Both the right and left ventricles are stimulated with transcutaneous pacing. The atria are frequently stimulated in a retrograde fashion; this produces atrioventricular dyssynchrony which decreases cardiac output by about 20% from the loss of an atrial kick. Although a patient with symptomatic bradycardia will experience an increase in cardiac output and mean arterial pressure because of pacing, the cardiac output will not usually return to pre-bradycardia levels. This 20% cardiac output decrease, however, will usually be well tolerated unless left ventricular function is severely diminished.3

Steps for transcutaneous pacing

1. IF time and patient condition permits, provide IV analgesia (e.g. fentanyl) and/or IV anxiolysis (e.g. midazolam).

2. Apply pads in either anterior-lateral (AL) configuration (to the patients right upper chest wall and left lower chest wall, mid axillary line) or in an anterior-posterior (AP) fashion (anterior lower left chest wall and posteriorly under the left scapula).

a. The AL configuration is often used in emergent situation as you do not have to roll the patient, however the AP fashion supports a more appropriate vector for electrical conduction through the heart should defibrillation or cardioversion be required and has been found to produce mechanical capture (described below) at a lower energy output.4

b. Good skin-to-electrode lowers transthoracic impedance and improves electrical capture of the heart. Hair should be clipped or removed prior to pad placement and skin should be dry.

3.Turn device to “pacing mode” and notify the Aeromedical Evacuation (AE) MCD and/or other appropriate teams (e.g. Boom Operator, Load Master, Front End crew)

4. Apply ECG electrodes, if necessary, to evaluate underlying rhythm.

5. Appropriately set the desired heart rate, usually at least 30 beats above native rhythm, and typically between 60-80 bpm.

6. Starting at 70 milliamperes (mA) slowly increase the device’s current output in 10 mA increments until you see electrical capture, reflected on the devices ECG rhythm.

a. Some devices will recognize pacing spikes if toggled on.

7. Confirm mechanical capture by palpating a pulse.

8. Once pacing is captured and confirmed, set output to 5-10 mA over the capture threshold.

9. Re-evaluate patient’s circulation and overall condition

10. If analgesia and anxiolysis has not already been provided, administer if appropriate as transcutaneous pacing is considerably uncomfortable and usually not well tolerated in the awake patient.

Transcutaneous pacing points to consider

- Pacer pads should be replaced every 24 hours due to accumulation of moisture and sweat which impedes capture
- Higher thresholds are sometimes noted in patients with concomitant hypoxemia, acidosis, pulmonary emphysema, pericardial effusions, significant musculature, obesity, or medications (e.g. antiarrhythmics, beta-blockers, calcium channel blockers)
- Consider prophylactic intubation prior to flight if the patient is already being transcutaneously paced, to facilitate patient tolerance

Trouble shooting transcutaneous pacing failure

1. Intermittent loss of capture must be addressed urgently, as sudden and complete loss of capture will likely result in hemodynamic instability or collapse. Consider in-flight diversion if possible or a communication patch to a Cardiologist
2. Increase the mA until electrical (i.e. ECG tracing) and mechanical capture (i.e. pulse) are confirmed.
3. Make sure the pacing electrodes are well adhered to the skin and correctly placed (i.e. not dislodged)
4. Move the anterior pacing electrode to another location on left precordium.
5. Treat any acidemia and/or hypoxemia present.
6. Consider an infusion of a chronotropic agent if the above steps fail to achieve capture