From the Guidelines
A murmur associated with anemia is typically systolic in nature. This is because anemia leads to a decrease in blood viscosity, resulting in increased blood flow velocity and turbulence across normal heart valves, particularly during systole 1. The physiological basis for this murmur relates to the body's compensatory mechanisms for anemia, including increased cardiac output and heart rate to maintain adequate oxygen delivery despite reduced oxygen-carrying capacity of the blood. Some key characteristics of this murmur include:
- It is usually soft (grade 1-2/6)
- Heard best at the left sternal border or apex
- Often described as having a "blowing" quality
- Typically begins after the first heart sound (S1) and ends before the second heart sound (S2), making it systolic in timing
- Resolves when the underlying anemia is corrected, with hemoglobin levels usually needing to fall below 9-10 g/dL before such murmurs become audible. As stated in the guidelines, midsystolic murmurs can occur due to increased flow rate, such as that seen in anemia, and are often crescendo-decrescendo in configuration 1.
From the Research
Murmur Associated with Anemia
- The murmur associated with anemia is systolic, as evidenced by studies that have investigated the relationship between anemia and heart murmurs 2, 3, 4, 5.
- A study published in the Bosnian journal of basic medical sciences found that iron-deficiency anemia often causes systolic heart murmurs and tachycardia in children 2.
- Another study published in The American journal of cardiology discussed the grading of systolic murmurs and noted that hypertension, fever, tachycardia, and anemia are common factors that can cause functional systolic murmurs 3.
- A case report published in the Journal of medical case reports described a patient with severe iron deficiency anemia who presented with a systolic flow murmur 4.
- A study published in Tropical medicine & international health found that the presence of a systolic ejection murmur was independently predictive of severe and moderately severe anemia 5.
Characteristics of Systolic Murmurs in Anemia
- Systolic murmurs associated with anemia can be graded on a scale of 1 to 6, with louder murmurs being more significant 3.
- The presence of a systolic murmur can be an indicator of underlying anemia, particularly in children and the elderly 2, 5, 6.
- Anemia can cause systolic murmurs due to the decreased viscosity of blood and increased cardiac output 2, 4.