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.



A  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...