A 70-year-old woman on digoxin for chronic atrial fibrillation presents with nausea and visual halos. ECG shows regular narrow-complex tachycardia at 130 bpm with distinct P waves and a 2:1 relationship between some P waves and QRS complexes. Serum potassium is 3.0 mEq/L. Which finding on this ECG is considered characteristic of her condition?

• A Sawtooth atrial waves
• B Alternating narrow and wide QRS complexes
• C Delta waves during sinus beats
• D Atrial tachycardia with AV block ✓

Explanation

Paroxysmal atrial tachycardia with AV block is the classic arrhythmia of digoxin toxicity, reflecting both enhanced automaticity and delayed AV nodal conduction. Hypokalemia potentiates digoxin binding to Na-K ATPase and precipitates toxicity, matching her potassium of 3.0 mEq/L. Treatment includes stopping digoxin, correcting potassium, and using digoxin-specific antibody fragments in severe cases.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.