Final answer:
Cardiac arrest is a severe medical emergency where the heart stops pumping blood effectively, leading to potential brain death if untreated. It can be caused by heart arrhythmias or as a result of a myocardial infarction, commonly known as a heart attack, which is caused by the blockage of a coronary artery.
Step-by-step explanation:
Cardiac arrest occurs when the heart fails to pump blood effectively, leading to the cessation of blood flow to vital organs. This is a critical medical emergency that requires immediate intervention. Cardiac arrest can be triggered by a variety of factors, including heart arrhythmias, which are abnormal heart rhythms that disrupt the heart's electrical activity. In some cases, these arrhythmias can be treated with a defibrillator, which delivers an electrical shock to reset the heart's rhythm.
A myocardial infarction (MI), often known as a heart attack, is the result of complete blockage of a coronary artery, typically due to blood clot formation or plaque rupture. This blockage stops blood flow to a portion of the heart, causing myocardial cells to die. These cells cannot be replaced, resulting in permanent damage to the heart muscle. An MI can lead to arrhythmias, heart failure, and eventually cardiac arrest if not promptly treated.
In emergencies, an automated external defibrillator (AED) can be life-saving by correcting ventricular fibrillation—an extremely irregular and ineffective heart rhythm. If this fibrillation occurs in the ventricles and goes untreated, it can quickly lead to brain death due to lack of blood flow.