Pacemakers: Nomenclature
Pacers use a 5-letter code: first 3 letters most important

1. First Letter: Chamber Paced

A= Atrium
V= Ventricle
D= Dual (A+V)
2. 2nd Letter: Chamber Sensed

A= Atrium
V= Ventricle
D= Dual (A+V)
O= None
3. 3rd Letter: Response after Sensing:

I = Pacing Inhibited
T= Pacing Triggered
D= Dual (I+T)
O= None
4. 4th Letter: Programmability

P = Rate & Output
M = Multiprogramable
C = Communicating
R = Rate adaptive
O = None
5. 5th Letter: Arrhythmia Control

P = pacing
S= shock
D= Dual (P+S)
O = None

• Unipolar vs. Bipolar:  Refers to electrode polarity. (Unipolar is more susceptible to malfunction secondary to interference.)
• Single vs. Dual leads:  self-explanatory.
• Asynchronous vs. Synchronous pacing:  Asynchronous pacers are fixed-rate, and do not sense atrial or ventricular myopotentials.

VVI = Ventricle paced, ventricle sensed; pacing inhibited if beat sensed.
VVIR = Demand ventricular pacing with physiologic response to exercise.
DDD = Atrium & ventricle can both be paced; atrium & ventricle both sensed; pacing triggered in each chamber if beat not sensed
DDDR = AV concordance with physiologic response.

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Pacemakers: Magnets

• In modern implantable pacers (>1990), magnets DO NOT predictably convert the pacer to asynchronous mode.
• Call cardiologist to re-program pacemaker for surgery.
• If cardiologist unavailable and surgery emergent, have Zoll external pacer outside the room.

Pacemakers: Electrocautery

• Potential effects of electrocautery
• Inhibition of a pacemaker
• Reprogramming of a pacemaker
• Resetting of a pacemaker to its “backup mode”
• Permanent damage to the pulse generator (rare)
• Induction of ventricular fibrillation: rarely energy can be picked up by the AICD/pacemaker and/or the leads and delivered directly to the heart.
• A rise in the capture threshold by causing an endocardial burn at the electrode-myocardial interface. This may lead to loss of capture (rare)

Pacemakers: Preoperative Evaluation
Ask Cardiology to evaluate/ re-program pacer for surgery.

• Evaluation includes documentation in the chart of the following
• Identification of pacemaker manufacturer and model
• Assessment of battery status using magnet or telemetered data
• Documentation of telemetered data, impedance readings and capture thresholds
• Determination of appropriate pacing mode for surgery
• Reprogramming
• The following changes may be made at the time of the evaluation or on the day of surgery:
• Pacer will likely be turned to DOO or VOO during surgery if there is no competition from intrinsic or ectopic beats
• If pacer is rate response activated, it will likely be turned off for surgery, particularly with thoracic surgery when chest wall movement occurs - this will prevent inappropriate rapid pacing
• Probably needed for:
• Pacer-dependent patient
• Major chest or abdomen case
• Pt. who has pacer for obstructive or dilated cardiomyopathy
• ICDs should be programmed off just before surgery, then on postoperatively.

Pacemakers: Intra-Operative Management

• No special anesthesia technique.
• EKG monitor
• disable filtering of pacer spikes.
• use lead that shows pacer spikes to confirm that pacemaker is functioning appropriately
• Pulse Oximeter +/or Art. Line: to detect mechanical systole (VF will not be seen on ECG during electrocautery)
• Electrocautery
• AVOID if possible
• Bipolar preferred (restricts the energy field to the areas around the cautery probe and minimizes its spread throughout the body).
• If monopolar necessary
• keep pacemaker generator out of path between cautery and "grounding" pad
• Use in short bursts to avoid long periods of asystole
• DO NOT use a magnet to convert the pace maker to a fixed asynchronous rate.  Many pacemakers (including Pacesetters, Medtronic, Telectronics, and Cordis) will be predisposed to inappropriate reprogramming if a magnet is over the pacemaker during the application of eletrocautery.
• Special Situations:
• Lithotripsy: keep generator out of shockwave path.
• ECT: requires asynchronous (non-sensing) mode
• Nerve Stimulator, TENS: potential problems
• MRI: Absolute contraindication

Temporary Pacing Techniques

Method	Chambers Paced	Uses
Transcutaneous	Right Ventricle	Arrest; Intraoperative and Prophylactic
Transesophageal	Left Atrium	Prophylactic atrial; intraop; overdriveSVT
Transvenous semirigid	Atrium and/or Vent	Arrest; prophylactic; maintenance
Transvenous flow-directed	Right Ventricle	Arrest; intraoperative;prophylactic; maintenance
Pacing PAC	Atrium and/or Vent	Arrest; intraoperative; prophylactic;maintenance
Epicardial	Atrium and/or Vent	Arrest; prophylactic; maintenance
Transthoracic	Ventricle	Arrest only

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Automatic Implantable Cardioverter-Defibrillator
AICDs: Nomenclature

Position I	Position II	Position III	Position IV
Chamber(s) shocked	Antitachicardia pacing chamber(s)	Tachycardiadetection	Antibradycardia pacing chamber(s)
O=None	O=None	E=Electrogram	O=None
A=Atrium	A=Atrium	H=Hemodynamic	A=Atrium
V=Ventricle	V=Ventricle		V=Ventricle
D=Dual	D=Dual		D=Dual

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AICDs: Additional points:
1. Newer devices can deliver “tiered therapy” (pacing, then increasing shocks)
2. Devices measure R-R interval over time
3. Pacemakers can function in presence of ICD as long as electrodes are bipolar.
4. Most ICDs have backup VVI pacing to protect against post shock bradycardia.
5. Magnet application in most newer models will suspend tachyarrhythmia detection.  This should be done before induction of anesthesia.

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