A 72-year-old woman on digoxin for heart failure presents with nausea and visual disturbances. ECG shows a regular narrow-complex tachycardia at 110 bpm with 2:1 AV block and a ventricular rate that doubles after withholding one dose. Which arrhythmia is the classic manifestation of digoxin toxicity?

• A Atrial fibrillation with rapid ventricular response
• B Ventricular bigeminy
• C Torsades de pointes
• D Paroxysmal atrial tachycardia with AV block ✓

Explanation

Paroxysmal atrial tachycardia with block (PAT with block) is the classic and most characteristic arrhythmia of digoxin toxicity. The combination of enhanced atrial automaticity with AV nodal blockade (due to increased vagal tone and direct toxic effect) produces this pattern. The ventricular rate often improves with dose reduction because the toxic concentration enhances AV block.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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