A 68-year-old man presents with a history of obstructive sleep apnea, pulmonary embolism, protein C deficiency, and bioprosthetic aortic valve replacement for aortic stenosis. He has been bothered by shortness of breath and palpitations for three days. An electrocardiogram (ECG) is performed (Figure 1).
The ECG shows which of the following?
The correct answer is: A. Atypical atrial flutter with 2:1 AV conduction.
The ECG shows a regular narrow complex tachycardia with a heart rate of 145 beats per minute. The QRS axis is normal in duration. The overall character is one of an atrial tachycardia. There are two flutter waves between two QRS complexes; this is best seen in lead II and lead aVF (inferior leads). The first flutter wave is noted immediately after the QRS complex, whereas the second flutter wave is seen at the peak of the T wave. The flutter wave polarity is upright in lead II and aVF as well as narrow in duration, which is consistent with either high right or left sided septal atypical atrial flutter with 2:1 AV conduction.
Typical AV nodal reentry tachycardia (AVNRT) is incorrect because the P is usually inverted in the inferior leads, and conducts in a 1:1 retrograde direction. The typical atrial flutter with 2:1 AV conduction is incorrect because it is dependent on the cavo-tricuspid isthmus (CTI), which is located in the low right atrium and results in negative P wave in the inferior leads. Wolff-Parkinson-White is the substrate for narrow-complex orthodromic AV reentrant tachycardia, or a wide complex antidromic variant. Both, like AVNRT, have 1:1 retrograde atrial activation. An EP study, or response to carotid sinus massage aid in the diagnosis of this narrow-complex atrial tachyarrhythmia, and clarify 2:1 conduction.
Glancy DL, Ali M. Epigastric pain in a 63-year-old woman. Atrial flutter with 2:1 atrioventricular block; acute inferoposterior myocardial infarction. J La State Med Soc 2013;165:286-7.