Heart murmurs are extra or abnormal heart sounds. There are two normal heart sounds during a heartbeat – S1 (first heart sound) and S2 (second heart sound). S1 is produced by the closure of valves located between the upper (atria) and lower (ventricles) chambers (atrioventricular valves) and S2 is produced by closure of valves located in the arteries leaving the heart (semilunar valves).
A heart murmur due to physiologic conditions outside the heart is called functional or innocent murmur. It can be due to fever, anemia, pregnancy, overactive thyroid gland, etc. Pathologic murmurs are due to structural defects in the heart like narrow valves (stenosis), leaking valves (regurgitation), abnormal passages, etc.
Types of heart murmur depending on when they occur:
Systolic heart murmurs – heard during heart contraction between heart sounds S1 and S2 caused mainly due to stenosis of the semilunar valves or regurgitation of the atrioventricular valves.
Diastolic heart murmurs – heard during heart relaxation between heart sounds S2 and S1 caused mainly due to stenosis of the atrioventricular valves or regurgitation of the semilunar valves.