined as a congenital heart disease with initially large systemic to pulmonary shunt, which in turn induces severe pulmonary vascular disease and pulmonary arterial hypertension, resulting in reversal of the shunt direction and central cyanosis.

The pathological lesions and the pathobiological changes of the pulmonary vasculature observed in patient with pulmonary arterial hypertension associated with congenital systemic to pulmonary shunts are considered to be very similar to those observed in the other pulmonary arterial hypertension forms. The monoclonal endothelial cell proliferation found in idiopathic pulmonary arterial hypertension has, however, not been confirmed in the other pulmonary arterial hypertension types, suggesting possible differences in  the altered cellular growth mechanisms. Endothelial dysfunction may include the shear stress and the circumferential stress  exerted on the pulmonary endothelium by the increased pulmonary flow and pressure. The initial morphological alterations (medial hypertrophy and intimal proliferation) are potentially reversible. However, as the disease progresses, the more advanced pathological changes (plexiform lesions and arteritis) appear to be irreversible.

Eisenmenger syndrome is a multi organ disorder with progressive deterioration over time. Clinical presentation include central cyanosis, dyspnoea, fatigue, hemoptysis, syncope and right heart failure in advanced stages. Since patients with reduced arterial oxygen saturation have abnormal haemostasis, including  thrombocytopenia, they are at risk for both bleeding and thrombosis. In particular, parietal thrombosis of enlarged proximal pulmonary arteries can be found up to 20% of patients, it may cause peripheral  embolization and pulmonary infaction, and associated with biventricular dysfunction and reduced pulmonary flow velocity.