Ventricular fibrillation (V-fib) is a chaotic electrical heart rhythm that constitutes a medical emergency. In this life-threatening state, the lower chambers of the heart, the ventricles, merely quiver instead of contracting in a coordinated way. This disorganized electrical activity prevents the heart from pumping blood effectively, immediately leading to cardiac arrest. Without immediate treatment, V-fib is fatal within minutes because blood flow to the brain and other organs ceases.
Basic Life Support and Emergency Response
The first moments after a person collapses from V-fib are time-sensitive, requiring rapid recognition and action from bystanders. A person experiencing cardiac arrest will be unresponsive, may not be breathing, or may only be gasping for air. Recognizing these signs means immediately activating the emergency medical system by calling 911 or the local emergency number.
Once emergency services have been alerted, the next step is to begin high-quality cardiopulmonary resuscitation (CPR). Chest compressions manually pump blood, sustaining minimal flow to the brain and heart until definitive care arrives. High-quality CPR involves pushing hard and fast in the center of the chest at a rate of 100 to 120 compressions per minute.
This mechanical support maintains perfusion, keeping the heart muscle and other vital organs viable. While CPR alone cannot stop the chaotic electrical activity of V-fib, it buys precious time. The goal is to preserve cellular function until an electrical intervention can be delivered to reset the heart’s rhythm.
The Role of Defibrillation
Defibrillation is the definitive treatment for ventricular fibrillation, as it is an electrical problem requiring an electrical solution. The process involves delivering a controlled electrical shock across the chest wall to the heart muscle. The shock momentarily depolarizes a critical mass of heart muscle cells, effectively stunning the entire heart. This terminates the disorganized electrical activity, allowing the heart’s natural pacemaker to restart a synchronized, effective rhythm.
The effectiveness of this treatment is highly dependent on how quickly it is administered. For every minute that defibrillation is delayed, the chance of survival for the patient drops significantly, estimated to be between 7% and 10%.
Automated External Defibrillators (AEDs) have made this life-saving intervention accessible to laypersons and first responders. The AED is designed to analyze the patient’s heart rhythm and will only advise and deliver a shock if a “shockable” rhythm, such as V-fib, is detected. The earliest possible application of an AED, combined with high-quality CPR, offers the best chance for a successful outcome.
Modern devices often utilize a biphasic waveform, which is more effective at lower energy levels than older monophasic devices. Once the AED is applied, the rescuer must follow the device’s prompts, which involve delivering the shock and immediately resuming chest compressions. This cycle continues until emergency medical professionals take over or the heart resumes a stable rhythm.
Medications Used During Resuscitation
If initial defibrillation attempts and CPR are unsuccessful, advanced medical professionals introduce pharmacological support. These drugs are administered intravenously (IV) or intraosseously (IO) while CPR is ongoing, alternating with defibrillation attempts.
One major category of medication used is vasopressors, primarily Epinephrine. This drug is given to increase the blood pressure and systemic vascular resistance, which helps increase the coronary perfusion pressure. By enhancing blood flow to the heart muscle, Epinephrine can improve the conditions within the heart, potentially making it more responsive to the next electrical shock.
The other category includes antiarrhythmics, which are used when V-fib is refractory, meaning it persists despite multiple shocks and Epinephrine administration. Amiodarone is the preferred antiarrhythmic agent in this scenario, as it works to stabilize the electrical properties of the heart muscle cells. Lidocaine is considered a reasonable alternative if Amiodarone is unavailable or contraindicated for the patient.
These medications chemically prime the heart rather than converting the rhythm directly. They suppress the irritability of the ventricular tissue and increase the threshold for successful defibrillation. This coordinated approach continues until a stable heart rhythm is restored.
Post-Resuscitation Care and Stabilization
Once the patient achieves a Return of Spontaneous Circulation (ROSC), meaning a sustained, stable heart rhythm and pulse are present, the focus shifts immediately to critical care. This phase involves stabilizing the patient and protecting against further injury, particularly to the brain.
A primary concern is identifying and treating the underlying cause that triggered the V-fib episode. If the cardiac arrest was caused by a heart attack (myocardial infarction), the patient will need an emergency cardiac catheterization and coronary intervention to open the blocked coronary artery. Correcting severe electrolyte imbalances, such as low potassium or magnesium, is another immediate action.
Supportive measures, such as Targeted Temperature Management (TTM), are often initiated to protect neurological function. This involves cooling the patient’s core body temperature to reduce the metabolic demand of the brain. Patients who survive V-fib frequently require an Implantable Cardioverter-Defibrillator (ICD), which monitors the heart and automatically delivers a life-saving shock if V-fib recurs.