A 58-year-old man with a history of anterior wall MI 6 months ago presents to the emergency department with palpitations and syncope. On examination, blood pressure is 80/50 mmHg, heart rate 160/min, and he is diaphoretic. ECG shows a wide-complex tachycardia with AV dissociation and fusion beats. What is the most appropriate immediate management?

## Clinical Diagnosis **Key Point:** The combination of wide-complex tachycardia with AV dissociation and fusion beats is pathognomonic for ventricular tachycardia (VT). **High-Yield:** AV dissociation is the gold standard ECG sign of VT — it proves the ventricles are depolarizing independently of atrial activity, confirming a ventricular origin. ## Hemodynamic Status Assessment This patient is hemodynamically unstable: - Systolic BP 80 mmHg (hypotensive) - Syncope (loss of consciousness) - Diaphoresis (sympathetic activation) **Clinical Pearl:** Hemodynamic instability in VT mandates immediate electrical therapy, not pharmacotherapy. ## Management Algorithm ```mermaid flowchart TD A[Wide-complex tachycardia]:::outcome --> B{Hemodynamically stable?}:::decision B -->|Yes| C[Pharmacotherapy: IV amiodarone or procainamide]:::action B -->|No| D[Immediate synchronized DC cardioversion]:::action D --> E[Start at 100 J, escalate if needed]:::action E --> F[Post-cardioversion: IV amiodarone infusion]:::action F --> G[Investigate cause: coronary angiography, imaging]:::action ``` **Key Point:** Synchronized DC cardioversion is the treatment of choice for hemodynamically unstable VT. The synchronization ensures the shock is delivered during the QRS complex, avoiding the vulnerable period (T wave) and reducing the risk of degeneration to VF. ## Why Cardioversion at 100 J? For monomorphic VT in an unstable patient: - Initial energy: **100 J** (biphasic defibrillator) - If unsuccessful: escalate to 200 J, then 360 J - Biphasic waveforms are more effective than monophasic **Mnemonic:** **SHOCK** = Synchronize, High-energy, Obtain IV access, Check rhythm, Know the diagnosis (VT) ## Post-Cardioversion Management 1. Confirm restoration of sinus rhythm 2. Initiate IV amiodarone infusion (150 mg over 10 min, then 1 mg/min) 3. Correct electrolytes (K^+^, Mg^2+^) 4. Investigate underlying cause (coronary angiography given prior MI) 5. Consider ICD if recurrent or inducible VT [cite:Harrison 21e Ch 297]