1. “Just Put a Magnet On It” An Update on Cardiac Implantable Electronic Devices
26 companies have produced nearly 2000 models of pacemakers. (source: Rozner- pacemaker misinformation)
Carolyn Boyle, RN, BSN, SRNA
Goldfarb School of Nursing at Barnes-Jewish College

2. Objectives
Review the perioperative implications of Cardiac Implantable Electronic Devices
Discuss the risks of Electromagnetic Interference (EMI)
Examine recommendations for preoperative assessment and preparation, intraoperative management, and postoperative recovery for patients with CIED’s

3. Outline Case Study CIED Review Magnet Mechanism
Practice Recommendations
The Future of CIED’s
Conclusions

4. Case Study 65 y.o. male with a hx of SCC of the head and neck
Presents with flap necrosis, osteonecrosis, orocutaneous fistula formation, & a complicated open wound
s/p mandibulectomy, tracheostomy, bil neck dissection, split thickness skin grafting, and G tube placement ~ 8 mos prior.
~2 mos prior, pt had flap and trach revision
presenting for removal of hardware with radial and scapular flap reconstruction
PMH: SCC of head and neck, HTN, CHF (EF 30-40%), AFlutter, DM, COPD, Cardiac Arrest
Torsades arrest following cardioversion in 2012, warranting AICD placement

5. Case Study con’t.
AICD last interrogated preoperatively 2 months prior with recommendations for magnet placement.
Uneventful induction of anesthesia, HOB turned 180 degrees, additional PIV’s and arterial line placed. Magnet placed over device and secured with 2 in silk tape.

6. Case Study con’t.
Approximately 10 min after incision, surgeon using Bovie electrocautery while exposing the mandible
Patient’s AICD fired
No hemodynamic compromise
No arrhythmias
What happened?
In order to explore why this patient’s device fired inappropriately, let’s review CIED’s and perioperative recommendations for their management.
Bovie - monopolar

7. Pacemakers In 2001, standardized programming codes were developed:
Can be single chamber, dual chamber (A-V), or multi-chamber (bi-V)
The leads can be either monopolar or bipolar
Bipolar is most common today – reduces the risk of electromagnetic interference (EMI)
In 2001, standardized programming codes were developed:
PACING
SENSING
RESPONSE
RATE MODULATION
MULTISITE PACING
A = Atrium
I = Inhibited
R = Rate-modulating
V = Ventricle
T = Triggered
O = none
D = Dual (A&V)
D = Dual (I and/or T)
O = None
Bipolar leads have the anode and cathode in the tip of the lead, only centimeters apart, whereas monopolar leads have the cathode in the tip and the device or pulse generator functions as the anode.
The reduced distance between the two in the bipolar leads reduces the likelihood of EMI.
Standardized programming codes developed by the north american society of pacing and electrophysiology and the british pacing and electrophysiology group in 2001
Rate Modulation: allows the pacemaker to increase the paced heart rate in response to certain physiologic situations such as exercise. This can be sensed using different technologies including an accelerometer, thoracic bioimpedance, or even minute ventilation.
Multisite Pacing or Cardiac Resynchronization Therapy: mostly used to notate Bi-ventricular pacing. This optimizes the timing of LV and RV systole in patients with severe HF (currently indicated NYHA class 3 or 4, and for LVEF<35%). CRT can improve cardiac output, hemodynamics, HF symptoms, and QOL.

8. Internal Cardioverter Defibrillators (ICD)
Detect & treat ventricular arrhythmias
Today, incorporate pacemakers in case defibrillation results in bradycardia or asystole
Can be single chamber (RV lead only), dual chamber (A&V leads), or triple chamber (atrial, RV, LV leads).
Pre-programmed ‘zones’ based on heart rates and chamber of origin.
Based on rate, the device can initiate anti-tachycardia pacing or deliver a defibrillatory shock
Programmed zones - allows the device to differentiate ventricular arrhythmias from SVT

9. Potential Perioperative Problem: Electromagnetic Interference (EMI)
Classic Causes:
Surgical electrocautery
Nerve stimulator
Evoked potential monitoring
Radiofrequency Ablation
Potential Causes:
Fasciculations
Shivering
Large tidal volumes
Lithotripsy
Pacemaker:
Inhibition of pacing due to oversensing
Brief exposure generally not a problem
Prolonged exposure can lead to conversion to asynchronous pacing mode
Defibrillator:
inappropriate defibrillation
EMI is the most common problem in the perioperative period for patients with devices.
EMI: Radiofrequency waves interfering with proper device function

10. Magnet Mechanism: The Reed Switch
A reed switch consists of two metal strips made of magnetic material in a glass capsule.
The strips are open and are not in contact.
Application of a magnet causes the strips to come in contact (closed) which triggers the pulse generator to switch to perform programmed functions such as asynchronous pacing or the suspension of anti-tachycardia therapies in ICD’s.
This mechanism can be effected by the body habitus of the patient (some manufacturers recommend 2 magnets for super morbidly obese patients), manufacturer, programmed settings, & battery life.
Sometimes the reed switch can malfunction by staying in the closed or open position regardless of magnet presence. This is known as a sticky reed switch. Malfunction can lead to anti-tachycardia therapy failure and accelerated battery depletion.
As an example of this - Guidant has had problems with this mechanism in a number of ICD’s used in patients with severe cardiomyopathies and they recommended that magnet function be permanently disabled by programming
Source: Sony et al 2011
***Magnet effect on CIED is extremely variable depending on the
device, body habitus, manufacturer, programmed settings,
and battery life.

11. Magnet + PACEMAKER
Usually, a magnet will convert a pacemaker to asynchronous mode
Device response to magnet can be programmed
Rate depends on the manufacturer and the battery life
Asynchronous pacing mode depends on prior settings
DDD  DOO VVI  VOO AAI  AOO
Caution: Asynchronous rate may not always meet the physiologic demands of the patient
Upon removal, device should revert to originally programmed pacing mode
Ie- Decreased SVR and hypovolemia may require increased HR

12. Source: Sony et al 2011 BOL – beginning of life
ERI – elective replacement interval
EOL – end of life
Source: Sony et al 2011

13. Magnet + DEFIBRILLATOR
Usually, a magnet will prevent antitachycardic pacing and defibrillation
In order to prevent oversensing of EMI
Modern AICD’s are also pacemakers – a magnet will not have any effect on the pacemaker function!!
For patients with AICD’s who are pacemaker dependent  preoperative interrogation and reprogramming is recommended

14. -magnet application will have NO effect on pacing.
-Boston Scientific and St. Jude devices can be programmed to ignore the magnet!
-some (but not all) will may audible noises to indicate that a magnet has been successfully placed
-most return to baseline upon magnet reapplication
-as always, when in doubt - interrogate
Source: Sony et al 2011

15. February, 2011

16. Focused Pre-Operative Evaluation
Presence of device
H&P, medical record review, CXR, EKG, physical exam
Type of device
Manufacturer ID card, CXR, supplemental records, consult cardiology, year placed
Dependency on pacemaker function
Verbal history of syncope or bradycardia requiring CIED placement, AV node ablation, 100% paced on EKG
Device function
Best way: comprehensive evaluation (interrogation)
At minimum: evaluation of EKG or rhythm strip, discussion with patient
has aicd fired? syncope? cardiology follow up? When was it placed?
On average – PM 5-8 years
AICD 3-6 years

17. CXR Interpretation
Female patient with single lead ventricular pacemaker – tip in the apex of the RV
-likely valve repl too – sternal wires visible

18. CXR Interpretation
Female patient with single lead atrial pacemaker (tip in right atrial appendage)

19. CXR Interpretation
Female with two lead pacemaker with leads in RA and RV

20. CXR Interpretation Male with Bi-V pacemaker. White arrow is RA lead.
Black arrow is RV lead.
While chevron is LV lead in the posterior coronary vein at the LV.

21. CXR Interpretation Patient with ICD.
Note the thickened coil representing the defibrillator lead in the RV.

22. Preparation is Everything!
Likelihood of Electromagnetic Interference (EMI)
Need for preoperative CIED reprogramming
Asynchronous pacing
Suspension anti-tachyarrhythmia functions
Suggest the use of Bipolar/ Harmonic electrocautery
Assure presence of external pacing/ defibrillation capabilities before, during, and after the procedure
Evaluating the possible effect of anesthetic technique on CIED function
Consider positioning of the patient
Specific anesthetic techniques are unlikely to alter CIED function BUT anesthesia-induced changes (such as HR, BP, rhythm, or ischemia) can lead to unexpected device function.
Positioning.
Bovie is monopolar

23. EMI above umbilicus? NO YES Pacemaker ICD
From: Neelankavil et al
EMI above umbilicus? NO
YES
Pacemaker
ICD
No reprogramming or magnet necessary. Have magnet available.
Deactivate ICD – magnet/ reprogram
Dependent?
Yes-
Magnet/ reprogram to asynch
No-
Consider reprogram/ magnet if source is <15 cm from generator. Have magnet avail.
Pacemaker
Dependent?
No-
No reprogram necessary
Yes-
Reprogram to asynch.

24. Intra-operative Management
If a magnet is placed or the device is reprogrammed, external defibrillation should be immediately available!
Place pads as far away from generator as possible
A-P placement is preferred

25. Intraoperative Management
Monitor patient appropriately, monitor function of device, and monitor for signs of EMI
Assure the cautery grounding pad is positioned so that the current pathway doesn’t cross through or near the device
This may mean that sites other than the thigh should be used
Surgeon should avoid cautery near the device
Short, intermittent bursts of cautery at the lowest possible energy level is ideal
Risk of EMI is much greater with monopolar than bipolar cautery
ASA gives the example of placing the grounding pad on the contralateral shoulder for a head and neck case!

26. Algorithm for Emergent Cardioversion or Defibrillation
Surgeon terminates all sources of EMI
Magnet placed preop
Remove Magnet!
Observe for appropriate CIED response
Prepare for external defib or cardioversion
Device reprogrammed preop
Re-enable therapies if programmer immediately available
This algorithm has been adapted from ASA practice advisory – for a patient with ICD facing VTACh in the clinical setting

27. Post-Operative Care Continuous monitoring
Pacing & defibrillation available
Regardless of the anesthetic approach to the CIED, electrocautery within 6 inches of the device can damage to the internal circuitry and post-operative interrogation is recommended
If there is any question, device should be interrogated to assess function

28. Case Study Conclusion
Electrocautery removed from the field, device representative called to the room
Interrogated device, confirmed defibrillation
Unsure why magnet failed
Manual reprogramming of defibrillator
Surgery proceeded without further incident
Device interrogated postoperatively and returned to preoperative settings

29. The Future of CIED’s

30. NanostimTM Leadless PM
Placed via groin access, battery life equivalent to current PPM. No pocket or leads req’d. Can communicate with interrogator similar to current devices.

31. Subcutaneous ICD Boston Scientific

32. Thank you! Questions?

33. References
American Society of Anesthesiologists Committee on Standards and Practice Parameters. (2011). Practice advisory for the perioperative management of patients with cardiac implantable electronic devices: Pacemakers and implantable cardioverter-defibrillators. Anesthesiology, 114, doi: /ALN.0b013e3181fbe7f6 Neelankavil, J. P., Thompson, A., Mahajan, A. (2013). Managing cardiovascular implantable electronic devices (CIED’s) during perioperative care. APSF Newsletter, 28, Jacob, S., Panaich, S. S., Maheshwari, R., Haddad, J. W., Padanilam, B. J., John, S. K. (2011). Clinical applications of magnets on cardiac rhythm management devices. Europace, 13, doi: /europace/eur137 Lanzman, R. S., Winter, J., Blondin, D., Furst, G., Scherer, A., Miese, F. R., Abbara, S., Kropil, P. (2011). Where does it lead? Imaging features of cardiovascular implantable electronic devices on chest radiograph and CT. Korean J Radiol, 12 (5), doi: /kjr Schulman, P. M., Rozner, M. A. (2013). Use caution when applying magnets to pacemakers or defibrillators during surgery. Anesthesia & Analgesia, 117, doi: /ANE.0b013e a1 Rooke, G. A., Bowdle, T. A. (2013). Perioperative management of pacemakers and implantable cardioverter defibrillators: It’s not just about the magnet. Anesthesia & Analgesia, 117, doi: /ANE.0b013e f3 Rozner, M. (2004). Pacemaker misinformation in the perioperative period: Programming around the problem. Anesthesia & Analgesia, 99, doi: /01.ANE D7