Cardiac arrest may be caused by almost any known heart condition. Most cardiac arrests occur when the diseased heart's electrical system malfunctions, producing an abnormal rhythm such as ventricular tachycardia or ventricular fibrillation. Some cardiac arrests are caused by extreme slowing of the heart's rhythm.
All of these events are called life-threatening arrhythmias.
- Scarring from a prior heart attack or other causes: 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 arrest in patients with atherosclerotic heart disease.
- A thickened heart muscle (cardiomyopathy) from any cause (typically high blood pressure or valvular heart disease) — especially if you also have heart failure — can make you more prone to sudden cardiac arrest.
Read more about cardiomyopathy
- Heart medications: Under certain conditions, various heart medications can set the stage for arrhythmias that cause sudden cardiac arrest. Paradoxically, antiarrhythmic drugs used to treat arrhythmias can sometimes produce lethal ventricular arrhythmias even at normally prescribed doses. This is called a "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.
- Electrical abnormalities: Certain electrical abnormalities such as Wolff-Parkinson-White syndrome and Long QT syndrome may cause sudden cardiac arrest in children and young people.
Read more about Wolff-Parkinson-White syndrome
Read more about Long QT syndrome
- 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 arrest when these abnormalities are present.
- Recreational drug use: In people without organic heart disease, recreational drug use is a cause of sudden cardiac arrest.
- Special considerations about cardiac arrest in children:
- In infants and children, most cardiac arrests result from progressive respiratory failure, shock, or both. Less commonly, pediatric cardiac arrests can occur without warning (ie. with sudden collapse) secondary to an arrhythmia (ventricular fibrillation or ventricular tachycardia)
- The combination of compressions and ventilations in CPR has been shown to improve survival better than compressions alone for cardiac arrest in children. Because of these reasons, the combination of compressions and ventilations is still recommended for pediatric resuscitation by all rescuers. However, compressions alone are preferable to no CPR for any victim of cardiac arrest.