Decreased cardiac output is when your heart can no longer pump enough oxygen to meet the demands of your body. A rapid heart rate is a common symptom, but there are others, too.

Your heart is responsible for pumping oxygenated blood to all the tissues and organs in your body. The amount of blood your heart can pump in a minute is referred to as your “cardiac output.”

The amount of oxygen your body needs increases during periods of physical activity. A healthy heart can adjust the amount of blood it pumps to meet the demands of your activity.

Decreased cardiac output is when your heart can’t pump enough blood to meet the needs of your body. It can develop as a side effect of heart surgery or a complication of heart disease. Decreased cardiac output is medically known as “low cardiac output syndrome.”

This article will take a closer look at the typical symptoms of decreased cardiac output as well as how it’s diagnosed and managed.

Cardiac output is a measure of how much blood your heart can pump in a certain amount of time. It’s usually measured in liters (L) per minute (min). A liter is a little more than a U.S. quart.

Sometimes your cardiac output is measured relative to your body surface area in square meters (m2). Medical professionals estimate your body surface area from your height and weight.

Your cardiac output is influenced by two factors:

  • Stroke volume: Stroke volume is the amount of blood your heart pumps with each beat.
  • Heart rate: Heart rate is how many times your heart beats per minute.

The amount of oxygen your body needs increases when you’re physically active. A healthy heart can meet this increased demand by increasing its cardiac output.

Decreased cardiac output is a state in which your heart can no longer pump enough oxygen to meet your body’s demands.

How is decreased cardiac output measured?

Cardiac output is measured using a cardiac index. An average cardiac index is between 2.5 and 4.2 L/min/m2. The most common definition of decreased cardiac output is measured by a cardiac index of less than 2.2 L/min/m2 with symptoms and signs such as:

  • confusion or clammy skin, indicating a lack of blood flow to your organs
  • systolic blood pressure under 90 mm Hg (the top number in your blood pressure reading)
  • no signs of hypovolemia (a decrease in blood volume from fluid loss)

According to a 2008 review, a cardiac index below 1.8 L/min/m2 is consistent with cardiogenic shock.

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If your heart can’t pump adequate blood to your organs and tissues, it will usually beat rapidly to try to deliver more oxygen. A significantly low cardiac output that leads to poor blood supply to the organs is called “cardiogenic shock.”

Other signs and symptoms of decreased cardiac output can include:

Laboratory tests of decreased cardiac output might show:

The severity of your symptoms depends on how little oxygen your tissues receive. Severe cases may lead to organ failure and death.

Decreased cardiac output means you have an issue with your heart that prevents it from pumping an adequate amount of blood to your lungs and the rest of your body. This state might result from a risk of surgery or a complication of an underlying health condition.

Decreased cardiac output has been reported after surgical procedures such as:

  • repair of congenital heart abnormalities
  • valve surgery
  • heart bypass

Risk factors for developing low cardiac output syndrome following surgery may include:

  • increased age (older adults)
  • left ventricle dysfunction (defect or damage) before surgery
  • undergoing emergency surgery
  • developing hypothermia during cardiopulmonary bypass
  • the use of cardioprotective drugs (e.g., beta-blockers) during surgery
  • abnormal values on an echocardiogram test

Low cardiac output can develop hours after surgery and when this happens, there may be an increased risk of complications and death.

Conditions that can contribute to heart failure and lead to decreased cardiac output include:

Low cardiac output is diagnosed by healthcare professionals who can recognize and understand the combination of symptoms, physical examination findings, and laboratory test results. Cardiologists specialize in the diagnosis and treatment of heart conditions and can also play an integral role in the management of these conditions.

Various vital measurements are tracked in people with low cardiac output and cardiogenic shock. These measurements include:

  • blood pressure
  • heart rate
  • central venous pressure (measurement of the pressure in the main vein in your chest)
  • oxygen saturation
  • urine output
  • blood tests to measure lactate levels

Tests used to diagnose heart conditions that can cause decreased cardiac output include:

Treatment for decreased cardiac output revolves around treating the underlying heart issue that’s causing the problem and getting adequate oxygen to your organs and tissues to prevent or reverse organ failure.

You may receive:

  • supplemental oxygen to help maintain appropriate oxygen levels in your blood
  • inotropic drugs to improve the contraction of your heart
  • vasopressor drugs to help maintain your blood pressure
  • vasodilator drugs to help your blood vessels relax
  • mechanical support through devices such as a left ventricular assist device

Decreased cardiac output is a state in which your heart doesn’t pump enough blood to supply your organs and tissues with adequate oxygen. It can be a risk of heart surgery or complication of heart disease.

Decreased cardiac output can lead to a rapid heart rate, as your heart works harder to try to pump more blood. Some other symptoms can include low blood pressure, confusion, cool extremities, and fatigue.

Treatment involves addressing the underlying heart issue that’s causing decreased cardiac output. This may include supplemental oxygen or different types of medications.