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#15 Cardiac Second Sounds

Key Learning Points

  • Basic physiology and technique for listening to second heart sounds
  • Key findings seen in the abnormal second heart sounds


Introduction: The cardiac second sound can be a source of some confusion. However, the subtle changes of the second heart sound can tell you a great deal about the heart. Here we discuss the basics of listening for the second heart sounds and review abnormal findings.


The Basics



ronald witteles


What causes the split second heart sounds?

There are believed to be multiple causes for the physiologic splitting of S2. Both A2 and P2 close when the pressure above the respective valves are greater than the pressure in the ventricles below. Given the lower vascular resistance of the pulmonary artery, during inspiration, the pulmonary artery is able to tolerate more volume of blood before the pressure above the valve increases. Additionally, during inspiration, more blood fills the right ventricle leading to a slightly longer ejection time, adding to the delayed pulmonic valve closure.


















Pathological Findings


Second Heart Sounds





This video was created by Dr. Eric Strong who is an internist working at Stanford-affiliated Veterans Affair's Hospital at Palo Alto, CA. Click this link to see his collection of medicine educational videos.