Ventricular fibrillation (V-fib) is a severe, life-threatening heart rhythm abnormality where the heart’s lower chambers, the ventricles, quiver ineffectively instead of pumping blood. This prevents blood circulation to the body, leading to immediate loss of consciousness and a medical emergency. Defibrillation, the delivery of a controlled electrical shock, is the primary treatment for V-fib. It is a “shockable rhythm,” meaning it responds to this electrical intervention, offering a chance to restore a normal heartbeat.
Understanding Ventricular Fibrillation
During V-fib, the heart’s organized electrical activity becomes chaotic. The lower chambers twitch or quiver instead of contracting, making the heart unable to effectively pump blood. This sudden cessation of blood flow deprives vital organs, especially the brain, of oxygen. This leads to immediate collapse and loss of consciousness, often within seconds. V-fib is a form of cardiac arrest that, if untreated, can rapidly cause irreversible organ damage and death.
How Defibrillation Works
Defibrillation delivers a controlled electrical current through the chest to the heart. This electrical shock momentarily stops all chaotic electrical activity within the heart, depolarizing a large portion of the heart muscle. By “resetting” the heart’s electrical system, the shock creates a brief period of electrical silence. This allows the heart’s natural pacemaker, the sinoatrial (SA) node, to regain control and re-establish a normal, organized rhythm. V-fib responds to this intervention because it involves disorganized electrical impulses, unlike asystole (a flatline ECG) where there is no electrical activity to reset.
The Role of Defibrillators
Automated External Defibrillators (AEDs) are portable devices designed to treat sudden cardiac arrest caused by rhythms like V-fib. These user-friendly devices analyze heart rhythms and, if a shockable rhythm is detected, advise or deliver an electrical shock. AEDs provide clear voice prompts and visual instructions, making them accessible even to individuals with minimal training.
AEDs use electrode pads placed on the chest to monitor heart activity. Once attached, the AED determines if defibrillation is necessary. If a shock is indicated, the device charges and instructs the user to deliver it, or automatically delivers it in some models. The increasing availability of public access AEDs in locations like schools, airports, and community centers improves outcomes for sudden cardiac arrest.
Why Rapid Intervention is Crucial
The time-sensitive nature of V-fib treatment is critical, as prompt defibrillation is vital for survival. For every minute defibrillation is delayed, the chance of survival decreases significantly, by 7% to 10%. Untreated V-fib quickly leads to a lack of oxygenated blood supply to the brain and other vital organs, resulting in brain damage and death. While Cardiopulmonary Resuscitation (CPR) helps maintain some blood flow to the brain and heart until a defibrillator is available, it cannot correct V-fib’s chaotic electrical activity. Defibrillation remains the definitive treatment to restore a normal heart rhythm, and early intervention improves survival and neurological outcomes.