ECG Pharmacology and Cardiac Medications Flashcards

A patient taking quinidine (Class IA) develops a QTc of 560 ms. What is the most serious arrhythmia risk associated with this finding?

Answer: Torsades de pointes

Marked QT prolongation from quinidine predisposes to torsades de pointes, a potentially fatal polymorphic ventricular tachycardia.

Hypocalcemia (e.g., from loop diuretics or hypoparathyroidism) produces which ECG finding?

Answer: Prolonged QT interval due to a long ST segment

Hypocalcemia prolongs the ST segment, lengthening the QT interval, because calcium is essential for the plateau phase of the cardiac action potential.

Which drug interaction should an ECG technician be aware of that can compound QT prolongation risk?

Answer: Amiodarone plus azithromycin

Amiodarone and azithromycin both independently prolong the QT interval; combining them significantly increases the risk of torsades de pointes.

Nitroglycerin relieves angina but its primary ECG effect during an acute ischemic episode would be:

Answer: Reducing or resolving ST segment depression or elevation as ischemia improves

Nitroglycerin reduces myocardial oxygen demand and improves coronary perfusion; resolution of ischemia-induced ST changes confirms its effectiveness.

A patient receiving thrombolytic therapy (e.g., tPA) for STEMI may show which ECG change that indicates successful reperfusion?

Answer: Accelerated idioventricular rhythm (AIVR)

Accelerated idioventricular rhythm is a classic reperfusion arrhythmia seen shortly after a blocked coronary artery reopens, indicating successful thrombolysis.

Lithium toxicity can cause which ECG finding that mimics a naturally occurring rhythm disturbance?

Answer: T wave flattening or inversion and sinoatrial block resembling sick sinus syndrome

Lithium toxicity can flatten or invert T waves and disrupt SA node function, producing sinoatrial block or sinus arrest patterns similar to sick sinus syndrome.

An ECG technician documents a QTc of 480 ms in a patient newly started on haloperidol (antipsychotic). What is the most appropriate action?

Answer: Document the finding and alert the supervising clinician for evaluation

A QTc ≥ 470 ms (men) or ≥ 480 ms (women) warrants clinical evaluation; the ECG technician should document the finding and promptly notify the supervising clinician.