A normal S2 heart sound has the following characteristics:
The extra volume in the right ventricle takes longer to eject, delaying P2.
An abnormal S2 is often the first clue in a physical exam for: Results in a "Loud P2." Severe Aortic Stenosis: Results in a "Soft or Absent A2."
The production of the second heart sound is directly related to the closure of the aortic valve and the pulmonary valve. When the ventricles contract, they eject blood into the aorta and pulmonary artery, respectively. As the ventricular pressure falls below the pressure in the aorta and pulmonary artery, these valves close to prevent backflow of blood into the ventricles. The closure of these valves generates the second heart sound.
