What clinical significance does a split S2 have during inspiration?

A split S2 during inspiration occurs due to changes in intrathoracic pressure, which affects the timing of the closure of the aortic and pulmonic valves. During inspiration, the decreased intrathoracic pressure leads to increased venous return to the right heart, which prolongs right ventricular systole. Consequently, the pulmonic valve closes slightly later than the aortic valve, making the split sound more pronounced.

This phenomenon is clinically significant because it reflects the normal physiological response of the heart to the respiratory cycle. As a result, the more pronounced split during inspiration indicates an intact physiological mechanism, allowing clinicians to differentiate between a normal finding and pathological conditions that may alter heart sounds.