A heart attack and cardiac arrest are fundamentally different medical emergencies affecting the heart. Both are life-threatening conditions requiring immediate action, but they involve distinct mechanisms. A heart attack is a plumbing problem related to blood flow, while cardiac arrest is an electrical problem that stops the heart’s ability to function entirely. Understanding this difference is crucial for determining the appropriate life-saving response.
Heart Attack Explained
A heart attack, or myocardial infarction (MI), is a circulatory issue where blood flow to a section of the heart muscle is abruptly cut off. This interruption typically occurs when a blood clot forms on a ruptured plaque deposit within a coronary artery, which supplies the heart muscle with oxygen-rich blood. When the blood supply is blocked, the affected portion of the heart muscle begins to suffer damage and die due to a lack of oxygen (infarction). During this event, the heart generally continues to beat, meaning the person is typically conscious and still breathing, but the pumping function is compromised.
The classic presentation involves crushing chest pain or pressure, which may radiate to the left arm, shoulder, jaw, or back. Other common symptoms include shortness of breath, cold sweats, and nausea or vomiting. In women, symptoms are often less traditional and may manifest as extreme fatigue, indigestion, or pain localized in the neck or upper abdomen. Recognizing these signs and acting quickly is important, as prolonged blockage causes greater irreversible damage to the heart muscle.
Cardiac Arrest Explained
Cardiac arrest, or sudden cardiac arrest (SCA), is an electrical malfunction where the heart suddenly stops beating effectively. This event is most often caused by ventricular fibrillation, a rapid, chaotic heart rhythm. During ventricular fibrillation, the heart’s lower chambers quiver uselessly instead of contracting to pump blood.
Since the heart is not pumping, blood flow to the brain and other vital organs ceases immediately. The onset is instantaneous, leading to a sudden collapse. The person will become unresponsive, will not be breathing normally, and will have no detectable pulse. Without intervention, the individual loses consciousness within seconds, and death can occur within minutes. Cardiac arrest is a system-wide failure of the heart’s electrical command center, focusing on a catastrophic disruption of the heart’s rhythm rather than a physical blockage.
The Critical Distinction in Emergency Response
The difference in underlying mechanism dictates a completely different emergency response for each event. For a heart attack, the person is typically awake, and the immediate response focuses on stabilizing the patient and restoring blood flow via advanced medical care. This involves calling emergency services immediately and having the person rest in a calm, comfortable position.
Emergency medical personnel can begin treatments, such as administering aspirin to prevent further clotting, before arrival at the hospital. The ultimate goal of hospital treatment is to reopen the blocked artery, often through a procedure like angioplasty.
Conversely, cardiac arrest demands immediate, bystander-initiated intervention to manually sustain blood flow and restart the electrical system. Since the heart has stopped pumping, cardiopulmonary resuscitation (CPR) must be started immediately to circulate oxygenated blood to the brain and other organs. The only definitive treatment for ventricular fibrillation is defibrillation, which requires using an Automated External Defibrillator (AED) to deliver an electric shock. Every minute lost without defibrillation dramatically reduces the chance of survival.
The Connection Between the Two Events
While a heart attack and cardiac arrest are separate entities, a heart attack is one of the leading causes of sudden cardiac arrest. The injury to the heart muscle caused by the initial blockage can destabilize the organ’s electrical pathways. This damage creates an environment for chaotic arrhythmias, such as ventricular fibrillation, which can trigger cardiac arrest.
Therefore, a heart attack can be a precursor to cardiac arrest, especially following the initial ischemic event. Cardiac arrest is not typically the cause of a heart attack; the circulatory problem precedes the electrical one.
Cardiac arrest can also be triggered by other factors unrelated to a heart attack. These include non-cardiac events like severe trauma, electrocution, drowning, or a drug overdose. Understanding this causal relationship emphasizes that while a heart attack is serious, its potential complication of cardiac arrest poses the most immediate threat to life.