Cardiac Pharmacology Effects on ECG Flashcards

Amiodarone is known to prolong which ECG interval, increasing the risk of Torsades de Pointes?

Answer: QT interval

Amiodarone prolongs the QT interval by blocking potassium channels, which can precipitate Torsades de Pointes in susceptible patients.

A patient receiving IV adenosine for SVT shows a brief pause on the ECG strip. What does this pause represent?

Answer: Transient AV block

Adenosine transiently blocks AV conduction, producing a brief AV block that terminates re-entrant SVT and appears as a pause on the ECG.

Which beta-blocker ECG effect helps differentiate it from calcium channel blocker toxicity on the ECG?

Answer: Bradycardia with narrow QRS vs. bradycardia with wide QRS

Beta-blocker toxicity typically causes bradycardia with a narrow QRS, while calcium channel blocker toxicity may cause bradycardia with a wide QRS and conduction abnormalities.

Sotalol combines beta-blocking and Class III antiarrhythmic properties. Which ECG change is most expected?

Answer: Prolonged QT interval

Sotalol's Class III action blocks potassium channels, prolonging repolarization and the QT interval.

A patient on procainamide develops a wide-complex tachycardia on ECG. What drug toxicity phenomenon is most likely?

Answer: Proarrhythmia with widened QRS

Procainamide toxicity causes QRS widening due to sodium channel blockade, which can lead to proarrhythmic ventricular tachycardia.

Which ECG finding in a digitalis-toxic patient most urgently requires physician notification?

Answer: Bidirectional ventricular tachycardia

Bidirectional ventricular tachycardia is a hallmark of severe digitalis toxicity and is a life-threatening emergency requiring immediate intervention.

Flecainide, a Class IC drug, primarily affects the ECG by:

Answer: Widening the QRS complex significantly

Flecainide blocks fast sodium channels, markedly slowing intraventricular conduction and widening the QRS complex.