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 of decreased cardiac output, but there are other signs and symptoms, 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.
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
- 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)
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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.”
- low blood pressure
- weak pulse
- cool extremities
- decreased urine output
- altered mental status such as confusion
- shortness of breath
- chest pain
- swelling in legs, feet, or ankles (edema)
Laboratory tests of decreased cardiac output might show:
- buildup of acid in your body from kidney failure (metabolic acidosis)
- elevated lactate levels (hyperlactatemia)
- elevated heart enzymes
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.
- high blood pressure
- coronary artery disease
- congenital heart irregularities
- heart attack
- congestive heart failure
- irregular heart rate (arrhythmia)
- genetic diseases
- fluid around your heart (pericardial effusion)
- blood vessel obstruction (embolism)
- blood or fluid buildup in the sac between your heart and heart muscles (tamponade)
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:
- echocardiogram (or heart ultrasound)
- chest X-rays
- cardiac catheterization
- laboratory tests such as a complete blood count and other blood chemistry tests
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.