A 58-year-old man with a history of anterior wall myocardial infarction 3 months ago presents to the emergency department with palpitations and syncope. His blood pressure is 80/50 mmHg, heart rate 180 bpm. ECG shows a regular wide-complex tachycardia with AV dissociation and fusion beats. What is the most appropriate immediate management?

Explanation

## Clinical Diagnosis **Key Point:** This patient has ventricular tachycardia (VT) with hemodynamic instability (syncope, hypotension, altered mental status implied by syncope). The ECG findings are pathognomonic: - Regular wide-complex tachycardia - AV dissociation (independent P waves and QRS complexes) - Fusion beats (hybrid complexes from simultaneous atrial and ventricular depolarization) These are diagnostic criteria for VT and exclude supraventricular tachycardia with aberrancy. ## Management Algorithm for Hemodynamically Unstable VT ```mermaid flowchart TD A[Wide-complex tachycardia]:::outcome --> B{Hemodynamically stable?}:::decision B -->|No: SBP < 90, syncope, shock| C[Synchronized DC cardioversion]:::action B -->|Yes| D{VT confirmed?}:::decision D -->|Yes| E[IV amiodarone or procainamide]:::action D -->|Uncertain| F[IV procainamide preferred]:::action C --> G[Immediate electrical therapy]:::urgent G --> H[Repeat if unsuccessful]:::action ``` **High-Yield:** Hemodynamic instability in VT is an absolute indication for **immediate synchronized DC cardioversion**, not pharmacological therapy. Drugs delay definitive treatment and may worsen shock. ## Why Cardioversion is First-Line Here | Feature | Implication | |---------|-------------| | SBP 80/50 mmHg | Cardiogenic shock from loss of coordinated contraction | | Syncope | Cerebral hypoperfusion; life-threatening | | Regular VT at 180 bpm | Rapid ventricular rate with poor diastolic filling | | AV dissociation + fusion beats | Confirms VT diagnosis; not SVT | **Clinical Pearl:** Synchronized cardioversion at 100 J is safe and effective for monomorphic VT. If unsuccessful, repeat at 200 J, then 300 J, then 360 J (or biphasic equivalent). Amiodarone is reserved for stable VT or post-cardioversion prophylaxis. **Warning:** Do NOT give IV verapamil or diltiazem in VT—these can cause hemodynamic collapse and are contraindicated. Procainamide is acceptable for stable VT but inappropriate here given shock.