Third-Degree AV Block: The Daily PANCE Blueprint
A 74-year-old woman is brought to the emergency department after fainting at home. She is confused and diaphoretic, with a blood pressure of 72/40 mm Hg and a pulse of 34/min. The ECG shows P waves at 80/min with no relationship to wide QRS complexes at 34/min. She has received atropine 1 mg IV twice with no change in her heart rate. Which is the most appropriate next step?
A. Observation on a cardiac monitor until cardiology arrives
B. Adenosine 6 mg IV push
C. Amiodarone 150 mg IV
D. Synchronized cardioversion
E. Transcutaneous pacing
Answer and topic summary
The answer is E. Transcutaneous pacing
This is third-degree (complete) heart block: the atria and ventricles beat independently, with P waves marching through at their own rate and a slow, wide-complex ventricular escape rhythm. She is unstable (hypotension, syncope, confusion), so her rate has to come up now. In the AHA bradycardia algorithm, atropine comes first, but it acts on the AV node and rarely helps when the block is below the node, which a wide escape rhythm suggests. When atropine fails, the next step is transcutaneous pacing (or a dopamine or epinephrine infusion) as a bridge to transvenous pacing and a permanent pacemaker. Observation is never appropriate for unstable bradycardia. Adenosine and amiodarone slow conduction further and can cause asystole, and synchronized cardioversion is for unstable tachycardias. While you pace, look for reversible causes: hyperkalemia, digoxin, beta-blocker or calcium channel blocker toxicity, inferior MI, and Lyme carditis.
View blueprint lesson
Smarty PANCE Content Blueprint Review:
Covered under ⇒ PANCE Blueprint Cardiology ⇒ ⇒
