Ventricular Tachycardia: Etiology and Management
Etiology
VTach arises from two primary substrate categories: scar-related structural heart disease and idiopathic VT in structurally normal hearts. 1
Structural Heart Disease (Scar-Related VT)
- Ischemic cardiomyopathy is the most common cause, with scar tissue from prior myocardial infarction creating re-entry circuits through areas of slow conduction (critical isthmus) 1
- Non-ischemic dilated cardiomyopathy (DCM) accounts for a significant proportion, with prevalence of 1 in 2500 individuals and genetic mutations found in at least 20% of adults 1
- Arrhythmogenic right ventricular cardiomyopathy (ARVC) with desmosomal protein mutations 1
- The re-entry circuit spans several centimeters and can involve endocardium, mid-myocardium, or epicardium in complex three-dimensional structures 1
Idiopathic VT (Structurally Normal Hearts)
- Right or left ventricular outflow tract (RVOT/LVOT) origins are most common, showing LBBB inferior axis morphology on ECG 1
- Left fascicular VT (verapamil-sensitive), predominantly left posterior fascicular (>90%), presenting with RBBB morphology and superior axis 1
- Aortic cusp origins account for 20% of idiopathic outflow tract VTs, most from left coronary cusp 1
- Papillary muscle, mitral and tricuspid annular origins comprise 5-8% of idiopathic VTs 1
Acute Management
Hemodynamically Unstable VT
Immediate synchronized DC cardioversion is the definitive treatment for any patient with VT presenting with hypotension, altered mental status, signs of shock, or hemodynamic compromise. 2, 3, 4
- Provide sedation before cardioversion if the patient is conscious 2, 4
- Use 100 J synchronized discharge for monomorphic VT with rates >150 bpm 2
- Use unsynchronized 200 J discharge for polymorphic VT that appears similar to VF 2
- Have resuscitation equipment immediately available 4
Hemodynamically Stable VT
For stable monomorphic VT, procainamide demonstrates the greatest efficacy and receives a IIa recommendation, compared to IIb for amiodarone and sotalol. 3, 5
Pharmacologic Options (in order of preference):
IV Procainamide: Maximum dose 10 mg/kg at 50-100 mg/min over 10-20 minutes with continuous blood pressure and ECG monitoring 3, 4, 5
- Avoid in patients with heart failure or acute MI 4
IV Amiodarone: Preferred in patients with heart failure, impaired left ventricular function, or suspected myocardial ischemia 2, 3, 6
IV Beta-blockers: Consider for recurrent episodes, especially if ischemia suspected, when no contraindications exist 4
Critical Pitfall:
Never use calcium channel blockers (verapamil, diltiazem) in patients with VT and structural heart disease—they may precipitate hemodynamic collapse. 2, 3 The only exception is confirmed fascicular VT in structurally normal hearts 2, 3
Diagnostic Workup During Stabilization
- Obtain 12-lead ECG to document rhythm, evaluate for ischemia, and identify VT origin 4
- Check and correct electrolyte abnormalities, particularly potassium and magnesium 4
- Assess for myocardial ischemia with cardiac enzymes 4
- Establish IV access and provide supplemental oxygen if needed 4
Long-Term Management
Catheter Ablation
Catheter ablation decreases ICD shocks and prevents recurrent VT episodes, with Class I recommendation for specific indications. 1
Strong Indications (Class I):
- Urgent ablation for incessant VT or electrical storm in scar-related heart disease 2
- Recurrent ICD shocks due to sustained VT in ischemic heart disease 2
- First-line treatment for idiopathic left fascicular VT in experienced centers (success rates 80-100%, recurrence 0-20%) 1
Efficacy Data:
- SMASH-VT trial: Substrate-guided ablation reduced VT episodes from 33% to 12% and appropriate ICD shocks from 31% to 9% over 23 months 1
- VTACH trial: 47% vs 29% survival free from recurrent VT at 24 months (HR 0.61, P=0.045) 1
- Acute success rates range 41-81% depending on substrate complexity 1
Technical Considerations:
- Epicardial ablation more often required in DCM and ARVC 1
- Pre-procedural cardiac MRI facilitates non-invasive substrate identification 1
- Complications include coronary artery damage, phrenic nerve palsy, and pericardial tamponade 1
ICD Therapy
ICD implantation is recommended for survivors of VT/VF and for primary prevention in structural heart disease with LVEF ≤30-35%, NYHA class II-III on optimal medical therapy. 1, 4
- ICDs effectively terminate VT but don't prevent recurrence 1
- ICD shocks are associated with higher mortality and impaired quality of life 1
- Beta-blockers combined with amiodarone reduce ICD shocks but may cause discontinuation due to side effects 1
Adjunctive Medical Therapy
- Beta-blockers are first-line for primary prevention of sudden cardiac death in CAD with VT 4
- Amiodarone serves as adjunctive therapy to suppress symptomatic ventricular arrhythmias 4
- Avoid class IC antiarrhythmics in patients with prior myocardial infarction 4
Surgical Ablation
Surgical ablation guided by electrophysiological mapping is recommended (Class I) in patients with VT refractory to antiarrhythmic drugs after failed catheter ablation by experienced electrophysiologists. 1
Special Populations
Non-Sustained VT (NSVT)
- Defined as <30 seconds duration (e.g., 6-beat run) 4
- Do not treat with antiarrhythmics in asymptomatic patients without structural heart disease 4
- If NSVT occurs with structural heart disease and reduced ejection fraction, cardiology consultation is mandatory 4
Post-MI VT
- Most VT/VF occurs within first 48 hours post-MI 2
- Sustained VT/VF outside this window requires careful evaluation including electrophysiology studies 2