1. Pacemakers

2. Outline
Basic Function and Types
Associated Morbidity
Specific Indications for Use
Follow Up

3. Basics
Pulse Generator

5. Purpose
Symptomatic bradyarrhythmia
Bradycardia
Block

6. Pacemaker Codes 1 Chambers Paced 2 Chambers Sensed 3
Response to Sensed Stimulus 4
Rate Modulation? 5
Multisite Pacing (ICD)
O (none) O O
O (non-rate responsive) O
A (atrium) A
T (triggered)
R (rate responsive) A
V (ventricle) V
I (inhibited) V
D (both atrium & ventricle) D

7. Paced Rhythm Stimulated P wave nearly normal in appearance
Wide complex QRS
Does not use the normal conduction system
Depolarizes ventricles from right to left and from apex to base
Resembles complete LBBB
Broad T wave and may include sharp inversions that mimic ischemia

8. Paced Rhythm Stimulated P wave nearly normal in appearance
Wide complex QRS
Does not use the normal conduction system
Depolarizes ventricles from right to left and from apex to base
Resembles complete LBBB
Broad T wave and may include sharp inversions that mimic ischemia

9. Paced Rhythm Stimulated P wave nearly normal in appearance
Wide complex QRS
Does not use the normal conduction system
Depolarizes ventricles from right to left and from apex to base
Resembles complete LBBB
Broad T wave and may include sharp inversions that mimic ischemia

11. AAI Pacing
Underlying sinus note dysfunction but intact cardiac conduction
Sense atrial activity
Inhibit pacing if the patient’s heart rate remains above prevent target
At lower rates, pacer stimulates atria

12. Pacemaker Configurations AAI
Indications
Sick sinus syndrome in the absence of AV node disease or atrial fibrillation.

13. VVI Pacing No useful atrial function eg Afib
Tracks ventricular activity
Paces ventricle only if a QRS complex is not sensed within a predefined interval

14. Pacemaker Configurations VVI
Indications
The combination of AV block and chronic atrial arrhythmias (particularly atrial fibrillation).

15. DDD Pacing Most common form of dual chamber pacing
Atrial impulse generated if native atrial activity fails to occur within a preset time period after the last atrial impulse
If a QRS complex does not occur during a preset interval after the atrial impulse, a ventricular impulse occurs

16. Pacemaker Configurations DDD
Indications
1. The combination of AV block and SSS.
2. Patients with LV dysfunction and LV hypertrophy who need coordination of atrial and ventricular contractions to maintain adequate CO.

17. Pacemaker Configurations VOO
Indications
Temporary mode some-times used during surgery to prevent interference from electrocautery

18. Pacemaker Configurations VDD
Indications
AV block with intact sinus node function (particularly useful in congenital AV block).

19. Basic Function and Types
Associated Morbidity
Specific Indications for Use
Follow Up

20. Associated Morbidity - Pacemaker Syndrome
Dizziness, weakness, dyspnea, presyncope, syncope, exertional-fatigue
AV dyssynchrony usu d/t VVI pacing with intact sino-atrial activity
Tx: Dual-chamber pacers which restore atrial kick
Complications: Afib, stroke

21. Associated Morbidity - Pacemaker-mediated Tachycardia
Rapid ventricular pacing at max programmed rate caused by an endless loop
PVC conducted retrograde via AV node to atrium
Retrograde signal sensed by atrial channel
Pacing of ventricle
Retrograde conduction to atria
Most pacemakers can recognize and terminate PMT

22. Basic Function and Types
Associated Morbidity
Specific Indications for Use
Follow Up

23. Indications Sinus Node Disease AV Conduction Disease and Heart Block
Neurocardiogenic Syndrome
Chronic Heart Failure

24. Class I: Conditions for which there is evidence and/or general agreement that a given procedure or treatment is useful and effective.
Class II: Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of a procedure or treatment.
Class III: Conditions for which there is evidence and/or general agreement that the procedure/treatment is not useful/ /effective and in some cases may be harmful.

25. Indications Sinus Node Disease
In general, pacemaker therapy is recommended only when symptoms are present
Class I
1. Sinus node dysfunction with documented symptomatic bradycardia
2. Symptomatic chronotropic incompetence (failure to increase HR with exercise or increased metabolic demand)

26. Indications Sinus Node Disease Class II
- Heart rate <40 beats/min spontaneously or in the presence of essential medical therapy when clinically important symptoms are not correlated with bradycardia
- Syncope and abnormal sinus node function documented in electrophysiologic study
- Heart rate <40 beats/min and minimal symptoms
Class III
- Asymptomatic sinus node disease
- Clear documentation that symptoms are unrelated to bradycardia
- Sinus node disease due to nonessential drug therapy

27. Pacemaker mode selection in sinus node disease may markedly affect patient outcomes

28. Indications Sinus Node Disease AV Conduction Disease and Heart Block
Neurocardiogenic Syndrome
Chronic Heart Failure

29. Common Causes of Acquired Atrioventricular Block
Degenerative disease
Lev disease
Lenègre disease
Secondary degeneration/calcification
Medications
β-Receptor blockers
Calcium channel antagonists
Digoxin
Other antiarrhythmic agents
Atherosclerotic heart disease
Myocardial ischemia
Myocardial infarction
Dilated cardiomyopathy
Infiltrative disease
Sarcoidosis
Amyloidosis
Metastasis
Infections
Endocarditis
Lyme disease
Chagas disease
Iatrogenic causes
After atrioventricular nodal ablation
After cardiac surgery
After radiation therapy
Enhanced parasympathetic activity

30. Indications Acquired AVB in adults Class I Third-degree AVB
Asystole >3 s or escape rate <40 beats/min
Associated neuromuscular disease (eg, Kearns-Sayre, Erb dystrophy)
After atrioventricular node ablation
After cardiac surgery
Symptomatic second-degree AVB
Alternating bundle branch block type II second-degree AVB with underlying bifascicular block

31. Indications Acquired AVB in adults Class II
Third-degree AVB with LV dysfunction
Type II second-degree AVB
Syncope with underlying bifascicular block when VT excluded
Neuromuscular diseases with any AVB or fascicular block
Class III
- Asymptomatic first-degree or type I second-degree AVB
AVB expected to resolve
Fascicular block with first-degree AVB or no AVB

32. Indications Sinus Node Disease AV Conduction Disease and Heart Block
Neurocardiogenic Syndrome
Chronic Heart Failure

33. Neurocardiogenic Syndrome
transient imbalance in the cardiovascular autonomic regulation that results in vasodilation with or without inappropriate bradycardia.
triggered by vasovagal syncope or by compression of the carotid sinus (carotid sinus hypersensitivity)

34. Neurocardiogenic Syndrome
Substantial bradycardia during tilt-table (not always needed for dx)
If vasodilation cause for hypotension = NOT a candidate for pacing
Ventricular pacing – frequent AV block

36. Indications Sinus Node Disease AV Conduction Disease and Heart Block
Neurocardiogenic Syndrome
Chronic Heart Failure

37. Indications Chronic Heart Failure
Interventricular conduction delay common • poor coordination of ventricular contraction
3 leads
Right ventricle
Coronary sinus to pace left ventricle
Right atrium to sense intrinsic rhythm to ensure appropriate AV timing interval

38. Indications NYHA III – IV on medical therapy
QRS duration > 130 msec (LBBB)
LV enlargement (end-diastolic dimension > 55 mm)
LV Ejection Fraction <35%

39. Indications

41. Basic Function and Types
Associated Morbidity
Specific Indications for Use
Follow Up

43. Follow Up Routine visits
Hx: palpitations, light-headedness, syncope, or change in exercise tolerance
12-lead EKG
Overpenetrated PA and lat CXR (to check placement of pulse generator and leads)

44. Pacemaker Failure Failure to sense Failure to pace
Internal malfunction of the pacer generator

45. Failure to Sense Undersensing
Lead related changes (dislodgement, lead fracture)
Change in lead-myocardium interface (change in activation sequence as in new BBB or PVCs, electrolyte abnormality, new med, lead maturation and fibrosis, infarction at lead tip)

46. Failure to Sense Oversensing – sensing of inappropriate signals
Other parts of the normal ECG
Electromagnetic interference when subjected to strong electrical field
Lead or pulse generator malfunction
Lead fracture
Loose set screw

48. Problems with Pacemakers Failure to Sense
Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005.
Causes:
Undersensing
Oversensing

49. Failure to Capture or Pace
Pacer lead (lead dislodgement, fracture)
Pulse generator (battery depletion, loose screw)
Change in interface (fibrosis, electrolyte, meds, infarctions)
Pacemaker-mediated tachycardia

50. Problems with Pacemakers Failure to Capture
Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005.
Causes:
Threshold rise (electrolytes, drugs)
Lead dislodgement
Lead fracture
RV infarct

51. Problems with Pacemakers Failure to Pace
Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005.
Causes:
Oversensing
Battery failure
Internal insulation failure
Conductor coil fracture

52. Problems with Pacemakers Failure to Pace
Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005.
Causes:
Crosstalk

54. Paced Rhythm Stimulated P wave nearly normal in appearance
Wide complex QRS
Does not use the normal conduction system
Depolarizes ventricles from right to left and from apex to base
Resembles complete LBBB
Broad T wave and may include sharp inversions that mimic ischemia

55. Acute MI – how to tell?
discordant - in the opposite direction of the QRS vector

57. Perioperative Mgmt Applicable to neck and chest surgeries
Obtain pacemaker programming info
Magnet may be placed over device to inhibit sensing or the pacemaker may be programmed to asynchronous mode before surgery
Ensure availability of temporary pacing in case of emergency
Use low energy and short bursts of electrocautery
Avoid electrocautery near device and place grounding pads away from device
Turn off program rate modulation during surgery
Interrogate and reprogram pacemaker after surgery

58. Ventricular paced, Ventricular sensed,
Example 1
The Alan E. Lindsay ECG Learning Center ;
Ventricular paced, Ventricular sensed,
Consistent with VVI

59. Example 2 Ventricular paced, Atrial sensed, Consistent with DDD or VDD
The Alan E. Lindsay ECG Learning Center ;
Ventricular paced, Atrial sensed,
Consistent with DDD or VDD

60. Consistent with AAI or DDD
Example 3
The Alan E. Lindsay ECG Learning Center ;
Atrial paced
Consistent with AAI or DDD

61. Example 4 Failure to Pace
The Alan E. Lindsay ECG Learning Center ;
Failure to Pace

62. Example 5 Failure to Sense
The Alan E. Lindsay ECG Learning Center ;
Failure to Sense

63. Key points
Find out pacemaker model, date of implantation, date of last pacemaker check, indication for pacemaker
Modes
VVI: permanent afib
AAI: SSS and normal AV conduction
DDD: Most common Sinus and AV nodal disease

64. Key points Modes VVI: permanent afib AAI: SSS and normal AV conduction
DDD: Most common Sinus and AV nodal disease

65. Key points Permanent pacing for
symptomatic bradycardia and complete heart block
Heart Failure on optimal medical tx for ≥ 3 mo

66. Key points Problems Pacemaker-mediated tachycardia Pacemaker syndrome
Failure to sense
Failure to pace

67. Sources
“Contemporary Pacemakers: What the Primary Care Physician Needs to Know” Mayo Clinic Proceedings 2008
“The Paced Electrocardiogram: Issues for the Emergency Physician” American J of Emergency Med
Dr. Huang’s Cardiology Handout
medresidents.stanford.edu/TeachingMaterials/Pacemakers/Pacemakers.ppt