Anemia is a condition in which there aren’t enough red blood cells to carry oxygen to tissues throughout the body. Heart failure is a cardiovascular disease in which the heart does not pump blood as well as it should. There is a strong link between anemia and heart failure. Please continue reading to learn more about how these two conditions are connected.

What is anemia?

Anemia, also called low hemoglobin, is a condition in which there aren’t enough red blood cells to transport oxygen to the tissues and organs of the body. The World Health Organization (WHO) defines anemia as a hemoglobin level below 13.0 g/dL in men and below 12.0 g/dL in women. 

Anemia can cause weakness and tiredness because the body’s tissues don’t get enough oxygen.

Different types of anemia occur due to different causes. Iron deficiency anemia can occur due to not eating enough iron-rich foods, problems with iron absorption, or blood loss due to heavy menstruation or gastrointestinal bleeding. Sickle cell anemia or sickle cell disease is an inherited condition caused by a defect in the gene that tells the body to make hemoglobin. In people with aplastic anemia, the stem cells in the bone marrow are damaged, leading to reduced or absent red blood cell production.

Anemia can range from temporary mild anemia to chronic severe anemia. Treatment for anemia depends on the cause and may include taking iron supplementation, having blood transfusions, or undergoing a bone marrow transplant. 

What is heart failure?

Heart failure, is when the heart muscle is weak and cannot perform its pumping action well. Congestive heart failure specifically refers to the stage in which fluid builds up within the heart and causes it to pump inefficiently. The pumping of the heart is vital to deliver oxygen and nutrient-rich blood to various organs throughout the body. When the heart does not pump well, blood gets backed up, and fluid builds up in the lungs. This can lead to symptoms such as fatigue and shortness of breath. In people with chronic heart failure, exercise capacity is greatly reduced, and even everyday activities such as walking or carrying groceries can cause shortness of breath.

Some symptoms are common between anemia and heart failure, such as fatigue, shortness of breath, and a fast heart rate at rest. 

Can heart failure lead to anemia?

Anemia is commonly seen in patients with heart failure. Moreover, anemia predicts mortality in heart failure patients. Meaning the presence of anemia in a person with heart failure is associated with a worse clinical outcome over the long term. 

The exact cause of anemia in heart failure remains unclear. However, scientists believe it has to do with cardiac and renal function. 

When the heart cannot pump enough blood, the various organs in the body don’t get enough oxygen, leading to complications. One such complication is renal insufficiency or chronic kidney disease, where the kidneys cannot filter blood properly because they aren’t getting enough oxygen. 

The reduced renal function in chronic kidney disease leads to reduced erythropoietin production by the kidneys. Erythropoietin (EPO) is a protein made by the kidneys that is required to make red blood cells. Therefore, heart failure leads to renal dysfunction, and renal dysfunction leads to low levels of EPO, which can cause anemia.

There may be other ways in which heart failure leads to anemia. For example, evidence suggests that severe heart failure leads to pro-inflammatory cytokine activation (activation of inflammatory molecules that trigger the immune system). This can lead to the development of anemia of chronic disease with defective iron utilization, decreased erythropoietin production, and bone marrow disease, which in turn can cause severe anemia.

Can anemia cause heart failure?

As mentioned, anemia is highly prevalent in patients with advanced heart failure. It is unclear how or why anemia worsens heart failure, but scientists believe it is related to an increased heart workload. 

Why does anemia cause heart failure?

In chronic severe anemia, hemoglobin levels are severely low. This leads to low blood pressure and water retention, which forces the heart to pump more blood to other organs to meet the oxygen demand because of low hemoglobin levels. This is known as functional heart failure; the heart is fine, but nevertheless has to make a greater effort to the amount of red blood cells with oxygen that would not occur under normal conditions. This over time causes the heart to have structural damage and cause heart failure. The increased fluid in the body places an excessive fluid load on the circulatory system. 

How do anemia and heart failure affect exercise capacity?

Hemoglobin in the red blood cells is vital for delivering oxygen to the muscles during exercise. Anemic patients have low hemoglobin levels. When anemia and heart failure are present together, they can significantly reduce exercise capacity. 

This is because patients with chronic heart failure (HF) don’t have a physiological reserve like healthy individuals to compensate for decreased hemoglobin. Therefore, patients with HF can experience reduced exercise tolerance even in the presence of mild anemia. 

Studies have shown a link between reduced hemoglobin and functional capacity of the heart as defined by the New York Heart Association functional cardiac class.

Can heart failure caused by anemia be reversed?

Anemia and heart failure are closely linked. Heart failure patients are at increased risk of anemia and vice versa. Both conditions, together or independently, are associated with poor outcomes in the long run. 

Therefore, one would think that correcting severe chronic anemia would be an effective therapeutic approach to improve long-term outcomes in heart failure patients. In other words, the correction of anemia should, at least theoretically, improve heart failure symptoms like reduced exercise capacity and improve a person’s quality of life.

The truth is that it is unclear whether iron deficiency and anemia are simply markers of the severity of heart failure or whether they are involved in the progression of heart failure and outcomes. Therefore, it is unclear whether treating anemia is advisable in heart failure patients.

Researchers have evaluated anemia treatment in patients with heart failure with erythropoiesis-stimulating agents (ESAs) such as epoetin alfa (Procrit, Epogen). Unfortunately, ESAs were found not to improve outcomes and were associated with a high risk of adverse events. 

Scientists have also evaluated whether the administration of intravenous iron therapy in heart failure patients with iron deficiency anemia can improve symptoms and exercise capacity, but the long-term outcomes and safety data from these studies are not yet available. 

Wrapping Up

Anemia and heart failure are serious conditions, but they can be successfully treated or managed if diagnosed early. Anemia is usually curable. Heart failure is a chronic condition that cannot be cured, but can be managed. 

If you have anemia and heart failure, you should follow the treatment plan developed by your healthcare team to give yourself the best chance of enjoying a good quality of life. 

References:

1. https://www.mayoclinic.org/diseases-conditions/anemia/symptoms-causes/syc-20351360
2. https://www.heart.org/en/health-topics/heart-failure/what-is-heart-failure
3. https://www.ahajournals.org/doi/10.1161/circulationaha.105.583666
4. https://www.sciencedirect.com/science/article/pii/S0735109708018342
5. https://pubmed.ncbi.nlm.nih.gov/34001233/
6. https://www.ahajournals.org/doi/10.1161/circulationaha.118.030099