Ventricular arrhythmias:  Monomorphic VT & Polymorphic VT

Outline

• Etiology of Ventricular Arrhythmias
• Mechanism of Ventricular Arrhythmias
• Management of Ventricular Arrhythmia

Note: Will not be discussing ECG diagnosis

Definitions

Definitions

• Sustained VT

• Electrical Storm

• 3 or more distinct episodes of VT or VF in 24 hours

• VT last over 30s or intervention before 30s

• Monomorphic VT

• Similar QRS

• Polymorphic VT

• Beat to beat variation in QRS

• Torsade de Pointes

• Polymorphic VT + QRS prolongation

Differential WCT

• VT
• SVT with BBB
• WPW (no isoelectric PR segment)
• Paced rhythm
• Artefact

ECG Diagnosis

• AV Dissociation (V faster than A)
  • Fusion, Capture Beats
• Morphology
  • QRS Axis (NW Axis = likely VT)
  • Precordial Transition
    • All + is activation from base
    • All - is activation from apex
  • V1 q wave in RBBB or V6 in LBBB
  • Initial Slope, Activation

Criteria

• AVR
• Brugada
• VT Score

Clinical Factors

• History of MI, 90% VT
• Rate not helpful
• Hemodynamic stability not helpful

Idiopathic VT

Idiopathic VT

Seen in a structurally normal heart

Examples:

• Outflow tract
• Papillary Muscle
• Perivenous

RVOT VT

• Most common idiopathic VT
• Structurally normal heart
• Rarely associated with sudden death
• Common trigger includes exercise and hormones
• If frequent cant cause cardiomyopathy

• Caused by triggered activity, calcium overload at cell
• Responsive to beta blockers, CCB and adenosine

• Most common LV idiopathic VT
• RBBB and LAFB
• Re-entry circuit
• Verapamil sensitive
• Adenosine insensitive

Tx symptoms with meds and ablation

Generally no ICDs

Idiopathic VT Management

Scar Based VT

Scar Based VT

• Most commonly encountered
• Ischemic Cardiomyopathy
• Are with WMA/scar, not completed dead
  • Areas in scar that conducts slowly to create reentry circuit

Reentry Mechanism

Morphology of VT depends on exit site

• Desmosome protein mutation
• Replacement of myocardium with fatty/fibrous tissue
• Re-entry mechanism
• ECG:
  • LBBB morphology
  • Epsilon wave (30%) (late conduction) 
  • TWI V1-V3 (85%)

LBBB, Superior Axis

ARVC vs RVOT VT

• Favour ARVC:
  • Anterior T wave inversions in sinus rhythm
  • Multiple VT forms
  • Wider QRS duration (lead I ≥ 120 ms)
  • QRS notching
  • Earliest onset QRS in lead V1 later
  • Precordial transition (>V5)

Further Reading:

• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3280482/
• Craig D Ainsworth, Allan C Skanes, George J Klein, Lorne J Gula, Raymond Yee, Andrew D Krahn
  • https://www.heartrhythmjournal.com/article/S1547-5271(05)02479-3/fulltext

• Heart block + VT = think sarcoid
  • More often affects septum
• Mechanism scar related and his purkinge
• Diagnose with PET, biopsy (granulomas)
• Immunosuppresion

• Think about in NICM, myotonic dystrophy
• Mechanism: down diseased bundle and back up normal bundle
• Can look similar to sinus rhythm (BBB and PR prolonged)

Scar VT Management

• Class III Antiarrhythmics
  • Amiodarone, Sotalol
• ICD
• Ablation (target slow zones)

Polymorphic VT

Polymorphic VT

• Ischemia
• Torsades
  • Long QT
    • Electrolye
    • Genetic

Polymorphic VT Management

• Magnesium
• Pacing (shortens QT)
  • Or Isuprel/dopamine
• Avoid offending drugs
• Correct underlying cause
  • ie. ischemia

Summary

CCS VT/VF Guidelines