A 52-year-old man with a history of anterior wall myocardial infarction 6 months ago presents with recurrent episodes of palpitations and syncope. On examination, blood pressure is 90/60 mmHg and heart rate is 160 bpm. A 12-lead ECG shows a wide complex tachycardia with AV dissociation. Which investigation is most appropriate to confirm the diagnosis and assess the substrate for arrhythmia?

Explanation

## Clinical Scenario Analysis The patient presents with: - Post-MI history (anterior wall) - Wide complex tachycardia with AV dissociation (diagnostic of VT) - Hemodynamic instability (BP 90/60, HR 160) - Recurrent syncope This is **ventricular tachycardia (VT)** secondary to structural heart disease (scar from prior MI). ## Investigation of Choice **Key Point:** Electrophysiology (EP) study with programmed ventricular stimulation is the gold standard for: 1. **Confirmation** of VT diagnosis (reproducible induction) 2. **Substrate mapping** (identification of scar-related reentry circuits) 3. **Risk stratification** for sudden cardiac death 4. **Therapeutic intervention** (ablation if indicated) ## Role of Other Investigations | Investigation | Purpose | Limitation in This Case | |---|---|---| | Transthoracic echo | Assess LV function, ejection fraction | Does NOT confirm VT diagnosis or map substrate | | Cardiac MRI with LGE | Visualize scar tissue, fibrosis pattern | Useful for substrate assessment but NOT diagnostic for active arrhythmia; cannot induce or map circuits | | Coronary angiography | Assess coronary patency | Already has known CAD history; does not address arrhythmia mechanism | | **EP study + PVS** | **Induce VT, map circuits, assess inducibility** | **Gold standard for VT diagnosis and substrate characterization** | ## High-Yield Facts **High-Yield:** AV dissociation on ECG is pathognomonic for VT. EP study confirms the diagnosis and identifies the reentry circuit location, enabling catheter ablation. **Clinical Pearl:** In post-MI patients with VT, EP study is essential before ICD implantation to determine if the patient is a candidate for ablation-first strategy (especially if single, mappable focus) versus ICD alone. **Mnemonic: VT-CONFIRM** — Ventricular Tachycardia diagnosis requires: - **C**linical presentation (palpitations, syncope) - **O**bservation of AV dissociation on ECG - **N**eed for **EP study** (induction + mapping) - **F**unctional assessment (substrate imaging) - **I**nterventional planning (ablation vs. ICD) - **R**isk stratification - **M**onitoring post-therapy