Cardiogenic Shock

What Is Cardiogenic Shock?

Cardiogenic (kar-dee-oh-JE-nik) shock is a state in which a weakened heart isn't able to pump enough blood to meet the body's needs. It is a medical emergency and is fatal if not treated right away. The most common cause of cardiogenic shock is damage to the heart muscle from a severe heart attack.

Not everyone who has a heart attack develops cardiogenic shock. In fact, less than 10 percent of people who have a heart attack develop it. But when cardiogenic shock does occur, it's very dangerous. For people who die from a heart attack in a hospital, cardiogenic shock is the most common cause.

What Is Shock?

The medical term "shock" refers to a state in which not enough blood and oxygen reach important organs in the body, such as the brain and kidneys. In a state of shock, a person's blood pressure is very low.

Shock can have a number of different causes. Cardiogenic shock is only one cause of shock. Other causes of shock include:

• Hypovolemic (hy-poe-voe-LEE-mik) shock. This is shock due to not enough blood in the body. The most common cause is severe bleeding.
• Vasodilatory (VAZ-oh-DILE-ah-tor-ee) shock. In this type of shock, the blood vessels relax too much and cause very low blood pressure. When the blood vessels are too relaxed, there isn't enough pressure to push the blood through them. Without enough pressure, blood doesn't reach the organs. A bacterial infection in the bloodstream, a severe allergic reaction, or damage to the nervous system (brain and nerves) may cause vasodilatory shock.

When a person is in shock (from any cause), not enough blood or oxygen is reaching the body's organs. If shock lasts more than several minutes, the lack of oxygen to the organs starts to damage them. If shock isn't treated quickly, the organ damage can become permanent, and the person can die.

Some of the signs and symptoms of shock include:

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

If you suspect that you or someone with you is in shock, call 9–1–1 and get emergency treatment right away. Prompt treatment can help prevent or limit lasting damage to the brain and other organs and can prevent death.

Outlook

In the past, almost no one survived cardiogenic shock. Now, thanks to improved treatments, around 50 percent of people who go into cardiogenic shock survive.

The reason more people are able to survive cardiogenic shock is because of treatments (medicines and devices) that restore blood flow to the heart and help the heart pump better. In some cases, devices that take over the pumping function of the heart are used. Implanting these devices requires major surgery.

How the Heart Works

To understand cardiogenic shock, it's helpful to understand how a normal heart works.

The heart is a muscle about the size of your fist. It works like a pump and beats 100,000 times a day.

The heart has two sides, separated by an inner wall called the septum. The right side of the heart pumps blood to the lungs to pick up oxygen. Then, oxygen-rich blood returns from the lungs to the left side of the heart, and the left side pumps it to the body.

The heart has four chambers and four valves and is connected to various blood vessels. Veins are the blood vessels that carry blood from the body to the heart. Arteries are the blood vessels that carry blood away from the heart to the body.

A Healthy Heart Cross-Section

The illustration shows a cross-section of a healthy heart and its inside structures. The blue arrow shows the direction in which oxygen-poor blood flows from the body to the lungs. The red arrow shows the direction in which oxygen-rich blood flows from the lungs to the rest of the body.

Heart Chambers

The heart has four chambers or "rooms."

• The atria (AY-tree-uh) are the two upper chambers that collect blood as it comes into the heart.
• The ventricles (VEN-trih-kuls) are the two lower chambers that pump blood out of the heart to the lungs or other parts of the body.

Heart Valves

Four valves control the flow of blood from the atria to the ventricles and from the ventricles into the two large arteries connected to the heart.

• The tricuspid (tri-CUSS-pid) valve is in the right side of the heart, between the right atrium and the right ventricle.
• The pulmonary (PULL-mun-ary) valve is in the right side of the heart, between the right ventricle and the entrance to the pulmonary artery, which carries blood to the lungs.
• The mitral (MI-trul) valve is in the left side of the heart, between the left atrium and the left ventricle.
• The aortic (ay-OR-tik) valve is in the left side of the heart, between the left ventricle and the entrance to the aorta, the artery that carries blood to the body.

Valves are like doors that open and close. They open to allow blood to flow through to the next chamber or to one of the arteries, and then they shut to keep blood from flowing backward.

When the heart's valves open and close, they make a "lub-DUB" sound that a doctor can hear using a stethoscope.

• The first sound—the "lub"—is made by the mitral and tricuspid valves closing at the beginning of systole (SIS-toe-lee). Systole is when the ventricles contract, or squeeze, and pump blood out of the heart.
• The second sound—the "DUB"—is made by the aortic and pulmonary valves closing at beginning of diastole (di-AS-toe-lee). Diastole is when the ventricles relax and fill with blood pumped into them by the atria.

Arteries

The arteries are major blood vessels connected to your heart.

• The pulmonary artery carries blood pumped from the right side of the heart to the lungs to pick up a fresh supply of oxygen.
• The aorta is the main artery that carries oxygen-rich blood pumped from the left side of the heart out to the body.
• The coronary arteries are the other important arteries attached to the heart. They carry oxygen-rich blood from the aorta to the heart muscle, which must have its own blood supply to function.

Veins

The veins are also major blood vessels connected to your heart.

• The pulmonary veins carry oxygen-rich blood from the lungs to the left side of the heart so it can be pumped out to the body.
• The vena cava is a large vein that carries oxygen-poor blood from the body back to the heart.

For more information on how a healthy heart works, see the Diseases and Conditions Index article on How the Heart Works. This article contains animations that show how your heart pumps blood and how your heart’s electrical system works.

What Causes Cardiogenic Shock?

Immediate Causes

Cardiogenic shock happens when the heart can't pump enough blood to the body. This mostly occurs when the left ventricle isn't working because the muscle isn't getting enough blood or oxygen due to an ongoing heart attack. The weakened heart muscle can't pump enough oxygen-rich blood to the rest of the body.

In about 3 percent of the cases of cardiogenic shock, the right ventricle isn't working. This means the heart can't effectively pump blood to the lungs, where the blood picks up oxygen to bring back to the heart and the rest of the body.

When the heart isn't pumping enough blood to the rest of the body, organs (such as the brain and kidneys) don't get enough oxygen and can be damaged. Some of the things that might happen include the following.

• Cardiogenic shock may result in death if the flow of blood and oxygen to the organs isn't restored quickly. This is why emergency medical treatment is essential.
• When organs don't get enough blood or oxygen and stop working, cells in the organs die, and the organs may never go back to working normally.
• As some organs stop working, they may cause problems with other bodily functions. This, in turn, can make the shock worse. For example:
  • When the kidneys aren't working right, 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.
  • When the liver isn't working right, the body stops making proteins that cause the blood to clot. This can lead to more bleeding if the shock is due to blood loss.
• How well the brain, kidneys, and other organs recover depends on how long a person is in shock. The shorter the time in shock, the less damage to the organs. This is another reason why it's so important to get emergency treatment right away.

Underlying Causes

The underlying causes of cardiogenic shock are conditions that weaken the heart and make it unable to pump enough blood and oxygen to the body.

These conditions include:

• Heart attack. Coronary artery disease (CAD) usually causes heart attack. CAD is a condition in which a material called plaque (plak) narrows or blocks the coronary arteries.
• Serious heart conditions that may cause a heart attack and lead to cardiogenic shock, such as:
  • Ventricular septal rupture. This is when the wall between the two ventricles breaks down because cells in part of the wall have died due to a heart attack. If the ventricles aren't separated, they can't pump properly.
  • Papillary muscle infarction or rupture. This is when the muscles that help anchor the heart valves stop working or break because their blood supply is cut off due to a heart attack. When this happens, blood doesn't flow in the right way between the different chambers of the heart, and they can't pump properly.
• Serious heart conditions that may happen with or without a heart attack, including:
  • Myocarditis, or inflammation of the heart muscle.
  • Endocarditis, or infection of the heart valves.
  • Arrhythmias, or problems with the speed or rhythm of the heartbeat.
  • Pericardial tamponade, or too much fluid or blood around the heart. The fluid squeezes the heart muscle so it can't pump properly.
• Pulmonary embolism. This is a sudden blockage in a lung artery, usually due to a blood clot that traveled to the lung from a vein in the leg.

Who Is At Risk for Cardiogenic Shock?

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:

• Older age
• Having a history of heart attacks or heart failure
• Having coronary artery disease in all the major heart blood vessels

What Are the Signs and Symptoms of Cardiogenic Shock?

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

The signs and symptoms of cardiogenic shock include:

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

If you or someone with you is having these signs and symptoms, call 9–1–1 right away for emergency treatment. Prompt treatment can help prevent or limit lasting damage to the heart and other organs and can prevent sudden death.

How Is Cardiogenic Shock Diagnosed?

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

Once emergency treatment is started, 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 that are useful in diagnosing cardiogenic shock include:

• Blood pressure. Using a simple blood pressure sleeve and stethoscope, doctors can check to see if a person has very low blood pressure, the most common sign of shock. This can easily be done before the patient goes to the hospital. Very low blood pressure also can have less serious causes, including simple fainting and side effects of medicines, such as medicines that treat high blood pressure.
• EKG (electrocardiogram). This test detects and records the electrical activity of the heart, measuring the rate and regularity of the heartbeat. Doctors use EKG to diagnose severe heart attack and monitor your heart's condition.
• Chest x ray. This test takes pictures of organs and structures inside your chest, including the heart, lungs, and blood vessels. A chest x ray shows whether the heart is enlarged or whether there is fluid in the lungs, which can be signs of cardiogenic shock.
• Echocardiography. This test uses sound waves to create a moving picture of your heart. Echocardiography provides information about the size and shape of your heart and how well your heart chambers and valves are working. The test also can identify areas of heart muscle that aren't contracting normally. Not enough blood is flowing to these areas.
• Coronary angiography. This test is an x-ray exam of the heart and blood vessels. The doctor passes a catheter (a thin, flexible tube) through an artery in your leg or arm to your heart. The catheter can measure the pressure inside the various chambers of your heart. A dye that can be seen on x ray is injected into the blood 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 that exist.

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

• Arterial blood gas measurement. In this test, a blood sample is taken from an artery to measure oxygen, carbon dioxide, and pH (acidity) in the blood. Doctors look for abnormalities in these levels that are associated with shock.
• Cardiac enzymes. When cells in the heart die, they release enzymes into the blood called markers or biomarkers. Measuring these markers can show whether the heart is damaged and the extent of the damage.
• Tests that measure the function of various organs, such as the kidneys and liver. If these organs aren't working right, it could be a sign that they aren't getting enough blood and oxygen, which could be a sign of cardiogenic shock.

How Is Cardiogenic Shock Treated?

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

The goals of emergency treatment for cardiogenic shock are first to treat the shock and then to treat the underlying cause or causes of the shock.

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 causing damage to the heart. Often, opening the blood vessel can get the patient out of shock with little or no additional treatment.

Emergency Life Support

Emergency life support treatment is required for any type of shock. This treatment helps get blood and oxygen flowing to the brain, kidneys, and other organs. Restoring blood flow to the organs is essential to keep the patient alive and to try to 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.
• Giving the patient fluids, including blood and blood products, through a needle inserted in a vein (when the shock is due to blood loss). Putting more blood into the bloodstream can help get more blood to important organs and to the rest of the body. This is usually not done for cardiogenic shock because the heart can't pump the blood that's already in the body and too much fluid is in the lungs, making it difficult to breathe.

Medicines

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

Depending on what is causing the cardiogenic shock, treatment may include medicines to:

• Increase the force with which the heart muscle contracts
• Treat the heart attack that may have caused the shock

Medical Devices and Procedures

In addition to medicines, there are medical devices that can help the heart pump and improve blood flow. The devices most commonly used to treat cardiogenic shock include:

• 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 large balloon at the tip of the device is inflated and deflated in a rhythm that exactly matches the rhythm of the heart's pumping action. This helps the weakened heart muscle pump as much blood as it can, and gets more blood to vital organs such as the brain and kidneys.
• Angioplasty and stents. Angioplasty is a procedure used to restore blood flow through blocked coronary arteries and to treat an ongoing heart attack. A stent is a small device that's placed in a coronary artery during angioplasty to help keep it open.

Surgery

Sometimes medicine and medical devices aren't enough to treat cardiogenic shock. Surgery can restore blood flow to the heart and the rest of the body and repair damage to the heart. Surgery can help keep a patient alive while recovering from shock and improve the chances for long-term survival.

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

• Coronary artery bypass grafting. In this surgery, arteries or veins from other parts of the body are used to bypass (that is, go around) narrowed coronary arteries.
• Surgery to repair damaged heart valves.
• Surgery to repair a break in the wall between two chambers of the heart. This break is called a septal rupture.
• Surgery to implant a device to help the heart pump blood to the body. This device is called a left ventricular assist device (LVAD) or mechanical circulatory assist. This surgery may be done if damage to the left ventricle is causing the shock. The implanted device is a battery-operated pump that takes over part of the pumping action of the heart.
• Heart transplant. This is rarely done during an emergency situation like cardiogenic shock due to the other available devices and surgery options. Also, doctors need to do very careful tests 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 the patient's chances of long-term survival.

How Can Cardiogenic Shock Be Prevented?

The best way to prevent cardiogenic shock is to do as much as you can to lower your risk for heart disease and prevent a heart attack. (See the National Heart, Lung, and Blood Institute's "Your Guide to a Healthy Heart.")

If you have a heart attack, you should get immediate treatment 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. Delay in seeking treatment increases the chances of complications and death.
• If you think you're having a heart attack, or if you have angina (chest pain or discomfort) that doesn't go away as usual when you take your angina medicine as directed, call 9–1–1 for help. You can begin to receive life-saving treatment as soon as medical personnel arrive.

Key Points

• Cardiogenic shock is a state in which a weakened heart isn't able to pump enough blood to meet the body's needs. It is a medical emergency and is fatal if not treated right away.
• The medical term "shock" refers to a state in which not enough blood and oxygen reach important organs in the body, such as the brain and kidneys.
• The most common cause of cardiogenic shock is damage to the heart muscle from a severe heart attack. However, less than 10 percent of people who have a heart attack develop cardiogenic shock.
• Common signs and symptoms of cardiogenic shock include:
  • Confusion or lack of alertness
  • Loss of consciousness
  • A sudden, rapid heartbeat
  • Sweating
  • Pale skin
  • Weak pulse
  • Rapid breathing
  • Decreased or no urine output
  • Cool hands and feet
• If you or someone with you is having these signs and symptoms, call 9–1–1 right away for emergency treatment. Prompt treatment can help prevent or limit lasting damage to the heart and other organs and can prevent sudden death.
• Blood pressure tests, EKG (electrocardiogram), chest x ray, echocardiography, coronary angiography, and blood tests are used to diagnose cardiogenic shock.
• Treatment for cardiogenic shock starts with emergency life support to keep the patient alive. Once doctors know that a person is in cardiogenic shock, they can use medicines, medical devices, and different types of surgery to treat the underlying causes of the shock.
• The best way to prevent cardiogenic shock is to do as much as you can to lower your risk for heart disease and prevent a heart attack. (See the National Heart, Lung, and Blood Institute's "Your Guide to a Healthy Heart.")

Source : http://www.nhlbi.nih.gov/health/dci/Diseases/shock/shock_summary.html