Eisenmenger Syndrome

A patient with Eisenmenger syndrome may look chronically blue, have a low oxygen saturation that is usual for them, and still be clinically stable. The danger is not the number alone; it is a change from the patient’s baseline or a loss of the conditions that support forward systemic blood flow. The congenital defect created a large left-to-right shunt early in life. Pulmonary vascular resistance then rose progressively until blood could no longer move easily through the pulmonary circulation. The shunt became bidirectional or right-to-left, allowing deoxygenated blood to bypass the lungs and enter systemic circulation. That model explains the cyanosis, secondary erythrocytosis, exercise limitation, paradoxical emboli, and intolerance of dehydration, vasodilatation, and anaesthesia. For Canadian practice, this is advanced pulmonary arterial hypertension associated with congenital heart disease. Assessment and treatment should be shared with an adult congenital heart disease and pulmonary hypertension centre; decisions that might be routine in idiopathic pulmonary arterial hypertension cannot automatically be applied to Eisenmenger physiology.