Ventricular Tachycardia and Ventricular Fibrillation

Introduction and Definitions

• VT and VF are common arrhythmias encountered within perioperative, critical care, emergency, cardiac, and other fields of medicine. These can be differentiated based on duration and morphology of the arrhythmia on the electrocardiogram (ECG).⁸
• VT is a wide QRS-complex tachycardia that originates in the ventricular myocardium, below the AV node.³ VT is important to recognize and treat, as it may cause ischemia, which can lead to degeneration from VT to VF. VF is the most common mechanism of sudden cardiac death.⁴
• VT: wide QRS complex (QRS more than 120ms) tachycardia, cardiac arrhythmia of 3 or more consecutive complexes originating in the ventricles at a rate of more than100 beats per minute.^4,5,7,8
  • Nonsustained VT (NSVT): Duration of less than 30 seconds, spontaneously terminating.^4,9
  • Sustained monomorphic VT (SMVT): Regular (less than 50 msec beat-to-beat cycle length variation); Consecutive beats have a uniform and stable QRS morphology; Arrythmia lasts more than 30 seconds or causes hemodynamic collapse in less than

• • Polymorphic VT (PVT): Continuously varying QRS complex morphology in any recorded ECG lead.⁴

• VF is a rapid, disorganized rhythm that results in a loss of uniform ventricular contraction, subsequently leading to loss of cardiac output and blood pressure, and hemodynamic collapse (syncope, cardiac arrest).⁴
• VF: Rapid, grossly irregular electrical activity with marked variability in ECG waveform, ventricular rate usually more than 300 beats per minute.¹

Causes

Clinical Presentation

• Ventricular arrhythmias can produce a wide array of symptoms ranging from no symptoms at all to cardiac arrest and sudden cardiac death.^3,5,9

Evaluation and Acute Management

Evaluation

• The initial evaluation of a patient with ventricular arrhythmia must include assessment of the patient’s hemodynamic stability, including vital signs, symptoms, and level of consciousness.^2,7
• Adenosine can be administered to help distinguish between SMVT and SVT and may also work to terminate the abnormal rhythm. Do not administer adenosine if the rhythm is irregular or if the QRS is polymorphic. The Brugada criteria can also be used to differentiate VT from SVT; the Brugada algorithm can be accessed here.^2,12 Link.
• An evaluation of patients with VT may include the following elements, some of which are more suitable for inpatient versus outpatient workup.^2,5,8,9
  • Thorough history, including past medical history, medications, family history, and physical examination
  • 12-lead ECG
  • Transthoracic echocardiogram
  • Exercise stress testing
  • Cardiac monitoring
  • Cardiac imaging, including echocardiogram and cardiac magnetic resonance (CMR)
  • Genetic testing (if there is a strong suspicion for an inherited cause)

Acute Management

• The 2017 American Heart Association (AHA)/American College of Cardiology (ACC)/Heart Rhythm Society (HRS) guidelines for the management of ventricular arrhythmias, including an algorithm for the management of SMVT, can be accessed here.¹ Link
• Unresponsive or pulseless patients should be treated according to standard resuscitation Advanced Cardiac Life Support (ACLS) algorithms found here.^1,2,7,10,12 Link
• Unstable patients with evidence of hemodynamic compromise but who are awake with a palpable pulse should be treated with emergency synchronized cardioversion.^1,2,7,12
• VF requires immediate treatment following ACLS protocols.^1,2
  • During cardiopulmonary resuscitation, administer intravenous (IV) epinephrine 1mg every 3-5 minutes as well as amiodarone 300mg for the first dose, then 150mg for two subsequent doses.^10,12
• IV analgesics or sedatives should be administered if blood pressures are sufficient to tolerate their use.⁷
• Stable patients should undergo continuous monitoring and frequent reevaluation. Underlying causes should be investigated and treated accordingly.^2,7
• Once VT has been identified, initiate IV antiarrhythmic medication for pharmacologic cardioversion.^7,11
  • Amiodarone: initial dose of 150 mg IV over 10 minutes followed by an infusion of 1 mg/minute for six hours, then 0.5 mg/minute for an additional 18 hours or longer. Repeat amiodarone boluses can be administered if necessary.
  • Procainamide: initial dose of 15-17 mg/kg IV administered as slow infusion over 25-30 minutes, followed by 1-4 mg/minute by continuous infusion.
  • Lidocaine may be used, particularly in patients with acute myocardial infarction (MI): initial dose of 1-1.5 mg/kg (typically 75-100 mg at a rate of 25-50 mg/minute); lower doses of 0.5-0.75 mg/kg can be repeated every 5-10 minutes as needed.
  • Additional pharmacologic treatments for specific PVTs:¹¹
    • Torsades de pointes:
  • IV magnesium sulfate; initial dose of 1-2 grams IV over 15 minutes, may be followed by an infusion.
    • PVT due to MI:
  • Metoprolol 5 mg IV every 5 minutes to a total of 15 mg may be given if the blood pressure is stable.
  • IV amiodarone may prevent a recurrent episode.
    • Other causes of polymorphic VT:
  • Catecholaminergic PVT: beta blockers should be used.
  • Brugada syndrome: isoproterenol should be initiated.
• Electrical cardioversion should be used if pharmacologic cardioversion is unsuccessful.^1,7
• For patients with an ICD, antitachycardia pacing is recommended for cardioversion if it can be performed promptly.⁷