systolic murmur

A heart murmur is the swishing sound of turbulent blood flow, like water rushing past an obstacle in a stream rather than gliding smoothly. A systolic murmur is one heard during systole — the phase when the ventricles contract and eject blood — falling between the first and second heart sounds.

Timing tells the listener a great deal. During systole the aortic and pulmonary valves should be open (so a narrowed one creates an ejection murmur) while the mitral and tricuspid valves should be shut (so a leaking one creates a regurgitant murmur). Thus aortic or pulmonary stenosis and mitral or tricuspid regurgitation all produce systolic murmurs, distinguished further by their location, character, and where they radiate.

Importantly, not all systolic murmurs signal disease. Soft, brief systolic murmurs are very common and often innocent, especially in children, pregnancy, fever, or anemia, when blood simply flows faster. The clinician's task is to separate these harmless flow murmurs from pathological ones, frequently confirming the cause with echocardiography.

Deciding whether a murmur is innocent or significant is a clinical judgement; this entry describes the concept, not a self-assessment tool.