From the Guidelines
The murmur of anemia is not heard during diastole, but rather is a systolic murmur. Anemic murmurs are typically soft, blowing systolic murmurs that are best heard at the left sternal border or over the apex of the heart. They occur during systole, which is the phase of the cardiac cycle when the ventricles contract and blood is ejected from the heart. The murmur develops because anemia causes decreased blood viscosity and increased blood flow velocity, creating turbulent flow across normal heart valves during systole, as noted in the context of increased flow rates such as those seen in anemia 1. This happens because in anemia, the reduced oxygen-carrying capacity of the blood leads to compensatory increases in cardiac output, which increases the speed of blood flow. Key characteristics of murmurs and their timing are discussed in the guidelines for the management of patients with valvular heart disease 1, which helps in understanding the nature of anemic murmurs. The intensity of anemic murmurs typically correlates with the severity of anemia, becoming more noticeable when hemoglobin levels fall below 7-8 g/dL. These murmurs generally disappear once the underlying anemia is corrected through appropriate treatment.
Some key points to consider about murmurs and their classification include:
- Holosystolic (pansystolic) murmurs are generated when there is flow between chambers that have widely different pressures throughout systole 1.
- Midsystolic (systolic ejection) murmurs occur when blood is ejected across the aortic or pulmonic outflow tracts, and can be caused by increased flow rates such as those seen in anemia 1.
- The presence of anemic murmurs is indicative of the body's compensatory mechanisms to increase oxygen delivery in the setting of reduced oxygen-carrying capacity of the blood.
- Correcting the underlying anemia is crucial for resolving the murmur and improving patient outcomes.
From the Research
Murmur of Anemia
- The murmur associated with iron deficiency anemia is typically a systolic murmur, not a diastolic murmur 2, 3.
- Systolic murmurs are often heard during the systolic phase of the heartbeat, which is the period when the heart muscle contracts and pumps blood out of the heart 3.
- In the context of iron deficiency anemia, systolic murmurs may be caused by the increased cardiac output and subsequent turbulence of blood flow, which can lead to the production of a murmur 2.
- The intensity of the murmur can vary, but it is often graded on a scale of 1 to 6, with higher grades indicating louder murmurs 3.
- In some cases, iron deficiency anemia can be associated with other cardiac conditions, such as aortic stenosis, which can also produce systolic murmurs 4, 5.
Echocardiographic Features
- Anemia and iron deficiency can affect echocardiographic parameters, including ventricular and atrial remodeling, ventricular contractility, and ventricular relaxation 6.
- Correction of anemia and iron deficiency can lead to improvements in these parameters, including a reduction in preload and left ventricular cavity dimensions, and an improvement in diastolic and load-independent ventricular systolic function parameters 6.
- However, the evidence is less consistent about the changes produced in ventricular hypertrophy, load-dependent systolic function parameters, and E-wave 6.