Chapter 15. Anesthesia in the Electrophysiology and Catheterization Laboratories

• The number of diagnostic and therapeutic interventions performed outside of the operating room requiring anesthesia services has increased exponentially over the past 10 years. Anesthesiologists of all varieties are engaged in doctor's offices, ambulatory surgery centers, and endoscopy suites. Although cardiac anesthesiologists are most often involved with highly invasive heart surgery procedures, they too find an increasing part of their practice spent outside of the operating theatre. Evermore complicated catheter-mediated procedures are completed in ever sicker patients in the cardiac catheterization and electrophysiological laboratories. Common procedures include: diagnostic coronary angiography, coronary stenting, percutaneous closure of septal defects, electrophysiology (EP) studies, arrhythmia ablations, and implantations of pacemakers/cardioverter defibrillators. Also, as was previously discussed, catheter-based valve replacements and repairs are also being performed.

Cardiac EP is the medical specialty devoted to the diagnosis and treatment of abnormal heart rhythms. It involves diagnostic electrophysiology testing, radiofrequency catheter ablation, and implantation of antiarrhythmic devices such as pacemakers and cardio-defibrillators.

Advanced medical research, new technology, an aging population, and the prolonged survival of very ill patients have added to the complexity of procedures performed and management of patients requiring EP therapies.1-4 The anesthesiologist is frequently consulted in both the cardiac catheterization and electrophysiology laboratories to help manage patients with severe coronary, valvular, and vascular diseases. Patients can experience hemodynamic perturbations secondary to arrhythmias, poor baseline ventricular function, or procedurally related iatrogenic myocardial perforation and tamponade. Anesthesiologists are called upon not only to maintain patient comfort during these procedures but also to be available to resuscitate the patient should hemodynamic or airway complications present.1 Consistent guidelines have yet to be established regarding the nature of procedures and the complexity of patients which warrant the involvement of the anesthesia team.

Procedures that might involve the anesthesia team include:

1. Coronary artery stenting is used in the treatment of ST-elevation myocardial infarction, in-stent restenosis, stenting of saphenous vein grafts, and treatment of chronic coronary artery occlusions. Most of these procedures are performed under moderate sedation given by the nursing staff of the catheterization laboratory. Involvement of the anesthesia team typically is requested when the patient is hemodynamically unstable or there is a need for emergent airway management.5

2. Percutaneous ventricular assist devices (VADs): Until recently, intra-aortic balloon contrapulsation with inotropic support was the main therapeutic option for supporting the failing ventricle. Implantable ventricular assist devices have been and are being used now as "bridge to recovery or to transplantation" for the failing ventricle. Implantable VADs are placed in the cardiac surgery operating room. However, during the past few years a number of percutaneous designs have appeared which can be placed in the catheterization laboratory to provide emergent support for the failed heart.

   Two percutaneous ventricular assist devices (PVAD) that can be placed in the cardiac catheterization laboratory are the TandemHeart (Cardiac Assist, Inc., Pittsburg, PA) and the Impella Recover LP 2.5 and 5.0 (Abiomed Inc., Danvers, MA). Both of these devices can be placed with moderate sedation; however, general anesthesia is preferred to secure the airway and to facilitate the use of TEE should it be required during PVAD placement.5

3. Percutaneous closure of septal defects: Increasingly closure of atrial septal defects has been accomplished through the placement of a variety of catheter-delivered occluding devices. A similar device is under development to treat postmyocardial infarction ventricular septal defects. Most of those devices are placed under general anesthesia with transesophageal echocardiography guidance for device positioning.

4. Percutaneous valve repair and replacement: Percutaneous valvuloplasty or valvotomy has been performed for decades, but new interventions now focus not only on opening stenotic valves but also on actual percutaneous valve repair and replacement.

The introduction of nonsurgical catheter-based approaches to the management of valvular disease is in a phase of rapid development. Initially, the patient population considered suitable for percutaneous aortic valve replacement was that thought high risk for surgery or nonsurgical candidates with significant comorbidities. Although early mortality with this approach was high, rapid improvements continue to better the patient outcomes. The initial approach to the aortic valve was accomplished via passage of the catheter-based valve from the femoral vein to the right atrium and then trans-septally to the left atrium, left ventricle, and into the aortic root. As this approach has yielded poor outcomes in a significant number of patients, more recently the valve has been placed into the aortic position via the femoral artery, or antegrade, via a small chest incision, and puncture of the left ventricular apex.6

Catheter-based approaches to the mitral valve are quite complex as there is no single therapeutic approach for repair for every etiology of mitral regurgitation.7

Catheter-based treatments for mitral regurgitation include clipping together the anterior and posterior leaflets of the mitral valve at the midpoint yielding a double-barrel mitral orifice. Alternatively, a device can be placed in the coronary sinus to tighten the mitral annulus. These procedures are completed using echocardiographic and fluoroscopic guidance.

Indications for EP studies include:

1. Determine the precise mechanism of tachyarrhythmia.

2. Perform catheter ablation for treatment of a medically refractory arrhythmia.

3. Evaluate the need for placement of implantable defibrillators in patients with or at risk of life-threatening ventricular arrhythmias.

4. Risk stratification for sudden cardiac death syndrome (SCD).

EP procedures include percutaneous catheter-based therapy/ablation for atrial and ventricular arrhythmias, pacemaker, and/or defibrillator implantation.

Electrophysiology studies are performed in specialized EP laboratories, equipped with a fluoroscopy (x-ray) machine. During an EP study peripherally inserted catheters are advanced into the heart to identify areas of altered cardiac electrical conduction.

Intracardiac measurements of electrical activity are recorded at different parts of the heart at baseline or following administration of chronotropic agents.

During an EP procedure, two to four temporary electrode catheters are inserted and positioned into the heart chambers (with the x-ray guidance) via a large vein either in the groin or in the neck.

These wires permit electrical stimulation and recording of electrical responses. An important part of the EP study is to induce the arrhythmia in order to locate the abnormal circuit.

Treatment options for cardiac arrhythmias include the following2,3:

1. Antiarrhythmic drug therapy

2. Catheter ablation therapy

3. Implantable device therapy (pacemakers, defibrillators)

The decision of choosing one option over another depends on the severity of cardiac arrhythmia and the impact of therapy options upon the patient's quality of life.

Catheter-Based Ablation

Until 20 to 25 years ago, the only viable treatment for most arrhythmias was medication. On rare occasions open-heart surgeries with mapping and ablation or high-energy direct current internal ablation were performed.

In the 1990s, radiofrequency (RF) catheter ablation was developed. Catheter ablation has evolved over the past two decades to become first-line therapy for many cardiac arrhythmias. Catheter ablation often eliminates the need for chronic drug therapy and can result in significant long-term cost savings.8,9

Tachyarrhythmias amenable to RF catheter ablation include:

• AV nodal reentrant tachycardia
• AV reciprocating tachycardia (WPW syndrome)
• Some forms of atrial tachycardia and flutter
• Selected patients with paroxysmal atrial fibrillation (AF)
• Some of the ventricular tachycardias

Catheter ablation in the setting of reentrant supraventricular tachycardia (SVT) and atrial flutter is associated with both low complication and high success rates. It can be safer, more effective, and less expensive than chronic medical therapy for all age groups. Catheter ablation has expanded to include the treatment of more complex arrhythmias such as atrial fibrillation (AF), unstable ventricular tachycardia (VT), and epicardial VT.

Catheter-based EP studies first identify the area responsible for arrhythmia generation. Using radio frequency (RF) energy the small focus of heart tissue responsible for initiating the arrhythmia is ablated. Catheter-based ablation is limited by: inability to precisely localize (map) the area responsible, difficulty in positioning the catheter tip at the critical site, or inability to deliver adequate energy to the target.

Catheter ablation procedures are tripartite by nature involving:

1. Placement of electrode catheters inside the heart through veins and arteries

2. Performance of an EP study to detect the mechanism of arrhythmia and localize the responsible area

3. Performance of the actual RF ablation to destroy the target tissue

Atrial fibrillation is one of the more common arrhythmias successfully treated by RF catheter ablation and is the most common sustained cardiac rhythm disturbance associated with an increased risk of stoke, heart failure, and death.

The pulmonary veins (PV) have been demonstrated to play an important and mischievous role in generating atrial fibrillation. Because of their critical role in AF, a variety of surgical and catheter ablation techniques are used to isolate the PV within the left atrium.10

Before the procedure, computerized tomography (CT) scan of the heart with three-dimensional reconstruction is performed in order to define the anatomy of the pulmonary veins.

The procedure involves positioning a catheter in the right atrium via the femoral vein. The patient is anticoagulated with heparin and transeptal catheterization of the left atrium is achieved after systemic anticoagulation to a target activated clotting time (ACT) of 250 to 350 seconds. Angiograms of the four pulmonary veins are performed. Once identified, pulmonary vein isolation is performed by the delivery of RF energy at the pulmonary vein's ostium for a target temperature of 52 °C and a maximum power of 30 to 35 W for 30 to 45 seconds. Elimination of all ostial pulmonary vein potentials and complete entrance block into the pulmonary veins are considered indicative of complete PV electrical isolation.

Potential limitations of PV ablation include technical failure due to variations in anatomy and difficulty in mapping the focus. The procedure may result in complications, including pulmonary vein stenosis (up to 45%), hemopericardium (1%), and chronic thromboembolic events (1%).9,10

Most ablative procedures can be performed with moderate sedation and standard monitoring. However, some of the percutaneous ablation procedures can be very lengthy (6-8 h). Also, coughing or partial airway obstruction with abdominal paradoxical motion can interfere with the procedure, so moderate to deep sedation or even general anesthesia with controlled respiration might be required. In patients with compromised ventricular function, inotropic/pressor support with invasive monitoring might be necessary.

Implantation of Cardioverter Defibrillators (ICD/Biventricular Pacemakers)

The placement and testing of ICDs has increased exponentially in recent years, mostly secondary to an expanded list of indications. Biventricular pacing and cardiac resynchronization therapy (CRT) permits better timing of global left ventricular depolarization and improves mechanical contractility and mitral regurgitation in selected patients with heart failure. Many clinical trials have shown that CRT results in improved quality of life,11 lower mortality rate, and improved functional class in heart failure patients.12

Standard indications for ICD therapy include4,12,13:

• 1. Primary prevention of sudden cardiac death (SCD) for patients who have not yet sustained a clinical event, but who are at risk for SCD:
  • a. Prior myocardial infarction with left ventricular ejection fraction (LVEF) of less than 35% (by cardiac imaging, echocardiography, nuclear study, or cardiac catheterization)
  • b. Nonischemic cardiomyopathy (CMP) with LVEF less than 35%
  • c. Hypertrophic cardiomyopathy and risk for sudden cardiac death (SCD)
  • d. Primary electrical disorders (long QT, Brugada syndrome)
• 2. Secondary prevention of SCD for patients who have already had a clinical event:
  • a. Survived cardiac arrest due to ventricular tachycardia (VT) or ventricularfibrillation (VF)
  • b. Sustained VT
  • c. Syncope in the setting of high-risk disorders
• 3. Cardiac resynchronization therapy through biventricular pacing in selected patients5,11,14:
  • a. CHF class III-IV
  • b. LVEF less than 35%
  • c. QRS duration more than 120 milliseconds

The majority of these devices are placed percutaneously with mild to moderate sedation; however, the placement of a biventricular pacemaker can be a lengthy procedure. Testing of the device (defibrillating threshold [DFT] testing) requires deep sedation or general anesthesia to keep the patient comfortable. Particular attention should be paid to patients undergoing biventricular lead placement for CRT. They typically have very poor cardiac function, so sedation must be titrated carefully, since these patients may poorly tolerate deep sedation or general anesthesia.

Lead Extraction

As more patients are having pacemakers and ICDs implanted, the need for explantation of these devices is likewise increasing. Pacemaker leads can fracture, insulations can become worn, and leads can dislodge or become infected. All of these complications require lead extraction. Overtime pacemaker leads become attached to the heart and tissue grows around them. Consequently, they simply cannot just be pulled out easily and their removal has the potential for morbidity and mortality. Powered sheaths have been introduced to facilitate the removal of leads which are adherent to the superior vena cava, tricuspid valve, or right ventricle. These powered sheaths burn through scar tissue with either laser or electrocautery. Many patients requiring lead extraction have low ejection fractions, coronary artery disease, and rhythm disturbances. Extracting the lead can be very difficult even with laser or electrocautery and can cause severe hypotension, blood loss, tamponade, and arrhythmias.1,15

Short Procedures: Cardioversion, ICD Testing Noninvasive Programmed Stimulation-Nips

Elective cardioversion is a short procedure performed under brief general anesthesia for the treatment of cardiac arrhythmias. It is frequently performed in areas outside the operating room often at the patient's bedside in the ICU or postanesthesia care unit. Before administering general anesthesia for elective cardioversion, it is paramount to ensure the ability of providing full resuscitation and airway management. In patients who are not anticoagulated a TEE examination is performed prior to cardioversion to examine the left atrial appendage for the presence of clot.

With the expansion of the number and complexity of procedures in the cardiac catheterization and EP laboratories, the once occasional involvement of the anesthesiologist (mostly for monitoring/managing of patients with difficult airway or morbid obesity) has become quite frequent.1,5,16 Out-of-the-operating room demand for cardiac anesthesiologists is ever increasing to provide assistance for increasingly sicker patients who are treated by percutaneous modalities. Anesthesia personnel working in these locations often find themselves in corners of dark rooms, which have not been designed to accommodate the presence of anesthesia equipment and personnel. Consequently, there is often too little space for the anesthesia machine and supply cart. Anesthesia staff should make sure that they have adequate access to the airway during all phases of the procedure as well as adequate oxygen and suction before they agree to provide sedation or general anesthesia in any out-of-the-OR location.

1. Preoperative assessment

   In addition to the routine anesthetic assessment, a targeted cardiovascular review is required, with particular attention to history of dyspnea, orthopnea, or any sign/symptom of ventricular failure. The ability of the patient to breathe comfortably while lying flat should be assessed although sedation often facilitates recumbent breathing.

2. Preoperative medication

   Mild sedation of the patient before induction may be performed with the use of benzodiazepines but close monitoring of the patient is warranted. The cardiology team may discontinue antiarrhythmic medications before electrophysiological studies as they may prevent detection of accessory conducting pathways and arrhythmogenic foci. Consequently, it is advised that should the anesthesia team administer any medication in the pre-procedure holding area, they constantly monitor the patient since the discontinuation of routine medications may make the patient at increased risk for arrhythmia in the holding area.

3. Monitoring

   Standard ASA monitors should be used for all procedures.

   Additional monitors should be tailored to the specific procedure, patient status, and possible complications associated with either the procedure itself or the anesthesia technique.

   Arterial lines are occasionally placed in patients with compromised ventricular function who undergo lengthy procedures (where there may be a need for blood gases monitoring) or for procedures with the potential for blood loss or hemodynamic compromise.

   External defibrillation pads are placed on the patient, as a "backup" in case the internal catheters or ICD fail to terminate the induced arrhythmia during the device testing or catheter manipulation.

   Temperature monitoring is important since hypothermia can be a problem. Esophageal temperature monitoring specific for PV ablation of AF is desirable in order to alert physicians to the possibility of atrial perforation.

4. Anesthesia techniques

   Anesthesia techniques range from local anesthesia alone17 to sedation (mild to deep) or general anesthesia, depending on the procedure and patient characteristics.

1. Sedation

   Most cases can be performed under monitored anesthesia care and/or deep sedation with supplemental oxygen.

   A variety of agents, including benzodiazepines, propofol, etomidate, ketamine, dexmedetomidine, and opioids have been used to sedate patients during cardiac catheterization and EP laboratory procedures.

   Propofol is associated with a high incidence of hypotension;18 however, it is an effective sedative. A prolonged procedure time requires a higher dose of sedative agents, which may over time lead to more pronounced hemodynamic consequences. Propofol should be used with caution in patients with the combined risk factors of advanced heart failure, poor ejection fraction, and severe renal dysfunction.19 Although the incidence of propofol infusion syndrome is not known in the context of sedation during lengthy EP procedures, the high incidence of metabolic acidosis detected by arterial blood gases during these procedures suggests that it is not rare.19,20,21

   During ICD placement, there is a need for deepening the sedation during device testing. A variety of intravenous anesthetics can be used to produce a deeper level of sedation when necessary. There are advantages and disadvantages associated with each agent, such as delay in recovery of arterial pressure after device testing with propofol and delay in arousal and discharge of patients with thiopental.22,23

   Radiofrequency treatment during ablation therapy generates short, acute pain during the heating process, and it is very important that adequate sedation and patient immobility be assured during such periods. No single anesthetic drug or sedation regimen has been demonstrated to be superior to any other. Patients sedated primarily with propofol have been shown to have higher sedation scores; however, some require supplementation with opioids and airway control. Other patients managed primarily with a remifentanil infusion can experience apneic episodes.24

2. General anesthesia

   General anesthesia is at times preferred for management of the EP or out-of-the- OR patient when the procedure is lengthy or painful and performed on very young patients or on patients at risk for airway collapse under sedation.

   The choice of induction technique is dictated by cardiac function, expected procedure duration, and the usual anesthesia concerns. A variety of anesthesia induction and maintenance agents can be employed. Both laryngeal mask airway and/or general endotracheal anesthesia with muscle relaxation can be used. In patients with poor ventricular function hemodynamic instability can occur secondary to anesthesia induction and maintenance. Sudden, sustained loss of blood pressure during performance of a catheter-based procedure should raise the immediate specter of cardiac perforation and tamponade in addition to the usual hemodynamic variations associated with general anesthesia in a patient with poor ventricular function.

3. Postoperative care

   The patient should be monitored and observed after all sedation and general anesthesia procedures in a postoperative care unit or ICU if indicated, and the puncture or procedure site should be observed for signs of bleeding. A CXR may be required to confirm correct placement of devices and exclude possible complications such as pneumothorax or CHF exacerbation.

The risks and complications of out-of-the-OR cardiac procedures are related to the procedure itself, the patient's characteristics, and the usual anesthesia problems associated with care of the patient with poor cardiac function. Additionally there are risks associated with exposure to radiation secondary to the fluoroscopy used in these procedures.

Complications Related to the Anesthetic Management

Patients treated in the cardiology suite frequently have multiple and significant comorbidities such as coronary artery disease, valvular disease, heart failure, diabetes, renal insufficiency, obstructive lung disease, and morbid obesity. Consequently, anesthetic management is challenging, as almost all patients are ASA class III or higher. Many of the procedures can be performed under minimal or moderate sedation, but many others require deep sedation or even general anesthesia, often of prolonged duration.

Possible complications associated with anesthetic management include airway obstruction, hypoxemia, hypercarbia, aspiration, and hypotension. Studies suggest25 that a large percentage of patients undergoing electrophysiologic procedures (40%), require some type of airway intervention, from nasal/oral airway insertion to laryngeal mask airway (LMA) or endotracheal tube placement.

Also, of note are the effects of anesthetic agents on cardiac conduction. Volatile agents can affect the sinoatrial node automaticity, shorten cardiac potential, and prolong atrioventricular conduction time.

Factors such as increased patient weight and prolonged anesthesia time increase the chance of conversion from sedation to general anesthesia.

Complications Related to the Procedure

Nearly all procedures in the electrophysiology laboratory require percutaneous intravenous access with sizable catheters.

Potential complications related to the percutaneous access (common to most procedures) include bleeding, hematoma, pneumothorax, and occasional arrhythmias.

Some risks and complications are procedure specific:

1. Cardioverter defibrillators placement and testing requires the induction of ventricular arrhythmias which are recognized and converted by the devices. The effect of multiple trials of ventricular fibrillation with electrical conversion can produce hypotension during or immediately after testing.22,23,26

2. Intraoperative complications related to catheter-based radiofrequency ablation are relatively uncommon. They include esophageal rupture, atrial-esophageal fistula, pulmonary vein stenosis, thromboembolism, left atrial flutter, and atrial perforation.27,28

When using radiofrequency ablation for atrial fibrillation, the goal is to create a series of lesions in the atrium. The probe is set to deliver energy to a preset temperature and time, but the depth of the lesion is not easily controlled, hence the possibility of through the atrial wall injuries to adjacent structures. The esophagus sits behind the atria and as such can be injured leading to life-threatening mediastinitis.29

In this era of increased interventional cardiology, acute tamponade from cardiac perforation is encountered more frequently. Perforation of either the atrium or the ventricle is potentially fatal. The incidence of perforation is about 1% during PV isolation.30,31

Cardiac tamponade is life threatening. The rapid accumulation of blood in the pericardial sac leads to compression of all chambers as a result of increased intrapericardial pressure, which ultimately leads to a severely diminished filling of the heart. The clinical picture depends on the rate of fluid accumulation and the effectiveness of compensatory mechanisms. Therefore, the intrapericardial hemorrhage from cardiac perforation can become very dangerous, very fast.

Clinical findings include tachypnea and dyspnea, which are difficult to evaluate in the anesthetized/sedated patient. Physical findings are nonspecific. Tachycardia, hypotension and diminished heart sounds may be suggestive. Hypotension is almost always present and any change in blood pressure downward should raise the alert of the possibility of tamponade and myocardial perforation. A key finding is pulsus paradoxus, defined as an inspiratory systolic fall in arterial pressure of 10 mm Hg or more during normal breathing. This may be difficult to assess in the EP laboratory.

Echocardiography is of great importance in the diagnosis of pericardial tamponade. Among some of the echocardiographic signs, characteristic, although not very specific, are right atrial collapse during late diastole and right ventricle collapse during early diastole.32,33 Intracardiac echocardiography has been advocated as a method to prevent serious or fatal complications.

The treatment of cardiac tamponade involves drainage of the pericardial contents, preferably by needle pericardiocentesis, with the use of echocardiographic guidance.

Surgical exploration or intervention is indicated when complete control of the bleeding is in question or hemodynamic stability is not rapidly restored with pericardiocentesis alone.

The use of laser-assisted lead extractions techniques for chronically implanted pacemaker and ICDs leads are associated with potentially fatal complications from cardiac perforation, as well, and in addition to superior vena cava disruption and subclavian vein injury. The current literature cites mortality from laser-lead extraction ranging from 1.9% to 3.4%.15

Given the severity and acuteness of the pericardial tamponade secondary to perforation of the above-mentioned chamber/structures, it is not always possible to perform needle pericardiocentesis in a timely manner, and emergent surgical intervention may be required, sometimes with the help of cardiopulmonary bypass. One study15 suggests that laser-assisted lead extractions should be performed in the operating room in the presence of a cardiac surgery team in order to optimize the chances of survival in the event of complications.

In the view of the increasing number of patients with implanted cardiac rhythm management devices (pacemakers and defibrillators) requiring anesthesia for various procedures, the perioperative management of those patients may present a challenge for the anesthesiologist.

The American Society of Anesthesiologists has published guidelines regarding their management.34

The management of patients with implanted devices is a three-step process:

• 1. Preoperative management centers upon:
  • • Establishing whether or not a patient has a cardiac rhythm management device (CRMD), by focused history, review of chest radiography (CXR), electrocardiogram (ECG), and physical examination
  • • Defining the type of device by reviewing the manufacturer's card, interrogating it with a CRMD programming device, CXR, or querying the manufacturer's databases
  • • Determining whether a patient is device dependent for antibradycardia pacing by patient history and device interrogation
  • • Determining the device's function through consultation with a cardiologist or CRMD service
  • Next the preoperative preparation should include the following steps:
  • • Determine whether electromagnetic interference would be present during the planned procedure.
  • • Determine whether reprogramming the device to asynchronous pacing mode or disabling the rate responsiveness function is needed.
  • • Suspend the device's antitachyarrhythmia functions, if present.
  • • Advise the use of bipolar electrocautery system if the patient is pacemaker dependent. If monopolar electrocautery must be used, recommend the use of short, irregular bursts.
  • • Assure the availability of temporary pacing and external defibrillation equipment.
  • The task force recommends changing to an asynchronous pacing mode for all patients who are pacer-dependent. This can be accomplished either by programming or magnet application.
  • CAUTION: There is no reliable way to assess proper magnet placement.
  • • Magnet application to a combined ICD/pacemaker may disable the tachyarrhythmia therapy function depending on the manufacturer of the device but not alter the pacing mode to an asynchronous mode. Therefore, in these devices only a consultant can change the pacing mode by using a device programmer.
  • • Not all ICDs respond to magnet placement.
  • • Some ICDs are permanently disabled by magnet placement.
• 2. Intraoperative management includes:
  • • Managing potential sources of electromagnetic interference:
    • • Electrocautery: Position the return pad in such a way that the current pathway does not pass through or in the vicinity of the device; suggest the use of short, intermittent bursts of cautery; suggest the use a bipolar cautery which reduces the current flow through the body.
    • • RF ablation: Keep the RF current path as far away from the device as possible.
    • • Lithotripsy: Avoid focusing of the lithotripsy beam near the generator, disable atrial pacing if the lithotripsy triggers on the R wave.
    • • MRI is contraindicated for all devices.
  • The external defibrillation pads should be placed as far away from the generator as possible in order to minimize damaging the device in case of emergency defibrillation. Before attempting emergency defibrillation or cardioversion in patients with disabled ICDs, the magnet should be removed to re-enable the tachyarrhythmia therapy function of the device. If the device does not deliver the appropriate shock then external defibrillation or cardioversion should be immediately performed.
• 3. Postoperative management
  • The postoperative management should include interrogation of the device and restoration of the tachyarrhythmia therapy function of the device in the postanesthesia care unit or intensive care unit.34 Until the defibrillating function of the device is restored the function should be monitored with continuous ECG.
  • No patient should be discharged from a monitored area until the device has been interrogated postoperatively.