A 10-day-old boy born at home is brought to the emergency department due to difficulty breathing and sweating with feeds. He was born at 38 weeks gestation via spontaneous vaginal delivery. The patient has been breastfeeding every 2 hours for 5-10 minutes per side. The mother notes that he sweats while he feeds, and his lips turn blue. Weight is at the 5th percentile and length is at the 50th percentile. On examination, the patient is currently not cyanotic. There is a III/VI systolic crescendo-decrescendo murmur best heard along the left upper sternal border. Chest x-ray is shown below: Which of the following most likely represents the pressure changes that take place in this patient during feedings?

Question

A 10-day-old boy born at home is brought to the emergency department due to difficulty breathing and sweating with feeds. He was born at 38 weeks gestation via spontaneous vaginal delivery. The patient has been breastfeeding every 2 hours for 5-10 minutes per side. The mother notes that he sweats while he feeds, and his lips turn blue. Weight is at the 5th percentile and length is at the 50th percentile. On examination, the patient is currently not cyanotic. There is a III/VI systolic crescendo-decrescendo murmur best heard along the left upper sternal border. Chest x-ray is shown below:

Which of the following most likely represents the pressure changes that take place in this patient during feedings?

Quizplus · Accepted Answer

11ec160b_3aa2_5107_9249_6d21d84852ac_MD0001_00 This neonate has diaphoresis and episodic cyanosis with feeding, suggesting cyanotic congenital heart disease. The murmur of pulmonic stenosis and evidence of right ventricular hypertrophy (ie, boot-shaped heart) on chest x-ray are consistent with tetralogy of Fallot (ToF). The major defects in ToF are right ventricular outflow tract (RVOT) obstruction (caused by an overriding aorta) and a ventricular septal defect (VSD); concentric right ventricular hypertrophy develops due to increased right ventricular pressure load compared to normal. The degree of RVOT obstruction is the major driver of symptoms in ToF because it determines how much blood flows through the pulmonary artery to the lungs and the magnitude and direction of shunting through the VSD. Because some degree of RVOT obstruction is fixed and some degree is dynamic (ie, subject to an increase with activity [eg, crying, feeding]), many patients have left-to-right or neutral shunting through the VSD at rest (and are acyanotic) but develop cyanosis when a dynamic increase in RVOT obstruction forces blood through the VSD to create a right-to-left shunt (ie, tet episode). During a tet episode, the dynamic increase in RVOT obstruction leads to increased right ventricular pressure, facilitating the right-to-left shunting through the VSD. There is also decreased pulmonary arterial pressure (blood cannot pass through the RVOT tract into the pulmonary artery, reducing pulmonary blood flow), and decreased left atrial pressure (the left atrium receives less blood returning from the lungs). Due to the large size of the VSD in ToF, left ventricular pressure usually closely matches right ventricular pressure (ie, the ventricles are somewhat like a single chamber). A tet episode may be improved by bringing the knees to the chest. This maneuver increases systemic vascular resistance and afterload, reducing right-to-left shunting through the VSD and forcing more blood through the RVOT. Educational objective: The major defects in tetralogy of Fallot are right ventricular outflow tract (RVOT) obstruction and a ventricular septal defect (VSD). In many patients, activities (eg, feeding, crying) can precipitate cyanotic episodes (tet episodes) by causing a dynamic increase in RVOT obstruction. During these episodes right ventricular pressure is increased and pulmonary arterial and left atrial pressures are decreased as blood is shunted away from the pulmonary circulation (ie, right-to-left shunting through the VSD).

A 10-Day-Old Boy Born at Home Is Brought to the Emergency