Transcutaneous pacing

Transcutaneous pacing (also called external pacing) is a temporary means of pacing a patient's heart during a medical emergency. It is accomplished by delivering pulses of electric current through the patient's chest, which stimulates the heart to contract.

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The most common indication for transcutaneous pacing is an abnormally slow heart rate. By convention, a heart rate of less than 60 beats per minute in the adult patient is called bradycardia. Not all bradycardias require medical treatment. Many athletes have a slow resting heart rate. In addition, the heart rate is known to slow down with age. It is only when bradycardia causes signs and symptoms of shock that it requires emergency treatment with transcutaneous pacing.

Some common causes of hemodynamically significant bradycardia include acute myocardial infarction, sinus node dysfunction and complete heart block. Transcutaneous pacing is no longer indicated for the treatment of asystole (cardiac arrest associated with a "flat line" on the ECG), with the possible exception of witnessed asystole (as in the case of bifascicular block that progresses to complete heart block without an escape rhythm).

During transcutaneous pacing, pads are placed on the patient's chest, either in the anterior/lateral position or the anterior/posterior position. The anterior/posterior position is preferred as it minimizes transthoracic impedance by "sandwiching" the left ventricle between the two pads. The pads are then attached to a monitor/defibrillator, a heart rate is selected, and current (measured in milliamps) is increased until electrical capture (characterized by a wide QRS complex with tall, broad T wave on the ECG) is obtained, with a corresponding pulse. Pacing artifact on the ECG and severe muscle twitching may make this determination difficult. It is therefore advisable to use another instrument (e.g. SpO2 monitor or bedside doppler) to confirm mechanical capture.

Transcutaneous pacing may be uncomfortable for the patient. Sedation should therefore be considered. Prolonged transcutaneous pacing may cause burns on the skin. It is meant to stabilize the patient until a more permanent means of pacing is achieved.

Other forms of cardiac pacing are transvenous pacing, epicardial pacing, and permanent pacing with an implantable pacemaker.

References

1. Urden, L., Stacy, K., and Lough, M. Thelan's Critical Care Nursing: Diagnosis and Management. Fourth Edition, Mosby, 1998. ISBN 0-323-01461-5
2. Handbook of Emergency Cardiovacular Care for Healthcare Providers. Editors Hazinski, M., Cummins, R., and Field, J. 2004. ISBN 0-87493-448-6