Echocardiographic Evaluation of Transitional Circulation for the Neonatologists

Abstract

The hemodynamic changes during the first few breaths after birth are probably the most significant and drastic adaptation in the human life. These changes are critical for a smooth transition of fetal to neonatal circulation. With the cord clamping, lungs take over as the source of oxygenation from placenta. A smooth transition of circulation is a complex mechanism and primarily depends upon the drop in pulmonary vascular resistance (PVR) and increase in systemic vascular resistance (SVR). Understanding the normal transition physiology and the adverse adaptation is of utmost importance to the clinicians looking after neonates. It may have a significant influence on the presentation of congenital heart defects (CHDs) in infants. Bedside echocardiography may help in understanding the transition physiology, especially the hemodynamic changes and shunting across ductus arteriosus and foramen ovale, and it may play an important role in making judicious clinical decisions based upon the altered physiology.

Cardiovascular and respiratory physiology in children

“…Premature infants and infants with underlying congenital heart disease and diaphragmatic hernia may have altered transitional physiology. [23]…”

Echocardiographic analysis of left ventricular function in term and preterm neonates at week 40 of postconceptional life

“…left ventricular (LV) afterload, whereas the fetal pulmonary circulation changes from a high--resistance and low-flow to a low-resistance and high-flow circulation, with increased ventricular preload. [2][3][4][5] Moreover, the closure of fetal shunts and an increased oxygen demand after birth nearly double cardiac output. 6 The transition from fetal to neonatal circulation puts a high strain on the myocardium in children born at term and is even more stressful for the myocardium in preterm neonates.…”

Evolution of left ventricular function in preterm infants: long‑term significance

“…From animal studies on cardiac modeling in preterm infants, Bensley et al 10 concluded that The hemodynamic changes during the transition from fetal to neonatal circulation are probably the most significant and drastic adaptation in the human life. 1 These changes are well studied in term infants. However, the transition from fetal to neonatal circulation in preterm neonates is poorly understood.…”

“…Therefore, understanding the transitional physiology and cardiac function is of paramount importance in managing preterm infants with hemodynamic instability. 1 The transition process from fetal to neonatal circulation may be more challenging in preterm infants because of the following factors: 1) impaired myocardial performance due to immature myocardium possessing an inefficient contractile mechanism leading to inherited impaired cardiac functions; 2) higher incidence of persistent shunting across the patent ductus arteriosus, which plays an important role in cardiovascular physiology and affects cardiac functions; 3) limited ability to increase heart rate to increase cardiac output; 4) increased cardiac demand from higher baseline heart rate; and 5) premature myocardium may lack adequate adrenergic innervation and underdeveloped hypothalamic-pituitary-adrenal axis. Therefore, preterm infants may have limited ability to increase cardiac output during adverse adaptation and they may show inadequate response to stressful situations.…”

“…Therefore, preterm infants may have limited ability to increase cardiac output during adverse adaptation and they may show inadequate response to stressful situations. [1][2][3] Recently, there has been a great interest among clinicians to acquire skills in neo nato-differences in their myocardium and cardiac function at term-equivalent age when compared with term infants. Preterm infants have a higher risk of adverse cardiovascular events and heart failure in early adulthood.…”