CBQ: Case based MCQ for FMGE/MCI screening - 002
Published on Sept. 14, 2021, 1:31 p.m.

You are asked to see a 52-year-old woman with no prior medical history admitted to the neurosurgery service with a nontraumatic subarachnoid bleed. She was just placed on a ventilator, and an urgent craniotomy is planned. Based on the above ECG done 2 hours earlier, what would be the next best step before proceeding to surgery?

A. Echocardiogram to assess for right ventricular hypokinesis
B. Repeat ECG
C. Look at the chest x-ray to confirm a congenital heart abnormality
D. Stress test to assess for significant ischemia

The answer is B: Repeat ECG. 

This ECG demonstrates sinus tachycardia with apparent right axis deviation. However, make note that the predominantly positive precordial P waves appear to support a sinus mechanism from the high right atrium, but the negative P waves in I and flat P waves in II do not. This suggests limb lead reversal. With right arm–left arm lead reversal, as in this case, lead I is inverted, leads II and III are reversed, leads aVR and aVL are reversed, and lead aVF is unchanged. Right arm left–arm lead reversal is one of the more common reasons for right axis deviation, and assessing the P wave morphology as explained helps distinguish this. This abnormality needs to be distinguished from rare dextrocardia, which can also produce these limb lead findings. However, the precordial leads would show a lack of normal R wave progression as the heart would be in the other side of the chest. 

A. Despite what appears to be right axis deviation at first, there is no evidence of right ventricular hypertrophy or enlargement on this ECG, and therefore echocardiogram is not indicated.
C. As the ECG pattern is most consistent with limb lead reversal, the chest x-ray is unlikely to be helpful unless there was a lack of precordial R wave transition in which dextrocardia would be more likely.
D. There is no role for a stress test in this patient who has an urgent noncardiac surgical indication.