Several categories of heart problems can cause a sudden cardiac arrest episode. The immediate cause of sudden cardiac arrest is usually an abnormal heart rhythm (arrhythmia). Arrhythmias are triggered by a malfunction in the heart's electrical system due to a pre-existing heart condition or disease.
Cardiac-arrest-inducing arrhythmias can develop from the following heart conditions or diseases:
- Coronary artery disease — More than 80 percent of sudden cardiac arrest episodes occur in people who have coronary artery disease. In coronary artery disease, the heart's arteries become blocked with cholesterol and other deposits, reducing blood flow to the heart. This affects the heart's ability to conduct electrical signals smoothly.
- Heart attack — A heart attack often occurs as a result of severe coronary artery disease and can trigger an arrhythmia and subsequent episode of sudden cardiac arrest. In addition, a heart attack can leave behind areas of dead scar tissue on the heart, which also may lead to arrhythmias.
- Cardiomyopathy — Cardiomyopathy usually occurs because the muscular walls of the heart stretch and enlarge or thicken, which can lead to an arrhythmia.
- Heart valve disease — When heart valves leak or narrow, the heart muscle stretches or thickens, increasing the risk of developing an arrhythmia.
- Congenital heart disease — In children and teens, sudden cardiac arrest typically results from congenital heart disease (hereditary heart defects present at birth).
- Hypertrophic cardiomyopathy — is the most common form of congenital heart disease that causes sudden cardiac arrest in young people and is a hereditary disorder. Even adults who have been treated with corrective surgery for hypertrophic cardiomyopathy remain at increased risk for sudden cardiac arrest. Mayo Clinic in Minnesota has a Hypertrophic Cardiomyopathy Clinic dedicated to diagnosing and treating patients with this condition.
- Heart rhythm abnormalities (electrophysiological abnormalities) — Some people experience arrhythmias because of hereditary problems with the heart's electrical system. Mayo Clinic in Minnesota has a designated Heart Rhythm Clinic and a Long QT Syndrome/Inherited Arrhythmia Clinic dedicated to diagnosing and treating patients with heart rhythm abnormalities. Mayo Clinic in Arizona and Florida also have specialized clinics for diagnosing and treating arrhythmias.
Conditions caused by heart rhythm abnormalities include long QT syndrome and Brugada syndrome.
Sudden cardiac arrest also can occur rarely under the following circumstances:
- Severe blood loss from an injury or internal bleeding
- Electrical shock injury
- Lack of oxygen to the heart and brain because of events such as choking, drowning or a severe asthma attack
- Severe physical stress
- Cardiogenic shock (heart failure because of inadequate heart pumping function)