Neonatal Cardiac Physiology Quiz

Neonatal Cardiac Physiology: Understanding Fetal and Transitional Circulation

• Neonatal cardiac physiology is different from adult cardiac physiology and is designed to meet the unique needs of the neonate.
• To understand neonatal cardiac physiology, one must first understand fetal circulation and the changes that occur during the transitional circulation at birth.
• The fetal circulation is in parallel, with the RV ejecting approximately two-thirds of the combined ventricular output compared to one-third ejected by the LV.
• At birth, the lungs open, and pulmonary vascular resistance (PVR) drops considerably, leading to changes in circulation.
• The pressure in the LA becomes higher than the RA, resulting in the functional closure of the foramen ovale, which will permanently seal in most babies over several weeks.
• The ductus arteriosus briefly becomes bidirectional and then reverses to become a left-to-right shunt, with functional closure typically occurring in the first 24 hours of life.
• With the functional closure of these shunts, the neonatal circulation transitions from a parallel circulation to one in series, with the RV workload decreasing and the LV workload increasing.
• The neonatal heart has more noncontractile connective tissue elements relative to sarcomere volume, resulting in a stiffer ventricle with impaired relaxation.
• The neonatal heart operates at a lower “break point” on the Frank Starling curve, making cardiac output more heart rate dependent.
• Normal age-related values for heart rate and blood pressure are shown in Table 131-1.
• Pulmonary hypertension can result in respiratory failure if not treated, with three possible mechanisms leading to persistent pulmonary hypertension of the newborn (PPHN).
• Aggressive treatment of the cause of persistent pulmonary hypertension is necessary to prevent the development of Eisenmenger’s syndrome.

Neonatal Cardiac Physiology: Understanding Fetal and Transitional Circulation

• Neonatal cardiac physiology is different from adult cardiac physiology and is designed to meet the unique needs of the neonate.
• To understand neonatal cardiac physiology, one must first understand fetal circulation and the changes that occur during the transitional circulation at birth.
• The fetal circulation is in parallel, with the RV ejecting approximately two-thirds of the combined ventricular output compared to one-third ejected by the LV.
• At birth, the lungs open, and pulmonary vascular resistance (PVR) drops considerably, leading to changes in circulation.
• The pressure in the LA becomes higher than the RA, resulting in the functional closure of the foramen ovale, which will permanently seal in most babies over several weeks.
• The ductus arteriosus briefly becomes bidirectional and then reverses to become a left-to-right shunt, with functional closure typically occurring in the first 24 hours of life.
• With the functional closure of these shunts, the neonatal circulation transitions from a parallel circulation to one in series, with the RV workload decreasing and the LV workload increasing.
• The neonatal heart has more noncontractile connective tissue elements relative to sarcomere volume, resulting in a stiffer ventricle with impaired relaxation.
• The neonatal heart operates at a lower “break point” on the Frank Starling curve, making cardiac output more heart rate dependent.
• Normal age-related values for heart rate and blood pressure are shown in Table 131-1.
• Pulmonary hypertension can result in respiratory failure if not treated, with three possible mechanisms leading to persistent pulmonary hypertension of the newborn (PPHN).
• Aggressive treatment of the cause of persistent pulmonary hypertension is necessary to prevent the development of Eisenmenger’s syndrome.

Neonatal Cardiac Physiology: Understanding Fetal and Transitional Circulation

• Neonatal cardiac physiology is different from adult cardiac physiology and is designed to meet the unique needs of the neonate.
• To understand neonatal cardiac physiology, one must first understand fetal circulation and the changes that occur during the transitional circulation at birth.
• The fetal circulation is in parallel, with the RV ejecting approximately two-thirds of the combined ventricular output compared to one-third ejected by the LV.
• At birth, the lungs open, and pulmonary vascular resistance (PVR) drops considerably, leading to changes in circulation.
• The pressure in the LA becomes higher than the RA, resulting in the functional closure of the foramen ovale, which will permanently seal in most babies over several weeks.
• The ductus arteriosus briefly becomes bidirectional and then reverses to become a left-to-right shunt, with functional closure typically occurring in the first 24 hours of life.
• With the functional closure of these shunts, the neonatal circulation transitions from a parallel circulation to one in series, with the RV workload decreasing and the LV workload increasing.
• The neonatal heart has more noncontractile connective tissue elements relative to sarcomere volume, resulting in a stiffer ventricle with impaired relaxation.
• The neonatal heart operates at a lower “break point” on the Frank Starling curve, making cardiac output more heart rate dependent.
• Normal age-related values for heart rate and blood pressure are shown in Table 131-1.
• Pulmonary hypertension can result in respiratory failure if not treated, with three possible mechanisms leading to persistent pulmonary hypertension of the newborn (PPHN).
• Aggressive treatment of the cause of persistent pulmonary hypertension is necessary to prevent the development of Eisenmenger’s syndrome.