Heart failure is characterized by your heart’s inability to pump enough blood to your body. Heart failure weakens or stiffens your heart over time.

Many people with heart failure have low cardiac output. Cardiac output is the amount of blood your heart pumps in 1 minute. When your cardiac output is low, your body’s organs don’t get enough blood.

A smaller number of people with heart failure have a high cardiac output. This is called high-output heart failure.

If you have high-output heart failure, even though your heart is pumping out enough blood, your body’s need for blood is unusually high or your blood vessels are very relaxed. That causes your heart’s work to increase. In other words, heart failure symptoms still happen even though your heart is functioning well.

Typically, an underlying condition (such as sepsis, obesity, hyperthyroidism, or anemia), growth hormone excess, or thiamine deficiency causes high-output heart failure. Like low-output heart failure, it’s a serious medical condition that requires treatment.

If you have congestive heart failure, it means your heart isn’t able to pump enough blood to the rest of your body.

In most cases, this is because your heart is weak or stiff and can’t function well enough to pump blood efficiently. This is called low-output heart failure.

There are two types of low-output heart failure:

  • Heart failure with reduced ejection fraction, or systolic heart failure, happens when your heart muscle loses its ability to contract. Ejection fraction is the percentage of blood that leaves your heart each time it contracts.
  • Heart failure with preserved ejection fraction (HFpEF), or diastolic heart failure, occurs when your heart becomes abnormally stiff. This is usually due to heart disease or risk factors such as high blood pressure.

To compensate for low output, your body releases specific chemicals to make your blood vessels constrict. People with low-output heart failure typically have what’s known as “increased systemic vascular resistance.”

Less commonly, if you have heart failure, you may have a heart that’s able to pump out enough blood to the body. However, the heart still can’t meet the body’s demands for blood due to an underlying condition. This is called high-output heart failure.

In this case, your body will instead release chemicals that dilate (open up) your blood vessels. This is known as “decreased systemic vascular resistance.”

In high-output cardiac failure, ejection fraction is typically normal (preserved) or high (hyperdynamic). For this reason, people’s high-output heart failure is often misdiagnosed as HFpEF until doctors or healthcare professionals complete more tests.

The exact mechanism by which high-output heart failure occurs isn’t fully understood, and it often depends on the underlying cause. A wide range of conditions can cause high-output heart failure.

In general, these conditions lead to a rise in your body’s demand for blood. One way that your body adjusts to the increase in demand is by relaxing cells in the walls of your blood vessels. This causes your vessels to dilate, lower resistance to blood flow, and increase blood flow volume.

Underlying conditions that cause high-output heart failure include:

Many of these conditions increase your body’s metabolic needs or, in some way, result in low systemic vascular resistance.

Obesity is the most common cause of high-output heart failure. How obesity causes high-output heart failure isn’t fully understood. Researchers suspect that an excess of fat tissue causes an increase in your metabolic activity, which may lead to the dilation of your blood vessels, and there may also be an increase in your blood volume.

Symptoms of high-output heart failure are similar to those of low-output heart failure. These include:

Since high-output heart failure is often due to an underlying condition, such as anemia or sepsis, you might also have other symptoms of these conditions.

Symptoms of high-output heart failure are often similar to low-output heart failure, so a medical history and physical exam are very important during the diagnostic process. During the physical exam, be sure to tell your doctor of any underlying medical conditions or medications you’re taking.

A doctor may perform various heart function tests to diagnose heart failure and understand what type of heart failure you have. They may also refer you to a cardiologist.

These tests may include:

  • cardiac imaging to assess abnormalities in your cardiac function and structure
  • chest radiography (X-ray) to see if your heart is enlarged or there’s fluid in your lungs
  • echocardiogram to measure your ejection fraction
  • tests that measure the amount of oxygen in your blood to help determine your cardiac output
  • stress tests, which involve you running on a treadmill while an electrocardiogram (EKG) machine monitors your heart function
  • blood tests

Once your high-output heart failure has been diagnosed, a doctor may run additional tests to understand if you have an underlying medical condition that might be causing this type of heart failure.

Options for treating high-output heart failure are limited. Treatments typically used for low-output heart failure, such as angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), and beta-blockers, may not be as effective in treating high-output heart failure. Still, they may be used to help manage chronic high-output heart failure.

The first goal of treatment is to stabilize your body. This may involve reducing the amount of salt and water in your diet. You may also need diuretics, commonly known as water pills, or oxygen supplementation. In some cases, you might need ventilation therapy or intubation.

A doctor may recommend medications that constrict your blood vessels, such as noradrenaline, ephedrine, and phenylephrine. However, the safety and efficacy of these medications haven’t been shown in clinical trials.

Once stabilized, management of high-output heart failure will target the specific underlying cause. For example:

  • Treatment for hyperthyroidism may involve antithyroid medication, radiotherapy, or surgery.
  • Treatment for sepsis involves intravenous (IV) fluids and antibiotics.
  • End stage liver cirrhosis may require a liver transplant.

You can’t always prevent high-output heart failure. If you have any of the underlying conditions that can cause this type of heart failure, it’s important to get treatment right away. If you have obesity, losing weight can help lower your risk of developing heart failure and other conditions.

Some strategies may help prevent obesity or other underlying conditions that can eventually result in heart failure. These include:

  • exercising regularly
  • eating a low-sodium diet
  • managing stress
  • not smoking
  • getting adequate sleep
  • eating a well-balanced diet
  • limiting alcohol intake

Researchers are still trying to understand the outlook for people with high-output heart failure.

In one retrospective analysis, people with high-output heart failure had a higher 3-year mortality rate compared with people in the healthy control group. But this differed based on the underlying condition. Of the types of high-output heart failure, obesity-related high-output heart failure had a lower 5-year mortality rate, while high-output heart failure caused by liver disease and arteriovenous shunts had the highest.

High-output heart failure is a rare form of heart failure often caused by an underlying condition. Obesity is the most common cause, but we still don’t fully understand why.

With the growing rate of obesity in the United States, doctors are caring for more people with high-output heart failure.

At the moment, there are no short-term medical therapies for high-output heart failure that research has shown to be safe and effective in clinical trials.

If you have received a diagnosis of high-output heart failure, talk with a doctor about the underlying cause and available treatment options. Always talk with a doctor if you suddenly have any new or unexplained symptoms with your heart.