NTA NTA Pharmacology and Medications 2 — Questions and Answers
Question 1: Which drug classes are known to prolong the QT interval and increase the risk of Torsades de Pointes?
- Beta-blockers and ACE inhibitors
- Loop diuretics and potassium supplements
- Certain antipsychotics and certain antibiotics (Correct answer)
- Calcium supplements and antacids
Correct answer: Certain antipsychotics and certain antibiotics
Drugs such as haloperidol (antipsychotic) and azithromycin (antibiotic) can prolong ventricular repolarization, widening the QT interval and predisposing the patient to Torsades de Pointes.
Question 2: Hypokalemia resulting from diuretic use typically produces which ECG changes?
- Tall, peaked T waves
- Flattened T waves and prominent U waves (Correct answer)
- Shortened PR interval
- Widened and notched P waves
Correct answer: Flattened T waves and prominent U waves
Low serum potassium flattens or inverts T waves and unmasks the U wave (a positive deflection after the T wave), and increases the risk of ventricular arrhythmias.
Question 3: Which electrolyte imbalance, commonly caused by medications like potassium-sparing diuretics, produces tall peaked T waves on ECG?
- Hyponatremia
- Hyperkalemia (Correct answer)
- Hypocalcemia
- Hypomagnesemia
Correct answer: Hyperkalemia
Hyperkalemia causes tall, narrow, tent-shaped T waves on ECG and can progress to widened QRS, sine-wave pattern, and cardiac arrest if untreated.
Question 4: Calcium channel blocker overdose characteristically produces which ECG finding?
- Sinus tachycardia with shortened PR interval
- Bradycardia with prolonged PR interval and possible heart block (Correct answer)
- Peaked T waves suggesting hyperkalemia
- ST elevation in anterior leads
Correct answer: Bradycardia with prolonged PR interval and possible heart block
Calcium channel blockers slow AV node conduction; in overdose this manifests as bradycardia, prolonged PR interval, and potentially complete heart block.
Question 5: Hypocalcemia — which can be caused by certain medications — produces which ECG change?
- Shortened QT interval
- Prolonged QT interval (Correct answer)
- Tall peaked T waves
- Delta waves indicating pre-excitation
Correct answer: Prolonged QT interval
Hypocalcemia delays ventricular repolarization, lengthening the QT interval on ECG and increasing the risk of ventricular arrhythmias.
Question 6: A patient receiving IV magnesium sulfate develops bradycardia. What is the most likely explanation?
- Hypernatremia from concurrent saline infusion
- Hypermagnesemia slowing cardiac conduction (Correct answer)
- Hypocalcemia triggered by the infusion
- New-onset atrial fibrillation
Correct answer: Hypermagnesemia slowing cardiac conduction
Elevated serum magnesium acts as a natural calcium channel antagonist, slowing cardiac conduction and causing bradycardia or heart block in excess.
NTA NTA Pharmacology and Medications 2
Which drug classes are known to prolong the QT interval and increase the risk of Torsades de Pointes?