Cardiogenic Shock

Causes

Immediate Causes

Cardiogenic shock occurs if the heart suddenly can't pump enough oxygen-rich blood to the body. The most common cause of cardiogenic shock is damage to the heart muscle from a severe heart attack.

This damage prevents the heart’s main pumping chamber, the left ventricle (VEN-trih-kul), from working well. As a result, the heart can't pump enough oxygen-rich blood to the rest of the body.

In about 3 percent of cardiogenic shock cases, the heart’s lower right chamber, the right ventricle, doesn’t work well. This means the heart can't properly pump blood to the lungs, where it picks up oxygen to bring back to the heart and the rest of the body.

Without enough oxygen-rich blood reaching the body’s major organs, many problems can occur. For example:

  • Cardiogenic shock can cause death if the flow of oxygen-rich blood to the organs isn't restored quickly. This is why emergency medical treatment is required.
  • If organs don't get enough oxygen-rich blood, they won't work well. Cells in the organs die, and the organs may never work well again.
  • As some organs stop working, they may cause problems with other bodily functions. This, in turn, can worsen shock. For example:
    • If the kidneys aren't working well, the levels of important chemicals in the body change. This may cause the heart and other muscles to become even weaker, limiting blood flow even more.
    • If the liver isn't working well, the body stops making proteins that help the blood clot. This can lead to more bleeding if the shock is due to blood loss.

How well the brain, kidneys, and other organs recover will depend on how long a person is in shock. The less time a person is in shock, the less damage will occur to the organs. This is another reason why emergency treatment is so important.

Underlying Causes

The underlying causes of cardiogenic shock are conditions that weaken the heart and prevent it from pumping enough oxygen-rich blood to the body.

Heart Attack

Most heart attacks occur as a result of coronary heart disease (CHD). CHD is a condition in which a waxy substance called plaque (plak) narrows or blocks the coronary (heart) arteries.

Plaque reduces blood flow to your heart muscle. It also makes it more likely that blood clots will form in your arteries. Blood clots can partially or completely block blood flow.

Conditions Caused by Heart Attack

Heart attacks can cause some serious heart conditions that can lead to cardiogenic shock. One example is ventricular septal rupture. This condition occurs if the wall that separates the ventricles (the heart’s two lower chambers) breaks down.

The breakdown happens because cells in the wall have died due to a heart attack. Without the wall to separate them, the ventricles can’t pump properly.

Heart attacks also can cause papillary muscle infarction or rupture. This condition occurs if the muscles that help anchor the heart valves stop working or break because a heart attack cuts off their blood supply. If this happens, blood doesn't flow correctly between the heart’s chambers. This prevents the heart from pumping properly.

Other Heart Conditions

Serious heart conditions that may occur with or without a heart attack can cause cardiogenic shock. Examples include:

  • Myocarditis (MI-o-kar-DI-tis). This is inflammation of the heart muscle.
  • Endocarditis (EN-do-kar-DI-tis). This is an infection of the inner lining of the heart chambers and valves.
  • Life-threatening arrhythmias (ah-RITH-me-ahs). These are problems with the rate or rhythm of the heartbeat.
  • Pericardial tamponade (per-ih-KAR-de-al tam-po-NADE). This is too much fluid or blood around the heart. The fluid squeezes the heart muscle so it can't pump properly.

Pulmonary Embolism

Pulmonary embolism (PE) is a sudden blockage in a lung artery. This condition usually is caused by a blood clot that travels to the lung from a vein in the leg. PE can damage your heart and other organs in your body.

Risk Factors

The most common risk factor for cardiogenic shock is having a heart attack. If you've had a heart attack, the following factors can further increase your risk for cardiogenic shock:

Women who have heart attacks are at higher risk for cardiogenic shock than men who have heart attacks.

Screening and Prevention

The best way to prevent cardiogenic shock is to lower your risk for coronary heart disease (CHD) and heart attack. (For more information, go to the National Heart, Lung, and Blood Institute's "Your Guide to a Healthy Heart.")

If you already have CHD, it’s important to get ongoing treatment from a doctor who has experience treating heart problems.

If you have a heart attack, you should get treatment right away to try to prevent cardiogenic shock and other possible complications.

  • Act in time. Know the warning signs of a heart attack so you can act fast to get treatment. Many heart attack victims wait 2 hours or more after their symptoms begin before they seek medical help. Delays in treatment increase the risk of complications and death.
  • If you think you're having a heart attack, call 9–1–1 for help. Don't drive yourself or have friends or family drive you to the hospital. Call an ambulance so that medical personnel can begin life-saving treatment on the way to the emergency room.

Signs, Symptoms, and Complications

A lack of oxygen-rich blood reaching the brain, kidneys, skin, and other parts of the body causes the signs and symptoms of cardiogenic shock.

Some of the typical signs and symptoms of shock usually include at least two or more of the following:

  • Confusion or lack of alertness
  • Loss of consciousness
  • A sudden and ongoing rapid heartbeat
  • Sweating
  • Pale skin
  • A weak pulse
  • Rapid breathing
  • Decreased or no urine output
  • Cool hands and feet

Any of these alone is unlikely to be a sign or symptom of shock.

If you or someone else is having these signs and symptoms, call 9–1–1 right away for emergency treatment. Prompt medical care can save your life and prevent or limit organ damage.

Diagnosis

The first step in diagnosing cardiogenic shock is to identify that a person is in shock. At that point, emergency treatment should begin.

Once emergency treatment starts, doctors can look for the specific cause of the shock. If the reason for the shock is that the heart isn't pumping strongly enough, then the diagnosis is cardiogenic shock.

Tests and Procedures To Diagnose Shock and Its Underlying Causes

Blood Pressure Test

Medical personnel can use a simple blood pressure cuff and stethoscope to check whether a person has very low blood pressure. This is the most common sign of shock. A blood pressure test can be done before the person goes to a hospital.

Less serious conditions also can cause low blood pressure, such as fainting or taking certain medicines, such as those used to treat high blood pressure.

EKG (Electrocardiogram)

An EKG is a simple test that detects and records the heart's electrical activity. The test shows how fast the heart is beating and its rhythm (steady or irregular).

An EKG also records the strength and timing of electrical signals as they pass through each part of the heart. Doctors use EKGs to diagnose severe heart attacks and monitor the heart's condition.

Echocardiography

Echocardiography (echo) uses sound waves to create a moving picture of the heart. The test provides information about the size and shape of the heart and how well the heart chambers and valves are working.

Echo also can identify areas of poor blood flow to the heart, areas of heart muscle that aren't contracting normally, and previous injury to the heart muscle caused by poor blood flow.

Chest X Ray

A chest x ray takes pictures of organs and structures in the chest, including the heart, lungs, and blood vessels. This test shows whether the heart is enlarged or whether fluid is present in the lungs. These can be signs of cardiogenic shock.

Cardiac Enzyme Test

When cells in the heart die, they release enzymes into the blood. These enzymes are called markers or biomarkers. Measuring these markers can show whether the heart is damaged and the extent of the damage.

Coronary Angiography

Coronary angiography (an-jee-OG-ra-fee) is an x-ray exam of the heart and blood vessels. The doctor passes a catheter (a thin, flexible tube) through an artery in the leg or arm to the heart. The catheter can measure the pressure inside the heart chambers.

Dye that can be seen on an x-ray image is injected into the bloodstream through the tip of the catheter. The dye lets the doctor study the flow of blood through the heart and blood vessels and see any blockages.

Pulmonary Artery Catheterization

For this procedure, a catheter is inserted into a vein in the arm or neck or near the collarbone. Then, the catheter is moved into the pulmonary artery. This artery connects the right side of the heart to the lungs.

The catheter is used to check blood pressure in the pulmonary artery. If the blood pressure is too high or too low, treatment may be needed.

Blood Tests

Some blood tests also are used to help diagnose cardiogenic shock, including:

  • Arterial blood gas measurement. For this test, a blood sample is taken from an artery. The sample is used to measure oxygen, carbon dioxide, and pH (acidity) levels in the blood. Certain levels of these substances are associated with shock.
  • Tests that measure the function of various organs, such as the kidneys and liver. If these organs aren't working well, they may not be getting enough oxygen-rich blood. This could be a sign of cardiogenic shock.

Treatment

Cardiogenic shock is life threatening and requires emergency medical treatment. The condition usually is diagnosed after a person has been admitted to a hospital for a heart attack. If the person isn't already in a hospital, emergency treatment can start as soon as medical personnel arrive.

The first goal of emergency treatment for cardiogenic shock is to improve the flow of blood and oxygen to the body’s organs.

Sometimes both the shock and its cause are treated at the same time. For example, doctors may quickly open a blocked blood vessel that's damaging the heart. Often, this can get the patient out of shock with little or no additional treatment.

Emergency Life Support

Emergency life support treatment is needed for any type of shock. This treatment helps get oxygen-rich blood flowing to the brain, kidneys, and other organs.

Restoring blood flow to the organs keeps the patient alive and may prevent long-term damage to the organs. Emergency life support treatment includes:

  • Giving the patient extra oxygen to breathe so that more oxygen reaches the lungs, the heart, and the rest of the body.
  • Providing breathing support if needed. A ventilator might be used to protect the airway and provide the patient with extra oxygen. A ventilator is a machine that supports breathing.
  • Giving the patient fluids, including blood and blood products, through a needle inserted in a vein (when the shock is due to blood loss). This can help get more blood to major organs and the rest of the body. This treatment usually isn’t used for cardiogenic shock because the heart can't pump the blood that's already in the body. Also, too much fluid is in the lungs, making it hard to breathe.

Medicines

During and after emergency life support treatment, doctors will try to find out what’s causing the shock. If the reason for the shock is that the heart isn't pumping strongly enough, then the diagnosis is cardiogenic shock.

Treatment for cardiogenic shock will depend on its cause. Doctors may prescribe medicines to:

  • Prevent blood clots from forming
  • Increase the force with which the heart muscle contracts
  • Treat a heart attack

Medical Devices

Medical devices can help the heart pump and improve blood flow. Devices used to treat cardiogenic shock may include:

  • An intra-aortic balloon pump. This device is placed in the aorta, the main blood vessel that carries blood from the heart to the body. A balloon at the tip of the device is inflated and deflated in a rhythm that matches the heart’s pumping rhythm. This allows the weakened heart muscle to pump as much blood as it can, which helps get more blood to vital organs, such as the brain and kidneys.
  • A left ventricular assist device (LVAD). This device is a battery-operated pump that takes over part of the heart’s pumping action. An LVAD helps the heart pump blood to the body. This device may be used if damage to the left ventricle, the heart’s main pumping chamber, is causing shock.

Medical Procedures and Surgery

Sometimes medicines and medical devices aren't enough to treat cardiogenic shock.

Medical procedures and surgery can restore blood flow to the heart and the rest of the body, repair heart damage, and help keep a patient alive while he or she recovers from shock.

Surgery also can improve the chances of long-term survival. Surgery done within 6 hours of the onset of shock symptoms has the greatest chance of improving survival.

The types of procedures and surgery used to treat underlying causes of cardiogenic shock include:

  • Percutaneous coronary intervention (PCI) and stents. PCI, also known as coronary angioplasty, is a procedure used to open narrowed or blocked coronary (heart) arteries and treat an ongoing heart attack. A stent is a small mesh tube that's placed in a coronary artery during PCI to help keep it open.
  • Coronary artery bypass grafting. For this surgery, arteries or veins from other parts of the body are used to bypass (that is, go around) narrowed coronary arteries. This creates a new passage for oxygen-rich blood to reach the heart.
  • Surgery to repair damaged heart valves.
  • Surgery to repair a break in the wall that separates the heart’s chambers. This break is called a septal rupture.
  • Heart transplant. This type of surgery rarely is done during an emergency situation like cardiogenic shock because of other available options. Also, doctors need to do very careful testing to make sure a patient will benefit from a heart transplant and to find a matching heart from a donor. Still, in some cases, doctors may recommend a transplant if they feel it's the best way to improve a patient's chances of long-term survival.
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