Chapter 33: Cardiac Pacing and Implanted Defibrillation

PURPOSE OF PROCEDURE

Cardiac pacing serves to maintain or restore myocardial depolarization and thus ensure adequate cardiac output. In the ED, pacing is performed therapeutically to correct an ongoing rhythm disturbance or in anticipation of the onset of a conduction problem with hemodynamic impact.¹

Indications for emergency pacing are listed in Table 33-1.

The indications for emergency cardiac pacing are found in chapter 18, "Cardiac Rhythm Disturbances."

GENERAL EQUIPMENT

All cardiac pacemakers deliver an electrical stimulus to the heart by electrodes that cause depolarization and subsequent cardiac contraction.² The modern pacemaker only stimulates the heart chamber if it does not recognize (sense) intrinsic electrical activity from that chamber after a selected time interval. Impulses are delivered to either the atria or ventricles, or to both.

Components of a cardiac pacemaker include:

• Pulse generator

• Electronic circuitry for sensing and pacing

• Lead system that connects the pulse generator to the electrode(s) and stimulates the myocardium

Relevant clinical details of these components are listed in Table 33-2.

TRANSCUTANEOUS PACING

Transcutaneous pacing is the emergency technique of choice because of its easy application. It uses externally applied electrodes to deliver an electric impulse directly across the intact chest wall to stimulate the myocardium. Transcutaneous pacers differ from standard pulse generators in several important ways. The pulse duration of the stimulating impulse is longer and the current output higher than in internal pacing. Muscle contraction (usually the ...