A common source of confusion


This patient came in due to altered level of consciousness. 

Is there pacemaker malfunction?


Figure 1 - ECG case

There is no malfunction here. R8 to R11 are pseudofusion complexes. Pacer artifacts are seen ON the  QRS complexes (native looking or intrinsic or normal-looking complexes) but the pacer impulse did not change the shape or morphology of the QRS complex.

Pseudofusion beats (together with fusion) on the ECG is a common source of confusion. It indicates that the pacemaker stimulus did not alter the intrinsic QRS morphology on the surface ECG. This is because the pacemaker stimulus occurred after the normal depolarization of the ventricles has started. Thus, it cannot be affected by the pacemaker stimulus. 

Reference:

Bonnow et al. 2011. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 9th Edition. PA.Saunders 

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