This is a 71 year old patient admitted to the ER for a "Fall". She has a significant medical History of CAD, MI 5 years ago, and Osteoperosis. Her is her EKG done in the ER. What is your interpretation? Answer below

Click here for Better Image EKG

Interpretation

Sinus Rhythm at 63. Presence of Age Indeterminate Inferior Infarct (Q waves in the inferior leads II, III, AvF), Right Bundle Branch Block and Fusion Complex (7th complex)

Sinus is the underlying Rhythm. Significant Q waves in II, III, and AVF, with the significant history of MI in the past makes the old inferior infarct obvious. RBBB is diagnosed by wide QRS duration (128 msec) and RsR' in v1.

The tough one is the 7th complex on the rhythm strip. All the other complexes are RBBB morphology but the 7th ones is normal. Most likely the RBBB is also a result of the infarct because the artery that usually supplies the apex (inferior) of the heart most likely also supplies the RBBB. So the chances that this was a normally conducted impulse are not likely. This is most likely a Fusion Complex. A complex which is composed of two different pacemakers going off at the same time. The p wave in the complex looks the same so most likely it is started off as a sinus beat. As the impulse is making its way through the atrium, a PVC develops and starts the depolerization of the ventricles. As the impulse from the atrium meets the impulse from the ventricles it makes the complex looks narrow. Hence, because there were two different pace makers started at two different places, even though there is a block, the ventricle was depolerized in a "normal" duration because instead of waiting for the delayed impulse from the sinus node through the blocked RBBB, the ventricle already was half way depolerized when the other impulse arrived leading to a normal duration complex.