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AV Pacer: Atrial Ventricular Pacemaker  

Definition: An AV Pacer is a rhythm in which the heart rhythm is completely produced from the implanted pacemaker. The pacemaker is a device that delivers electrical stimulus which depolarizes the myocardium producing a mechanical contraction. The AV Pacer delivers an atrial impulse and a ventricular impulse that causes contractions respectively.

EKG Characteristics. Rate: Usually 60-100 beats per minute, but it can vary according to the rate at which it has been programmed. Rhythm: Pacemaker spikes are one atrial spike followed by a  P wave, then one ventricular spike followed by a wide QRS complex and T wave. P Wave: P waves may be present or absent or they may be dissociated from the QRS Complex. Usually wide. T Wave: Usually wider than usual.

Nursing Intervention: There are no nursing interventions for a normally functioning AV pace rhythm. Continue to monitor for failure to capture and failure to sense.

V Pacer: Ventricular Pacemaker

Definition: A ventricular pacemaker is a device that electronically depolarizes the ventricles and produces a mechanical contraction. Pacemakers are used when a patient's own heart is too slow, for example such as sinus arrest, sick sinus syndrome, symptomatic sinus brady, slow atrial fibrillation, ventricular standstill, mobitz II, and third degree heart block.

EKG Characteristics: Usually 60-100 beats per minute, but may vary according to the programed rate, or demand of the patient. Rhythm: There is one pacemaker spike before the QRS complex, initiating and followed by the QRS complex. P Wave: There may be a P wave present, absent, or it may be dissociated from the QRS complex depending upon the intrinsic rhythm.

Nursing Interventions: There are no nursing interventions for a normally functioning V paced rhythm. Continue to monitor for failure to capture and failure to sense.

Failure to Sense Pacemaker

Definition:  

failure to sense occurs when the pacemaker fails to sense the patient's own intrinsic rhythm and generates a pacer spike in the intrinsic rhythm and generates a pacer spike in the intrinsic rhythm's own QRS, absolute or relative refractory period of the T wave. The ventricular capture following the pacer spike may or may not occur. This can cause lethal arrhythmia. Failure to sense can be caused when the sensitivity setting is too low. 

EKG Characteristics: Rate: It may be regular or irregular. Rhythm: It can be any intrinsic rhythm in which the pacemaker spike is in the QRS, absolute, or relative refractory period of the T wave. QRS complex: It is within the normal limits of the intrinsic rhythm.

Nursing Intervention: Obtain the blood pressure, pulse, respiratory rate, Q2 saturation and notify the MD. Closely observe for ventricular tachycardia caused by failure to sense.

Failure of a Pacemaker to Capture

Definition: Failure to capture of a pacemaker happens when the output is too low, resulting in a failure to depolarize the ventricle, which causes an absence of a mechanical contraction of the ventricle, or no QRS. It can occasionally happen or be constantly happening which results in ventricular standstill and a pulse-less patient.

EKG Characteristics: Rate: It will be irregular due to the failure to produce QRS. Rhythm: The pacemaker spike or spikes will not have a QRS following them. P Wave: It may be absent or present. QRS Complex: A loss of a QRS behind a pacer spike.

Nursing Intervention: Should the loss to capture be occasional, one should get a blood pressure, pulse rate, respiration rate, and O2 saturation. This is to determine if the patient is tolerating the failure to capture. If the failure to capture is continuous, the patient will be pulse-less or have a symptomatic brady cardia. This can range from a situation in which edication may be needed, or a code situation in which one would follow hospital protocol. External pacing may be an option for this patient.

EKG Library:  http://sprojects.mmi.mcgill.ca/heart/egcyhome.html