LBBB causes a paradoxical splitting of the (S1/S2) heart sound. This means that it is split on expiration but not on inspiration. What is the correct heart sound?

LBBB causes a paradoxical splitting of the (S1/S2) heart sound. This means that it is split on expiration but not on inspiration. What is the correct heart sound?

• A. S1
• B. S2
• C. S3
• D. S4

Answer: (B)

In the context of a left bundle branch block (LBBB), the S2 heart sound is indeed the correct choice to note for paradoxical splitting. In a typical heart sound sequence, S2 is the closure of the aortic and pulmonic valves. During inspiration, the increased venous return to the right side of the heart typically causes the right ventricle to take longer to finish ejecting, which creates a wider split between the closure of the pulmonic valve (P2) and aortic valve (A2). However, with LBBB, the left ventricular contraction is delayed, causing the aortic valve to close later than normal, resulting in a paradoxical split that becomes more pronounced during expiration and may fuse during inspiration. This unique behavior is a hallmark of LBBB and highlights how abnormal conduction patterns can affect heart sounds and their timing. Thus, when discussing paradoxical splitting, S2 is the sound that exhibits this characteristic behavior.

In the context of a left bundle branch block (LBBB), the S2 heart sound is indeed the correct choice to note for paradoxical splitting. In a typical heart sound sequence, S2 is the closure of the aortic and pulmonic valves. During inspiration, the increased venous return to the right side of the heart typically causes the right ventricle to take longer to finish ejecting, which creates a wider split between the closure of the pulmonic valve (P2) and aortic valve (A2). However, with LBBB, the left ventricular contraction is delayed, causing the aortic valve to close later than normal, resulting in a paradoxical split that becomes more pronounced during expiration and may fuse during inspiration. This unique behavior is a hallmark of LBBB and highlights how abnormal conduction patterns can affect heart sounds and their timing. Thus, when discussing paradoxical splitting, S2 is the sound that exhibits this characteristic behavior.