R-on-T & R-on-P at the Same Time

Report:

Sinus tachycardia 124/min

VEBs

in bigeminy & trigeminy

R-on-T phenomenon

Right bundle branch block

Comment:

The bigeminal VEBs would be still narrower were it not for the superimposition of sinus P waves on their initial vector. The VEBs not only look narrower than the sinus beats - they are so, even in the 12-lead ECG (Fig 162a). This is because the patient has a LAHB + RBBB impeding the sinus impulses; the ectopic focus may have an easier job depolarising the ventricles synchronously from below the block! The VEB axis is opposite of sinus beats’ axis in the standard leads. Her full ECG also indicates a recent anterior MI and LAA to go with history of pain and current shortness of breath, respectively.

These VEBs are very closely coupled (R-R’ 380 ms, 0.38”). There is R-on-T as well as R-on-P phenomenon!

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