Monday, 25 October 2010

MRCP revision battle 34.2: The second heart sound

The second heart sound comprises of the closure of the aortic and pulmonary valves.They usually close <0.05secs apart and in alphabetical order, with the aortic valve closing first.

A loud S2 may be due to:
  • systemic hypertension (=loud A2)
  • pulmonary hypertension (=loud P2)
  • tachycardia

A soft S2 may be due to aortic stenosis.

w i d e l y   s p l i t  second heart sound occurs in:
  • RBBB
  • deep inspiration
  • mitral regurgitation
  • pulmonary stenosis

A reverse split (=paradoxical split) second heart sound occurs in:
  • LBBB
  • severe aortic stenosis
  • right ventricular pacing
  • WPW type 2
  • patent ductus arteriosus

Onwards for the third and fourth heart sounds...