The patient is a 75-year-old man with a history of fatigue and shortness of breath due to paroxysmal atrial fibrillation. He was recently found to have esophageal carcinoma. During indwelling catheter placement for the delivery of chemotherapy, he developed bradycardia. His electrocardiogram (ECG) is shown in Figure 1.
Figure 1
Figure 1
The ECG shows which of the following?
Show Answer
The correct answer is: D. Left bundle branch block with blocked premature atrial contractions (PAC's).
The patient has sinus rhythm with left bundle branch block. The ST and T waves are discordant with the QRS vector. Therefore, anterior infarction is unlikely. The P waves are broad, suggesting intra-atrial disease. The bradycardia is secondary to early premature atrial contractions, which fall on the T wave during the AV node refractory period and hence do not conduct to the ventricles (blocked PACs), shown by red arrows in Figure 2.1-3
Figure 2
Figure 2
References
Spodick DH. Blocked atrial bigeminy. Am Heart Hosp J 2007;5:122.
Trombert V, Barro J. Bradycardia due to blocked atrial bigeminy: ECG. Rev Med Suisse 2008;4:864-5.
Akdeniz C, Tanidir IC, Tuzcu V. Blocked atrial bigeminy presenting with bradycardia. Congenit Heart Dis 2012;7:E82-4.
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