Ventricular Tachycardia, Emergency Medicine

Basics

Description

A wide complex tachydysrhythmia with a quasirandom signal (QRS) >120 and a rate >100
Rapid and regular depolarization of the ventricles independent of the atria and the normal conduction system
Re-entry:
- Structural heart disease most common
- Seen in dilated cardiomyopathy, ischemia, and infiltrative heart disease, previous MI, scarring
- May be pharmacologically induced
- Usually produces a regular and monomorphic rhythm
Triggered automaticity:
- Minority of ventricular tachycardia (VT)
- Caused by repetitive firing of a ventricular focus
Torsades de pointes:
- Polymorphic form of VT
- Alternating electrical polarity and amplitude
- Prolongation in repolarization necessary
- Usually pharmacologically induced
Regardless of the mechanism, all VT may degenerate to ventricular fibrillation (VF).

Etiology

Wide complex tachycardia:
- 80% likelihood of being VT
- 20% supraventricular tachycardia (SVT) with a baseline left bundle branch block (LBBB) or aberrancy
Wide complex tachycardia and a history of MI:
- >98% likelihood of being VT
- Age >35: 80% risk of VT
- Age <35: 75% risk of SVT
Incidence of nonsustained VT:
- 0 " 4% in the general population
- Up to 60% of patients with dilated cardiomyopathy
Associated with increased risk for sudden cardiac death (SCD)

Diagnosis

Signs and Symptoms

History

Asymptomatic
Syncope/near syncope
Lightheadedness/dizziness
Shortness of breath
Palpitations
Chest discomfort/pain
Diaphoresis
Cannon A-waves
Hypotension
CHF
Beat-to-beat variability of systolic BP
Variability in heart tones, especially S1

Physical Exam

Establish presence of pulses, mental status and vital sign abnormalities.
Auscultation of heart will reveal tachycardia.

Essential Workup

EKG:
- Most important initial test to differentiate VT from SVT with aberrancy or LBBB
VT definition:
- ≥3 consecutive QRS complexes with a ventricular rate over 100 bpm and a QRS duration >120 msec
Torsades de pointes:
- Polymorphic VT that rotates its axis every 10 " 20 beats
Criteria to determine VT:
- Atrial ventricular (AV) dissociation (present in 60 " 75%)
- Fusion beats (P-wave partially activates ventricle in advance of next VT cycle), capture beats (P-wave totally activates ventricle)
- Uniform morphology (except in the case of torsades)
- Extreme axis deviation ( " 90 ° to +180 °)
- QRS >140 msec, with right bundle branch block (RBBB) morphology; or QRS >160 msec, with LBBB morphology, but >160 suggests VT regardless of bunch branch morphology
- QRS concordance in the precordial leads
- RBBB pattern V1 with R > R ' is VT 50:1.
- LBBB pattern with Q or QS pattern in V 6 is VT 50:1.
- Brugada criteria defines VT in wide complex tachycardia:
  - 99% sensitivity, 97% specificity
  - Only need to meet 1 criterion
  - AV dissociation
  - R-S interval absent in all precordial leads
  - QRS onset to the nadir of S >100 msec in any precordial lead
  - V1 R-wave >30 msec; R-S interval >70 msec, slurred, notched S
  - Wide QRS with LBBB in precordium
- Indicators of SVT with aberrancy include:
  - Normal-axis QRS <140 msec
  - Absence of Q-waves
  - RBBB in V1 with rsR " ² triphasic pattern
  - AV nodal blockade: Slowing of impulse conduction velocity seen with antiarrhythmic drugs is more pronounced at faster rates, so may result in wide complex SVT (SVT with aberrancy)

Diagnosis Tests & Interpretation

Lab

Cardiac enzymes
Electrolytes, BUN, creatinine, glucose
Magnesium level
Calcium level
Digoxin level if toxicity suspected

Imaging
CXR:

Cardiomegaly or other cardiac anomalies may be apparent.

ECHO:

Structural disease may be identified.

Diagnostic Procedures/Surgery
Esophageal pacing catheters:

May be able to detect atrial activity to establish AV dissociation and therefore diagnose VT
Catheters can then be used to overdrive pace if refractory to cardioversion/antiarrhythmics.

Differential Diagnosis

SVT with aberrancy or baseline LBBB
Proarrhythmia secondary to antidysrhythmia medications; suspect if:
- VT morphology is different than previous episodes of VT
- Medications have recently been started or changed
- QT interval is >440 msec.
- Torsades de pointes
- If VT continues to recur after cardioversion

Treatment

Pre-Hospital

Cautions:
- Transport stable patients suspected of being in VT without attempting to convert them.
- Synchronized cardioversion for unstable patients with a pulse
- Defibrillation for pulseless VT
Controversies:
- Lidocaine:
  - No benefit in the prevention of VT in patients with isolated premature ventricular contractions, regardless of the frequency

Initial Stabilization/Therapy

Pulseless VT: Defibrillate immediately and follow the VF treatment plan.

Ed Treatment/Procedures

Unstable patient:
- Definition:
  - Chest pain
  - Hypotension
  - Evidence of worsening heart failure
- Initiate immediate synchronized cardioversion with 100 J, quickly progressing to 200 J, 300 J, and 360 J if no response.
  - If the VT is polymorphic, begin cardioversion at 200 J.
- Sedate the patient before cardioversion if at all possible.
- If unable to terminate the VT, administer lidocaine and repeat the cardioversion.
- Antitachycardia overdrive pacing if torsades
- After successful return of sinus rhythm, begin amiodarone.
Stable patient, monomorphic VT:
- Normal cardiac function at baseline:
  - Procainamideorsotalol; may also consider amiodarone or lidocaine
  - Avoid sotalol if evidence of prolonged QT or known long QT syndrome.
- Impaired cardiac function at baseline:
  - Amiodarone bolus, then infusion or lidocaine, then synchronized cardioversion
Stable patient, polymorphic VT:
- Normal QT interval at baseline:
  - Correct electrolyte abnormalities.
  - Treat ischemia if present.
  - Then begin 1 of the following: b2-blockers, lidocaine, amiodarone, procainamide, or sotalol.
- Prolonged QT Torsades de pointes:
  - Correct electrolytes.
  - Magnesium sulfateor overdrive pacing or 1 of the following: Isoproterenol, phenytoin, lidocaine
  - Isoproterenol is used to overdrive the tachycardia if the patient has no history of coronary artery disease or long QT syndrome.
  - Temporizing measure until external pacing available
- Impaired cardiac function at baseline
- Amiodarone bolus or lidocaine bolus then synchronized cardioversion

Primary cardiac arrest and VT are rare in children.
Usually secondary to hypoxia and acidosis
VT is tolerated for longer periods in children than adults and is less likely to degenerate to VF.
Infants in VT most commonly present with CHF.
VT in children results from:
- Cardiomyopathy
- Congenital structural heart disease
- Congenital prolonged QT syndromes
- Coronary artery disease secondary to vasculitis
- Toxins, poisons, drugs
- Severe electrolyte imbalances, especially of potassium

Medication

First Line

Procainamide: 3 " 6 mg/kg over 5 min, may repeat every 5 " 10 min to max. total dose of 15 mg/kg. Do not exceed 100 mg/dose or 500 mg in 30 min (peds: 15 mg/kg IV/IO over 30 " 60 min).
Amiodarone: 150 mg IV bolus over 10 min, may repeat; arrest dose is 300 mg IV/IO max. cumulative dose 2.2 g IV/24 h; followed by 1 mg/min for 6 hr, then 0.5 mg/min for 18 hr. (peds: 5 mg/kg IV or IO over 20 " 60 min, max. 15 mg/kg/d)
MgSO4: 2 g in D5W over 5 " 10 min followed by infusion of 0.5 " 1 g/h IV, titrate to control torsades (peds: 25 " 50 mg/kg IV/IO over 10 min, max. dose 2 g)

Second Line

Lidocaine: 1 " 1.5 mg/kg bolus IV push 1st dose, 0.5 " 0.75 mg/kg 2nd dose, and q5 " 10min for a max. of 3 mg/kg; tracheal administration 2 " 4 mg/kg; maintenance infusion 1 " 4 mg/min if converted. Not recommended for ACS induced VT(peds: 1 mg/kg bolus with infusion 20 " 50 Όg/kg/min)
Adenosine: 6 mg IV push followed by 12 mg IV push if needed in 1 " 2 min (peds: 1 mg/kg, max. 6 mg). Note: Does not convert VT, do not use if unstable or irregular WCT.
Isoproterenol: 2 " 10 Όg/min, titrate to heart rate (peds: 0.1 Όg/kg/min). Note: Do not give with epinephrine, may precipitate VT/VF (no longer part of ACLS protocol), do not give if prolonged QT.
Sotalol: 100 mg IV over 5 min. (peds: Use not recommended for initial management). Note: Do not give if prolonged QT.

Follow-Up

Disposition

Admission Criteria

Admit sustained VT to a critical care setting.
Admit nonsustained VT and a history of MI or dilated cardiomyopathy for electrophysiologic studies.

Discharge Criteria

Rare patients with nonsustained VT and a previous evaluation that revealed no structural heart disease can be discharged:
- At low risk for SCD
Patients with automatic internal cardiac defibrillators that are well functioning can also be discharged.

Issues for Referral
All patients discharged with VT should be followed by a cardiologist within 48 hr.

Followup Recommendations

Patients should follow-up with a cardiologist.

Pearls and Pitfalls

Search for contributing factors such as toxins, metabolic abnormalities, trauma, hypothermia, thrombosis.
Unstable VT requires early cardioversion.
Administer postresuscitation maintenance medications to prevent recurrence.
Watch for bradycardia and GI toxicity after amiodarone administration.
Discontinue any proarrhythmic drugs
Consider b2-blockade for ischemia-induced VT and polymorphic VT.

Additional Reading

Connolly SJ, Dorian P, Roberts RS, et al. Comparison of beta-blocker, amiodarone plus beta-blockers, or sotalol for prevention of shocks from implantable cardioverter defibrillators: The OPTIC Study: A randomized trial. JAMA. 2006;295:165 " 171.
Pellegrini CN, Scheinman MM. Clinical management of ventricular tachycardia. Curr Probl Cardiol. 2010;35(9):453 " 504.
Zipes DP, Camm AJ, Borggrefe M, et al. ACC/AHA ESC 2006 guidelines for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death " executive summary. J Am Coll Cardiol. 2006;48:1064 " 1108.

Acknowledgments

Thank you to the prior authors of this chapter, Jennifer Audi and Shannon Straszewski

Codes

ICD9

427.1 Paroxysmal ventricular tachycardia

ICD10

I47.2 Ventricular tachycardia

SNOMED

25569003 Ventricular tachycardia (disorder)
31722008 Torsades de pointes (disorder)

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