Question

An adult has a ventricular demand pacemaker that is set at 72 bpm. The nurse knows that the client’s pacemaker is functioning correctly if which of the following appears on the ECG?

a.	Pacemaker spikes before each P wave
b.	Pacemaker spikes appearing only if the heart rate is over 72
c.	Pacemaker spikes followed by QRS complexes
d.	Pacemaker spikes instead of QRS complexes

Answer 1

C.Pacemaker spike followed by QRS complexes

The appearance of the ECG in a paced patient is dependent on the pacing mode used, placement of pacing leads, device pacing thresholds, and the presence of native electrical activity.

Ventricular Pacing:

• Pacing spike precedes the QRS complex.
• Right ventricle pacing lead placement results in a QRS morphology similar to LBBB.(Left bundle branch block)
• Left epicardial pacing lead placement results in a QRS morphology similar to RBBB.(Right bundle branch block).
• ST segments and T waves should be discordant with the QRS complex i.e. the major terminal portion of the QRS complex is located on the opposite side of the baseline from the ST segment and T wave.

Atrial Pacing: Pacing spike precedes the p wave.