1.08 S2 Splitting

Cardiovascular system review for the USMLE Step 1 exam

• S2 splitting is a phenomenon where the closure of the aortic and pulmonic valves occur at different times, resulting in two heart sounds heard at what is normally S2.
• Four types of splitting: physiologic or normal splitting, wide splitting, fixed splitting, and paradoxical splitting.
• Physiologic splitting is normal and occurs when a person takes a deep breath and the difference between the closure of the aortic and pulmonic valves can be heard.
• Wide splitting is a symptom that is not normal and is associated with diseases that delay right ventricle emptying, such as right bundle branch block and pulmonary stenosis. It gets worse with inhalation.
  • Wide split, worsened by inhalation
• Fixed splitting is similar to wide splitting, but it is not made worse when the patient inhales. It is seen in patients with an atrial septal defect.
  • Fixed split, fixed in place
• Paradoxical splitting is a wide split that is fixed by inspiration and is caused by diseases that delay aortic valve closure, such as aortic stenosis and left bundle branch block.
  • Paradoxially fixded by inspiration