Causes of Congestive Heart Failure
Underlying conditions that increase the risk for heart failure include the following:
- Abnormal heart rhythm (arrhythmia)
- Abnormal heart valve(s), which may be congenital (present at birth) or caused by disease or infection (e.g., aortic stenosis, mitral regurgitation)
- Alcoholism and drug abuse
- Coronary heart disease (CHD; also called atherosclerosis)
- Damaged heart muscle, which may be caused by disease (e.g., cardiomyopathies) or inflammation (e.g., myocarditis)
- High blood pressure (hypertension)
- Low red blood cell count (severe anemia)
- Lung disease
- Overactive thyroid gland (hyperthyroidism)
- Prior history of heart attack (myocardial infarction)
- Vitamin deficiency
The most common cause for heart failure is dysfunction of the left ventricle. Normally, every time the heart "beats," the left ventricle contracts and ejects approximately 60% of the blood in the chamber into the main artery (aorta). The percentage of blood pumped out of the left ventricle with each contraction is called the ejection fraction.
Measuring the ejection fraction is a way to determine left ventricle function. In patients with left ventricular dysfunction, the ejection fraction may be as little as 10%. An ejection fraction of approximately 40–45% indicates mild dysfunction; 30–40% indicates moderate dysfunction; and 10–25% indicates severe dysfunction.
Other Congestive Heart Failure Causes
Heart failure may develop during the last 3 months of pregnancy or several months after pregnancy. The cause of this is not well understood, but it may be due to an abnormal immune system response.
In some cases, the cause of heart failure is never identified (called idiopathic cardiomyopathy). Idiopathic cardiomyopathy may be due to a past, unidentified viral infection.