What is the management approach for a patient presenting with ventricular tachycardia (VT), considering their hemodynamic stability and potential underlying causes such as ischemic heart disease or channelopathies?

Management of Ventricular Tachycardia

For hemodynamically unstable VT (hypotension, altered mental status, shock), perform immediate synchronized cardioversion without delay—do not attempt pharmacologic therapy first. 1, 2, 3

Initial Assessment and Stabilization

Hemodynamic Status Determines Everything

• Assess blood pressure, mental status, and signs of hypoperfusion immediately 3
• Unstable indicators: systolic BP <90 mmHg, altered consciousness, chest pain with ischemia, pulmonary edema, heart rate >150 bpm 2, 4
• Critical principle: Presume any wide-QRS tachycardia is VT if diagnosis unclear—treating SVT as VT is safer than the reverse 2, 3, 4

Obtain 12-Lead ECG During Tachycardia (if stable)

• Document rhythm before treatment in hemodynamically stable patients 1, 3
• VT diagnostic criteria: QRS >140ms, AV dissociation, fusion/capture beats, RS interval >100ms in any precordial lead, negative concordance in precordial leads 1, 4
• Classify as monomorphic (consistent QRS) versus polymorphic (changing QRS morphology) 3

Management Algorithm by Hemodynamic Status

UNSTABLE VT: Immediate Cardioversion

Synchronized DC cardioversion is the only appropriate first-line treatment 1, 2, 3

• Monomorphic VT: Start with 100-200 J synchronized 2, 4
• Polymorphic VT (rate ≥200 bpm): Use unsynchronized 200 J defibrillation—treat like VF 2, 4
• Provide sedation if patient conscious before cardioversion 2, 4
• Have full resuscitation equipment immediately available 3
• Do not delay cardioversion for IV access or medication administration—this is a Class I recommendation 2

Post-Cardioversion Management

• If VT recurs after cardioversion, administer IV amiodarone 150 mg over 10 minutes to prevent reinitiation 4, 5
• Follow with maintenance infusion: 1 mg/min for 6 hours, then 0.5 mg/min 5
• For breakthrough episodes, repeat 150 mg bolus over 10 minutes 5

STABLE VT: Pharmacologic Approach

For hemodynamically stable monomorphic VT, IV procainamide is the preferred first-line agent 2, 3, 4, 6

Procainamide Protocol (First-Line)

• Dose: 10 mg/kg IV at 50-100 mg/min over 10-20 minutes 2, 4, 6
• Monitor blood pressure and ECG continuously during infusion 2, 6
• Stop if: QRS widens >50%, hypotension develops, or arrhythmia terminates 6
• Contraindications: Severe heart failure, acute MI with significant LV dysfunction 4

Amiodarone (Alternative First-Line)

• Preferred over procainamide when: heart failure present, suspected myocardial ischemia, or impaired LV function 4, 5
• Loading dose: 150 mg IV over 10 minutes 4, 5
• Maintenance: 1 mg/min for 6 hours, then 0.5 mg/min 5
• FDA-indicated for hemodynamically unstable VT and frequently recurring VF/VT refractory to other therapy 5

Lidocaine (Second-Line)

• Only moderately effective—reserve for VT associated with acute myocardial ischemia 1, 2, 3
• Dose: 1 mg/kg IV bolus 2
• Less effective than procainamide or amiodarone for rhythm conversion 6

If Pharmacologic Therapy Fails

• Proceed to synchronized cardioversion even in stable patients 3, 4
• Consider transvenous catheter pace termination for refractory or frequently recurrent VT 1, 3

POLYMORPHIC VT: Special Considerations

Without QT Prolongation (Ischemic)

• IV beta-blockers are first-line, especially if ischemia suspected or cannot be excluded 3, 4
• IV amiodarone useful in absence of QT prolongation 3, 4
• Urgent revascularization should be considered when ischemia cannot be excluded 4
• Beta-blockers improve mortality in acute MI with recurrent polymorphic VT 3, 4

With QT Prolongation (Torsades de Pointes)

• IV magnesium sulfate for recurrences 4
• Overdrive pacing (atrial or ventricular) 4
• Beta-blockers for congenital long QT syndrome 4
• Avoid: QT-prolonging antiarrhythmics (amiodarone, procainamide, sotalol) 4

Post-Conversion and Definitive Management

Identify and Treat Underlying Cause

• Evaluate for acute myocardial ischemia—most VT occurs with ischemic heart disease 1, 7, 8
• Correct electrolyte abnormalities: hypokalemia, hypomagnesemia, hypocalcemia 1
• Review medications for QT-prolonging drugs (clarithromycin, erythromycin, metoclopramide, haloperidol, TCAs, methadone) 1
• Assess for structural heart disease: prior MI, cardiomyopathy, valvular disease 1

Catheter Ablation Indications

• Urgent ablation (Class I): Scar-related heart disease with incessant VT or electrical storm 1, 3, 4
• Recommended (Class I): Ischemic heart disease with recurrent ICD shocks from sustained VT 1
• Consider (Class IIa): After first episode of sustained VT in ischemic heart disease patients with ICD 1

ICD Evaluation

• Consider ICD for patients with structural heart disease and sustained VT—high risk of recurrence and sudden death 3
• "Stable" VT carries 33.6% 3-year mortality—not a benign rhythm 9

Critical Pitfalls to Avoid

Never Assume Wide-Complex Tachycardia is SVT

• When uncertain, always treat as VT 2, 3, 4
• Treating VT as SVT can cause hemodynamic collapse 4

Avoid Calcium Channel Blockers

• Never use verapamil or diltiazem for wide-complex tachycardia unless absolutely certain of fascicular VT 1, 4
• Exception: IV verapamil or beta-blockers appropriate for LV fascicular VT (RBBB morphology with left axis deviation) 1

Recognize High-Risk Presentations

• VT during acute MI: 65% are unstable versus 21% in chronic ischemic disease 7
• Polymorphic VT pattern: 5 of 7 patients unstable in one series 7
• Old age, hemodynamic instability, and low ejection fraction predict mortality 8

Dosing Errors with IV Amiodarone

• Use volumetric infusion pump—drop counters may underdose by 30% 5
• Concentrations >2 mg/mL require central venous catheter to avoid phlebitis 5
• Rapid loading at higher concentrations than recommended has caused hepatocellular necrosis and acute renal failure 5