Ventricular Fibrillation and Pulseless Ventricular Tachycardia: Diagnosis and Management

1. Pathophysiology

• VF: Chaotic, irregular waveforms with no discernible P waves or QRS complexes; amplitude varies from coarse (larger deflections, more likely to respond to shock) to fine (smaller, lower-amplitude).
• Pulseless VT: Wide QRS complexes (>120 ms), regular rate typically >100 bpm, no palpable pulse despite organized electrical activity.

2. Immediate Management Algorithm

3. Step-by-Step Resuscitation Protocol

Step 1 - Immediate CPR + Defibrillation

• Begin chest compressions immediately upon confirming the patient is unresponsive and pulseless; continue until a defibrillator is available.
• Compression rate: 100-120/min, depth 2-2.4 inches, allow full chest recoil, minimize interruptions.
• Deliver a single shock with minimal interruption to CPR. Immediately resume compressions after the shock for 2 minutes before the next rhythm check.
• Biphasic defibrillators: use manufacturer-recommended energy (typically starting at 200 J, escalating to 360 J if needed). Monophasic: 360 J for all shocks.
• Biphasic waveforms lower the defibrillation threshold and reduce post-shock myocardial dysfunction vs. monophasic. However, superiority for ROSC or survival to discharge has not been conclusively demonstrated. - Rosen's EM, p. 80
• Placing defibrillation pads early allows continuous compressions while the device charges - this maximizes compression fraction.

Step 2 - Vascular Access + Advanced Airway (if no ROSC after 1st shock)

• Establish IV or intraosseous (IO) access while CPR continues.
• Advanced airway (endotracheal intubation or supraglottic airway) should be placed with minimal interruption to compressions.
• Monitor PetCO₂ - target >10 mmHg; values >20 mmHg suggest adequate CPR quality and correlate with ROSC.

Step 3 - Vasopressor Therapy

• Epinephrine 1 mg IV/IO every 3-5 minutes.
• Mechanism: increases myocardial contractility, elevates perfusion pressure, may convert electromechanical dissociation, and improves chances of successful defibrillation. - Braunwald's Heart Disease
• Vasopressin was previously listed as an alternative but has been removed from current ACLS algorithms due to lack of added benefit. - Tintinalli's EM

Step 4 - Antidysrhythmic Therapy (if VF/pVT persists after epinephrine + shocks)

Step 5 - Continue the Cycle

4. Refractory VF/pVT

• Appropriate for shock-refractory VF (defined as ≥3 sustained episodes of VT/VF or ICD shocks within 24 hours).
• A second set of defibrillator pads is placed in the anterior-posterior position (if the first set is apex-sternum), for a total of 4 pads. Both defibrillators are charged to maximum and discharged simultaneously.
• Theorized mechanism: reduces VF threshold and overrides the relative refractory period of cardiac tissue. - Tintinalli's EM, p. 201

• Consider if CPR is inadequate and there is potential for good neurologic outcome, and resources are available. - Rosen's EM algorithm

5. Specific Therapies Based on Rhythm Subtype

6. Post-ROSC (Post-Cardiac Arrest) Care

Hemodynamic Stabilization

• Maintain systolic BP >90 mmHg and mean arterial pressure >65 mmHg.
• Use vasopressors and volume adjustment as needed.
• Correct electrolyte abnormalities: hyperkalemia, severe hypokalemia, drug toxicity causing QT prolongation.

Coronary Angiography Considerations

• ST-elevation on post-ROSC ECG → emergent coronary angiography and PCI is recommended (majority will have a culprit lesion). - Harrison's 22E
• No ST-elevation → emergent angiography has NOT been shown to improve outcomes vs. delayed angiography; decisions are guided by hemodynamic/electrical instability and ongoing ischemia.

Targeted Temperature Management (TTM)

• Therapeutic hypothermia / TTM improves survival and neurologic recovery in patients presenting with shockable rhythms (VT/VF).
• Recommended for all post-arrest patients who remain comatose (lack of purposeful response to verbal commands) after ROSC, regardless of presenting rhythm.
• Target temperature: 32-37.5°C for at least 24 hours.
• A recent trial failed to demonstrate benefit of TTM vs. targeted normothermia with aggressive fever treatment, so active fever prevention remains a key component.
• Shivering suppression with analgesics and sedatives is often required.
• Do not initiate TTM pre-hospital with large-volume cold saline - this increased pulmonary edema risk without benefit. - Harrison's 22E, p. 2381

Neurological Monitoring

• Seizures and status epilepticus post-arrest worsen outcomes; monitor with periodic or continuous EEG.
• Treat clinically apparent seizures; also reasonable to treat ictal-interictal EEG patterns.
• Prognostication should be deferred ≥72 hours after return to normothermia (typically 4-5 days post-arrest) due to hypothermia and sedation confounding exam findings.

• Absent pupillary light reflex
• Status myoclonus
• Absence of EEG reactivity to external stimuli
• Persistent burst suppression on EEG

ICD for Secondary Prevention

• Patients with shockable arrest rhythms (VF/VT) not due to a transient reversible cause should receive an ICD for secondary prevention of sudden cardiac death (SCA/SCD). - Harrison's 22E
• Exception: VF occurring within the first 48 hours of a documented acute MI does not require ICD (similar 5-year SCD risk as non-arrest infarct survivors).
• However, large infarction with acutely depressed LVEF (e.g., <35%) warrants reassessment for ICD after recovery.

7. Long-Term Evaluation After Survival

• Coronary artery disease: stress testing or angiography
• Structural heart disease: echocardiography, cardiac MRI (for cardiomyopathy, prior MI, valvular disease, LVEF)
• Inflammatory cardiomyopathy (sarcoidosis, myocarditis): cardiac PET scan, endomyocardial biopsy
• Primary electrical disease: Long QT syndrome, Brugada syndrome, early repolarization syndrome, WPW
  • Epinephrine challenge for LQTS
  • Sodium channel blocker challenge (procainamide) for Brugada
• Genetic evaluation if heritable syndrome suspected
• Catheter ablation: role in polymorphic VT and VF is rapidly evolving - simultaneous electrical recordings from basket catheters are being used to define critical ablation sites. - Harrison's 22E, p. 2015

Key Drug Summary