By Ken Grauer, MD
Professor Emeritus in Family Medicine, College of Medicine, University of Florida
Dr. Grauer reports no financial relationships relevant to this field of study.
The ECG in the figure below was obtained from a man with new onset palpitations. What is the probable cause of his symptoms? Is there high lateral infarction, or is something else accounting for the Q waves in leads I and aVL?
The long lead II rhythm strip at the bottom of the tracing shows the rhythm to be rapid, irregularly irregular, and without P waves. The rhythm is rapid atrial fibrillation. But there is much more. How often does one see Q waves this deep in lead I? Is R wave progression in the precordial leads normal?
It is extremely uncommon to see a QRS complex with a predominant Q wave in lead I, especially when the T wave in this lead also is negative (as seen in the figure). In combination with a significantly positive QRS complex in lead aVR, the predominant Q wave that visible in lead I should suggest the possibility of either lead reversal (caused by mix up of the left and right arm electrodes) or dextrocardia.
Dextrocardia is rare. Most providers can count on the fingers of one hand the number of cases they have seen during their careers. That said, there is reverse R wave progression in the chest leads of this tracing. That is, instead of the R wave progressively increasing in amplitude as one moves across the chest leads, the reverse occurs. The tallest R wave is in lead V1, after which R wave amplitude decreases. In fact, we see no more than highly unusual, low-amplitude rSr’ complexes in leads V3 through V6 of this tracing.
This patient had dextrocardia. Heart sounds were heard on the right side of the chest, and a chest X-ray confirmed mirror-image reversal of the aortic knob and heart shadow. Follow-up ECG with chest leads placed on the right side of the chest showed a much more normal pattern of R wave progression.
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