Cardiac arrest

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at September 6, 2016
StartDiseasesCardiac arrest

Cardiac arrest is a sudden loss of heart function. An electrical failure in the heart halts pumping action, immediately stopping blood flow to the body. Respiratory failure and unconsciousness results. Cardiac arrest is a medical emergency.

Contents

Definition & Facts

Cardiac arrest can be understood via the electrical system that powers the heart. The system provides the rate and rhythm of the heartbeat. When the rhythm is disturbed, abnormal heartbeats called arrhythmias occur.

There are many varieties of arrhythmias, not all of them leading to cardiac arrest. Some cause the heart to beat too slowly (bradycardia) or irregularly, but do not cause it to stop.

Cardiac arrest is not a heart attack. When a heart attack occurs, the heart does not usually stop beating entirely though there is a blockage of blood flow to to the heart and cardiac muscle dies. There is danger of sudden cardiac arrest during a heart attack, as the electrical system of the heart may have been damaged.

Symptoms & Complaints

Sometimes, but not always, certain warning signs may precede a cardiac arrest. Irregular or rapid heart beat, feeling faint, shortness of breath and dizziness may be indications of oncoming cardiac arrest.

Vomiting is a sign that few people will interpret as impending heart malfunction, but it is a strong warning, especially when combined with the previous symptoms. Many times cardiac arrest occurs suddenly and without warning. 

Causes

Cardiac arrest is due to a fault in the electrical system of the heart. Cells located in the sinoatrial node (also known as the pacemaker), found in the upper right chamber of the heart (the atirum), send out electrical impulses that initiate the cardiac cycle. This keeps the heart rate and pumping action working in tandem. If the sinus node cells malfunction, an arrhythmia occurs. Sometimes brief interruption occurs in normal hearts, but the rhythm soon rights itself. However, in cases of cardiac arrest, the electrical malfunction causes the heart to stop beating altogether.

Life-threatening heart conditions, electrical shock, trauma, or illicit drug use are the most frequent causes of cardiac arrest. Risk factors include:

Previous heart attack or other history of cardiovascular disease as well as age and male gender all raise the risk for cardiac arrest. Malnutrition such as magnesium deficiency or potassium deficiency may contribute. 

Diagnosis & Tests

If a person survives cardiac arrest, a physician will investigate to determine the cause of the incident and hopefully, prevent a recurrence. An electrocardiogram (EKG) may be recommended. Sensors that detect the electrical activity of the heart are attached to the chest and limbs. The EKG detects heart rhythm disturbances that can raise risk of sudden death.

A blood test will check potassium levels and other chemicals that affect the ability of the heart to perform in rhythm. Blood tests can also determine injury to the heart and recent heart attacks.

Determining how well the heart is able to pump blood through ejection fraction testing is an important marker for future cardiac arrest events. Normal ejection fraction, or how much blood the pumps out is between 55-70 percent. A fraction below 40 percent raises risk. 

Treatment & Therapy

Sudden cardiac arrest is deadly. Every minute is crucial to saving life, and the sooner help is called for and arrives, the better the survival chances. Cardiopulmonary resuscitation (CPR) should be started at once. Health officials have now determined that chest compressions are enough to maintain blood flow until assistance arrives.

A person in cardiac arrest needs immediate treatment with a defibrillator. To be truly effective, defibrillation should be started at once. Automated external defibrillators are defibrillators that any bystander can use. They are located in public areas. AEDs give an electrical shock to the heart when the program detects a rhythm malfunction. In 2008, AEDs were determined by the National Institutes of Health to be safe and effective for home use in the event of cardiac arrest.

Hospital admittance is the next step after successful resuscitation. Medicines will be given to reduce risk of another SCA, or sudden cardiac arrest. Tests will be made to determine the cause of the arrest. Coronary angioplasty and stenting may be performed to open arteries and restore blood flow if there are blockages. 

Sometimes the surgical insertion of an implantable cardioverter-defibrillator or ICD, is performed. The device controls arrhythmias through electrical pulses.

Prevention & Prophylaxis

Prevention is the best method for addressing cardiac arrest. If elevated risk factors, such as diabetes or high blood pressure are noted, a medication called a beta blocker may be prescribed.

Statins may be given to reduce cholesterol levels in the blood. Reducing the levels lowers the risk of blockages causing strokes or heart attacks. The efficacy of statin drugs in preventing strokes, heart attacks and death is 25-35 percent.

Following a heart-healthy eating plan is essential to prevention of sudden cardiac arrest, as well as maintaining a healthy weight. Obesity is a risk factor for all heart ailments. Quitting smoking is difficult, but it can be achieved. There are many programs designed to assist people to conquer nicotine addiction. 

Like a program to quit smoking, an exercise plan is essential to maintaining cardiovascular health or improving it. A plan involves regular exercise performed every day with intention of meeting goals and surpassing them with physical conditioning. Cardiovascular health maintenance may be a simple walking routine, with mileage and speed raised as fitness improves.

Resistance and strength training have been found to be important components of any fitness program. Improved muscular strength aids in arterial function as well as reducing blood pressure. Research reports indicate that regular weight training decreases blood pressure in middle-aged hypertensive men. Muscle burns fat, an important weight-training benefit. 

Stress management and relaxation techniques are very helpful to those who have experienced cardiac arrest. Anxiety disorders are thought to be linked to heart disease as is depression.  Stress and anxiety management may include exercises for relaxation, cognitive behavioral therapy, a form of psychotherapy, and psychiatric medications like antidepressants.