Eisenmenger syndrome: current perspectives Heba Nashat,1–3 Aleksander Kempny,1–3 Colm McCabe,1 Laura C Price,1–3 Carl Harries,1 Rafael Alonso-Gonzalez,1–3 Michael A Gatzoulis,1–3 Stephen J Wort,1–3 Konstantinos Dimopoulos1–3 1Adult Congenital Heart Centre and National Centre for Pulmonary Hypertension, Royal Brompton Hospital, 2National Heart and Lung Institute (NHLI), Imperial College, 3National Institute for Health Research (NIHR) Cardiovascular Biomedical Research Unit, Royal Brompton Hospital and National Heart and Lung Institute, Imperial College, London, UK Abstract: Eisenmenger syndrome (ES) is the most severe form of pulmonary arterial hypertension (PAH) related to congenital heart disease (CHD). It results from a cardiac defect allowing significant systemic-to-pulmonary (left-to-right) shunting, which triggers the development of pulmonary vascular disease (PVD) if the defect is not repaired in a timely fashion. Once severe PVD has developed, the defect cannot be repaired. With advances in pediatric cardiology and surgery, the prevalence of ES is steadily falling in developed countries; nonetheless, there will always be patients who are unsuitable for repair at the time of diagnosis, or emigrating from countries with less advanced healthcare, who will develop ES. ES is a multisystem disorder causing chronic hypoxemia and reduced cardiac output resulting in significant morbidity and mortality. While lung (plus defect repair) or combined heart and lung transplantation is thought be the definitive treatment for ES, transplant organs are a limited resource and long-term results are still suboptimal. PAH pharmacotherapy was, until quite recently, largely directed at symptomatic relief and had no impact on morbidity and mortality. Targeted PAH therapies have recently been proven to be beneficial in various forms of PAH in terms of functional status, progression of disease, and prognosis. Data on the effect of PAH therapies in the ES cohort remain limited, but available studies demonstrate evidence of improvement in symptoms, exercise capacity, and some evidence of survival benefit. ES patients should be followed in specialized centers, by means of an interdisciplinary approach by clinicians experienced in PAH and CHD. However, local physicians working in cardiology, respiratory medicine, primary care, and emergency services are likely to encounter ES patients and need to be aware of the main issues and pitfalls in their care. The authors present an overview of the management of ES, focusing on the most common issues and complications. Keywords: Eisenmenger syndrome, pulmonary arterial hypertension, congenital heart disease, cyanosis, pulmonary arterial hypertension therapies, hyperviscosity, thrombosis, bleeding, pregnancy, Down syndrome