Conduction Disorders: The Daily PANCE Blueprint
A 68-year-old woman with a history of hypertension and type 2 diabetes presents to the emergency department with palpitations and mild shortness of breath for the past 12 hours. Her medications include metformin and lisinopril. Her pulse rate is 150/min, blood pressure is 110/70 mm Hg, respiratory rate is 18/min, and temperature is 37.2°C (99°F). She is alert and oriented. Her ECG shows a saw-tooth pattern in leads II, III, and aVF with narrow QRS complexes. Which of the following medications is the most appropriate to control this patient's heart rate?
A. Digoxin
B. Amiodarone
C. Intravenous diltiazem
D. Metoprolol
E. Adenosine
Answer and topic summary
The answer is C. Intravenous diltiazem
Explanation: Intravenous diltiazem is often the drug of choice for acutely controlling the rapid ventricular response in atrial flutter. It increases AV nodal refractoriness and slows conduction velocity in the AV node, thereby decreasing the ventricular response. Diltiazem has a rapid onset of action and is generally well-tolerated, with less negative inotropic effect than verapamil.
Incorrect Answer Explanations:
- A. Digoxin: While historically used for rate control in atrial flutter, digoxin has a slow onset of action (peak effect in 1-5 hours) and is less effective than calcium channel blockers or beta blockers. It is generally reserved for patients whose rate has not been adequately controlled with other agents.
- B. Amiodarone: Although amiodarone can be used for rate control, it has a slower onset of action compared to diltiazem and carries a risk of cardioversion to sinus rhythm. This could be problematic if the patient is not adequately anticoagulated. Amiodarone is generally reserved for critically ill patients or those with severe hemodynamic compromise.
- D. Metoprolol: While beta blockers can be effective for rate control in atrial flutter, they have a slower onset of action compared to intravenous diltiazem. They are more commonly used for long-term oral therapy rather than acute rate control in the emergency setting.
- E. Adenosine: Adenosine is not appropriate for rate control in atrial flutter. It is used primarily for diagnosis and treatment of paroxysmal supraventricular tachycardia involving the AV node. In atrial flutter, adenosine may cause transient AV block but will not provide sustained rate control.
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Smarty PANCE Content Blueprint Review:
Covered under ⇒ PANCE Cardiology Blueprint ⇒ Conduction Disorders ⇒ Atrial Fibrillation/flutter
