Sudden cardiac arrest (SCA) is a medical emergency in which the heart suddenly and unexpectedly stops pumping blood effectively. When this happens, blood flow to the brain and vital organs ceases, leading to loss of consciousness within seconds and death within minutes if not treated immediately.
Sudden cardiac arrest is not the same as a heart attack. While a heart attack is caused by a blockage in a coronary artery, sudden cardiac arrest is most often caused by a dangerous heart rhythm disturbance. A heart attack can trigger cardiac arrest, but the two conditions are distinct.
What Happens During Sudden Cardiac Arrest
In a healthy heart, electrical signals follow an organized pathway that produces a coordinated heartbeat. During sudden cardiac arrest, this electrical system fails abruptly.
Most commonly, the heart develops a chaotic rhythm such as Ventricular Fibrillation, or a very fast, unstable rhythm like Ventricular Tachycardia. In these rhythms, the ventricles cannot pump blood effectively, causing circulation to stop.
Less commonly, sudden cardiac arrest can occur when the heart’s electrical system slows or stops completely.
Signs and Symptoms
Sudden cardiac arrest usually occurs without warning. When it happens, symptoms are immediate and dramatic.
Typical signs include:
- Sudden collapse
- Loss of consciousness
- Absence of a pulse
- No normal breathing
Because symptoms progress so rapidly, immediate recognition and response are essential for survival.
Common Causes of Sudden Cardiac Arrest
Sudden cardiac arrest is most often related to underlying heart disease, even if it has not been previously diagnosed.
Common causes include coronary artery disease, prior heart attack with scar tissue, heart failure, and cardiomyopathies. In younger individuals or those without known structural heart disease, inherited electrical disorders such as Brugada Syndrome or long QT syndrome may be responsible.
Electrolyte imbalances, severe oxygen deprivation, drug toxicity, and extreme physical stress can also precipitate cardiac arrest in susceptible individuals.
Cardiac Arrest vs Heart Attack
Understanding the difference between these two terms is important.
A heart attack occurs when blood flow to part of the heart muscle is blocked, causing tissue damage. The heart usually continues to beat during a heart attack.
Sudden cardiac arrest, on the other hand, is an electrical failure. The heart stops pumping blood effectively and collapse occurs almost immediately. A heart attack can trigger sudden cardiac arrest, but many cardiac arrests occur without an active heart attack.
Immediate Treatment: Why Time Matters
Sudden cardiac arrest requires immediate intervention. The two critical actions are cardiopulmonary resuscitation (CPR) and defibrillation.
CPR helps maintain a minimal flow of oxygenated blood to the brain and organs. Defibrillation, delivered by an automated external defibrillator (AED) or medical equipment, can stop the chaotic rhythm and allow the heart’s normal rhythm to resume.
For every minute without defibrillation, the chance of survival decreases dramatically. This is why rapid emergency response and public access to AEDs save lives.
Survival and What Happens Next
If a person survives sudden cardiac arrest, careful evaluation is required to determine the cause and prevent recurrence.
Most survivors are considered at high risk for another event. For this reason, implantation of an Implantable Cardioverter-Defibrillator is often recommended. An ICD continuously monitors heart rhythm and can deliver a life-saving shock if a dangerous arrhythmia occurs again.
Additional treatment focuses on managing underlying heart disease, correcting reversible triggers, and addressing inherited conditions when present.
Living After Sudden Cardiac Arrest
Surviving sudden cardiac arrest is a life-altering experience. Recovery involves not only physical healing but also emotional adjustment. Fear, anxiety, and uncertainty are common and should be addressed as part of comprehensive care.
With modern emergency care, ICD therapy, and appropriate long-term management, many survivors are able to return to active and fulfilling lives.
In Summary
Sudden cardiac arrest is the abrupt loss of effective heart function, most often caused by dangerous heart rhythm disturbances. It is a medical emergency that requires immediate CPR and defibrillation. Although often fatal without rapid treatment, advances in emergency response and long-term therapies have dramatically improved survival and outcomes.
Reference: Sudden Cardiac Arrest
