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Pacemakers and Internal Cardiac Defibrillators Mark Wahba Resident Rounds September 11, 2003.

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Presentation on theme: "Pacemakers and Internal Cardiac Defibrillators Mark Wahba Resident Rounds September 11, 2003."— Presentation transcript:

1 Pacemakers and Internal Cardiac Defibrillators Mark Wahba Resident Rounds September 11, 2003

2 See: Brady’s, Blocks, & Pacers Moritz Haager 1 hr rounds July 17, 2002

3 Brief History First described in 1952 Introduced into clinical practice in 1960 First endocardial defibrillators in in USA 1 million people had permanent pacemakers

4 Outline Indications Basics, Pacemaker Components and Code Complications of Implantation Pacemaker Malfunction Management Disposition ICD Guest

5 Basically: Device that provides electrical stimulation to cause cardiac contraction when intrinsic cardiac electrical activity is slow or absent

6 Pacemaker Functions 1. Stimulate cardiac depolarization 2. Sense intrinsic cardiac function 3. Respond to increased metabolic demand by providing rate responsive pacing 4. Provide diagnostic information stored by the pacemaker

7 Indications for Pacer 3 0 AVB and any of: –Symptomatic bradycardia –Asystole >3 sec or vent escape <40bpm –Post-AVN ablation –Post-op and not expected to improve –Neuromuscular disease 2 0 AVB + symptomatic bradycardia Chronic bi-/trifasicular block w/ intermittent 3 0 AVB or 2 0 AVB Type II Post-MI and any of: –Persistent 2 0 AVB or 3 0 AVB –Transient 2 0 AVB or 3 0 AVB and BBB SAN dysfunction + symptomatic brady’s (e.g. SSS) Recurrent syncope due to carotid sinus stimulation

8 Pacemaker Components and Anatomy

9 Pacemaker Components Pulse Generator Electronic Circuitry Lead System

10 Pulse Generator Subcutaneous or submuscular Lithium battery 4-10 years lifespan long life and gradual decrease in power  sudden pulse generator failure is an unlikely cause of pacemaker malfunction

11 Electronic Circuitry Sensing circuit Timing circuit Output circuit

12 Lead System Bipolar Lead has both negative, (Cathode) distal and positive, (Anode) proximal electrodes Separated by 1 cm Larger diameter: more prone to fracture Compatible with ICD Unipolar Negative (Cathode) electrode in contact with heart Positive (Anode) electrode: metal casing of pulse generator Prone to oversensing Not compatible with ICD

13 Difference on an ECG? Bipolar current travels only a short distance between electrodes small pacing spike: <5mm Anode Cathode + -

14 Difference on an ECG? Unipolar current travels a longer distance between electrodes larger pacing spike: >20mm Anode Cathode + -

15 Pacemaker Code I Chamber Paced II Chamber Sensed III Response to Sensing IV Programmable Functions/Rate Modulation V Antitachy Function(s) V: Ventricle T: Triggered P: Simple programmable P: Pace A: Atrium I: Inhibited M: Multi- programmable S: Shock D: Dual (A+V) D: Dual (T+I) C: Communicating D: Dual (P+S) O: None R: Rate modulating O: None S: Single (A or V) S: Single (A or V) O: None

16 Common Pacemakers VVI –Ventricular Pacing : Ventricular sensing; intrinsic QRS Inhibits pacer discharge VVIR –As above + has biosensor to provide Rate- responsiveness DDD –Paces + Senses both atrium + ventricle, intrinsic cardiac activity inhibits pacer d/c, no activity: trigger d/c DDDR –As above but adds rate responsiveness to allow for exercise

17 Rate Responsive Pacing When the need for oxygenated blood increases, the pacemaker ensures that the heart rate increases to provide additional cardiac output Adjusting Heart Rate to Activity Normal Heart Rate Rate Responsive Pacing Fixed-Rate Pacing Daily Activities

18 Determining type of pacemaker Wallet card: 5 letter code CXR: code visible Single lead in ventricle: VVI Separate leads DDD or DVI

19 Single Chamber VVI - lead lies in right ventricle Independent of atrial activity Use in AV conduction disease

20 Paced Rhythm Recognition VVI / 60

21 Dual Chamber Typically in pts with nonfibrillating atria and intact AV conduction Native P, paced P, native QRS, paced QRS ECG may be interpreted as malfunction when none is present May have fusion beats

22 Rate = 60 bpm / 1000 ms A-A = 1000 ms AP VP AP VP V-A AV V-A AV Atrial Pace, Ventricular Pace (AP/VP) Four “Faces” of Dual Chamber Pacing

23 Rate = 60 ppm / 1000 ms A-A = 1000 ms AP VS AP VS V-A AV V-A AV Atrial Pace, Ventricular Sense (AP/VS) Four “Faces” of Dual Chamber Pacing

24 AS VP AS VP Rate (sinus driven) = 70 bpm / 857 ms A-A = 857 ms Atrial Sense, Ventricular Pace (AS/ VP) V-A AV V-A Four “Faces” of Dual Chamber Pacing

25 Rate (sinus driven) = 70 bpm / 857 ms Spontaneous conduction at 150 ms A-A = 857 ms AS VS AS VS V-A AV V-A Atrial Sense, Ventricular Sense (AS/VS) Four “Faces” of Dual Chamber Pacing

26 Pacemaker Interventions Magnet application –No universal function of magnet –Model-specific magnet, some activate reed switch  asynchronous pacing at pre-set rate Interrogation / Programming –Model-specific pacemaker programmer can non-invasively obtain data on function and reset parameters

27 Magnet Application

28 Complications of Pacemaker Implantation

29 Venous access Infection Thrombophelbitis Pacemaker Syndrome

30 Venous Access Bleeding Pneumo / hemothorax Air embolism

31 Infection 2% for wound and ‘pocket’ infection 1% for bacteremia with sepsis S. aureus and S. epidermidis If bacteremic: start Vancomycin, remove system, TV pacemaker and IV abx for 4-6 weeks, new system

32 Thrombophlebitis Incidence 30-50% 1/3 have complete venous obstruction b/c of collateralization only % devp symptoms Swelling, pain, venous engorgement Heparin, lifetime warfarin

33 Pacemaker Syndrome Presents w/ worsening of original Sx post- implant of single chamber pacer AV asynchrony  retrograde VA conduction  atrial contraction against closed MV + TV  jugular venous distention + atrial dilation  sx of CHF and reflex vasodepressor effects Dx of exclusion Tx w/ dual chamber pacer

34 Pacemaker syndrome

35 Pacemaker Malfunction

36 4 broad categories 1. Failure to Output 2. Failure to Capture 3. Inappropriate sensing: under or over 4. Inappropriate pacemaker rate

37 Failure to Output absence of pacemaker spikes despite indication to pace dead battery fracture of pacemaker lead disconnection of lead from pulse generator unit Oversensing Cross-talk: atrial output sensed by vent lead

38 No Output Pacemaker artifacts do not appear on the ECG; rate is less than the lower rate Pacing output delivered; no evidence of pacing spike is seen

39 spikes not followed by a stimulus-induced complex change in endocardium: ischemia, infarction, hyperkalemia, class III antiarrhythmics (amiodarone, bertylium) Failure to capture

40 Failure to sense or capture in VVI

41 A: failure to capture atria in DDD

42 Inappropriate sensing: Undersensing Pacemaker incorrectly misses an intrinsic deoplarization  paces despite intrinsic activity Appearance of pacemaker spikes occurring earlier than the programmed rate: “overpacing” may or may not be followed by paced complex: depends on timing with respect to refractory period AMI, progressive fibrosis, lead displacement, fracture, poor contact with endocardium

43 Undersensing Pacemaker does not “see” the intrinsic beat, and therefore does not respond appropriately Intrinsic beat not sensed Scheduled pace delivered VVI / 60

44 Undersensing An intrinsic depolarization that is present, yet not seen or sensed by the pacemaker P-wave not sensed Atrial Undersensing

45 Inappropriate sensing: Oversensing Detection of electrical activity not of cardiac origin  inhibition of pacing activity “underpacing” pectoralis major: myopotentials oversensed Electrocautery MRI: alters pacemaker circuitry and results in fixed-rate or asynchronous pacing Cellular phone: pacemaker inhibition, asynchronous pacing

46 Oversensing An electrical signal other than the intended P or R wave is detected Marker channel shows intrinsic activity......though no activity is present VVI / 60

47 Inappropriate Pacemaker Rate Rare reentrant tachycardia seen w/ dual chamber pacers Premature atrial or vent contraction  sensed by atrial lead  triggers vent contraction  retrograde VA conduction  sensed by atrial lead  triggers vent contraction  etc etc etc Tx: Magnet application: fixed rate, terminates tachyarrthymia, reprogram to decrease atrial sensing

48 Causes of Pacemaker Malfunction Circuitry or power source of pulse generator Pacemaker leads Interface between pacing electrode and myocardium Environmental factors interfering with normal function

49 Pulse Generator Loose connections –Similar to lead fracture –Intermittent failure to sense or pace Migration –Dissects along pectoral fascial plane –Failure to pace Twiddlers syndrome –Manipulation  lead dislodgement

50 Twiddler’s Syndrome

51

52 Leads Dislodgement or fracture (anytime) –Incidence 2-3% –Failure to sense or pace –Dx w/ CXR, lead impedance Insulation breaks –Current leaks  failure to capture –Dx w/ measuring lead impedance (low)

53 Cardiac Perforation Early or late Usually well tolerated –Asymptomatic  inc’d pacing threshold, hiccups –Dx: P/E (hiccups, pericardial friction rub), CXR, Echo

54 Environmental Factors Interfering with Sensing MRI Electrocautery Arc welding Lithotripsy Cell phones Microwaves Mypotentials from muscle

55 Management

56 Management: History Most complications and malfunctions occur within first few weeks or months pacemaker identification card Syncope, near syncope, orthostatic dizziness, lightheaded, dyspnea, palpitations Pacemaker syndrome: diagnosis of exclusion

57 Management: Physical Exam Fever: think pacemaker infection Cannon “a” waves: AV asynchrony Bibasilar crackles if CHF Pericardial friction rub if perforation of RV

58 Management: adjuncts CXR: determine tip position ECG

59 Potential Problems Identifiable on an ECG Can Generally Be Assigned to Five Categories: Failure to output Failure to capture Undersensing Oversensing Pseudomalfunction

60 Pseudomalfunction: Hysteresis Allows a lower rate between sensed events to occur; paced rate is higher Lower Rate 70 ppm Hysteresis Rate 50 ppm

61 Management: ACLS Drug and Defibrillate as per ACLS guidelines However keep paddles >10cm from pulse generator May transcutaneously pace Transvenous pacing may be inhibited by venous thrombosis: may need flouroscopic guidance

62 AMI + Pacers Difficult Dx; most sensitive indicator is ST-T wave changes on serial ECG If clinical presentation strongly suggestive then should treat as AMI Coarse VF may inhibit pacer (oversensing) Successful resuscitation may lead to failure to capture (catecholamines, ischemia)

63 Disposition

64 Admit –Pacemaker infections /unexplained fever or WBC –Myocardial perforation –Lead # or dislodgement –Wound dehiscence / extrusion or erosion –Failure to pace, sense, or capture –Ipsilateral venous thrombosis –Unexplained syncope –Twiddlers syndrome

65 Disposition Potentially fixable in ED w/ help –Pacemaker syndrome –Pacemaker-mediated tachycardia –Cross-talk –Oversensing –Diaphragmatic pacing –Myopotential inhibitors

66 Internal Cardiac Defibrillators

67 Device to treat tachydysrhythmias If ICD senses a vent rate > programmed cut- off rate of the ICD  device performs cardioversion/defibrillation All ICDs are also vent pacemakers Required shock is approximately <15 Joules Similar problems with implantation as pacemakers

68 Indications for ICD Cardiac arrest from VF or VT not due to reversible etiology Spontaneous sustained VT Syncope NYD + inducible symptomatic VF or VT in setting of poor drug tolerance or efficacy Non-sustained VF or VT + CAD, prior MI, LV dysfunction and inducible VF or VT not responding to Class I antiarrhythmic Tx

69 ICD Malfunction Inappropriate Cardioversion Ineffective Cardioversion Failure to Deliver Cardioversion

70 Inappropriate Cardioversion Most frequently associated problem Sensing malfunction: SVT sensed as VT Shocks for nonsustained VT T waves detected as QRS complex and interpreted as  HR h/r Could be  incidence of VT, VF (hypoK, hypoMg, ischemia +/- infarction)

71 Ineffective Cardioversion Inadequate energy output Rise in defibrillation threshold  antiarrhythmics MI at lead site Lead fracture Dislodgement of leads

72 Failure to Deliver Cardioversion Failure to sense Lead fracture Electromagnetic interference Inadvertent deactivation

73 ACLS Interventions ICD may not prevent sudden cardiac death Same approach as with pacemakers Person performing CPR may feel a mild shock if ICD discharges during compressions Can deactivate device with magnet during resuscitation efforts

74 Disposition “in almost all instances, admission to a monitored setting with extended telemetric observation will be necessary” Rosen’s

75 Thanks to: Calgary Health Region Pacemaker nurses Karen and Sandra

76 References Brady et al EM Clinics NA. 16(2): Xie et al Em Clinics NA. 16(2): Shah et al EM Clinics NA. 16(2): Harrigan and Brady EMR 21(19): Rosen American College of Cardiology ECG of the Month Feb 2001: Pacemaker and Automatic Internal Cardiac Defibrillator, Weinberger et. al CorePace presentation by Medtronic Inc available from Pacmaker Nurses at Foothills Hospital,

77 Pacemaker and Defibrillator Clinics -Open Mon.-Fri hrs. -Electrophysiology for ICD’s Pacemaker Clinic On call pager #0569

78 ECG analysis Building on routine ECG interpretation skills Low Rate –Pacemakers not programmed below 50 BPM –ICD’s often low rate of 40 BPM

79 Assess atrial rhythm P waves and rate Atrial sensing Any atrial pacing Atrial capture

80 Assess Ventricular Rhythm QRS rate and morphology Relation to atrial rhythm Ventricular pacing Ventricular capture

81 Upper Rate Pacemakers do not prevent intrinsic heart rate from going too fast Pacing therapy and Drug therapy is required to suppress rapid rhythms like atrial fibrillation Mode switching devices recognize fast atrial rhythms and automatically switch to a non-tracking mode Some pacemakers Medtronic AT501 have anti-tachycardia therapies to treat Atrial Flutter but they cannot terminate atrial fibrillation

82 Defibrillators Most often ICD patient are not paced VT/VF detection and treatment with pacing or shock is their primary purpose Event memory to analyze rhythm detected and treated.

83 PM and ICD Pts in ER -Direction of Medical Director is that Cardiology should be consulted. -Cardiologist to initiate calling in On-Call Pacemaker Clinic nurse to assess device function and diagnostics.

84 Complete assessment in ER Assess symptoms ECG Look for Pacing and sensing, Atrial/Ventricular Obtain patients device info from card or old chart if possible Medications and compliance

85 Surgical Complications Incision issues: Infected pacemaker site presents risk for endocarditis Needs to be brought to Pacemaker or ICD clinic attention

86 Cardiac perforation/Tamponade –Early Post implant –New or unusual symptoms of sharp, stabbing chest pain. –Worse with deep breath –Usual cause is atrial perforation or tear –PACE, Vol. 25, No.5 Post Pacemaker Implant Pericarditis: Incidence and Outcomes with Active Fixation Leads. Soori Kivakumaran, M. E. Irwin, S. S. Gulamhusein

87 Management in ER Echocardiogram –Look for blood in pericardium –CV surgery consult –Don’t anticoagulate

88 Less than appropriate reasons we are called.. Don’t need to bother Cardiologist Will call Cardiology after device assessed Pt in ER with angina, not appropriate to assess device at that time We do follow patients with devices on a routine basis so they don’t need to be checked just because they have a device.

89 Magnets and devices No universal response to magnet application with cardiac devices.

90 Pacemaker Clinic FMC Monday to Friday Phone

91 EP Clinic ICD patient issues Monday to Friday hrs Phone

92 Nurse on Call CHR pager Please consult Cardiology Medical Director: Dr. A. M. Gillis –Electrophysiology


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