Automatic Implantable Cardiovertor Defibrillator Case File

Automatic Implantable Cardiovertor Defibrillator Case File

Lydia Conlay, MD, PhD, MBA, Julia Pollock, MD, Mary Ann Vann, MD, Sheela Pai, MD, Eugene C. Toy, MD

Case 19

A 59-year-old man with a left indirect inguinal hernia was admitted for left-sided herniorrhaphy. He had undergone a coronary artery bypass surgery (CABG) 6 months ago, and an automatic implantable cardioverter defibrillator (AICD) was implanted 4 months ago because of recurrent episodes of ventricular tachycardia (VT) unresponsive to amiodarone therapy.

The patient’s medical history is remarkable for one episode of an irregular cardiac rhythm 2 months ago that responded to activation of the AICD. He denies any other episodes since that event. He also notes a history of hypertension, which is treated with lisinopril. He denies symptoms of angina, dyspnea on exertion, or paroxysmal nocturnal dyspnea. He has no history of complications with previous anesthetics or a family history of problems with anesthesia. He has no allergies to medications, does not smoke or consume alcohol.

Echocardiography revealed a left ventricular ejection fraction (LVEF) of 25% with trace mitral regurgitation. The chest x-ray showed an AICD in situ and an enlarged heart size. The hematological, liver, and kidney function tests were normal. On examination, the patient weighs 180 lb and is 5 ft, 10 in tall. His neck appears to be normal and mobile. He opens his mouth without difficulty, and with his head extended and tongue protruding, his uvula is completely visible. His lung and cardiac examination is normal.

➤ How are AICD devices managed in patients undergoing surgery?

➤ What factors are important to address preoperatively in the patient with an AICD?

➤ What are the special concerns applicable to patients with an AICD in the operative setting?

ANSWERS TO CASE 19:

Automatic Implantable Cardiovertor Defibrillator

Summary: A 59-year-old man with a left indirect inguinal hernia admitted for a left-sided herniorrhaphy. He has a history of recurrent episodes of ventricular tachycardia (VT), which has been treated with an AICD device.

➤ AICD in surgery: An AICD is disabled before the start of surgery using a noninvasive programming device. It is reprogrammed (reactivated) in post-anesthesia care unit (PACU) postoperatively.

➤ Important factors: Most patients with an AICD have poor left ventricular function, with a low ejection fraction and coexisting systemic disease. Primary management of the patient includes evaluation and optimization of his coexisting disease, and evaluating the defibrillator. Most patients with an AICD carry a wallet-sized card which lists the specific type of device. If not already easily accessible in the patient’s medical record, this information should be added. The AICD is also interrogated preoperatively to determine whether it is operating properly, whether it has fired and if so, what conditions triggered the firing. This can provide useful information for the patient’s intraoperative management, when the device will be turned off. At this time, arrangements should also be made for the AICD to be turned off prior to the surgery, and back on in the PACU after the procedure.

➤ Special concerns: Ensure the safety of the patient and of the operating room personnel. Electromagnetic interference from the electrocautery or from external defibrillation can affect the AICD. If unintentionally left in the activated mode, sudden movements such as those occurring during positioning, or muscle fasciculations such as with succinylcholine can cause the device to fire inappropriately, potentially posing a hazard to operating room personnel and the patient.

ANALYSIS

Objectives

1. Become familiar with the preoperative care of a patient with an AICD.

2. Understand how AICDs are managed in the perioperative setting.

3. Understand the special intraoperative concerns in patients with an AICD.

Considerations

An inguinal herniorrhaphy is readily amenable to repair under a regional anesthetic approach such as a spinal or a peripheral field block. Because of this patient’s left ventricular dysfunction and the type of surgery, an epidural anesthetic was chosen. An epidural has the advantage of administering multiple doses of an anesthetic as opposed to a single dosed spinal, allowing the level of sensory block to be carefully titrated so that it is sufficient, without being too high.

The patient’s AICD was turned off prior to the procedure, and an external pulse generator and external pacing were kept ready in the operating room (OR). External counter shock paddles were also checked and brought into the operating room, so they were immediately available. The monitoring during surgery included a continuous two-lead electrocardiogram (lead II and V5), a pulse oximeter, and a noninvasive arterial pressure monitor. An epidural catheter was inserted, and after a test dose, ropivacaine was injected and a T10 sensory block obtained. Oxygen was given via nasal prongs at 4 L/min. The patient did not require any sedation. His AICD was re-activated in the PACU postoperatively.

APPROACH TO

Automatic Implantable Cardiovertor Defibrillator

Automatic internal cardiac defibrillation has significantly reduced the risk of sudden cardiac death in patients with known life-threatening ventricular arrhythmias. The ability of an AICD to provide therapy within 5 to 15 seconds of arrhythmia detection allows a defibrillation success rate approaching 100%.

An ICD system consists of a pulse generator and leads for detection and therapy of tachyarrhythmias. It may provide antitachycardia, antibradycardia pacing, synchronized or nonsynchronized shocks, telemetry, and diagnostic storage. Many devices use adaptive rate pacing to modify the pacing rate for changing metabolic needs. The AICD batteries contain up to 20,000 J of energy. Most AICD designs use two capacitors in series to achieve the maximum voltage for defibrillation. High energy discharges of 10 to 40 J, delivered asynchronously are used to treat ventricular fibrillation (VF). Cardioversion with energy exceeding 2 J results in skeletal and diaphragmatic muscle depolarization. This is painful to the conscious patient, although if sleeping or syncopal, the patient may be unaware that the device has fired.

AICDs terminate VF successfully in 98% of cases. Supraventricular tachycardia (SVT) remains the most common etiology of inappropriate shock therapy. According to one report, antitachycardia pacing successfully terminated spontaneous VT in greater than 90% of cases. Approximately 20% of AICD patients require pacing for bradycardia, and 80% of those requiring pacing benefit from dual chamber pacing. ICD devices are placed adjacent to the heart via either a central transvenous route or epicardial location.

For 25 years, the accepted method for ensuring appropriate function of an AICD has included the intentional induction of ventricular fibrillation (VF) to ensure that the ICD will sense, detect, and defibrillate VF. At the time of implantation, this method is used to determine the smallest possible shock that will successfully manage the arrhythmia. Occasionally, these “AICD checks” cause complications, and rarely, death. The risks of implant testing include those related to VF (circulatory arrest, albeit brief), those related to shocks of the myocardium, or the combination of circulatory arrest and shocks. In general, the poorer a patient’s myocardial function, the slower he or she will recover from the induced arrest. With better understanding of defibrillation coupled with today’s improved technology, and use of AICDs for primary prevention of ventricular tachycardia (VT) or VF, some question the need for either defibrillation testing or any assessment of defibrillation efficacy at ICD implantation. However, the device is to be periodically checked to determine that its leads are functioning appropriately, and the clinical parameters under which it has fired are appropriate.

For a pacemaker-dependent patient undergoing surgery, the AICD should be reprogrammed to an asynchronous mode, the tachycardia sensing and adaptive rate pacing functions turned off, and alternative facilities for pacing should be available. Sudden movements such as fasciculations following succinylcholine, or sudden movements during positioning may otherwise trigger the device to inappropriately fire.

The use of electrocautery in the presence of a functioning AICD is particularly hazardous. If the AICD is inadvertently left on during surgery, electrocautery treatment for hemostasis during surgery may inappropriately signal the AICD that the patient has developed a malignant dysrhythmia. The

detection of the “false rhythm abnormality” by the AICD would trigger the delivery of a therapeutic shock. Even worse, electrocautery has been associated with the reprogramming of the AICD to a ventricular rate of 300, with disastrous results.

In patients with an AICD, the cautery grounding tool should be placed as far as possible from the AICD (at least 15 cm), and in such a way that the pulse generator and the leads are not in the current pathway between the device and the electrocautery. Only the lowest possible energies and short bursts of cautery should be used to minimize adverse effects of electromagnetic interference. If electrocautery is to be used within 15 cm of AICD, a compatible programming device and a pulse generator should be accessible in the operating room. In the event that external defibrillation is required, the pads or paddles should be placed 10 cm from the pulse generator and implanted electrodes. The use of sutures instead of cautery, or bipolar instead of unipolar cautery can also be employed to minimize the risk of an AICD malfunction. In all cases, the AICD is reactivated after the electrocautery is no longer required.

A magnet placed over the AICD will inactivate the defibrillator function (not the pacemaker function) appropriately during surgery. When the magnet is removed, normal function returns. However, use of a magnet should not be substituted for inactivating the defibrillator device prior to the procedure, and

reprogramming it afterwards.

The perioperative management of patients with a cardiac rhythm management devices is as complicated and constantly evolving as its corresponding field of technology. Understanding of the basic principles as to how these devices function, and how to make use of available resources such as consulting the provider responsible for device follow-up or even the device manufacturer, is strongly encouraged to make anesthesia safer for these high-risk cases.

Comprehension Questions

19.1. A 72-year-old man presents for a left colon resection for cancer. He has an AICD which was placed 2 years prior to this admission. The preoperative visit confirms that the patient’s medical condition is optimized, an ECG is performed, and the device is interrogated to determine its activity history. Just prior to surgery, which of the following actions is appropriate?

A. Have a pacemaker/AICD technician available in the operating room to reprogram the device if needed.

B. Deactivate the defibrillator.

C. Place external pacing pads.

D. Put a magnet over the pacemaker/defibrillator.

19.2. Optimal perioperative management of a patient with an AICD includes which of the following?

A. Placing the electrocautery pad (“grounding”) on any large surface area of the patient’s body is appropriate.

B. Reactivating the AICD following a surgical procedure is required.

C. The immediate availability of external pacing or defibrillation equipment is not necessary.

D. The patient may have his AICD turned off the day prior to surgery at his primary care physician’s office.

19.3. Muscle fasciculations following succinylcholine, sudden patient movement such as may occur in positioning, and the use of electrocautery may result in which of the following?

A. Cause a deactivated defibrillator to fire in the operating room.

B. Cause an active defibrillator to fire inappropriately in the operating room.

C. Necessitate the use of a magnet.

D. Interfere with the delivery of a shock if it is needed.

ANSWERS

19.1. B. Immediately prior to the procedure, the AICD’s defibrillator mode is deactivated, and it is reactivated immediately post-op in the PACU. Alternatively, and if compatible with the type of defibrillator, a magnet may be placed over the defibrillator to temporarily inactivate it. However, some AICD’s may be reprogrammed in an uncontrolled fashion by a magnet, leading to rapid ventricular rate and catastrophe. It is not necessary to place external pacing pads, or to have a pacemaker/ AICD technician available in the operating room.

19.2. B. The patient may have his AICD turned off at the hospital, immediately prior to surgery. External pacing or defibrillation equipment must be immediately available. Placing the electrocautery pad (“grounding”) on any large surface area of the patient’s body is appropriate, provided the pad is at least 15 cm away from the AICD, and that it is placed in such a way that the pulse generator and the leads are not in the pathway between the device and the electrocautery. Reactivation and evaluation of the AICD following the procedure is required.

19.3. B. Muscle fasciculations, sudden patient movement, and electrocautery may trigger an active AICD to fire inappropriately in the operating room. A magnet placed over the AICD inactivates the defibrillator function, or reprograms the defibrillator in an uncontrollable fashion.

Clinical Pearls

➤ The preoperative evaluation of a patient with an AICD includes an evaluation and optimization of the underlying heart disease and left ventricular function as well as determination that the AICD is functioning well.

➤ The perioperative monitoring of such a patient is mainly guided by the degree of left ventricular function, and the type of surgery.

➤ The AICD is deactivated prior to the procedure and reactivated afterward.

➤ An external cardiac defibrillator should always be available in the operating room, with the external defibrillator pads in place so that an effective cardioversion or defibrillation can be performed without interfering with the surgical field.

➤ Any electromagnetic force can interfere the functioning of the AICD.

➤ It is essential to monitor patients with an AICD continuously in the postoperative period until the vital signs are stable.

References

Practice Advisory for the perioperative management of patients with cardiac rhythm devices: Pacemakers and implantable cardioverter-defibrillators. Anesthesiology. 2005;103:186-198.

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