ECG Interpretation Basics

A 72-year-old woman from Mumbai presents with palpitations and dizziness for 30 minutes. She denies chest pain. Vital signs: BP 110/68 mmHg, HR 165 bpm (irregular), RR 20/min. On auscultation, the heart sounds are irregularly irregular. Her ECG shows a ventricular rate of 160–180 bpm with no discernible P waves, and the baseline appears to have a fine, irregular undulation. Her troponin is normal. What is the most likely diagnosis?

A 58-year-old man from Delhi presents to the emergency department with acute onset chest pain radiating to the left arm for 2 hours. He is diaphoretic and anxious. Vital signs: BP 128/82 mmHg, HR 92 bpm, RR 18/min. On examination, he has no murmurs or crackles. His ECG shows ST-segment elevation in leads II, III, and aVF with reciprocal ST depression in leads I and aVL. Troponin I is elevated at 2.8 ng/mL. What is the most likely diagnosis?

In a standard 12-lead ECG, which of the following represents the normal duration of the QRS complex?

Which of the following ECG intervals represents the total time from the beginning of atrial depolarization to the beginning of ventricular depolarization?

A 62-year-old woman with chronic atrial fibrillation and a rapid ventricular response (heart rate 135 bpm) presents to the emergency department. Her ECG shows irregular narrow-complex tachycardia with an absent P wave and a ventricular rate of 130–140 bpm. She is hemodynamically stable. What is the drug of choice for rate control in this acute presentation?