SCA - Understanding Sudden Cardiac Arrest

Sudden cardiac arrest takes place when the heart is no longer pumping blood through the body.

Usually, this is caused by an electrical problem in the heart. The victim is unconscious and doesn't breathe normally.

The victim has no pulse and may have some movement (seizure type activity). Approximately 1,000 people die every day because they suffered a cardiac arrest outside of the hospital.

Sudden cardiac arrest is a medical emergency. It is fatal if not treated immediately. With fast medical care, survival is possible.

Cardiopulmonary resuscitation can improve the chances of survival until emergency personnel arrive.

Cardiac arrhythmia is a term to define an abnormal electrical activity in the heart.

The heart beat may be too fast or too slow, and may be regular or irregular.

Some arrhythmias are life-threatening medical emergencies and others may not be associated with any symptoms at all.

The arrhythmias related with the cardiac arrest are:

• Ventricular Tachycardia
• Ventricular Fibrillation

Ventricular Tachycardia: Tachycardia refers to a heartrate that exceeds the range of the normal resting heartrate.

Ventricular tachycardia is a fast heart rhythm that originates in one of the ventricles of the heart.

Ventricular Fibrillation: Is a condition in which there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart.

Sudden cardiac arrest is not the same as heart attack. Sudden cardiac arrest is often a complication of a heart attack.

In sudden cardiac arrest the heart’s electrical signals that control its pumping suddenly become rapid and chaotic. The ventricles (the lower chambers of the heart) begin to quiver instead of contract and are no longer able to pump blood to the rest of the body.

A heart attack is caused by abrupt blockage in one of the heart’s major blood vessels, shutting off oxygen and blood flow to the heart muscle.

• Usually is caused by an electrical problem in the heart.
• Occasionally where there may be a normal electrical signal, there is a mechanical problem. The heart muscle fails to pump.
• Sometimes severe hemorrhage and other issues cause SCA.

• Is caused by a circulation or plumbing problem of the heart, when one or more of the arteries (that supply blood to the heart) are blocked. The heart muscle becomes damaged because the oxygen in the bloodcannot reach the heart.
• The damage produced at the heart muscle can alter the heart's electrical system. This may cause dangerously fast or slow heart rhythms that can cause SCA.
• If the victim suffers a heart attack, there is a higher risk for SCA.

Coronary heart disease is the most common reason to sustain sudden cardiac arrest. Most cardiac arrests occur when the heart experiences ventricular tachycardia, ventricular fibrillation or both.

This arrhythmia causes the heart to suddenly stop beating. Other factors can cause cardiac arrest:

• Respiratory arrest
• Drowning
• Electrocution
• Choking and trauma

Sudden cardiac arrest can also occur without any known cause and can strike victims at any age.

To reduce the risk of being victim of sudden cardiac arrest, several actions can be taken:

• Living a heart healthy life : eating healthful foods, avoiding smoking, exercising regularly and maintaining a reasonable weight.
• Treating and monitoring diseases : high blood pressure, high cholesterol and diabetes.
• Controlling or stopping abnormal heart rhythms

Abnormal heart rhythms can be controlled by means of:

• Medications – Antiarrhythmics can control abnormal heart rhythms.
• Implantable cardioverter defibrillators (ICDs) – ICDs are implanted under the skin, have been very successful in preventing sudden cardiac death in certain high-risk patients. The ICD can also act like a pacemaker if the heart is beating too slowly.
• Catheter Ablation – Radiofrequency, cryotherapy or other energy forms are used to destroy small areas of heart muscle that give rise to the abnormal electrical signals.

Sudden cardiac death is not a random event. Although they may not know it, most victims do have heart diseases or other health problems. Two of the most important contributors to cardiac arrest are:

• A previous heart attack: 75% of sudden cardiac arrest victims.
• Coronary artery disease: 80% of sudden cardiac arrest victims.

Other symptoms and signs that may indicate risk of sudden cardiac arres are:

• Arrhythmia of unknown cause
• Tachycardia that comes and goes, even at rest
• Fainting of unknown cause
• A low ejection fraction (EF)

Knowing your risk is critical specially if you have had a heart attack or a heart failure. Sudden cardiac arrest strikes without warning symptoms, so even though you feel fine, you could still be at serious risk.

You know your numbers when it comes to blood pressure and cholesterol.

If you have had a heart disease, there’s another number you need to know: the ejection fraction (EF). It is measured with a test called an echocardiogram.

Ejection fraction is a measure of how well your heart pumps blood with each heart beat. A healthy heart pumps 55% or more of its blood with each beat. People at highest risk for sudden cardiac arrest have ejection fractions of less than 40%.

To determine if you are at risk of sudden cardiac arrest there are a number of tests that can be performed:

• Electrocardiogram – Record the electrical activity of the heart in order to identify abnormal heart rhythms. Certain arrhythmias could point to an increased risk of sudden cardiac arrest.
• Echocardiogram – The test measure the pumping ability of the heart and identify other problems that may increase the risk for sudden cardiac arrest.
• Electrophysiology – Studies the speed and flow of electrical signals through the heart, identifies rhythm problems and pinpoints areas in the heart that may be the sources of abnormal electrical signals that trigger arrhythmias.
• Event recorder – Records the electrical activity of the heart over a longer period of time. Patients turn on the device whenever they feel their heart beating too quickly or chaotically.
• Holter monitor – Records a long sampling of the heart rhythm for one to two day. The tape is later analyzed in the laboratory for signs of arrhythmia.

When the heart is no longer able to pump, the absence of oxygenated blood can cause brain damage in a few minutes.

Within eight to ten minutes death will occur. When sudden cardiac arrest strikes time is critical. Quick action can truly make a difference in saving a life:

• Position the victim on his or her back on the floor.

• Place one hand on top of the other and place the heel of the bottom hand on the center of the victim’s chest.

• Lock your elbows and begin forceful chest compressions at a rate of 100 per minute.

• If an automated external defibrillator is available, attach it to the victim and follow the machine’s instructions. If no AED is available, perform continuous chest compressions until paramedics arrive.

Portable automatic external defibrillators are available in an increasing number of places.

A chain of survival is the worldwide guidelines for response to sudden cardiac arrest.

1. Early access to care: Call 911 immediately!
2. Early Cardiopulmonary Resuscitation: Provide CPR to help maintain blood flow to the brain until the next step
3. Early defibrillation: Defibrillation is the only way to restart a heart in cardiac arrest
4. Early advanced care: After defibrillation, an emergency team provides advanced cardiac care on scene, such as intravenous medications

FACT SHEET: Sudden Cardiac Arrest vs. Heart Attack

  The Sudden Cardiac Arrest Association.

It’s Time To Know If You Are At Risk

  Heart Rhythm Foundation.

Paul Lewis; Lady AnnDerground.