Arrhythmias USMLE Step 1 Practice Question
A 68-year-old man with a history of myocardial infarction presents with palpitations and dyspnea. Vital signs show BP 128/82 mmHg, HR 142 bpm, RR 18, temperature 37.2°C, and SpO2 98% on room air. ECG demonstrates wide-complex tachycardia. He denies chest pain. The patient takes metoprolol and atorvastatin. A researcher studying this arrhythmia's electrophysiology notes that a novel antiarrhythmic drug slows the rapid upstroke of phase 0 in ventricular myocytes. Which ion current is primarily affected?
Answer choices
- ASlow calcium influx through L-type channels
- BPotassium efflux through delayed rectifier channels
- CFunny current in pacemaker cells
- DChloride influx
- EFast sodium influxCorrect answer
- FFast potassium influx through inward rectifier channels
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.