Sudden cardiac arrest is a medical emergency that occurs when the heart unexpectedly stops beating. This can happen due to various reasons, including heart disease, arrhythmias, or other underlying health conditions. When the heart stops, blood flow to the brain and other vital organs ceases, leading to loss of consciousness and, if not treated immediately, death. Immediate treatment is crucial for survival, often involving CPR (cardiopulmonary resuscitation) and the use of a defibrillator to restore the heart's normal rhythm. Recognizing the signs, such as sudden collapse or unresponsiveness, can help bystanders act quickly and potentially save a life.