High output and low output heart failure refer to how much blood your heart pumps to your body with each heartbeat. In both cases, the output is not enough to meet your body’s needs.

A diagnosis of heart failure means your heart cannot pump enough blood to meet your body’s needs. Usually, this results in a reduced amount of blood leaving the heart with every contraction. This is known as low output heart failure.

Conversely, high output heart failure means the heart pumps a greater amount than usual, but it is still not enough to meet the demands of the body’s organs, muscles, and other tissues.

Some symptoms of high output and low output heart failure are similar, but treatments can differ because the underlying causes of each condition may be very different.

This article compares the symptoms, causes, and treatments of both types of heart failure.

High output heart failure is an uncommon form of heart failure. Cardiac function is still relatively normal. The problem lies with the body’s increasing demand for more blood.

Definition

Having high output heart failure means your heart pumps at least 8 liters per minute (L/min) or you have a cardiac index of 4.0 L/min/m2.

Cardiac index is an assessment of how much blood is pumped out in relation to a person’s body surface area, which is represented as m2.

Symptoms

The main symptoms of high output heart failure include:

  • fatigue
  • reduced ability to exercise
  • heart palpitations
  • shortness of breath, especially when lying flat
  • swelling in the abdomen, lower limbs, or both
  • tachycardia, which is an abnormally fast heart rate

Causes and risk factors

Some main causes of high output heart failure are:

Treatment

Treating high output heart failure is usually a twofold strategy. The goal is to ease your symptoms and address the underlying cause of your heart failure.

To relieve symptoms, doctors may prescribe:

  • Diuretics: These medications help lower blood pressure and reduce fluid levels in the body.
  • Inotropes: These medications affect how much force your heart muscle uses to contract.
  • Oxygen therapy: This type of therapy makes it easier for you to breathe.

Other treatments are specific to the cause. For example, if a high BMI is believed to have triggered high output heart failure, a safe but aggressive weight loss plan may be advisable.

If hyperthyroidism is the root cause, medications that reduce your body’s production of thyroid hormones may be helpful.

Is high output heart failure systolic or diastolic?

Heart failure is often categorized as systolic or diastolic.

With systolic heart failure, the left ventricle (which pumps blood out to the body) is weak and can’t contract effectively.

With diastolic heart failure, the left ventricle is too stiff to relax normally and fill up with blood between heartbeats.

High output heart failure usually starts with normal systolic function and elevated diastolic pressure (blood pressure measured between contractions). As the condition progresses, however, eventually systolic function starts to fail, too.

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Low output heart failure is the more common form of heart failure. It means the heart pumps less blood than is necessary to meet the body’s basic needs.

Definition

Normal cardiac output is about 5–6 L/min at rest. Low output heart failure means the heart consistently pumps out less than that amount while at rest.

Symptoms

Some of the more common symptoms of low output heart failure include:

  • confusion and difficulty concentrating, which are caused by reduced blood flow to the brain
  • fatigue
  • nausea and vomiting
  • abdominal pain
  • reduced ability to exercise
  • shortness of breath
  • swelling in the arms and legs

Causes and risk factors

Low output heart failure is typically a complication of:

Treatment

Treatment options for low output heart failure usually include one or more medications to improve blood pressure and reduce the heart’s workload. The goal is to slow the progression of the condition.

Some commonly prescribed medications for heart failure include:

Other possible treatments include surgical procedures or the use of implanted devices. For example, you may need an implantable cardioverter defibrillator placed in your chest to help your heart beat in a steady rhythm.

For more advanced cases of low output heart failure, a left ventricular assist device, or artificial heart pump, is necessary to maintain cardiac output.

If you have coronary artery disease or valve disease, procedures to treat these problems may help improve overall heart function, including cardiac output.

Any type of heart failure is a cause for concern because it means the heart is not meeting the body’s need for consistent, robust circulation.

However, with ongoing research into ways to prevent or treat high output and low output heart failure, you and your doctor can often manage these cardiac conditions well enough to meet your needs for a good quality of life.