Collaterals in congenital heart disease: when and how to treat?

The development of collateral circulation is not that rare in patients with congenital heart defects. These collaterals can affect cardiovascular hemodynamics and cause systemic arterial desaturation, which arises the question whether these should be closed. To date, few if any reports have been published on the therapeutic management of collaterals in adult patients with congenital heart disease in heart failure (HF). The focus of this article is to provide a pragmatic approach in the assessment of collateral circulation of the patient with HF. By considering the underlying hemodynamics and overall effects of the collateral circulation, we aim to provide a practical tool useful in clinical decision making. The paper highlights mainly the systemic venous to systemic venous collaterals, systemic venous to pulmonary venous (or pulmonary venous atrium) collaterals, and pulmonary arterio-venous malformations. Systemic venous anomalies are frequent and reported in 20% to 40% of patients who underwent Glenn or Fontan procedure. A reduction in effective pulmonary blood flow, coupled with increasing oxygen demands with growth, as well as a pressure difference between the higher pressure caval venous system and lower pressure atria (so called decompressing collaterals) are potential causes of collateral formation. Whether angiogenesis de novo or reappearance of embryological venous channels is responsible for collateral formation remains to be elucidated.