When assessing the apical pulse in a 3-month-old infant, where is the apex located?

• A. 5th intercostal space midclavicular line
• B. 4th intercostal space to the left of the sternum
• C. 3rd intercostal space left sternal border
• D. 2nd intercostal space right sternal border

Answer: (B)

In infants, the apical impulse sits higher and more toward the left side of the chest because the heart is positioned more horizontally in a smaller thorax. For a 3-month-old, the apical impulse is typically felt at the left fourth intercostal space along the sternal border. This placement reflects how the infant heart lies closer to the sternum and higher up compared to adults. As children grow, the apex shifts downward and laterally toward the left midclavicular line, nearing the adult location near the 5th intercostal space. So the expected site in a young infant is the left chest at the fourth intercostal space near the sternum.