Sudden Cardiac Arrest

Sudden cardiac arrest (SCA) is a condition in which the heart suddenly and unexpectedly stops beating. When this happens, blood stops flowing to the brain and other vital organs as a result of which death occurs.

The heart is an electrical pump, where the electricity is generated in special pacemaker cells in atrium of the heart. This electrical spark is carried through pathways in the heart so that all the muscle cells contract at once and produce a heartbeat. This pumps blood through the heart valves and into all the organs of the body so that they can do their work.

This mechanism can break down in a number of ways, but the final pathway in sudden death is the same: the electrical system is irritated and fails to produce electrical activity that causes the heart to beat. The heart muscle can’t supply blood to the body, particularly the brain, and the body dies. Without a coordinated electrical signal, the ventricles stop beating.

Causes of Sudden Cardiac Arrest

1. Heart Disease: Sudden death is most often caused by heart disease. When blood vessels narrow, lack of blood supply is there in the heart muscle. In heart attack (acute myocardial infarction), a blood vessel becomes completely blocked by a blood clot, and there is enough irritability of the muscle to cause ventricular fibrillation. Sudden death may be the initiation of heart disease.

2. Congestive heart failure and heart valve problems, like aortic stenosis (narrowing of the aortic valve) also increase the risk of sudden cardiac arrest.

3. Cardiomyopathy is a heart disease where the heart muscle does not contract properly. Often it is ischemic, where part of the heart muscle doesn’t get an adequate blood supply for a prolonged period of time and no longer can efficiently pump blood. In some people, cardiomyopathy may develop even if the ischemic heart disease is not there.

4. Myocarditis: Inflammation of the heart muscle, known as myocarditis It is one of the main reasons to cause rhythm disturbances.

5. Pulmonary embolus, a blood clot to the lung, can also cause sudden death. Clots form in the leg or arm and may break off and flow to the lung where they decrease the lung’s ability to get oxygen from the air to the body. Risk factors for blood clots include surgery, prolonged immobilization (for example, hospitalization, long car rides or plane trips), trauma, or certain diseases like cancer.

6. Blunt chest trauma, such is in a motor vehicle accident, may result in ventricular fibrillation.

7. Coronary artery disease (CAD), which reduces blood flow to the heart muscle. CAD occurs when a fatty material called plaque builds up in the coronary arteries. These arteries supply your heart muscle with oxygen-rich blood. Plaque narrows the arteries and reduces blood flow to your heart muscle. Eventually, an area of plaque can rupture, causing a blood clot to form on the surface of the plaque. A blood clot can mostly or completely block the flow of oxygen-rich blood to the part of the heart muscle fed by the artery. This causes a heart attack.

8. Physical Stress: Certain types of physical stress can cause your heart’s electrical system to fail. Examples include:

• Intense physical activity. The hormone adrenaline is released during intense physical activity. This hormone can trigger SCA in people who have other heart problems.
• Very low blood levels of potassium or magnesium. These minerals play an important role in your heart’s electrical signaling.
• Major blood loss.
• Severe lack of oxygen.

9. Inherited Disorders: A tendency to have arrhythmias runs in some families. For example, LQTS is a disorder of the heart’s electrical activity due to problems with tiny pores on the surface of heart muscle cells. LQTS can cause sudden, uncontrollable, dangerous heart rhythms.

People who inherit structural heart problems also may be at increased risk for SCA. Many cases of SCA in children are due to these problems.

10. Structural Changes in the Heart: Changes in the heart’s normal size or structure may affect its electrical system. Examples of such changes include an enlarged heart due to high blood pressure or advanced heart disease. Heart infections also may cause structural changes in the heart.

Signs and Symptoms

1. Loss of Consciousness: Usually, the first sign of sudden cardiac arrest (SCA) is fainting. At the same time, no heartbeat (or pulse) can be felt.

2. Within an hour before SCA, some people have chest pain, shortness of breath, nausea (feeling sick to the stomach), or vomiting

Diagnosis for Sudden Cardiac Arrest

Sudden cardiac arrest is an unexpected death in a person who had no known previous diagnosis of a fatal disease or condition. The person may or may not have heart disease.


The vast majority of people whose heart stops beating unexpectedly have ventricular fibrillation. The definitive treatment for this is defibrillation using electricity to shock the heart back into a regular rhythm.

ABCs of resuscitation will be re-evaluated. Airway, Breathing, and Circulation (heart beat and blood pressure) will be supported, and admission to an intensive care unit is most likely.

Diagnostic tests may include repeated electrocardiograms (EKGs), echocardiogram (ultrasounds of the heart), and cardiac catheterization and electro physiologic studies, in which the electrical pathways of the heart are mapped.

Survivors of sudden cardiac arrest are often candidates for implantable cardiac defibrillators.


1. Use of electro physiologic testing may help identify high risk patients (the electrical pathways are mapped using techniques similar to heart catheterization).

2. In people with chest pain, aside from making the diagnosis, monitoring both the heart rate and rhythm are emphasized. The purpose of watching people with chest pain in a hospital setting is to prevent sudden cardiac arrest.

3. Using implantable defibrillators in high risk patients, especially those with markedly decreased ejection fractions can reduce the incidence of sudden cardiac arrest. These devices are placed under the skin in the chest wall and have wires that are attached to the heart itself. When they detect ventricular fibrillation, a shock is automatically delivered to the heart, restoring a heartbeat and averting sudden death.

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