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Patients With a Cardiovascular Implantable Electronic Device Undergoing Surgery
Case Synopsis
A 55-year-old man with a Medtronic Micra Leadless pacemaker (programmed VVIR) undergoes right total hip arthroplasty under general anesthesia. His past medical history is significant for atrial fibrillation and complete heart block. In the operating room the anesthesiologist intends to temporarily program the pacemaker to an asynchronous pacing mode (i.e., VOO) by applying a magnet. Before the start of surgery the nurse places the electrosurgery dispersive electrode (i.e., “bovie pad”) on the patient’s mid back. Initially the patient has a blood pressure of 155/80 mm Hg and a 100% ventricular paced heart rate of 70 beats per minute that does not appear to change after the magnet is applied. Several minutes into surgery and as soon as monopolar electrosurgery is used, the patient is asystolic.
Problem Analysis
Definition
Several million patients in the United States have an implantable pacemaker (PM) or implantable cardioverter-defibrillator (ICD), and hundreds of thousands of these cardiovascular implantable electronic devices (CIEDs) are implanted annually. The number of patients with a CIED will likely continue to increase because of population aging, new indications for these devices, and technologic advances. Consequently, anesthesia providers and other operative personnel should expect to routinely encounter CIED patients and care for them with increasing frequency.
Transvenous CIEDs consistent of a pulse generator that is typically implanted under the clavicle in a prepectoral pocket, and one to three leads inserted into the right atrium (RA), right ventricle (RV), and/or coronary sinus (CS). The device type (i.e., PM or ICD) and number and location of leads (RA, RV, CS) depends on the patient’s underlying pathologic condition(s) and indications(s) for implant. Table 16.1 summarizes general indications for CIED implant.
TABLE 16.1
General Indications for CIED Implant
Modified from Schulman PM, Rozner MA, Sera V, et al: Patients with pacemaker or implantable cardioverter-defibrillator. Med Clin North Am 97(6):1051-1075, 2013.
| Device Type | Left Ventricular Ejection Fraction (%) | QRS Duration (msec) | Heart Failure Class | Atrioventricular Block | Sinoatrial Node Dysfunction |
|---|---|---|---|---|---|
| Transvenous PM | >35 | Any | Any | Yes or no | Yes or no |
| Leadless PM | >35 | Any | Any | Yes | No |
| Transvenous ICD | ≤35 a | Any | I, II, III | Yes or no | Yes or no |
| Subcutaneous ICD | ≤35 a | Any | I, II, III | No | No |
| Biventricular PM (CRT-P) | ≤35 b | ≥150 c or ≥120 d | II, III, ambulatory IV e | Yes or no | Yes or no |
| Biventricular ICD (CRT-D) | ≤35 | ≥150 c or ≥120 d | II, III, ambulatory IV e | Yes or no | Yes or no |
a ICD sometimes indicated for secondary prevention even when left ventricular ejection fraction ≥35%.
b Most patients with left ventricular ejection fraction ≤35% receive an ICD.
e Class IV heart failure with no active acute coronary syndrome, no inotropes, and on guideline-directed medical therapy.
Transvenous CIEDs virtually always have an RV lead and often also have an RA lead. When indicated, a CS lead is additionally implanted to pace the left ventricle for patients with heart failure and an intraventricular conduction delay. In select patients this treatment, termed cardiac resynchronization therapy (CRT) or biventricular pacing, improves cardiac output, heart failure symptoms, and mortality risk.
In addition to delivering high-voltage therapy (i.e., shocks and antitachycardia pacing [ATP]), transvenous ICDs are capable of performing all of the functions of a transvenous pacemaker. In 2012 a subcutaneous ICD (S-ICD) that uses a subcutaneous electrode instead of traditional transvenous (or epicardial) leads was granted Food and Drug Administration (FDA) approval. Compared with transvenous ICDs, this device has more limited functionality; it has no permanent antibradycardia pacing capability and cannot deliver ATP. In 2016 the first percutaneously implantable leadless pacemaker was FDA approved, and another leadless pacemaker is likely to be available in the United States soon. These devices are substantially smaller than a conventional pacemaker, but their only available pacing mode is VVI(R) (i.e., they cannot pace or sense the atrium).
Perioperative CIED management is complex and challenging. Issues include confusing nomenclature (see Table 16.2 for the pacemaker code), evolving technology (i.e., leadless pacemaker, subcutaneous ICD), distinct and proprietary features that are often not standardized among device types and manufacturers (including variable responses to magnet application), and published literature that is often outdated or sometimes even incorrect.
TABLE 16.2
North American Society of Pacing and Electrophysiology/British Pacing and Electrophysiology Group (NASPE/BPEG) Generic PM Code (NBG) (revised 2002)
Modified from Bernstein AD, Daubert JC, Fletcher RD, et al: The revised NASPE/BPEG generic code for antibradycardia, adaptive-rate, and multisite pacing. North American Society of Pacing and Electrophysiology/British Pacing and Electrophysiology Group. Pacing Clin Electrophysiol 25(2):260-264, 2002.
| Position I | Position II | Position III | Position IV | Position V |
|---|---|---|---|---|
| Chambers paced | Chambers sensed | Response to sensing | Programmability | Multisite pacing |
| O = none | O = none | O = none | O = none | O = none |
| A = atrium | A = atrium | I = inhibited | R = rate modulation | A = atrium |
| V = ventricle | V = ventricle | T = triggered | V = ventricle | |
| D = dual (A + V) | D = dual (A + V) | D = dual (T + I) | D = dual (A + V) |
Additionally, electrical equipment such as monopolar electrosurgery (i.e., the “bovie”) frequently used during surgery produce electromagnetic interference (EMI) that might adversely affect CIED function and lead to CIED damage and patient injury. Common problems include pacing inhibition (potentially causing profound bradycardia or asystole in the pacing dependent patient) and inappropriate high voltage therapy (including shocks and ATP) in the patient with an ICD.
Recognition
The case synopsis highlights three potential causes of CIED-related complications: (1) electromagnetic interference (EMI), (2) incorrect electrosurgery dispersive electrode positioning, and (3) improper magnet use.
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