Second heart sound in TOF is often single and loud . It is often best heard in left 2nd intercostal space as well as on right 2nd space.
This is primarily due
- Presence of pulmonary stenosis and resultant reduced pulmonary blood flow makes P2 soft or absent .Hence A2 becomes loud by default.
- In tune with any cono -truncal anomaly , aortic root is anteriorly malposed in TOF. This brings the aorta closer to chest wall (Nullifying the aquastic insulation of main pulmonary trunk ) and results in a booming aortic second heart sound.
- Increased flow across aortic valve . In cyanotic heart disease with reduced pulmonary blood flow aortic flow is augmented and may even result in dilatation of aorta . A large aorta with increased flow is perfect setting for generating a loud A2 . It is common to hear a aortic ejection click as well in these situations .
When you hear a single second heart sound at the base of heart , how do you recognise it to be A2 or P2 ?
Will be answered shortly.
Dr.S.Venkatesan MD 