What causes heart murmurs?
Heart murmurs are most often caused by defective heart valves. A stenotic (sten-OT’ik) heart valve has a smaller-than-normal opening and can’t open completely. A valve may also be unable to close completely. This leads to regurgitation, which is blood leaking backward through the valve when it should be closed. Murmurs also can be caused by conditions such as pregnancy, fever, thyrotoxicosis (thi”ro-toks”ih-KO’sis) (a diseased condition resulting from an overactive thyroid gland) or anemia. A diastolic (di”as-TOL’ik) murmur occurs when the heart muscle relaxes between beats. A systolic (sis-TOL’ik) murmur occurs when the heart muscle contracts. Systolic murmurs are graded by intensity (loudness) from one to six. A grade 1/6 is very faint, heard only with a special effort. A grade 6/6 is extremely loud. It’s heard with a stethoscope slightly removed from the chest.
