If you hear a systolic murmur in an asymptomatic child, the odds are on your side. All pansystolic murmurs are pathological. They almost always are VSDs. In a child with a VSD, the louder the murmur, the smaller the shunt . The softer the murmur, the larger the shunt, and the sicker the child.
Children develop bi-ventricular failure.
Palpate the liver. If a child has CHF, the liver will be enlarged and often tender. All you need to do is palpate the liver. All murmurs that radiate are pathological. Take upper and lower extremity BP in a child with a murmur.