A 1-month-old girl is brought to the office for a routine well-child visit. The patient has no symptoms and is feeding well. Weight and length are stable at the 45th percentile. Pulse is 120/min, and respirations are 35/min. Oxygen saturation is 97% on room air. She is breathing comfortably without retractions or grunting. There is no cyanosis. Jugular venous pressure is not elevated. The lungs are clear to auscultation. A grade 3/6 holosystolic murmur and a systolic thrill are present at the left lower sternal border. Blood pressure is 80/40 mm Hg in her right arm and 78/38 mm Hg in her right leg. A chest x-ray reveals an enlarged left heart contour. What is the most likely cause of this patient's x-ray findings?

Question

A 1-month-old girl is brought to the office for a routine well-child visit.  The patient has no symptoms and is feeding well.  Weight and length are stable at the 45th percentile.  Pulse is 120/min, and respirations are 35/min.  Oxygen saturation is 97% on room air.  She is breathing comfortably without retractions or grunting.  There is no cyanosis.  Jugular venous pressure is not elevated.  The lungs are clear to auscultation.  A grade 3/6 holosystolic murmur and a systolic thrill are present at the left lower sternal border.  Blood pressure is 80/40 mm Hg in her right arm and 78/38 mm Hg in her right leg.  A chest x-ray reveals an enlarged left heart contour.  What is the most likely cause of this patient's x-ray findings?

Quizplus · Accepted Answer

11ec25c8_d615_9c38_bc81_6563cb1db51a_MD0003_00 This patient's holosystolic murmur and thrill along the left sternal border are consistent with a ventricular septal defect (VSD). After birth, pulmonary vascular resistance (PVR) begins to decline, with the right ventricle contracting against PVR and the left ventricle contracting against the relatively higher systemic vascular resistance. This pressure differential between the right- and left-sided chambers of the heart causes left-to-right shunting via the VSD. ventricular septal defect Small VSDs are usually hemodynamically insignificant due to a small volume of shunted blood. However, a larger VSD leads to volume overload and dilation of the right ventricle. The excess volume is then pumped through the lungs and delivered to the left atrium. This increased left atrial preload leads to left atrial and ventricular chamber enlargement, seen on chest x-ray as an enlarged left heart contour. Presentation of VSD ranges from asymptomatic in patients with small VSDs to acute heart failure in the neonatal period or infancy in patients with moderate to large VSDs. This infant with radiographic evidence of left-sided chamber enlargement likely has a relatively large VSD; she will likely develop signs of heart failure (eg, increased work of breathing, failure to thrive) due to continued pulmonary overcirculation and biventricular volume overload. (Choice A) Asymmetric septal hypertrophy describes hypertrophic cardiomyopathy, a diagnosis rarely made during infancy. Left ventricular (LV) outflow tract obstruction causes a crescendo-decrescendo systolic murmur, and septal enlargement has minimal effect on the cardiac appearance on x-ray. hypertrophic cardiomyopathy (Choice B) Decreased LV contractility with reduced cardiac output (ie, low-output heart failure) can cause left-sided volume overload with an enlarged left heart contour on chest x-ray. However, with VSD, LV contractility and cardiac output are maintained, and high-output heart failure occurs due to inability of the LV to keep up with the increased venous return from the pulmonary circulation. (Choice D) LV inflow obstruction (ie, mitral stenosis) is a rare congenital abnormality. Mitral stenosis causes left atrial enlargement with straightening of the upper left heart border on chest x-ray, and a diastolic (not systolic) murmur is expected. (Choice E) Over years (not months), the left-to-right shunt through a large VSD can reverse to right-to-left flow (ie, Eisenmenger syndrome), causing cyanosis, which is not present in this patient. right-to-left flow Educational objective: A ventricular septal defect causes a holosystolic murmur at the left sternal border due to left-to-right intracardiac shunting. Right ventricular volume overload leads to increased left atrial preload and enlargement of both the right ventricle and left-sided chambers. Chest x-ray typically reveals an enlarged left heart contour.

A 1-Month-Old Girl Is Brought to the Office for a Routine