Ventricular fibrillation (VF) is a life-threatening cardiac emergency and a form of cardiac arrest. It arises from highly abnormal electrical activity within the heart, demanding immediate recognition and intervention.
Understanding Ventricular Fibrillation
Ventricular fibrillation occurs when the heart’s lower chambers, the ventricles, do not contract in an organized manner but instead quiver chaotically. This disordered electrical activity prevents the heart from effectively pumping blood to the body and brain. The result is an immediate loss of consciousness and collapse.
The underlying cause of this chaotic electrical behavior often relates to issues such as insufficient blood flow to the heart muscle, damage from a heart attack, or conditions like cardiomyopathy. Without prompt intervention, the lack of blood circulation leads to irreversible damage within approximately five minutes.
What Makes a Rhythm Shockable?
A “shockable rhythm” in the context of cardiac arrest refers to an electrical pattern in the heart that can be reset by a controlled electrical shock. Ventricular fibrillation is a shockable rhythm. The heart’s electrical system remains active during VF, albeit in a disorganized state.
A controlled electrical shock aims to depolarize a significant portion of the heart muscle, effectively ending the chaotic electrical activity. This momentary cessation provides an opportunity for the heart’s natural pacemaker to regain control and re-establish a normal, organized rhythm. In contrast, non-shockable rhythms, such as asystole (a flatline on an electrocardiogram) or pulseless electrical activity (organized electrical activity without effective pumping), lack the disorganized electrical chaos that a shock can reset. In these cases, a defibrillation shock would be ineffective and potentially harmful.
Defibrillation as Treatment
Defibrillation is the immediate treatment for ventricular fibrillation, involving the delivery of a controlled electrical current to the heart using a defibrillator. This current momentarily stops all electrical activity within the heart, allowing the heart’s natural pacemaker to potentially restart with a normal, organized rhythm.
The promptness of defibrillation influences survival. For every minute defibrillation is delayed, the chance of survival from sudden cardiac arrest decreases by approximately 7-10%. Automated external defibrillators (AEDs) play a role in public settings, designed to detect shockable rhythms and guide lay responders on when to deliver a life-saving shock. Their increasing availability and ease of use are expanding access to this intervention.