Practice Test Geeks(CET) Certified Electrocardiogram Technician Practice Test
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Cardiac Pharmacology Effects on ECG Flashcards

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  1. A patient taking magnesium sulfate for eclampsia is monitored via ECG. Which change would indicate magnesium toxicity?

    Answer: Prolonged PR and QRS with bradycardia

    Magnesium toxicity suppresses conduction, leading to prolonged PR and QRS intervals, bradycardia, and potentially complete heart block.

  2. Which antiarrhythmic drug class is most associated with causing a lupus-like syndrome AND QRS widening on ECG?

    Answer: Class IA (procainamide)

    Class IA drug procainamide can cause drug-induced lupus syndrome and, due to sodium channel blockade, prolongs the QRS complex.

  3. During an ECG, a patient on quinidine shows a markedly prolonged QT and polymorphic ventricular tachycardia. This is best described as:

    Answer: Quinidine syncope / Torsades de Pointes

    Quinidine-induced QT prolongation can trigger Torsades de Pointes, historically called 'quinidine syncope,' a polymorphic VT that is life-threatening.

  4. Verapamil given for rate control in atrial fibrillation most directly produces which measurable ECG change?

    Answer: Slowing of the ventricular rate

    Verapamil blocks calcium channels in the AV node, slowing conduction and thereby reducing the ventricular rate in atrial fibrillation.

  5. A patient on chronic amiodarone therapy develops thyroid dysfunction. Which ECG finding might accompany amiodarone-induced hypothyroidism?

    Answer: Prolonged QT with bradycardia

    Hypothyroidism slows the heart rate and prolongs the QT interval; amiodarone-induced hypothyroidism can exaggerate these effects.

  6. Lidocaine (Class IB) is preferred for ventricular arrhythmias post-MI because it:

    Answer: Selectively suppresses depolarization in ischemic tissue with minimal effect on normal tissue

    Lidocaine preferentially binds to inactivated sodium channels in ischemic myocardium, suppressing ventricular ectopy with little effect on normal conduction.

  7. Which drug given for rate control in atrial flutter is most likely to show a sudden conversion to sinus rhythm on the ECG monitor?

    Answer: Ibutilide

    Ibutilide is a Class III antiarrhythmic used for chemical cardioversion of atrial flutter and fibrillation, and may produce sudden conversion to sinus rhythm.