A 48-year-old woman with dilated cardiomyopathy (EF 25%) presents with a single episode of syncope. Baseline 12-lead ECG shows sinus rhythm with frequent premature ventricular contractions (PVCs). She is on optimal medical therapy (ACE inhibitor, beta-blocker, aldosterone antagonist). Which investigation is most appropriate to risk-stratify her for sudden cardiac death and guide ICD therapy?

Explanation

## Clinical Scenario A patient with dilated cardiomyopathy (DCM), severely reduced EF, and syncope is at high risk for sudden cardiac death. The question asks which investigation best risk-stratifies her and guides ICD therapy. ## Role of Investigations in DCM Risk Stratification **Key Point:** In patients with DCM and reduced EF, EP study with programmed ventricular stimulation is the most specific investigation for identifying inducible VT and determining ICD candidacy. ### Comparison of Investigations | Investigation | Mechanism | Utility in DCM | ICD Guidance | |---|---|---|---| | **EP Study + PVS** | Induces VT with programmed stimulation | High specificity for inducible VT | Directly guides ICD implantation decision | | **Signal-averaged ECG** | Detects late potentials | Identifies electrical instability; lower specificity | Prognostic but not diagnostic | | **Exercise stress test** | Provokes ischaemia-induced arrhythmias | Not indicated in DCM without CAD | Does not assess re-entrant substrate | | **Cardiac catheterization** | Assesses coronary anatomy | Rules out CAD as cause | Does not assess arrhythmia risk | **High-Yield:** In DCM patients with: - EF ≤35% AND - Syncope or sustained VT EP study is indicated to: 1. Induce VT (if inducible → ICD recommended) 2. Assess risk of future arrhythmias 3. Determine if ablation is feasible **Clinical Pearl:** The patient has already met criteria for ICD consideration (EF 25%, syncope). EP study helps determine if she has an inducible re-entrant substrate. If VT is induced, ICD is strongly recommended. If not inducible, clinical judgment and other risk factors guide the decision. **Mnemonic: SAECG limitations** — Signal-Averaged ECG is **Sensitive but not Specific** for VT risk in DCM. Late potentials indicate electrical instability but do not confirm arrhythmia mechanism. **Warning:** Do not confuse prognostic markers (late potentials on SAECG, reduced EF) with diagnostic confirmation. Only EP study can induce and confirm VT.