An 89-year-old male with a medical history significant for single vessel coronary artery bypass grafting, recent stroke, and peripheral vascular disease presents from his nursing home with respiratory distress, hyperkalemia, and lactic acidosis. He has a previously known left bundle branch block. The following ECG is obtained:
Figure 1
The ECG shows which of the following:
Show Answer
The correct answer is: B. Sinus tachycardia.
The ECG shows sinus tachycardia with 2:1 AV block with left bundle branch block. The atrial rate is 136 beats per minute; thus, this is sinus tachycardia. However, there is 2:1 atrioventricular conduction (P waves marked in red), therefore the ventricular rate is slower. The since the sinus rate is not over 100 or less than 60 beats per minute, this is not sinus bradycardia or sinus rhythm. The P wave morphology is consistent with sinus origin: upright in the inferior leads (II, III, aVF) and in lead 1, and biphasic in lead V1.1 Therefore, this is unlikely an atrial tachycardia.
Figure 2
References
Meek S, Morris F. ABC of clinical electrocardiography. Introduction. I-Leads, rate, rhythm, and cardiac axis. BMJ 2002;324:415-8.
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