<P> Systolic heart murmurs are heart murmurs heard during systole . </P> <P> They can be classified by when the murmur begins and ends, between S1 and S2 . </P> <P> Many involve stenosis of the semilunar valves or regurgitation of the atrioventricular valves . </P>

When is a systolic murmur heard with relation to s1 and s2