1. Emergency Medicine Ryan Ngiam
Pacemakers and AICD’s
Emergency Medicine
Ryan Ngiam

2. Historical Perspective
1905 – Einthoven
Published first two human AV block using string galvanometer
1958 – Senning and Elmqvist
Asynchronous (VVI) pacemaker implanted by thoracostomy and functioned for 3 hours
Arne Larsson
First pacemaker patient
Used 23 pulse generators and 5 electrode systems
Died 2001 at age 86 of cancer

3. Historical Perspective
1960 – First atrial triggered pacemaker
1964 – First on demand pacemaker (DVI)
1977 – First atrial and ventricular demand pacing (DDD)
1980 – Griffin published first successful pacemaker intervention for supraventricular tachycardias

4. Historical Perspective
1981 – Rate responsive pacing by QT interval, respiration, and movement
1994 – Cardiac resynchronization pacing
1998 – Automatic capture detection
Now
Approximately 3 million with pacemakers
Approximately 1 million with ICD device

5. Pacemaker Basics
Provides electrical stimuli to cause cardiac contraction when intrinsic cardiac activity is inappropriately slow or absent
Sense intrinsic cardiac electric potentials

6. ICD Basics Designed to treat a cardiac tachydysrythmia
Performs cardioversion/defibrillation
Ventricular rate exceeds programmed cut-off rate
ATP (antitachycardia pacing)
Overdrive pacing in an attempt to terminate ventricular tachycardias
Some have pacemaker function (combo devices)

8. Pacemaker and ICD Basics
Pulse Generators
Placed subcutaneously or submuscularly
Connected to leads
Battery
Most commonly lithium-iodide type
Life span 5 to 8 years
Output voltage decreases gradually
Makes sudden battery failure unlikely

9. Pacemaker and ICD Basics
Asynchronous
Fixed rate
Impulse produced at a set rate
No relation to patients intrinsic cardiac activity
Susceptible to Torsades if impulse coincides with t wave

10. Pacemaker and ICD Basics
Synchronous
Demand mode
Sensing circuit searches for intrinsic depolarization potential
If absent, a pacing response is generated
Can mimic intrinsic electrical activity pattern of the heart

11. Pacemaker NomenclatureI II
III IV V
Chamber Paced
Chamber Sensed
Response to Sensing
Rate Modulation, Programmability
Anti-tachycardia Features
A=Atrium
T=Triggered
P=Simple
P=Pacing
V=Ventricle
I=Inhibited
M=Multi-programmable
S=Shock
D=Dual
R=Rate Adaptive
O=None
C=Communicating

12. Pacemaker Nomenclature
1st letter – chamber paced
2nd letter – chamber sensed
3rd letter – Response to chamber sensed

13. Examples VVI Paces ventricle Senses ventricle
Inhibited by a sensed ventricular event

14. Pacing Nomenclature Examples
AAT
Paces atria
Senses atria
Triggers generator to fire if atria sensed
DDD
Paces atria and ventricle
Senses atria and ventricle
Atrial triggered and ventricular inhibited
EKG – 2 spikes

15. DDD
Atrial Spike
Ventricular Spike

16. Pacemaker Lead System Endocardial leads placed via central access
Placed in right ventricle and/or atria
Fixed to the endocardium via screws or tines
Experimental pacing systems
2 atrial leads (minimize afib)
Biventricular pacing

19. Magnet Inhibition Closes an internal reed switch
Causes sensing to be inhibited
Temporarily turns pacemaker into “asynchronous” mode (set rate)
Does NOT turn pacemaker off
Rate can confer info regarding battery life
Distinct rates for BOL, ERI, EOL

20. Pacemaker Indications
Absolute indications
Sick sinus syndrome
Symptomatic sinus bradycardia
Tachy-brady syndrome
Afib with slow ventricular response
3rd degree heart block
Chronotropic incompetence
Inability to increase heart rate to match exercise
Prolonged QT syndrome

21. Pacemaker Indications
3rd Degree heart block

22. Pacemaker Indications
Relative indications
Cardiomyopathy
Dilated
Hypertrophic
Severe refractory neurocardiogenic syncope
Paroxysmal atrial fibrillation

23. ICD Indications Generally
Used in cases where there was a previous cardiac arrest
Or, patients with undetermined origin or continued VT or VF despite medical interventions

24. Pacemaker Complications
EKG abnormalities due to
Failure to output
Failure to capture
Sensing abnormalities
Operative failures

25. Pacemaker Failure to Output
Definition
No pacing spike present despite indication to pace
Etiology
Battery failure, lead fracture, break in lead insulation, oversensing, poor lead connection, “cross-talk”
Atrial output is sensed by ventricular lead

26. Pacemaker Failure to Capture
Definition
Pacing spike is not followed by either an atrial or ventricular complex
Etiology
Lead fracture or dislodgement, break in lead insulation, elevated pacing threshold, MI at lead tip, drugs, metabolic abnormalities, cardiac perforation, poor lead connection

27. Pacemaker Sensing Abnormalities
Oversensing
Senses noncardiac electrical activity and is inhibited from correctly pacing
Etiology
Muscular activity (diaphragm or pecs), EMI, cell phone held within 10cm of pulse generator
Undersensing
Incorrectly misses intrinsic depolarization and paces
Poor lead positioning, lead dislodgement, magnet application, low battery states, MI

28. Pacemaker Operative Failures
Due to pacemaker placement
Pneumothorax
Pericarditis
Perforated atrium or ventricle
Dislodgement of leads
Infection or erosion of pacemaker pocket
Infective endocarditis (rare)
Venous thrombosis

29. Pacemaker Complications
Pacemaker syndrome
Patient feels worse after pacemaker placement
Presents with progressive worsening of CHF symptoms
Due to loss of atrioventricular synchrony, pathway now reversed and ventricular origin of beat

30. Impact on ALS protocols
Not many
Can defibrillate
Sternal paddles should be placed a safe distance (10 cm) from pulse generator
In case of MI
May require temporary transcutaneous pacing

31. ICD Complications Similar to pacemaker complications
Operative failures
Same as pacemakers
Sensing and pacing failures
Inappropriate cardioversion
Ineffective cardioversion/defibrillation
Device deactivation

32. ICD Sensing failures Similar to pacmakers Appropriate failure to treat
Oversensing
Undersensing
Appropriate failure to treat
Programmed cut off at 180 bpm
If V Tach occurs at 160 bpms, appropriately fails to cardiovert

33. ICD Inappropriate Cardioversion
Most frequent complications
Provokes pain and anxiety in pts
Consider when
Pt is in afib
With ventricular response > programmed cut off
Received multiple shocks in rapid succession
Etiology
Afib, T-wave oversensing, lead fracture, insulation breakage, MRI, EMI

34. ICD Inappropriate Cardioversion
Treatment
Magnet over ICD inhibits further shocks
Does NOT inhibit bradycardiac pacing
Note
Some older devices produce beep with each QRS
If left on for >30 seconds, ICD disabled and continous beep
To reactivate, lift off magnet and then replace for > 30 seconds, beep will return with each QRS

35. ICD Failure to Deliver Cardioversion
Etiology
Failure to sense, lead fracture, EMI, inadvertent ICD deactivation
Management
External defibrillation and cardioversion
Do not withhold therapy for fear of damaging ICD
If pt’s internal defibrillator activates during chest compressions, you may feel a mild shock (no reports of deaths related to this)
Antidysrhymthic medications

36. ICD Ineffective Cardioversion
Etiology
Inadequate energy output
Rise in the defibrillation threshold
MI at the lead site
Lead fracture
Insulation breakage
Pre-programmed set of therapies per dysrythmia
Manufacturer specific
Once number of attempts reached, will not deliver further shocks until new episode is declared

37. Electromagnetic Interference
Can interfere with function of pacemaker or ICD
Device misinterprets the EMI causing
Rate alteration
Sensing abnormalities
Asynchronous pacing
Noise reversion
Reprogramming

38. Electromagnetic Interference
Examples
Metal detectors
Cell phones
High voltage power lines
Some home appliances (microwave)

39. Electromagnetic Interference
Intensity of electromagnetic field decreases inversely with the square of the distance from the source
Newer pacemakers and ICDs are being built with increased internal shielding

40. Case 1 CC: Chills, rigors HPI: PMH: PSHx:
65 yom c/o fevers, chills, rigors x 1 day. Positive n/v and anorexia. Pt states he had recent pacemaker insertion 4 days ago for an arrhythmia.
PMH:
HTN
Arrythmia
Hypercholesterolemia
PSHx:
As stated above

41. Case 1
Physical exam
Temp 101.2, HR 110, BP 90/55
EKG
Diagnosis?

42. Case 1 Pocket Infection Pacemaker insertion is a surgical procedure
1% risk for bacteremia
2% risk for pocket infection
Usually occurs within 7 days of pacemaker insertion
May have tenderness and redness over pacemaker site

43. Case 2 CC: SOB HPI: PMHx: PSHx:
65 yom states he had onset of shortness of breath and left sided pleuritic chest pain. Pt states he awoke with pain and difficulty breathing. Had pacemaker placed yesterday.
PMHx:
HTN, Diabetes, Hypercholesterolemia, Arrythmia, CAD
PSHx:
Pacemaker, left knee surgery, b/l cataract

44. Case 2 Physical Exam BP 146/85, HR 80s, RR 30s, O2 Sat 88% Lungs EKG
Decreased breath sounds on left
EKG
Diagnosis?

45. Case 2 Pneumothorax Occurs during cannulation of central veins
Incidence
Cardiologist dependent
Treatment
Small or asymptomatic – observation
Large or symptomatic – Chest tube

46. Case 3 CC: Cardiac arrest
HPI: 59 yom found on couch. Wife states they were watching TV when patient let out a moan and then became unconscious. She states, he has a bad heart and had “something” put in a few years ago.
PMHx: unknown
Meds: bottles in bathroom

47. Case 3 Physical Exam Airway patent, no visible chest rise, no pulses
Generally: cool, clammy, diaphoretic
EKG:
Diagnosis?

48. Case 3 Cardiac Arrest with ICD (V-fib) 2% annual incidence with ICD
Etiology
ICD delivered predetermined shocks for identified event and patient failed to respond
ICD failed to recognize event and failed to shock appropriately
Failure to sense, lead fracture, EMI, inadvertent ICD deactivation

49. Case 3 Cardiac Arrest with ICD Treat using ACLS protocols
Secure airway
CPR
Defibrillate/shock as warranted
Keep sternal pad 10 cm away from pulse generator
Meds

50. Questions

51. References Emedicine http://www.emedicine.com/emerg/topic805.htm
Minish, Travis. Pacemaker Emergencies.
The Implantable Pacemaker, a short historical overview.
Healthy Hearts
Medtronic
Shelton State University
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