Emergent Care / Stabilization:
If the patient is unresponsive and without a pulse, immediately start cardiopulmonary resuscitation (CPR). Immediately place the patient on a cardiac defibrillator. If the patient is in ventricular fibrillation, immediately defibrillate.

Obtain large-bore intravenous (IV) access. Connect the patient to the defibrillator device. Proceed with advanced cardiac life support (ACLS) protocol.

Diagnosis Overview:
Ventricular fibrillation (VF) is unsynchronized excitation of the ventricles resulting in cardiac arrest. The ECG may show rapid, grossly irregular, wide undulations with marked variability in cycle length, morphology, and amplitude. This rhythm does not have distinct P waves, QRS complexes, or T waves. The rate is typically above 300 beats per minute (bpm). VF is the most common arrhythmia identified in cardiac arrest patients and leads to death within minutes if not promptly corrected.

VF is the initial rhythm in approximately 24% of prehospital cardiac arrests. VF is most common in males and Black individuals.

Risk factors for VF include coronary artery disease, heart failure with ejection fraction (EF) less than 35%, recent myocardial infarction (within the last 6 months), cardiomyopathies, previous cardiac surgery, blunt cardiac injury, congenital heart disease, substance use (cocaine, methamphetamines, alcohol), and certain medications (ionotropic, QTc prolonging, sodium channel blockers).

Presenting symptoms may include dizziness, shortness of breath, chest pain, and sudden collapse. These presenting symptoms are then followed by loss of consciousness and pulselessness.