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Atrial Pacing

Tue, 04/28/2015 - 20:22 -- Dawn

This is a good example of an AV Sequential pacemaker in a patient with an intact AV conduction system.  The pacemaker is pacing the right atrium, and the impulse is being transmitted normally down through the AV node and the interventricular conduction system.  The pacer spike is seen before the P waves, and the QRS complex is narrow, reflecting normal conduction through the ventricles.

If you are teaching about ST elevation MI, this patient has no ST elevation M.I., but this type of pacing does not affect the ST segments, and an M.I. will still show as ST elevation.

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Comments's picture

As per Dawn - this ECG provides a nice example of atrial pacing. As always with any pacemaker  it is essential to know what parameters have been set in order to interpret the tracing. It looks like the PR interval (duration from onset of atrial spike until onset of the QRS) = 0.24 second. Depending on the patient’s underlying disorder  the programming cardiologist can set parameters to optimize the chance for spontaneous initiation of ventricular contraction if the conduction system is intact.

  • It is of interest here that in some leads (ie, I, AVL, V2,V3) it looks like we DO see a ventricular spike in front of some complexes. This tells us that the pacemaker has indeed been set to accept a PR interval ~ 0.24 second, after which time if no spontaneous QRS complex occurs the pacemaker will stimulate the ventricles. That there is minimal difference in QRS morphology between QRS complexes with and without a ventricular spike indicates that the conduction system is indeed intact and still able to conduct with a PR interval of 0.24 second (or a slight bit more than this).

Ken Grauer, MD   [email protected] 

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