3 Brief History First described in 1952 Introduced into clinical practice in 1960First endocardial defibrillators in 19801991 in USA 1 million people had permanent pacemakers
4 Outline Indications Basics, Pacemaker Components and Code Complications of ImplantationPacemaker MalfunctionManagementDispositionICDGuest
5 Basically:Device that provides electrical stimulation to cause cardiac contraction when intrinsic cardiac electrical activity is slow or absent
6 Pacemaker Functions Stimulate cardiac depolarization Sense intrinsic cardiac functionRespond to increased metabolic demand by providing rate responsive pacingProvide diagnostic information stored by the pacemaker
7 Indications for Pacer 30 AVB and any of: Symptomatic bradycardiaAsystole >3 sec or vent escape <40bpmPost-AVN ablationPost-op and not expected to improveNeuromuscular disease20 AVB + symptomatic bradycardiaChronic bi-/trifasicular block w/ intermittent 30 AVB or 20 AVB Type IIPost-MI and any of:Persistent 20 AVB or 30 AVBTransient 20 AVB or 30 AVB and BBBSAN dysfunction + symptomatic brady’s (e.g. SSS)Recurrent syncope due to carotid sinus stimulationClass I recommendations From Rosen
12 Lead SystemBipolarLead has both negative, (Cathode) distal and positive, (Anode) proximal electrodesSeparated by 1 cmLarger diameter: more prone to fractureCompatible with ICDUnipolarNegative (Cathode) electrode in contact with heartPositive (Anode) electrode: metal casing of pulse generatorProne to oversensingNot compatible with ICDBoth are ONE wire. Don’t confuse bipolar and unipolar leads with single chamber and dual chamber pacemakers.Unipolar prone to oversensing because Anode may pick up myopotenials from muscle or other extrinsic source
13 Difference on an ECG? Bipolar current travels only a short distance between electrodessmall pacing spike: <5mm+Anode-Cathode
14 Difference on an ECG? Unipolar current travels a longer distance between electrodeslarger pacing spike: >20mm+Anode-Cathode
15 Pacemaker Code P: Simple programmable V: Ventricle V: Ventricle ChamberPacedIISensedIIIResponseto SensingIVProgrammableFunctions/RateModulationVAntitachyFunction(s)P: SimpleprogrammableV: VentricleV: VentricleT: TriggeredP: PaceM: Multi-programmableA: AtriumA: AtriumI: InhibitedS: ShockD: Dual (A+V)D: Dual (A+V)D: Dual (T+I)C: CommunicatingD: Dual (P+S)The first letter refers to the chamber(s) being pacedThe second letter refers to the chamber(s) being sensedThe third letter refers to the pacemaker’s response to a sensed event:T = Triggered D = Dual (inhibited and triggered*)I = Inhibited O = No response*In a single chamber mode, “triggered” means that when an intrinsic event is sensed, a pace is triggered immediately thereafter. In a dual chamber mode, “triggered” means that a sensed atrial event will initiate (trigger) an A-V delay.The fourth letter denotes the pacemaker’s programmability and whether it is capable of rate response:P = Simple Programmable (rate and/or output)M = Multiprogrammable (rate, output, sensitivity, etc.)C = Communicating (pacemaker can send/receive information to/from the programmer)R = Rate ModulationO = NoneNote that this sequence is hierarchical. In other words, it is assumed that if a pacemaker has rate modulation capabilities, “R”, that it also can communicate, “C”.The fifth letter represents the pacemaker’s antitachycardia functions:P = Pace D = Dual (pace and shock available)S = Shock O = NoneYou may want to test the audience by having them describe different pacing modes. More modes and ECG strips are found in Module 2.O: NoneO: NoneO: NoneR: Rate modulatingO: NoneS: Single(A or V)S: Single(A or V)O: None
16 Common PacemakersVVIVentricular Pacing : Ventricular sensing; intrinsic QRS Inhibits pacer dischargeVVIRAs above + has biosensor to provide Rate-responsivenessDDDPaces + Senses both atrium + ventricle, intrinsic cardiac activity inhibits pacer d/c, no activity: trigger d/cDDDRAs above but adds rate responsiveness to allow for exerciseBiosensors --- most are vibrations sensors that increase HR in proportion to activity sensed, but can also have pH, venous temp, resp rate, QT interval, stroke volume, O2 sat, RA pressure sensors less commonly.Dual chamber pacing allows for atrial contribution to CO (up to 30% of CO)
17 Rate Responsive Pacing When the need for oxygenated blood increases, the pacemaker ensures that the heart rate increases to provide additional cardiac outputAdjusting Heart Rate to ActivityNormal Heart RateRate Responsive PacingFixed-Rate PacingPiezoelectric crystal that detects mechanical signals produced by movement, mechanical signals translate into electrical signals that increase rate of the pacemakerDaily Activities
18 Determining type of pacemaker Wallet card: 5 letter codeCXR: code visibleSingle lead in ventricle: VVISeparate leads DDD or DVI
19 Single Chamber VVI - lead lies in right ventricle Independent of atrial activityUse in AV conduction disease
21 Dual ChamberTypically in pts with nonfibrillating atria and intact AV conductionNative P, paced P, native QRS, paced QRSECG may be interpreted as malfunction when none is presentMay have fusion beats
22 Four “Faces” of Dual Chamber Pacing Atrial Pace, Ventricular Pace (AP/VP)AVV-AAVV-AKnowing the basic A-V and V-A intervals will help in understanding the four modes or “faces” of dual chamber pacing. In the first example, the pacemaker is pacing in both the atrium and the ventricle–most likely a patient with sinus node dysfunction and AV block.APVPRate = 60 bpm / 1000 msA-A = 1000 ms
23 Four “Faces” of Dual Chamber Pacing Atrial Pace, Ventricular Sense (AP/VS)APVSV-AAVIn this example, the atrium is being paced, but AV conduction is intact, so the ventricular output is inhibited by a sensed ventricular event.Rate = 60 ppm / 1000 msA-A = 1000 ms
24 Four “Faces” of Dual Chamber Pacing Atrial Sense, Ventricular Pace (AS/ VP)V-AAVIn this example, the atrial rate is driving the ventricular rate–also called atrial tracking. This patient has adequate sinus node function with AV block.ASASVPVPRate (sinus driven) = 70 bpm / 857 msA-A = 857 ms
25 Four “Faces” of Dual Chamber Pacing Atrial Sense, Ventricular Sense (AS/VS)V-AAVASVSIn this example, the patient has adequate sinus node function and intact AV conduction, but may experience little to no increase in sinus rate with activity and/or AV block that occurs at increased rates. At appropriate rates, it is best to try and utilize the patient’s intrinsic rhythm when possible.Rate (sinus driven) = 70 bpm / 857 msSpontaneous conduction at 150 msA-A = 857 ms
26 Pacemaker Interventions Magnet applicationNo universal function of magnetModel-specific magnet, some activate reed switch asynchronous pacing at pre-set rateInterrogation / ProgrammingModel-specific pacemaker programmer can non-invasively obtain data on function and reset parametersMagnet applicationUseful to test pacemaker function and battery life, especially if intrinsic HR > paced ratePre-set paced rate dec’s w/ dec’g battery lifeProgrammable functions include lower rate limit, upper rate limit, AV interval, energy output, refractory periods, blanking period (interval after d/c during which no signals are sensed), mode of function (e.g. A, V, or D), max atrial tracking rate (fastest atrial rate pacer will keep up with), vent pacing response, algorithm for tachycardia termination, sensing parameters
27 Magnet Applicationdemand ventricular pacer: a low pacemaker rate of 50 beats/min was programmed to preserve the patient's intrinsic sinus rhythm. Magnet application (arrows) causes fixed-rate pacing (extremely small pacing artifacts are visible in lead V3) at 100 beats/min. The rapid magnet-induced pacing rate (asterisks on the lead-V1 rhythm strip) prevents competition with the intrinsic rhythm. Note the P waves following the pacemaker-induced QRS complexes, indicating 1:1 ventricular-to-atrial conduction.
31 Infection 2% for wound and ‘pocket’ infection 1% for bacteremia with sepsisS. aureus and S. epidermidisIf 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 symptomsSwelling, pain, venous engorgementHeparin, lifetime warfarin
33 Pacemaker SyndromePresents w/ worsening of original Sx post-implant of single chamber pacerAV asynchrony retrograde VA conduction atrial contraction against closed MV + TV jugular venous distention + atrial dilation sx of CHF and reflex vasodepressor effectsDx of exclusionTx w/ dual chamber pacerPresent w/ presyncope, syncope, orthostatic dizziness, lightheadedness, fatigue, lethargy, CP, neck fullness, other non-specific complaintsCan get w/ dual chamber pacer if SA node rate > paced rate in pts w/ AV block
34 Figure A 12-lead ECG from a 63-year-old woman with recurrent syncope several months after implantation of a VVI pacemaker. The arrows show the retrograde P waves of 1:1 ventricular-to-atrial conduction that may be associated with a pacemaker syndrome.Pacemaker syndrome
36 4 broad categories Failure to Output Failure to Capture Inappropriate sensing: under or overInappropriate pacemaker rate
37 Failure to Outputabsence of pacemaker spikes despite indication to pacedead batteryfracture of pacemaker leaddisconnection of lead from pulse generator unitOversensingCross-talk: atrial output sensed by vent leadCross-talk = oversensing of pacemaker generated electrical activity E.g. vent lead senses atrial pacing spike misinterprets as vent contraction inhibits pacer d/c skipped beat dizziness / syncope
38 CorePace Module 4: Troubleshooting No OutputPacemaker artifacts do not appear on the ECG; rate is less than the lower rateWhen the pacemaker problem is no output, the marker channel shows pacing markers—AP or VP—although no artifact appears on the ECG.No output is defined as the failure to pace. Impulses are generated from the IPG, but is not transferred to the lead.Pacing output delivered; no evidence of pacing spike is seen
39 Failure to capture spikes not followed by a stimulus-induced complex change in endocardium: ischemia, infarction, hyperkalemia, class III antiarrhythmics (amiodarone, bertylium)
40 Failure to sense or capture in VVI Figure A 12-lead ECG with a lead-V1 rhythm strip from an 84-year-old man who returned to a pacemaker clinic with dizziness 11 years after implantation of a VVI pacemaker. Arrows show pacing artifacts continuing regularly (68/min) not sensing for the patient's intrinsic beats and not producing paced beats. The asterisks indicate the single incidence of ventricular capture by the pacemakerFailure to sense or capture in VVI
41 A: failure to capture atria in DDD Figure A 12-lead ECG with a lead-V1 rhythm strip from a 73-year-old man seen in a pacemaker clinic 6 months after implantation of a DDD pacemaker. During the pause after the VPB, minimum-rate pacing occurs (the first six arrows), but with failure of atrial capture. An asterisk and the last arrow indicate the single incidence of atrial capture by the pacemaker.A: failure to capture atria in DDD
42 Inappropriate sensing: Undersensing Pacemaker incorrectly misses an intrinsic deoplarization paces despite intrinsic activityAppearance 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 periodAMI, progressive fibrosis, lead displacement, fracture, poor contact with endocardium
43 Scheduled pace delivered Intrinsic beat not sensed UndersensingPacemaker does not “see” the intrinsic beat, and therefore does not respond appropriatelyScheduled pace deliveredIntrinsic beat not sensedVVI / 60
44 CorePace Module 4: Troubleshooting UndersensingAn intrinsic depolarization that is present, yet not seen or sensed by the pacemakerP-wave not sensedAn intrinsic depolarization occurs in the atrium, but this depolarization is not sensed by the pacemaker. Therefore, the pacemaker sends an inappropriate pacing pulse to that chamber. Undersensing can be thought of as “overpacing.”In this example, an AAI pacemaker is programmed to inhibit the atrial pacing pulse when a P-wave is sensed. Because the P-wave was not sensed, the pacemaker delivered an atrial pulse. If a pacemaker is undersensing, you will not see appropriate atrial sense markers on the marker channel.Atrial Undersensing
45 Inappropriate sensing: Oversensing Detection of electrical activity not of cardiac origin inhibition of pacing activity“underpacing”pectoralis major: myopotentials oversensedElectrocauteryMRI: alters pacemaker circuitry and results in fixed-rate or asynchronous pacingCellular phone: pacemaker inhibition, asynchronous pacing
46 OversensingVVI / 60...though no activity is presentMarker channel shows intrinsic activity...An electrical signal other than the intended P or R wave is detectedOversensing will exhibit pauses in single chamber systems. In dual chamber systems, atrial oversensing may cause fast ventricular pacing without P waves preceding the paced ventricular events.
47 Inappropriate Pacemaker Rate Rare reentrant tachycardia seen w/ dual chamber pacersPremature atrial or vent contraction sensed by atrial lead triggers vent contraction retrograde VA conduction sensed by atrial lead triggers vent contraction etc etc etcTx: Magnet application: fixed rate, terminates tachyarrthymia,reprogram to decrease atrial sensing
48 Causes of Pacemaker Malfunction Circuitry or power source of pulse generatorPacemaker leadsInterface between pacing electrode and myocardiumEnvironmental factors interfering with normal function
49 Pulse Generator Loose connections Migration Twiddlers syndrome Similar to lead fractureIntermittent failure to sense or paceMigrationDissects along pectoral fascial planeFailure to paceTwiddlers syndromeManipulation lead dislodgement
52 Leads Dislodgement or fracture (anytime) Insulation breaks Incidence 2-3%Failure to sense or paceDx w/ CXR, lead impedanceInsulation breaksCurrent leaks failure to captureDx w/ measuring lead impedance (low)Fractures occur at sharp turns (pulse generator, entry into vein, in ventricle, most commonly occurring at the clavicle/first rib locationMeasure lead impedance w/ pacemaker programmerInsulation break like leaky garden hose
53 Cardiac Perforation Early or late Usually well tolerated Asymptomatic inc’d pacing threshold, hiccupsDx: P/E (hiccups, pericardial friction rub), CXR, Echo
54 Environmental Factors Interfering with Sensing MRIElectrocauteryArc weldingLithotripsyCell phonesMicrowavesMypotentials from muscle
56 Management: HistoryMost complications and malfunctions occur within first few weeks or monthspacemaker identification cardSyncope, near syncope, orthostatic dizziness, lightheaded, dyspnea, palpitationsPacemaker syndrome: diagnosis of exclusion
57 Management: Physical Exam Fever: think pacemaker infectionCannon “a” waves: AV asynchronyBibasilar crackles if CHFPericardial friction rub if perforation of RV
58 Management: adjunctsCXR: determine tip positionECG
59 CorePace Module 4: Troubleshooting Potential Problems Identifiable on an ECG Can Generally Be Assigned to Five Categories:Failure to outputFailure to captureUndersensingOversensingPseudomalfunctionThe causes of undersensing, oversensing, noncapture, lack of output, and pseudomalfunctions vary. However, each of these anomalies compromises the pacemaker’s ability to supplement intrinsic conduction.
60 Pseudomalfunction: Hysteresis CorePace Module 4: TroubleshootingPseudomalfunction: HysteresisAllows a lower rate between sensed events to occur; paced rate is higherHysteresis Rate 50 ppmLower Rate 70 ppmHysteresis provides the capability to maintain the patient’s intrinsic heart rhythm as long as possible, while providing back-up pacing if the intrinsic rhythm falls below the hysteresis rate. Because hysteresis exhibits longer intervals between sensed events, it may be perceived as oversensing.
61 Management: ACLS Drug and Defibrillate as per ACLS guidelines However keep paddles >10cm from pulse generatorMay transcutaneously paceTransvenous pacing may be inhibited by venous thrombosis: may need flouroscopic guidanceMay defibrillate in AP direction
62 AMI + PacersDifficult Dx; most sensitive indicator is ST-T wave changes on serial ECGIf clinical presentation strongly suggestive then should treat as AMICoarse VF may inhibit pacer (oversensing)Successful resuscitation may lead to failure to capture (catecholamines, ischemia)
67 Internal Cardiac Defibrillators Device to treat tachydysrhythmiasIf ICD senses a vent rate > programmed cut-off rate of the ICD device performs cardioversion/defibrillationAll ICDs are also vent pacemakersRequired shock is approximately <15 JoulesSimilar problems with implantation as pacemakers
68 Indications for ICDCardiac arrest from VF or VT not due to reversible etiologySpontaneous sustained VTSyncope NYD + inducible symptomatic VF or VT in setting of poor drug tolerance or efficacyNon-sustained VF or VT + CAD, prior MI, LV dysfunction and inducible VF or VT not responding to Class I antiarrhythmic Tx
70 Inappropriate Cardioversion Most frequently associated problemSensing malfunction: SVT sensed as VTShocks for nonsustained VTT waves detected as QRS complex and interpreted as HRh/r Could be incidence of VT, VF (hypoK, hypoMg, ischemia +/- infarction)
71 Ineffective Cardioversion Inadequate energy outputRise in defibrillation threshold antiarrhythmicsMI at lead siteLead fractureDislodgement of leads
72 Failure to Deliver Cardioversion Failure to senseLead fractureElectromagnetic interferenceInadvertent deactivation
73 ACLS Interventions ICD may not prevent sudden cardiac death Same approach as with pacemakersPerson performing CPR may feel a mild shock if ICD discharges during compressionsCan 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 nursesKaren and Sandra
76 References Brady et al. 1998. EM Clinics NA. 16(2): 361-388 Xie et al Em Clinics NA. 16(2):Shah et al EM Clinics NA. 16(2):Harrigan and Brady EMR 21(19):RosenAmerican College of Cardiology ECG of the Month Feb 2001:Pacemaker and Automatic Internal Cardiac Defibrillator, Weinberger et. alCorePace presentation by Medtronic Inc available from Pacmaker Nurses at Foothills Hospital,
77 Pacemaker and Defibrillator Clinics -Open Mon.-Fri hrs.-Electrophysiology for ICD’s 41248-Pacemaker Clinic 41188-On call pager #0569
78 ECG analysis Building on routine ECG interpretation skills Low RatePacemakers not programmed below 50 BPMICD’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 morphologyRelation to atrial rhythmVentricular pacingVentricular capture
81 Upper RatePacemakers do not prevent intrinsic heart rate from going too fastPacing therapy and Drug therapy is required to suppress rapid rhythms like atrial fibrillationMode switching devices recognize fast atrial rhythms and automatically switch to a non-tracking modeSome 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 purposeEvent memory to analyze rhythm detected and treated.
83 -Direction of Medical Director is that Cardiology should be consulted. 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 symptomsECG Look for Pacing and sensing, Atrial/VentricularObtain patients device info from card or old chart if possibleMedications and compliance
85 Surgical Complications Incision issues: Infected pacemaker site presents risk for endocarditisNeeds to be brought to Pacemaker or ICD clinic attention
86 Cardiac perforation/Tamponade Early Post implantNew or unusual symptoms of sharp, stabbing chest pain.Worse with deep breathUsual cause is atrial perforation or tearPACE, Vol. 25, No.5 Post Pacemaker Implant Pericarditis: Incidence and Outcomes with Active Fixation Leads. Soori Kivakumaran, M. E. Irwin, S. S. Gulamhusein
87 Echocardiogram Look for blood in pericardium CV surgery consult Management in EREchocardiogramLook for blood in pericardiumCV surgery consultDon’t anticoagulate
88 Less than appropriate reasons we are called.. Don’t need to bother CardiologistWill call Cardiology after device assessedPt in ER with angina, not appropriate to assess device at that timeWe 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 devicesNo universal response to magnet application with cardiac devices.
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