CHAPTER 216 Temporary Pacing
For various reasons, primary care clinicians may need to perform temporary cardiac pacing. Several types of pacing are available, with the primary purpose being to maintain circulatory stability until either the situation resolves or a permanent pacemaker can be installed. This chapter covers external (transcutaneous) and internal (transvenous) emergency ventricular pacing. Transesophageal pacing, usually limited to atrial pacing, and transmyocardial transthoracic pacing are beyond the scope of this chapter.
The basic uses for temporary cardiac pacing are as a standby should the patient become symptomatic or complete heart block occur and as a way to increase heart rate during periods of symptomatic bradycardia. In addition, overdrive pacing may be used to terminate arrhythmias (e.g., sustained supraventricular or ventricular tachycardia); atrioventricular (AV) sequential pacing may be used to prevent arrhythmias. “Medicinal” pacing (e.g., atropine, isoproterenol) is also available, with advanced cardiac life support (ACLS) guidelines being helpful to guide its use. Overall, the indications for temporary pacing can be divided into therapeutic, prophylactic, and diagnostic categories. For the purposes of this chapter, only therapeutic and prophylactic pacing are covered.
External (Transcutaneous) Pacing
Most defibrillator/cardioversion units are now capable of performing external transcutaneous pacing. Modern transcutaneous pacing units represent a major improvement over the units first developed in the 1950s. Those units frequently inflicted severe chest and back muscle stimulation and discomfort, and they often left burns on the skin. At least one suicide was recorded of a pacer-dependent patient who removed the leads from one of the older units to “end the pain.” In the 1960s, transcutaneous pacing was largely replaced with the newly available transvenous pacing.
Subsequent discoveries rejuvenated transcutaneous pacing, especially since the 1980s. Researchers found that increasing the pulse duration from 2 to 20 milliseconds (msec) not only increased the safety of transcutaneous pacing (reduced the risk of ventricular fibrillation), but reduced the required current. Reduced current meant less pain and fewer burns. The development of electrodes with a larger surface area also decreased the pain and risk of tissue burn. Use of larger electrodes allows for a reduction in the current density, or the amount of current penetrating per square unit of skin. These developments have resulted in more frequent use of transcutaneous pacing, especially on a standby basis, and consequently decreased the use of transvenous pacing.
One of the shortfalls of external pacing, even with today’s somewhat sophisticated equipment, is the difficulty of achieving capture in about one fifth of patients. Reasons for difficult or ineffective external pacing include increased intrathoracic air (such as barrel chests or chronic obstructive pulmonary disease), a large pericardial effusion or tamponade, recent thoracic surgery, obesity, and the improper placement of electrodes. Increased output for capture may be required in these individuals. Another shortfall is that it is rare for patients not to complain of some pectoral muscle stimulation. Although most patients rate the discomfort as mild or moderate and easily tolerable, approximately one third of patients rate the pain as severe or intolerable. Therefore, analgesics, narcotics, or sedatives should be considered when using the external pacer, especially if the required mean current for capture is 50 milliamperes (mA) or more (a common threshold).
Because the high voltages required for external pacing produce significant muscle twitching, conventional electrocardiographic (ECG) monitors and recorders are useless. To provide decent tracings despite the large pacer spikes and their aftermath, routine ECG monitors must be equipped with an output adapter. Fortunately, most external pacer units come equipped with a monitor capable of filtering the spikes. Without an adequate ECG monitor, treatable ventricular fibrillation could be masked by the large pacing spikes, with disastrous results. This is one of the grave risks of transcutaneous pacing.
Indications
note: Preliminary trial of pacing should be performed to ensure that capture is achievable and that pacing is tolerated by the patient.
Contraindications
All of the contraindications are relative.
Equipment
note: Most defibrillator/cardioversion units contain a transcutaneous pacing unit as an integral part of the system.
Preprocedure Patient Preparation
If time allows, explain the purpose and benefits of the procedure as well as the risks of not performing the procedure to the patient or representative. The patient should know what to expect, the sensations he or she may experience (e.g., muscle contractions, a slight tingling, burning or shocking sensation), and that although this may be uncomfortable, the majority of patients tolerate it well. Explain what will be done to minimize the discomfort (e.g., analgesic, sedation). A signed consent is not required to perform this procedure; however, implied consent should be documented in the medical record (e.g., “the risks and benefits have been explained to the patient, who agrees with having the procedure”).
Any dirt or debris should be cleaned from the skin; however, avoid using any flammable liquids such as alcohol. Patients with significant body hair may need to be shaved (unconscious patients) or the hair clipped or trimmed (conscious) to ensure good skin–electrode contact. Shaving should be avoided, if possible, in the conscious patient because any nicks or lacerations can increase the discomfort and skin irritation during pacing.
Technique

Figure 216-1 External (transcutaneous) pacing. The anterior electrode is placed at the apex (A), which is to the left of the sternum over the point of maximal impulse, or over the septum (B), which is the V3 position. The posterior electrode is placed to the left of the spinal column on the back, directly behind the anterior electrode.
(Adapted from Dahlberg ST, Benotti JR: Temporary cardiac pacing. In Rippe JM, Irwin RS, Alpert JS, Fink MP [eds]: Intensive Care Medicine, 2nd ed. Boston, Little, Brown, 1991.)
note: The increased use of external pacers has surely reduced the number of prophylactic internal pacers placed. However, in nontransient situations, external pacing is always a temporary measure until an internal pacer (probably transvenous, as described in the next section) can be placed.
Internal (Transvenous) Pacing
Clinicians who may need to insert a transvenous pacemaker should be familiar with the equipment and its use before needing it in an emergent situation. There are usually two lights, a sense indicator light, which is illuminated when a cardiac impulse is sensed, and a pace indicator light, which is illuminated whenever a pacing stimulus is generated. There is also usually a button to test the battery to ensure adequate voltage to operate the pacemaker generator. Although newer models have digital displays and more sophisticated pacing options, they function basically the same as older models.
Indications
Therapeutic
note: For tachyarrhythmias of less than 150 bpm, neither immediate cardioversion nor an immediate pacer is necessary.
Contraindications
Contraindications include those listed in Chapter 211, Central Venous Catheter Insertion, and those listed previously for external pacing. Other contraindications include the following:

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