Heart Failure - Causes - Causes

Chronic (long-term) heart failure is often caused by other medical conditions that damage or overwork your heart. Acute (sudden) heart failure can be caused by an injury or infection that damages your heart, a heart attack, or a blood clot in your lung. 

To understand heart failure, it helps to know how the heart works. The right side of your heart gets oxygen-low blood from your body. It pumps the blood to your lungs to pick up oxygen. The left side of your heart pumps oxygen-rich blood to the rest of your body. 

This animation describes heart failure and some of its causes. Medical Animation Copyright © 2021 Nucleus Medical Media Inc. All rights reserved. 

What causes left-sided heart failure? 

Left-sided heart failure is more common than right-sided heart failure. There are two types of left-sided heart failure, each based on how well your heart can pump. This measurement is called the ejection fraction. Visit the Diagnosis section to learn more about the ejection fraction. 

  • In heart failure with reduced ejection fraction (HFrEF), the left side of your heart is weak and can’t pump enough blood to the rest of your body. Chronic (long-term) conditions that damage or weaken the heart muscle are the main cause of heart failure with reduced ejection fraction. For example, coronary heart disease or a heart attack can prevent your heart muscle from getting enough oxygen (shown below). Other causes of this type of heart failure include faulty heart valves, an irregular heartbeat, or heart diseases that you are born with or  inherit .  

How a heart attack can lead to heart failure. Figure A shows dead heart muscle caused by a heart attack. Figure B is a close-up showing how a blocked artery in the heart prevents the heart muscle from getting oxygen. The heart muscle begins to die, weakening the heart
How a heart attack can lead to heart failure. Figure A shows dead heart muscle caused by a heart attack. Figure B is a close-up showing how a blocked artery in the heart prevents the heart muscle from getting oxygen. The heart muscle begins to die, weakening the heart

  • In heart failure with preserved ejection fraction (HFpEF), the left side of your heart is too stiff to fully relax between heartbeats. That means it can't fill up with enough blood to pump out to your body. High blood pressure and other conditions that make your heart work harder are the main causes of heart failure with preserved ejection fraction. Conditions that stiffen the chambers of the heart such as obesity and diabetes are also causes of this type of heart failure. Over time, your heart muscle thickens to adapt, which makes it stiffer. 

Visit the Diagnosis section to learn more about heart failure with preserved or reduced ejection fraction and how doctors diagnose it. 

What causes right-sided heart failure? 

Over time left-sided heart failure can lead to right-sided heart failure.  

In right-sided heart failure, your heart can't pump enough blood to your lungs to pick up oxygen. Left-sided heart failure is the main cause of right-sided heart failure. That’s because left-sided heart failure can cause blood to build up on the left side of your heart. The build-up of blood raises the pressure in the blood vessels that carry blood from your heart to your lungs. This is called pulmonary hypertension, and it can make the right side of your heart work harder.  

Congenital heart defects or conditions that damage the right side of your heart such as abnormal heart valves can also lead to right-side heart failure on its own. The same is true for conditions that damage the lungs, such as chronic obstructive pulmonary disease (COPD).