Monomorphic Ventricular Tachycardia (MVT) - Management

Definition & ECG Recognition

• Regular wide QRS tachycardia (rate typically 120-300 bpm)
• AV dissociation (P waves march independently from QRS)
• Fusion beats (narrow QRS intermixed - pathognomonic)
• Capture beats

Harrison's Fig 261-2: MVT in a patient with prior MI. Fusion beats (complexes 3, 9, 18) prove ventricular origin.

Belhassen/fascicular VT: RBBB morphology with left axis deviation - verapamil-sensitive.

Acute Management

Step 1: Assess Hemodynamics Immediately

• Defibrillation pads/external defibrillator must be connected immediately - VT can degenerate to VF at any time, including in response to drugs.
• If diagnosis uncertain in stable patient: IV adenosine bolus under ECG monitoring (transiently blocks AV/VA conduction to clarify rhythm).

Step 2: Pharmacologic Termination (Stable MVT)

Key point: IV calcium channel blockers are contraindicated in MVT unless idiopathic fascicular VT is confirmed in a patient WITHOUT structural heart disease. - Braunwald's Heart Disease

Step 3: Correct Reversible Precipitants

• Hypokalemia / hypomagnesemia
• Hypoxia / acidosis
• Elevated sympathetic tone (pain, anxiety, acute illness)
• Acute heart failure
• Myocardial ischemia (check ECG + troponins - though acute MI is rarely the cause of sustained MVT)
• Proarrhythmic drugs, beta-agonists, milrinone

Electrical Storm

1. ACLS - cardioversion for each episode
2. IV Amiodarone
3. Reduce sympathetic tone (most important):
   • Sedation → escalate to general anesthesia if needed
   • Beta-blockade: propranolol (non-selective) shown superior to metoprolol in one study
4. Check ICD function (if implanted): confirm appropriate sensing, pacing, rule out proarrhythmic medications
5. Stellate ganglion block or high thoracic epidural anesthesia
6. Emergent catheter ablation if refractory
7. Mechanical circulatory support: IABP, axial pump, percutaneous VAD, or ECMO if hemodynamically compromised
8. Consider LVAD or transplant workup if refractory

Long-Term / Definitive Management

Evaluation After First Presentation

• 12-lead ECG in sinus rhythm (look for prior MI, cardiomyopathy pattern)
• Echocardiography or cardiac MRI - assess LV/RV function and scar
• Coronary angiography if ischemic substrate suspected
• Genetic workup if no clear ischemic cause (~40% of non-ischemic cardiomyopathies are genetic)
• Rule out ARVC, cardiac sarcoidosis (especially for RV-origin VT)

Long-Term Management by Substrate

1. Structural Heart Disease (Ischemic or Non-Ischemic)

• Clearly indicated for secondary prevention (sustained VT or hemodynamically significant VT)
• ICDs reduce annual mortality from 12.3% to 8.8% and lower arrhythmic deaths by ~50% vs antiarrhythmic drugs alone - Harrison's 22E
• Antiarrhythmic drugs alone (without ICD) do not improve survival

• Recommended for patients failing or intolerant of antiarrhythmic drugs (strongest indication)
• The VANISH trial showed catheter ablation superior to escalating antiarrhythmic drug doses
• BERLIN VT trial: preventive ablation not shown superior to deferred strategy, but fewer VT recurrences
• Considered when long-term amiodarone therapy (with its toxicities) is not desired
• Emergent catheter ablation for incessant VT / electrical storm refractory to drugs

• Role: reduce ICD therapies (shocks + ATP), improve quality of life
• Amiodarone: most effective but significant long-term toxicity
• Sotalol: alternative
• Beta-blockers: guideline-directed medical therapy for all patients with HF/CAD + VT
• ACE inhibitors: standard heart failure therapy, important for VT substrate reduction

2. Idiopathic VT (No Structural Heart Disease)

• Cardiac arrest from idiopathic VT transforming to VF is exceedingly rare
• Catheter ablation is preferred - potentially curative
• Beta-blockers (metoprolol 50 mg BID, atenolol 50 mg OD): safe first-line for symptomatic PVCs/NSVT but not very effective
• ICD generally not indicated unless sustained VT causes syncope
• Fascicular (Belhassen) VT: verapamil-sensitive; IV verapamil terminates acutely; catheter ablation is curative long-term
• If PVC/NSVT burden is very high → risk of tachycardia-induced cardiomyopathy → aggressive ablation warranted even without symptoms

Summary Algorithm

MVT Diagnosed
     │
     ├─ Hemodynamically UNSTABLE?
     │        └─ YES → Synchronized DC Cardioversion (sedate if conscious)
     │
     └─ STABLE?
              └─ IV Procainamide (preferred) or Amiodarone or Lidocaine
                       │
                       ├─ Terminated? → Correct precipitants
                       │                 Evaluate for structural heart disease
                       │                 Long-term: ICD ± Ablation ± AAD
                       │
                       └─ Refractory / Electrical Storm?
                                 → IV Amiodarone + Beta-blocker
                                 → Reduce sympathetic tone (sedation/GA)
                                 → Emergent catheter ablation
                                 → Mechanical support (IABP/ECMO) if needed

Recent Evidence (2024-2025)

• A 2025 meta-analysis (PMID 39542872) found that ischemia testing and coronary revascularization does not reduce mortality or VT recurrence in MVT without acute coronary syndrome - supporting the guideline position that revascularization is not routinely indicated for MVT substrate control.
• A 2024 systematic review of VT trials (PMID 38821759) highlights catheter ablation as the most actively investigated intervention, reflecting its growing role over antiarrhythmic drugs.