Which statement is true regarding the splitting of the second heart sound?

The splitting of the second heart sound occurs due to the asynchronous closure of the aortic and pulmonic valves, which is most commonly pronounced during inhalation. This phenomenon can be best appreciated over the pulmonic area of the thorax, which is located in the second intercostal space at the left sternal border. Using the bell of the stethoscope may enhance the detection of low-pitched sounds, but the splitting itself, which is considered a high-frequency sound, is often better heard with the diaphragm. However, the anatomical location for optimal hearing remains valid.

Increased splitting tends to be noted during deep inhalation owing to the physiological changes in intrathoracic pressure and increased venous return to the right side of the heart, which causes the right ventricle to take longer to empty. Therefore, the statement regarding splitting increasing with exhalation is not true, as it actually increases with inhalation.

Additionally, the sound is not primarily best heard over the apex since that area primarily reflects the action of the mitral valve. Finally, the splitting does indeed vary with respiration; hence, the continuation of the sound regardless of breathing would contradict the physiological behavior of heart sounds.