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What is sudden cardiac arrest?

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Sudden Cardiac Arrest (SCA) is the leading cause of death in the United States claiming the lives of over 450,000 adults and 7,000 children each year, more than lung cancer, breast cancer and traffic accidents combined. Sudden Cardiac Arrest (SCA) can strike anyone, any time, anywhere without notice or prior warning signs. In the next 1 to 2 minutes, the time it takes you to read this article, someone from your community will collapse unconscious, suffering from a sudden cardiac arrest event.

Specifically, Sudden Cardiac Arrest (SCA) is the sudden, abrupt loss of heart function. The victim may or may not have diagnosed heart disease. Sudden death (also called sudden cardiac death) occurs within minutes after symptoms first appear.

What is sudden cardiac death (SCD)?
Sudden cardiac death (SCD), or cardiac arrest, is the sudden, abrupt loss of heart function in a person who may or may not have diagnosed heart disease. The time and mode of death are unexpected. It occurs instantly or shortly after symptoms appear. The most common reason for patients to die suddenly is cardiovascular disease, in particular, coronary heart disease. About half of all deaths from coronary heart disease are sudden and unexpected, regardless of the underlying disease. Thus, half of all deaths due to atherosclerosis (arteries lined with fatty deposits) are sudden. So are half of deaths due to degeneration of the heart muscle, or to cardiac enlargement in patients with high blood pressure.

The term "massive heart attack" is often mistakenly used in the media to describe sudden death. The term "heart attack" or myocardial infarction refers to death of heart muscle tissue due to the loss of blood supply, not necessarily resulting in the death of the heart attack victim. While a heart attack may cause cardiac arrest and sudden cardiac death, the terms aren't synonymous.

What causes cardiac arrest?
The most common underlying reason for patients to die suddenly from cardiac arrest is coronary heart disease. Most cardiac arrests that lead to sudden death occur when the electrical impulses in the diseased heart become rapid (ventricular tachycardia) or chaotic (ventricular fibrillation) or both. This irregular heart rhythm (arrhythmia) causes the heart to suddenly stop beating. Some cardiac arrests are do to extreme slowing of the heart, called bradycardia.

Other factors besides heart diseases and heart attack can cause cardiac arrest. They include respiratory arrest (asphyxiation), blunt force to the chest area, electrocution, near drowning or choking and trauma.

What causes sudden cardiac death?
SCD, or cardiac arrest, may be caused by almost all known heart diseases. Most cardiac arrests occur when the diseased heart begins to exhibit rapid and/or chaotic activity — ventricular tachycardia or fibrillation. Some are due to extreme slowing of the heart. All these events are called life-threatening arrhythmias.

Heart disease. Underlying heart disease is nearly always found in victims of sudden cardiac death. Typically in adults this takes the form of atherosclerosis. Two or more major coronary arteries are narrowed in 90 percent of cases; scarring from a prior heart attack is found in two-thirds of victims. Therefore, the risk factors for sudden cardiac death include similar risk factors for atherosclerosis, such as smoking and high blood pressure.

A heart that's scarred or enlarged from any cause is prone to develop life-threatening ventricular arrhythmias. The first six months after a heart attack is a particularly high-risk period for sudden cardiac death in patients with atherosclerotic heart disease. A thickened heart muscle from any cause (typically high blood pressure or valvular heart disease) — especially when there's congestive heart failure too — is an important predisposing factor for sudden cardiac death.

Heart medications. Under certain conditions, various heart medications can set the stage for arrhythmias that cause sudden cardiac death. In particular, so-called "antiarrhythmic" drugs, even at normally prescribed doses, sometimes may produce lethal ventricular arrhythmias ("proarrhythmic" effect). Regardless of whether there's organic heart disease, significant changes in blood levels of potassium and magnesium (from using diuretics, for example) also can cause life-threatening arrhythmias and cardiac arrest.

Hypertrophic cardiomyopathy. When sudden cardiac death occurs in young adults, atherosclerotic heart disease usually isn't the cause. More often these young victims have a thickened heart muscle (hypertrophic cardiomyopathy) without having high blood pressure.

Electrical abnormalities. Certain electrical abnormalities within the heart also may cause sudden cardiac death in the young. These include a short circuit between the upper and lower chambers (Wolff-Parkinson-White syndrome). This sometimes can allow dangerously rapid rates to develop in the lower chamber when there's a rapid rhythm disturbance in the upper chamber and a congenitally prolonged electrical recovery after each heartbea (long-QT syndrome). These may set the stage for fatal ventricular arrhythmias.

Blood vessel abnormalities. Less often, inborn blood vessel abnormalities, particularly in the coronary arteries and aorta, may be present in young sudden death victims. Adrenaline released during intense physical or athletic activity often acts as a trigger for sudden cardiac death when these predisposing conditions are present.

Recreational drug abuse. In people without organic heart disease, recreational drug abuse is an important cause of sudden cardiac death.

What are the signs of sudden cardiac arrest?
Signs of sudden cardiac arrest include sudden loss of responsiveness (no response to tapping on sholders) and lack of normal breathing patterns (the victim does not take a normal breath when head is tilted up after at least five seconds).

If someone may be experiencing ventricular fibrillation, seek help immediately. This problem can be corrected with a defibrillator, which gives an immediate shock to the heart. This must be done very soon after the start of fibrillation even when blood flow is partially maintained through CPR (cardiopulmonary resuscitation.)

What can be done to increase survival rates for victims of sudden cardiac arrest?
Early CPR and defribrillation combined with early advanced care can result in high long-term survival rates for witnessed cardiac arrest.

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