Ventricular Arrhythmias

Which of the following is the characteristic electrocardiographic finding in Brugada syndrome?

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 110/70 mmHg and heart rate is 140 bpm. A 12-lead ECG shows a wide complex tachycardia with a left axis deviation and concordance in the precordial leads. Which investigation is most appropriate to confirm the diagnosis and assess the substrate for arrhythmia?

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?

A 52-year-old man with dilated cardiomyopathy (ejection fraction 25%) and NYHA Class III heart failure is admitted with recurrent episodes of non-sustained ventricular tachycardia (NSVT) on 24-hour Holter monitoring. He is on optimal medical therapy (ACE inhibitor, beta-blocker, aldosterone antagonist). His electrolytes and renal function are normal. What is the most appropriate next step in management?

A 58-year-old man with a history of anterior wall myocardial infarction 3 months ago presents to the emergency department with palpitations and lightheadedness. His blood pressure is 85/50 mmHg, heart rate 180 bpm, and respiratory rate 22/min. Physical examination reveals an unresponsive patient. A 12-lead ECG shows a wide complex tachycardia with a rate of 180 bpm; the QRS duration is 160 ms. Cardiac biomarkers are negative. Chest X-ray shows mild cardiomegaly. What is the most appropriate immediate management?