Pregnancy in the FONTAN palliation: physiology, management and new insights from bioengineering

Abstract

Fontan palliation for the single ventricle results in a challenging and delicate physiological state. At rest, the body adapts to a low cardiac output and high systemic venous pressure. However, when physiological demands increase, such as in the case of exercise or pregnancy, this delicate physiology struggles to adapt due to the inability of the heart to pump blood into the lungs and the consequent lack of augmentation of the cardiac output.Due to the advances in paediatric cardiology, surgery and intensive care, today most patients born with congenital heart disease reach adulthood. Consequently, many women with a Fontan circulation are becoming pregnant and so far data suggest that, although maternal risk is not high, the outcomes are poor for the foetus. Little is known about the reasons for this disparity and how the Fontan circulation adapts to the physiological demands of pregnancy.Here we review current knowledge about pregnancy in Fontan patients and explore the potential role of computational modelling as a means of better understanding this complex physiology in order to potentially improve outcomes, particularly for the foetus.

Multifaceted Fontan Patients and Their Response to Pregnancy

“…Previous studies have shown various maternal complications in these patients, including arrhythmias, heart failure, and thromboembolism, as well as antepartum and postpartum haemorrhage. 1 , 2 Fetal complications include miscarriage, IUGR, prematurity, and emergency and operative delivery. 3 …”

Management of the Fontan patient during pregnancy

“…In patients with a normally functioning biventricular heart, blood volume can increase by up to 40%, and adaptive changes include an increase in heart rate by 15-30%, increase in stroke volume by 15-20% and progressive increase in cardiac output to nearly 50% at term [48,49]. Although the reduced cardiac output from a single ventricle may be reasonably tolerated at rest, it is not expected to increase by similar capacity during pregnancy [27,50]. Fortunately, the vascular tree does respond to accommodate the increased plasma volume, resulting in a lowered PVR and systemic vascular resistance (SVR) in the first trimester [50].…”

“…Although the reduced cardiac output from a single ventricle may be reasonably tolerated at rest, it is not expected to increase by similar capacity during pregnancy [27,50]. Fortunately, the vascular tree does respond to accommodate the increased plasma volume, resulting in a lowered PVR and systemic vascular resistance (SVR) in the first trimester [50]. As a result, a stable mean pulmonary artery pressure is maintained throughout pregnancy.…”