People often think a heart attack and cardiac arrest are the same thing. Prof Chris Semsarian explains the difference
Sudden cardiac arrest is one of Australia’s biggest causes of death and disability. It claims the lives of an estimated 22,000 to 33,000 Australians each year. But immediate CPR and defibrillation in the first few minutes may reverse a sudden cardiac arrest to save a person’s life and reduce any long-term neurological impairment.
What’s the difference between a heart attack and a sudden cardiac arrest?
A heart attack occurs when a blocked artery stops oxygen-rich blood reaching part of the heart muscle. This can lead to a cardiac arrest. If this is not quickly opened, that part of the heart will begin to die. Heart attack symptoms may occur suddenly but mostly the symptoms start slowly and persist for hours, days or even weeks before a heart attack. Heart attacks are more common in men over the age of 40 years.
A sudden cardiac arrest occurs suddenly and often without warning. It is caused by a glitch in the heart’s electrical system that causes an irregular heartbeat (known as an arrhythmia) that halts the pumping action of the heart. The most common arrhythmia in sudden cardiac arrest is ventricular fibrillation (VF). When the heart cannot pump blood to vital organs, the person becomes unconscious in seconds and death can occur in minutes if they do not receive immediate treatment. However, this life-threatening heart rhythm can be reversed if CPR with an emphasis on chest compressions or defibrillation either by an automated external defibrillator (AED) or an implantable cardioverter defibrillator (ICD) is used to shock the heart within minutes. Research has found survival from a sudden cardiac arrest is reduced by 7-10% every minute the person does not receive defibrillation.
Genetic heart diseases and sudden cardiac arrest
There are a number of heart conditions that can cause sudden cardiac arrest. One group is collectively known as genetic heart diseases. These often affect young people and are caused by an alteration in a gene that is present in the person at birth. Genetic heart diseases include structural heart conditions (e.g. hypertrophic cardiomyopathy, familial dilated cardiomyopathy) and rhythm disorders of the heart (e.g. long QT syndrome, Brugada syndrome). In most of these cases, the first-degree relatives (parents, siblings, children) of the person with disease have a one in two risk of having the same condition. So it is important that a cardiologist checks all first-degree relatives.