Definition and Overview
A cardiac arrest is a life-threatening medical emergency that occurs when the heart stops functioning often without any warning. As a result, the blood flow to the brain and other vital organs is totally cut off, causing the person to abruptly lose consciousness. Unless the person receives prompt emergency treatment, which includes CPR (cardiopulmonary resuscitation) and defibrillation (a process to shock the heart to quickly restore normal heart rhythm), death can be expected within just a few minutes.
Cardiac arrest is often mistaken with a heart attack or myocardial infarction. Although both conditions affect the heart and share a number of symptoms, they are different. The latter occurs when at least one of the arteries leading to the heart is blocked, which prevents the heart from receiving enough oxygen-rich blood. This can permanently damage the heart muscle, which is forced to work harder in order to pump enough blood to the rest of the body. In contrast, cardiac arrest is triggered by an electrical malfunction that causes irregular heartbeats, which disrupt its pumping action. The common cause is ventricular fibrillation, a type of arrhythmia that occurs when the heart’s lower chambers suddenly develop a rapid, irregular rhythm. However, these two heart conditions are linked; cardiac arrest can occur after a heart attack or during recovery. But it is important to note that most heart attacks do not lead to cardiac arrest.
According to statistics, up to 450,000 people in the United States suffer from cardiac arrest each year. Almost 95% die before or while receiving emergency medical treatment.
Causes of Condition
Cardiac arrest occurs when the heart’s electrical system has become diseased and malfunctions, resulting in cardiac rhythm disturbance, such as:
Ventricular fibrillation - The most serious cardiac rhythm disturbance that occurs when the heart beats with erratic, rapid impulses. As a result, the heart’s chambers quiver instead of pumping blood.
Ventricular tachycardia - Characterised by rapid heartbeats that originate in the ventricles.
Other conditions that can lead to cardiac arrest include:
Cardiomyopathy - A condition characterised by enlarged, thickened, or rigid heart muscle. It weakens the heart and limits its ability to maintain a normal electrical rhythm.
Congenital heart disease (CHD) - Cardiac arrest is very uncommon in children and adolescents but when it occurs, it is usually due to congenital heart disease.
Electrical abnormalities - Certain electrical abnormalities such as Long QT and Wolff-Parkinson-White syndromes may cause sudden cardiac arrest in children and adolescents.
Previous heart attack - A heart attack caused by severe coronary artery disease can trigger ventricular fibrillation and sudden cardiac arrest. The condition can also leave behind scar tissue, which can cause heart rhythm abnormalities.
The following factors can increase a person’s risk of cardiac arrest:
Family history of sudden cardiac arrest
History of syncope (fainting episodes of unknown cause)
Recreational drug abuse
A sedentary lifestyle
Intense physical activities
Significant blood loss
Cardiac arrest often occurs without any warning. In the majority of cases, patients suddenly lose consciousness and stop breathing. Unless CPR is immediately administered, the patient will die in a matter of minutes as the brain and vital organs are left without blood and oxygen supply.
In rare cases, patients experience the following symptoms within an hour before cardiac arrest:
Unexplained wheezing or shortness of breath
Who to See and Types of Treatments Available
The patient’s chances of surviving a cardiac arrest heavily rely on how soon CPR is administered. CPR helps maintain blood flow to the brain and other vital organs until an ambulance arrives or a defibrillator is used. A defibrillator is a device that delivers high-energy electric shocks to the heart through the chest wall to restore normal heart rhythm. Once the patient is stable, doctors recommend the implantation of cardioverter defibrillator or ICD to minimise the patient’s risk of suffering from another cardiac arrest in the future.
An ICD is a small device that is implanted either in the chest or abdomen. It has wires with electrodes that connect to the heart chambers and functions by monitoring the heart rhythm. If it detects any abnormalities, it sends out a controlled burst of impulses to stabilise the heart's rhythm.
ICD implant surgery is a very common procedure that can be performed under general anaesthesia. During surgery, the insulated wires are inserted into the veins near the collarbone and threaded to the heart using imaging technology for guidance. The ends of the leads are then secured to the heart and the other ends are attached to the generator, which is implanted just under the skin of the collarbone.
Patients who survive cardiac arrest must undergo a number of procedures to treat any underlying causes. These procedures typically include:
Coronary angioplasty - If a cardiac arrest was caused by blocked coronary arteries, doctors recommend coronary angioplasty, a minimally invasive procedure that opens up a blocked artery using a balloon catheter. It is an effective procedure in restoring normal blood flow to the heart.
Coronary bypass surgery - The procedure of choice for patients with severe coronary heart disease (CHD). It restores blood flow to the heart muscle by bypassing the blocked artery. The procedure can be performed using traditional open surgery or minimally invasive methods.
Corrective heart surgery - Fixes or treats congenital heart defects that increase the patient’s risk of cardiac arrest. Problems with the heart’s structure can involve the valves inside the heart, interior walls of the heart, as well as the veins and arteries that carry blood to the body or heart.
Radiofrequency catheter ablation - Works by destroying heart tissue that triggers abnormal heart rhythm. By preventing abnormal electrical signals from entering the heart, patients can avoid experiencing arrhythmia that can trigger a cardiac arrest.
The prognosis for cardiac arrest patients is generally poor with more than 9 out of 10 patients dying before or while receiving emergency medical treatment. Meanwhile, some of those who survive remain in a persistent vegetative state or suffer from some degree of brain injury and impaired consciousness.
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