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Principles 2 > Pacemakers & Implanted Devices > Flashcards

Pacemakers & Implanted Devices Flashcards

1
Q

What are indications for pacing?

A

-Bradycardia
-Sinus Node dysfunction (Tachy-brady syndrome or SSS)
-Syncope with intermittent 2nd or 3rd degree HB
-“Chronotropic incompetence” = heart won’t increase to meet metabolic needs
-Anti-tachy pacing (ATP) = pacer overrides natural HR to bring electrical activity down to a reasonable level
-Biventricular failure

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2
Q

What does the 1st letter indicate?

A

Chamber paced

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3
Q

What does the 2nd letter indicate?

A

Chamber sensed

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4
Q

What does the 3rd letter indicate?

A

Type of sensing

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5
Q

What does the 4th letter indicate?

A

Rate modulation

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6
Q

What does the 5th letter indicate?

A

Anti-tachy functions

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7
Q

What does the service life of the pacemaker depend on?

A

How often the pacemaker is “on”
-5 to 12 years

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8
Q

What are the options for Chamber Paced?

A

0 = none
A = Atrium
V = Ventricle
D = Dual
S = Single (rare, just in emergencies)

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9
Q

What are the options for Chamber Sensed?

A

0 = none
A = Atrium
V = Ventricle
D = Dual
S = Single (rare, just in emergencies)

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10
Q

What are the options for Response?

A

0 = node
I = Inhibit
T = Trigger
D = Dual

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11
Q

What are the options for Rate Response?

A

0 = none
R = Adaptive Rate

on or off

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12
Q

What are the options for Anti-tachy functions?

A

0 = none
P = ATP (Anti-Tachy Pacing)
S = Shock
D = Dual

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13
Q

What is VOO?

A

-Ventricular Lead only
-Ventricular Pacing
-NO sensing
-Ventricular asynchronous pacing at a lower programmed pacing rate
-Used if patient goes into HB

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14
Q

What is VVI?

A

-Ventricular Lead only
-Ventricular Pacing
-Ventricular Sensing
-If the pacer senses an intrinsic beat, it will not trigger a pacer spike (inhibits)

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15
Q

What is AOO?

A

-Atrial Lead only
-Atrial Pacing
-No Sensing
-Atrial asynchronous pacing at a lower programmed pacing rate
-Pacer triggers a P wave
-Ensures you retain synchrony of ventricles and atrium
-Used if patient has an inadequate Sinus Node.
-Pacer spike, triggered p wave, normal AV conduction and normal QRS.
-pacer pike will march out, can land on QRS (bad)

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16
Q

What is AAI?

A

-Atrial Lead only
-Atrial Pacing
-Atrial Sensing
-Presence of an intrinsic p wave inhibits atrial pacing
-Avoids spikes within the QRS complex.
-Only triggers a p wave. QRS complex that follows is native to the patient.

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17
Q

What is DDD?

A

Dual-chamber pacing capable of pacing and sensing in both the atrial and ventricular chambers of the heart.
-Pacing in Atrium and Ventricle
-Sensing in Atrium and Ventricle
-Intrinsic P-wave and intrinsic QRS can inhibit pacing
-Intrinsic P-wave can “trigger” a paced QRS
-Can turn one off depending on the intrinsic beat of the patient. Adapts to changes post-implant.

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18
Q

What are the 4 Distinct patterns that can be observed with DDD pacing?

A

1) Sensing in the atrium and sensing in the ventricle (AsVs).
-Native electrical activity
2) Sensing in the atrium and pacing in the ventricle (P wave tracking) (AsVp).
-Patient’s native p wave, and pacer makes a ventricular spike if PR interval is longer than what is programmed.
3) Pacing in the atrium and sensing in the ventricle (ApVs)
-Patient’s native QRS
4) Pacing in the atrium and pacing in the ventricle (ApVp)

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19
Q

What is VDD?

A

-Atrial Lead (T)
-Ventricular Lead (I)
-Pacing in ventricle
-Sensing in both atrium and ventricle
-Intrinsic QRS inhibits ventricular pacing
-Intrinsic P-wave can trigger ventricular pacing (P wave tracking)
-No atrial pacing: patient MUST have normal sinus node function

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20
Q

What is DDI?

A

-Atrial Lead (I)
-Ventricular Lead (I)
-Pacing in the atrium and ventricle
-Sensing in atrium and ventricle
-NO tracking of P-waves (no constant AV delay - PR interval is variable)
-Never triggers (starts) an AV delay following an intrinsic P-wave (no P-wave tracking)
-Similar to combining AAI and VVI modes
-Used primarily for atrial tachyarrhythmias and mode-switching algorithms.

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21
Q

What is DOO?

A

-Atrial and Ventricular Leads
-Pacing in the atrium and ventricle
-Intrinsic P-wave and QRS do not affect pacing (no sensing of intrinsic activity)
-Asynchronous pacing (always pace at lower pacing rate)

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22
Q

What is Rate-Responsive pacing?

A

-Modes ending in “R”
-Sensor(s) in the pacemaker are used to detect changes in physiologic needs and increase the pacing rate accordingly
-Sensors detect changes in metabolic demand
-Sensors sense motion or physiologic indicators (accelerometer or minute ventilation)
-Detects changes in needs to increase pacer rate.

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23
Q

What is Chronotropic Incompetence?

A

Inability to increase and maintain heart rate appropriately with exercise.

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24
Q

What are the risks/benefits of DDDR/ DDD pacing?

A

-Benefits: AV synchrony and Normal sinus response
-Risks: Loss of AV node conduction

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25
Q

What are the risks/benefits of VVIR/VVI pacing?

A

-Benefits: Maintain minimum cardiac output and single lead implantation (can be used in significant cardiomyopathy)
-Risks: Loss of AV synchrony, retrograde conduction, and increased incidence of atrial arrhythmias

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26
Q

What will Failure to Pace appear like on ECG?

A

Either no pacing spikes or will be present for one chamber but not the other

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27
Q

What causes failure to pace?

A

Oversensing, battery failure, lead malfunction, fibrosis at electrode- tissue interface

28
Q

What will Failure to Capture appear like on ECG?

A

Spike is present without corresponding atrial or ventricular contraction

29
Q

What causes failure to capture?

A

Lead displacement or conditions that change pacing thresholds (electrolyte imbalances or pH)

30
Q

What will pacing at abnormal rates appear like on ECG? (pacing above or below the thresholds of 60-100)

A

1) Rapid (rate >100)
2) Slow (rate <60)
3) Intrinsic rate below lower threshold

31
Q

What causes a pacer to pace at abnormal rates?

A

1) Adaptive rate pacing; oversensing (may be in overdrive mode)
2) Oversensing, rest or sleep rates
3) Power failure, lead disruption

32
Q

What will Failure to Sense appear like on ECG?

A

Pacing spikes in the middle of normal waves

33
Q

What causes failure to sense?

A

Inadequate signal strength, device malfunction

34
Q

What will Oversensing appear like on ECG?

A

Abnormal pacing rates with pauses

35
Q

What causes oversensing?

A

Inappropriate device trigger or inhibition

36
Q

What are the indications for Cardiac Resynchronization Therapy (CRT)?

A

Recommended for heart failure patients:
-LVEF <35%
-NYHA class III-IV symptoms refractory to medical therapy
-QRS duration >120msec on 12 lead EKG

37
Q

What are the goals of Cardiac Resynchronization Therapy (CRT)?

A

-Improve LV function without increasing MVO2 (Reduces LVEDP due to adequate ejection of blood volume from both ventricles)
-Reverse molecular remodeling: Improving contractile elements, excitation-contraction coupling, and improved Ca++ handling, and decrease the mitral regurgitant fraction
-Decreased risk of lethal arrhythmias
-Decreased hospitalizations; improvement in quality of life

Synchronize the ventricles!

38
Q

What effect do Biventricular Pacers (CRT) have on molecular remodeling?

A

Can reverse the maladaptive changes due to HF:
-Reverses molecular remodeling by improving contractile elements (Actin-myosin overlap. With HF, actin and myosin are further apart, and get less squeeze with every ejection).
-Better native full ejection of cardiac output.
-improves excitation-contraction coupling
-Improves handling of Ca within cardiac myocyte. Often, with HF we see that heart does not handle Ca within the cytosol adequately. With depolarization, we want to see opening of Calcium channels and cell-to-cell contraction. When contraction is over, use SER-CA2 receptor (receptor on mitochondria of the SR) to take Ca back up and store it.
-Patients in HF lose this ability to store calcium, so they lose lusitropy: relaxation.

39
Q

What effect do Biventricular Pacers (CRT) have on the Mitral regurgitant fraction?

A

With HF, as remodeling occurs and heart becomes more spherical, changes of shape of the heart cause stretch on mitral annulus.
-When this occurs, leaflets are also stretched, leading to Mitral Regurg.
-Leads to pulmonary volume overload -> pulm htn and decreased volume contracting through ventricle
-Biventricular pacers reduce molecular remodeling.

40
Q

What are the different options for Cardiac Resynchronization Therapy (CRT)?

A

-Biventricular Pacing: RV and LV
-Univentricular pacing with lead at the area of delayed conduction
-Triventricular Pacing: adds a lead in the Coronary sinus

41
Q

What is the pulse generator?

A

The part of the pacer that houses the battery and a tiny computer.

42
Q

What are the leads (PPM)?

A

Wires that send impulses from the pulse generator to the heart muscle, as well as sense the heart’s electrical activity.
-Each impulse causes the heart to contract

43
Q

What were the results of the Companion trial?

A

Study that found that Bivent pacer + ICD in same patient decreased mortality.

44
Q

Describe Current Leadless Systems.

A

-Single chamber RV pacing
-Percutaneous insertion

Medtronic Micra and St. Jude Nanostim:
-Similar complication rates
-Micra approved first
-Same insertion procedure

45
Q

How does a Leadless Pacemaker work?

A

1) Conventional pacemaker generates an electric pacing pulse
2) Pulse generator picks up electrical activity by pacemaker
3) Pulse generator sends an ultrasonic pulse to receiver-electrode, causing left ventricle to pace.

46
Q

What are the indications for an Implantable Cardioverter Defibrillator (ICD)?

A

-Primary Prevention of Cardiac Death
-Secondary Prevention of Cardiac Death

47
Q

What are the indications for ICD that fall under Primary prevention of cardiac death?

A

-Dilated CM with very low EF (<30%)
-NYHA III or IV and history of VT
-Long QT syndrome with syncope

Even if they have not had a sudden cardiac arrest, the ICD is implanted.

48
Q

What are the indications for ICD that fall under Secondary prevention of cardiac death?

A

-History of cardiac arrest with structural heart disease
-long QT syndrome
-primary VT
-Brugada Syndrome

Occurs after the patient has already had a sudden cardiac arrest

49
Q

What can ICDs do?

A

-Combination of pacing and shocking options

Shock is delivered based on:
-Rate
-Rhythm
-Morphology

Ex: May need ICD to shock and then pacing after arrhythmia is ended.

Surgical revision is not uncommon with a lead failure rate of up to 40% in 8 years

50
Q

What are the advantages/disadvantages of subcutaneous ICDs?

A

-Advantages: no leads, no access to large vessels.
-Disadvantages: no pacing capability

Done under GA
-Implantable generator on the side
-Plate on other side
-Shock is sent from generator, across heart, defibrillates ventricle, and plate attenuates the shock.

51
Q

What are the perioperative considerations for a patient with an implanted device?

A

-Know your device: What type? Why was it placed?
-Is the patient device dependent? (Patient history, s/p AV nodal ablation = no ability to create a ventricular QRS complex). May need external pacemaker
-Is the device functioning appropriately? (when was it last interrogated and what are the settings?)

For most ICDS, a magnet will suspend tachyarrythmia detection and therapy. However, a magnet will never change the pacing mode of an ICD, e.g. pacing inhibition may still occur.

52
Q

How soon prior to surgery should an ICD be interrogated?

A

Within 6 months

53
Q

How soon prior to surgery should a PPM be interrogated?

A

Within 12 months

54
Q

How soon prior to surgery should a CRT (Biventricular) be interrogated?

A

Within 3-6 months

55
Q

What are possible intraop considerations with an implanted device?

A

-Intraop monitoring of the PPM function
-Electromagnetic interference can impact the pacemaker.
-May need asynchronous mode
-Availability of backup pacing and defibrillation

56
Q

What are some examples of things that can cause interference with a pacemaker during surgery?

A

-Cautery: More likely unipolar. Coag setting more likely than cutting function
-EMI is more likely in surgeries above the umbilicus.
-Nerve stimulators
-TENs units
-Radiofrequency Ablation units

57
Q

What is Electromagnetic Interference (EMI)?

A

EMI is the potential disruption of the operation of an an electronic device when it is in the vicinity of an electromagnetic field generated by an external source.
-Cautery is the biggest culprit
-EMI more likely in surgeries above the umbilicus

58
Q

What are the risks associated with EMI?

A

-Inhibition of pacing due to ventricular oversensing of EMI: underpacing
-Misinterpretation of EMI as a tachyarrhythmia = Inappropriate shock or Anti-tachy pacing (MAJOR problem if crani or eye surgery)
-Activation of ”power on reset” (device reverts back to factory programmed settings)
-Total device failure (more common in older devices, have backup pacing available)

59
Q

What should you do if EMI is likely?

A

-ICD: disable tachyarrhythmia function
-PPM: If patient is dependent, program asynchronous mode.

60
Q

Regardless of EMI risk, what should you do with an ICD for surgery?

A

-If patient movement is dangerous (ex: Intraocular surgery), then disable ICD
-If there is risk to surgical personnel (ex: Use of scalpel), then disable ICD
-Disable rate responsive mode.

61
Q

What do you need to know about using a Magnet?

A

1) Most expert groups caution against in the routine use magnets
-More important to evaluate each patient for risk
2) Need to know PPM magnet rates. Usually DOO.
3) ICD diagnostic tones (can listen to hear them go off).
4) ICD magnet turns off tachy detection and shocking but NOT pacing mode (no async)
5) Issues with obese pts with deep device implants (may need 2 magnets put together)
6) Location of surgical field may impact magnet placement

62
Q

What is important to know regarding intraop meds and patients with implanted devices?

A

-High dose opioids: promote pacer dependence
-CEID pts with long QT syndrome: avoid QT prolonging medications (Zofran, Haldol be cautious)

63
Q

Describe ICD implantation.

A

-General or MAC (Potential for prolonged case)
-Percutaneous or thoracotomy (may have to convert to open, need adequate H&P for GA)
-Involved for the entire case or just for the defibrillator check (deeper sedation while shocking the patient)
-Subcut ICD: General anesthesia

64
Q

Describe PPM implantation

A

-Sedation or General
-Endovascular versus thoracotomy approach
-Often in conjunction with an ICD
-Usually need Arterial line

65
Q

What conditions would necessitate interrogation and reprogramming in the postop period?

A

-Pt underwent emergency surgery without appropriate preoperative CEID evaluation
-Observed delivery of inappropriate shocks
-Intraop exposure to strong EMI near the generator
-Hemodynamic instability

Principles 2 (45 decks)

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