Anti-arrhythmic Meds Vignette MCQs Flashcards
A 75-year-old male with a history of hypertension and coronary artery disease presents to the ED with shortness of breath and tachycardia. His BP is 90/58, and he is clammy. He is given a medication that slows Phase 0 and prolongs the cardiac action potential. Which of the following drugs was most likely given?
A. Adenosine
B. Diltiazem
C. Amiodarone
D. Sotalol
Answer: C. Amiodarone
Explanation: Amiodarone blocks K+, Na+, and Ca2+ channels, prolonging the cardiac action potential. It is commonly used for both atrial and ventricular arrhythmias, especially in hemodynamically unstable patients.
A 62-year-old male in the ICU after an anterior MI develops recurrent episodes of ventricular tachycardia. He remains conscious but experiences dizziness and hypotension. He is given an IV bolus of lidocaine. What is the primary mechanism of action of lidocaine?
A. Blocks L-type calcium channels
B. Blocks primarily fast sodium channels in their inactivated state
C. Blocks primarily K+ channels
D. Blocks Na+/K+ ATPase
Answer: B. Blocks primarily fast sodium channels in their inactivated state
Explanation: Lidocaine is a Class Ib antiarrhythmic that preferentially blocks inactivated Na+ channels in ischemic tissue, making it useful for ventricular arrhythmias post-MI.
A 55-year-old woman experiences syncope in a parking lot and reports lightheadedness and palpitations. She has been taking erythromycin and sotalol. ECG shows prolonged QT interval. Which of the following is the most likely mechanism of her condition?
A. Na+ channel blockade
B. K+ channel blockade leading to torsades de pointes
C. Ca2+ channel blockade
D. Beta-blockade-induced bradycardia
Answer: B. K+ channel blockade leading to torsades de pointes
Explanation: Sotalol (Class III) and erythromycin (macrolide antibiotic) both prolong the QT interval by blocking K+ channels, predisposing to torsades de pointes.
A 64-year-old male with heart failure and atrial fibrillation presents with palpitations for 7 days. He has been taking amiodarone for the past 8 months. Which of the following is a serious long-term adverse effect of amiodarone therapy?
A. Hyperkalemia
B. Pulmonary fibrosis
C. Agranulocytosis
D. Gingival hyperplasia
Answer: B. Pulmonary fibrosis
Explanation: Amiodarone has a long half-life and can accumulate in tissues, leading to pulmonary fibrosis, hepatotoxicity, and thyroid dysfunction.
A 70-year-old male with heart failure is started on digoxin for atrial fibrillation. Which electrolyte abnormality increases the risk of digoxin toxicity?
A. Hyperkalemia
B. Hypokalemia
C. Hypercalcemia
D. Hypomagnesemia
Answer: B. Hypokalemia
Explanation: Hypokalemia increases digoxin toxicity by enhancing its binding to Na+/K+ ATPase, leading to arrhythmias and other toxic effects.
A 68-year-old male with atrial fibrillation is started on amiodarone. After several months of therapy, he presents with progressive shortness of breath and dry cough. Which of the following is the most likely adverse effect of this medication?
A. Pulmonary fibrosis
B. Hepatotoxicity
C. Hypothyroidism
D. Bradycardia
Answer: A. Pulmonary fibrosis
Explanation: Amiodarone is associated with pulmonary toxicity, leading to progressive fibrosis. Patients should be monitored with periodic chest X-rays and pulmonary function tests.
A 72-year-old woman with atrial fibrillation develops nausea, vomiting, and blurry yellow vision. She is found to have a high serum digoxin level. Which of the following electrolyte disturbances most likely contributed to her symptoms?
A. Hyperkalemia
B. Hypokalemia
C. Hypernatremia
D. Hypocalcemia
Answer: B. Hypokalemia
Explanation: Hypokalemia enhances digoxin toxicity by increasing its binding to Na+/K+ ATPase, leading to arrhythmias and other toxic effects.
A 60-year-old male presents with tinnitus, headache, and dizziness after being treated for atrial fibrillation. Which antiarrhythmic is most likely responsible for these symptoms?
A. Lidocaine
B. Procainamide
C. Quinidine
D. Amiodarone
Answer: C. Quinidine
Explanation: Quinidine toxicity, known as cinchonism, is characterized by tinnitus, headache, dizziness, and visual disturbances.
A 55-year-old female with ventricular tachycardia is treated with procainamide. She later develops joint pain and a positive ANA test. Which of the following is the most likely diagnosis?
A. Myasthenia gravis
B. Rheumatoid arthritis
C. Systemic lupus erythematosus
D. Drug-induced lupus
Answer: D. Drug-induced lupus
Explanation: Procainamide is associated with drug-induced lupus, which presents with joint pain, fever, and a positive ANA test.
A 65-year-old man with heart failure is started on sotalol for atrial fibrillation. A week later, he experiences syncope. ECG shows prolonged QT interval with polymorphic ventricular tachycardia. Which arrhythmia is most likely responsible for his symptoms?
A. Atrial fibrillation
B. Torsades de pointes
C. Ventricular fibrillation
D. Junctional escape rhythm
Answer: B. Torsades de pointes
Explanation: Sotalol is a class III antiarrhythmic that prolongs the QT interval, increasing the risk of torsades de pointes.
Which of the following medications should be avoided in a patient with atrial fibrillation and heart failure with reduced ejection fraction?
A. Amiodarone
B. Diltiazem
C. Metoprolol succinate
D. Digoxin
Answer: B. DiltiazemExplanation: Non-dihydropyridine calcium channel blockers (e.g., diltiazem) can worsen heart failure due to their negative inotropic effects.
A 60-year-old male started on sotalol for atrial fibrillation develops dizziness and syncope. ECG shows prolonged QT interval. What is the best next step?
A. Stop sotalol and correct electrolyte imbalances
B. Continue sotalol and monitor
C. Switch to a Class Ic antiarrhythmic
D. Administer digoxin
Answer: A. Stop sotalol and correct electrolyte imbalancesExplanation: Sotalol can prolong QT and cause torsades de pointes; discontinuation and electrolyte correction are critical.
A 72-year-old female on warfarin for atrial fibrillation begins amiodarone therapy. What effect will amiodarone have on her INR?
A. Decrease INR
B. No effect
C. Increase INR
D. Cause unpredictable fluctuations
Answer: C. Increase INR
Explanation: Amiodarone inhibits CYP2C9, reducing warfarin metabolism and increasing INR, necessitating dose adjustments.
A 45-year-old male is started on a Class Ic antiarrhythmic for atrial fibrillation. He later develops wide complex tachycardia and syncope. Which of the following medications is most likely responsible?
A. Lidocaine
B. Flecainide
C. Amiodarone
D. Metoprolol
Answer: B. FlecainideExplanation: Flecainide is a Class Ic antiarrhythmic that can cause proarrhythmic effects, especially in patients with structural heart disease.
A patient with Wolff-Parkinson-White syndrome presents with supraventricular tachycardia. Which of the following medications is contraindicated in this patient?
A. Amiodarone
B. Procainamide
C. Adenosine
D. Digoxin
Answer: D. DigoxinExplanation: Digoxin enhances AV nodal conduction, which can lead to increased ventricular rates in WPW, worsening tachycardia.
