From the Guidelines
The murmur associated with anemia is heard during systole. This is because anemia leads to a hyperdynamic circulation state with increased cardiac output, resulting in increased blood flow velocity across the cardiac valves during systole, which creates turbulence and generates the characteristic murmur 1.
Key Characteristics of the Murmur
- The murmur is often described as a soft, blowing sound that is best heard at the left sternal border or over the pulmonic area
- It occurs due to increased blood flow velocity across the cardiac valves when a person has anemia
- The intensity of the murmur generally correlates with the severity of anemia, becoming more pronounced when hemoglobin levels fall below 7-8 g/dL
- These murmurs are considered "functional" or "physiologic" rather than pathologic, as they do not indicate structural heart disease and typically resolve once the underlying anemia is corrected
Clinical Implications
- The presence of a systolic murmur in a patient with anemia should prompt further evaluation to determine the underlying cause of the anemia
- Correction of the underlying anemia is typically associated with resolution of the murmur
- Echocardiography may be necessary to separate a prominent and exaggerated benign midsystolic murmur from one due to valvular disease, as noted in the acc/aha 2006 guidelines 1
From the Research
Murmur Associated with Anemia
- The murmur associated with anemia is heard during systole, as indicated by studies that have investigated the relationship between anemia and heart murmurs 2, 3, 4.
- Iron-deficiency anemia, in particular, has been found to cause systolic heart murmurs and tachycardia in children 2.
- A study of 120 patients with innocent heart murmurs found that 30 patients had iron-deficiency anemia, and 22 of these patients had systolic murmurs of I/II intensity 2.
- Another study found that systolic murmurs were common in patients with anemia, and that the murmurs often disappeared when the anemia was treated 3.
- The pathophysiology of anemia involves changes in blood flow and oxygen delivery, which can lead to increased cardiac output and the development of systolic murmurs 5.
Clinical Significance of Systolic Murmurs
- Systolic murmurs are common in older adults, and their presence is associated with an increased risk of cardiovascular disease and mortality 6.
- A study of 278 patients over the age of 60 found that 75% of systolic murmurs were judged to be aortic in origin, and that the presence of a systolic murmur was related to the presence of cardiac failure, ischemic heart disease, and other cardiovascular abnormalities 6.
- Clinical pallor, including pallor of the palms, nailbeds, conjunctivae, buccal mucosa, or tongue, can be used to identify children with moderate and severe anemia, and a systolic ejection murmur may be an additional tool in considering urgent referral for blood transfusion 4.