What causes ejection fraction to be low

What is Ejection Fraction?

Ejection fraction (EF) is a measurement, expressed as a percentage, of how much blood the left ventricle (the heart's main pumping chamber) pumps out with each contraction. A normal resting heart's EF is typically between 50% and 70%. An EF of 50% or higher is generally considered normal, while an EF below 40% may indicate heart failure.

Causes of Low Ejection Fraction

A low ejection fraction signifies that the heart is not pumping blood as efficiently as it should. This inefficiency is most often due to damage or weakening of the heart muscle. Several conditions can lead to this:

1. Coronary Artery Disease (CAD) and Heart Attack

Coronary artery disease is the most common cause of heart problems in many parts of the world. It occurs when the arteries that supply blood to the heart muscle become narrowed or blocked, usually by plaque buildup (atherosclerosis). If a blockage is severe or sudden, it can lead to a heart attack (myocardial infarction). During a heart attack, part of the heart muscle doesn't receive enough oxygen-rich blood and can become damaged or die. This dead or damaged tissue cannot contract properly, thus reducing the heart's overall pumping ability and lowering the ejection fraction.

2. High Blood Pressure (Hypertension)

Chronically high blood pressure forces the heart to work harder to pump blood against increased resistance in the arteries. Over time, this sustained extra effort can cause the heart muscle, particularly the left ventricle, to thicken and stiffen (a condition called left ventricular hypertrophy). While initially this thickening might seem like an adaptation, it eventually leads to a less flexible and less efficient heart that struggles to fill and pump effectively, resulting in a lower EF.

3. Heart Valve Disease

The heart has four valves that ensure blood flows in the correct direction. If these valves don't open properly (stenosis) or close completely (regurgitation or insufficiency), the heart has to work harder. For example, if a valve doesn't close fully, some blood leaks backward, meaning less blood is pumped forward with each beat. If a valve is narrowed, the heart must generate higher pressure to push blood through it. Both scenarios can strain and damage the heart muscle over time, contributing to a reduced ejection fraction.

4. Cardiomyopathy

Cardiomyopathy refers to a group of diseases that affect the heart muscle itself. There are several types:

• Dilated Cardiomyopathy: The heart's main pumping chamber (left ventricle) becomes enlarged (dilated) and weakened, making it unable to pump blood effectively. This is a common cause of low EF.
• Hypertrophic Cardiomyopathy: The heart muscle becomes abnormally thick, which can obstruct blood flow out of the heart and affect the ventricle's ability to fill.
• Restrictive Cardiomyopathy: The heart muscle becomes stiff and less flexible, preventing the ventricles from filling properly between beats.

These conditions directly impair the heart muscle's ability to contract and relax normally, leading to a lower ejection fraction.

5. Arrhythmias

Persistent irregular heart rhythms (arrhythmias) can also affect the heart's pumping efficiency. If the heart beats too fast, too slow, or irregularly, it may not have enough time to fill properly with blood or may pump blood ineffectively, potentially leading to a reduced EF over time.

6. Myocarditis

Myocarditis is inflammation of the heart muscle, often caused by viral infections (like Coxsackie B virus, influenza, or even COVID-19), but also by bacterial infections, autoimmune diseases, or exposure to certain toxins and drugs. This inflammation can weaken the heart muscle, leading to a reduced ejection fraction.

7. Other Causes

Less common causes include congenital heart defects (heart problems present at birth), certain chemotherapy drugs, long-term excessive alcohol consumption, severe thyroid problems, and certain genetic disorders.

Symptoms and Diagnosis

Symptoms of a low ejection fraction can include shortness of breath (especially during exertion or when lying down), fatigue, swelling in the legs, ankles, and feet (edema), rapid or irregular heartbeat, persistent cough, and a lack of appetite. Diagnosis typically involves a physical exam, patient history, and diagnostic tests such as an echocardiogram (ultrasound of the heart), electrocardiogram (ECG), chest X-ray, and sometimes cardiac MRI or stress tests.

Importance of Management

Understanding the cause of a low ejection fraction is crucial for effective treatment. Management strategies aim to treat the underlying condition, improve heart function, relieve symptoms, and prevent complications. This often involves lifestyle changes, medications, and sometimes medical procedures or surgery.