Clinical Significance of a Loud Second Heart Sound

Physiologic and Clinical Context

During normal pregnancy, a louder than normal first heart sound with prominent splitting can occur due to a 50% increase in circulating blood volume and increased cardiac output, as noted by the American College of Obstetricians and Gynecologists 1
The second heart sound may widen and appear fixed during later stages of pregnancy as a normal physiologic finding, according to the American Heart Association 2, 1

In patients with repaired tetralogy of Fallot, a mostly widely split second heart sound is the typical clinical finding rather than a loud S2, as reported by the European Society of Cardiology 3
When encountering a loud S2, the location of maximal intensity should be assessed, with a loud P2 best heard at the upper left sternal border and a loud A2 best heard at the upper right sternal border, as recommended by the American College of Cardiology 4
Respiratory variation should be evaluated by listening during normal and deep breathing to assess for splitting patterns that may indicate underlying pathology, according to the American Thoracic Society 4
Associated findings, such as signs of right ventricular hypertrophy, should be looked for if pulmonary hypertension is suspected, as suggested by the American College of Chest Physicians 4