By Ken Grauer, MD
Professor Emeritus in Family Medicine, College of Medicine, University of Florida
The ECG in the figure below was obtained from an elderly man who was admitted to the hospital with pneumonia. This ECG was obtained after his admission when he began to complain of chest pain. There are two important findings on this patient’s ECG. Can you identify them?
Although this tracing technically is limited, it is adequate for detecting two important findings. The overall rhythm looks to be fairly regular, with some early beats. The lack of a long lead rhythm strip, and the fact several beats may be hidden by the vertical black lead change markers, makes precise determination of the rhythm difficult. I suspect the underlying rhythm is supraventricular (sinus or ectopic atrial) with premature atrial contractions. That said, the rhythm is not one of the two most important ECG findings.
Something is wrong in lead I. You never normally see global negativity (of P wave, QRS, and T wave) in left-sided lead I. While no definite P wave is evident in lead I, the all negative QRS and inverted T wave in this lead should suggest left arm-right arm (LA-RA) lead reversal or dextrocardia.
This ECG does not look like dextrocardia because we do not see “reverse R wave progression” in the chest leads (i.e., R wave amplitude is not progressively decreasing as one moves across the precordial leads). LA-RA lead reversal is much more common than is appreciated, especially when a less experienced technician is recording the tracing, but even experienced technicians will at some time in their career commit this technical mishap.
With LA-RA lead reversal, left-sided lead I usually looks like we expect right-sided lead aVR to look, and vice versa. This is precisely what we see in the figure, as it is highly unusual to see both the QRS complex and T wave all be positive in lead aVR. LA-RA lead reversal affects the ECG in this way: lead I becomes inverted, leads II and III switch places, leads aVL and aVR switch places, and lead aVF remains unchanged.
Taking these effects into account would result in Q waves, ST elevation, and T wave inversion in each inferior lead. It also would result in reciprocal ST depression in lateral leads I and aVL. Both the lead reversal and acute inferior myocardial infarction initially were unrecognized until later in this patient’s hospital course.
For more information about and further discussion on this case, please visit here.
The ECG in the figure was obtained from an elderly man who was admitted to the hospital with pneumonia. This ECG was obtained after his admission when he began to complain of chest pain. There are two important findings on this patient’s ECG. Can you identify them?
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