ECG Pharmacology and Cardiac Medications Flashcards

Hypokalemia from loop diuretic use (e.g., furosemide) produces which characteristic ECG change?

Answer: Flat or inverted T waves and prominent U waves

Hypokalemia flattens or inverts the T wave and causes prominent U waves (deflection after the T wave) due to delayed ventricular repolarization.

A patient receiving IV procainamide (Class IA) for ventricular arrhythmia may develop which dangerous ECG pattern?

Answer: QRS widening greater than 50% of baseline

Procainamide can widen the QRS by more than 50% of the baseline width, signaling toxicity and increased risk of proarrhythmia.

Which ECG finding would suggest a patient has received too much atropine?

Answer: Sinus tachycardia with shortened PR interval

Atropine blocks muscarinic receptors, increasing SA node automaticity and speeding AV conduction, resulting in sinus tachycardia with a shortened PR interval.

Tricyclic antidepressant (TCA) overdose is classically recognized on the ECG by:

Answer: Widened QRS, right axis deviation, and prolonged QT

TCA overdose causes sodium channel blockade (widened QRS), potassium channel blockade (prolonged QT), and rightward axis shift, which is a life-threatening combination.

Heparin and warfarin are anticoagulants that do NOT directly alter the ECG. Which ECG change may appear indirectly if anticoagulation reverses a pulmonary embolism?

Answer: Resolution of the S1Q3T3 pattern

A pulmonary embolism can produce the S1Q3T3 pattern; successful anticoagulation and clot resolution can lead to normalization and disappearance of this pattern.

Sotalol (a Class III antiarrhythmic with beta-blocking properties) increases the risk of torsades de pointes primarily because it:

Answer: Prolongs the QT interval

Sotalol prolongs ventricular repolarization (QT interval), creating a vulnerable window for torsades de pointes, a polymorphic ventricular tachycardia.

An ECG technician notices a patient's rhythm strip shows bradycardia and first-degree AV block. Which medication history is most consistent with these findings?

Answer: Metoprolol (beta-blocker)

Metoprolol, a beta-blocker, reduces heart rate and slows AV node conduction, commonly producing bradycardia and a prolonged PR interval (first-degree AV block).