Chapter 4: DEVICES

DEVICES

TRANSCUTANEOUS PACEMAKER

Benjamin C. Smith III

Indications

Symptomatic Bradyarrhythmias

Unstable bradycardic patients who do not respond to a trial of atropine should be considered candidates for transcutaneous pacing. One important exception is hypothermia-induced bradycardia, where pacing may induce more unstable rhythms.

Recalcitrant Tachyarrhythmias

Patients who have tachyarrhythmias recalcitrant to one or more pharmacological interventions can be considered for transcutaneous overdrive pacing. In particular, patients with torsades recalcitrant to magnesium may respond to overdrive pacing. Use caution, however, overdrive pacing ventricular dysrhythmias can induce ventricular fibrillation.

Technique

Pacer pads preferably should be placed on the left anterior and posterior chest wall, or the less desirable left and right anterior chest walls. To enable the defibrillator to sense the patient’s intrinsic rhythm, the three-pacer electrocardiogram (ECG) leads should be placed on the patient’s chest.

The pacing function should be enabled at a rate of 70 to 80 beats per minute when treating bradycardia, and the current (in milliamperes, mA) should be increased until 100% electromechanical capture is verified. Mechanical capture should be verified by palpating a coincident central pulse, verifying distal flow with Doppler ultrasound, or performing a bedside echocardiogram. Transcutaneous pacing causes muscle twitches of the thorax and upper extremities that can cloud the reader’s visualization of ventricular capture on the rhythm strip, so electrical capture alone is insufficient to verify cardiac stimulation. Demand pacemaker mode should be used unless significant artifact is present that falsely inhibits pacing. This mode is usually on by default and senses the patient’s intrinsic rhythm, inhibiting pacing unless the patient’s ventricular rate drops below the set threshold.

When treating recalcitrant tachyarrhythmias, the pacer mode should be in “nondemand” mode. The rate should be set at, or just above, the patient’s intrinsic ventricular rate and the current should be increased until mechanical capture is obtained. The pacer rate can then slowly be lowered to a normal level over several minutes.