Tall R Waves in the Right Precordial Leads

Explanation

The deeply negative initial deflections, which are wide in the inferior leads, certainly suggest an old inferior infarction. Combined with tall R waves in the right precordial leads, these deflections can make one consider an old infero-posterior infarction. However, the PR interval is short, and typical delta waves are seen in many leads, especially in leads V3 and V4, and the tracing is diagnostic of ventricular pre-excitation. The initial negative deflections in leads ll, lll, and aVF are not Q waves of an infarction but negative delta waves. In ventricular pre-excitation, the delta waves can be upright in some leads, inverted in other leads, or even isoelectric in other leads. If it is isoelectric, the PR interval will not be short and there won't be a delta wave in that lead. The absence of right axis deviation rules out right ventricular hypertrophy. It's not often that we encounter ECGs of ventricular pre-excitation, but they can mislead us in so many different ways, such as the tracing suggesting either myocardial infarction (as in this case) or ventricular bigeminy, electrical alternans, accelerated idioventricular rhythm, etc.^[1,2]

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Cite this: Tall R Waves in the Right Precordial Leads - Medscape - Feb 14, 2014.