Where is a fourth heart sound (S4) most commonly heard in neonates?

The fourth heart sound (S4) in neonates is typically associated with increased resistance to filling of the ventricles, often due to conditions such as decreased compliance of the heart muscle or increased ventricular stiffness. In healthy neonates, S4 is most commonly heard at the apex of the heart, where the heart’s left ventricle is closest to the chest wall and where the sounds generated during the filling phase of the diastole can be best appreciated.

The apex of the heart is located near the left fourth or fifth intercostal space at the midclavicular line. This position allows for optimal acoustic transmission of heart sounds. The S4 sound is not commonly associated with the other locations noted, as they are not where the left ventricle is best auscultated and do not typically provide the same clarity for diastolic sounds. Thus, auscultation at the apex allows clinicians to accurately assess the cardiopulmonary status of the neonate.