Single hea sound (S2) is heard in:

--> Single second hea sound: It is either A2 / P2/ combination of both. Decision whether it is aoic / pulmonic / combination depends on location, intensity of S2 & clinical profile of pt Seen in: *Tetralogy of fallot --> S2 represents A2 component since pulmonic component is delayed, soft & inaudible. *Eisenmenger complex --> S2 represents combination of A2 & P2 - Thus, based on auscultation alone, it might be difficult to differentiate b/w TOF & Eisenmenger complex. History & chest X-ray can distinguish these conditions.