Pacemakers and AICD ’ s

1. PacemakersandAICD’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 Nomenclature

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 • Etiology • 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 • 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: • 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: • 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 • 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