Ventricular fibrillation ECG recognition
Ventricular fibrillation is characterized by completely chaotic electrical activity with no organized QRS complexes, P waves, or T waves. The baseline shows irregular, rapid oscillations of varying amplitude and morphology — 'coarse' VF has larger oscillations; 'fine' VF has lower amplitude and can be confused with asystole.
Critical safety rule: NEVER diagnose VF or initiate defibrillation based solely on the monitor. Confirm the patient is unresponsive and pulseless before beginning CPR and defibrillation. Motion artifact can perfectly mimic coarse VF — a responsive, perfusing patient cannot be in ventricular fibrillation.
Fine vs coarse VF: coarse VF (higher amplitude) responds better to defibrillation. If fine VF is suspected, confirm in a second lead — perpendicular lead orientation may reveal residual waveform amplitude confirming VF over asystole. VF is always shockable; asystole is not.
VF ACLS management: defibrillation sequence
ACLS pulseless VF algorithm: (1) Begin CPR immediately. (2) Apply defibrillator pads — biphasic energy 120–200J (device-specific); monophasic 360J. (3) Shock → immediately resume CPR for 2 minutes without checking rhythm first. (4) After 2 minutes: rhythm check. If persistent VF/pVT → shock again. (5) Epinephrine 1mg IV/IO after 3rd cycle, then every 3–5 minutes. (6) Amiodarone 300mg IV/IO for refractory VF (second dose 150mg if needed). (7) Search for reversible causes: 6Hs and 5Ts.
Post-ROSC priorities: avoid hyperoxia (target SpO₂ 94–99%), maintain MAP ≥ 65 mmHg, consider targeted temperature management (TTM) per institutional protocol, 12-lead ECG for STEMI evaluation, continuous ST monitoring.