Electrical testing of pacemaker


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Electrical Testing Of Pacemaker & Pacemaker Complications

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Electrical testing of pacemaker

  1. 1. Electrical Testing Of Pacemaker & Pacemaker Complications Msn Pavan Kumar,DM,NIMS.
  2. 2. Electrical Testing Of PacemakerPacemaker complications
  3. 3. Electrical Testing Of Pacemaker Pacemaker components  Battery  Pacing impedance  Pulse generator 1. Output circuit 2. Sensing circuit 3. Timing circuit 4. Rate adaptive sensor 5. Modes and mode switching
  4. 4. Electrical Testing Of Pacemaker  Battery : Lithium iodine battery  High energy density ,  Long shelf life ,  Predictable loss of battery BOL (vol) – 2.8v  BOL (res) - <1komhs
  5. 5. Electrical Testing Of Pacemaker Pacing impedance : Pacing impedance refers to the opposition to current flow. Three sources contribute to pacing impedance: 1. Pacing lead conductor coil 2. Electrode-tissue interface  Electrode resistance  Polarization Normal lead impedance vary from 250-1200ohms. Single impedance value may be of little use with out previous values for comparison.
  6. 6. Electrical Testing Of Pacemaker1.Pulse generator output circuit Capture threshold , Pacing threshold , stimulation threshold Minimum amount of energy required to constantly cause depolarization Volts and pulse duration
  7. 7. Electrical Testing Of Pacemaker1. Pulse generator output circuit 2.0 v 1.5 v 1v
  8. 8. Electrical Testing Of Pacemaker 1. Pulse generator output circuitSite At implantation Acute ChronicAtrium <1.5mv 3-5 times Twice the threshold Threshold voltage voltageVentricle <1mv With PW 0.5ms With PW of 0.5ms
  9. 9. Electrical Testing Of Pacemaker1.Pulse generator output circuit High Pacemaker Output can cause Reduce longevity Diaphragmatic stimulation Muscle Sti. in Unipolar pacemakers Patient may “feel” heart beat Algorithm for checking pacemaker output threshold every beat and maintaining threshold just above it - Auto capture.
  10. 10. Electrical Testing Of Pacemaker2.Pulse generator sensing circuit : Ability of the device to detect intrinsic beat of the heart Measured - peak to peak magnitude (mv) & slew rate(mv/ms)
  11. 11. Electrical Testing Of Pacemaker2. Pulse generator sensing circuit : Reduce Lower Rate below intrinsic rate to inhibit pacing and ensure intrinsic activity Increase sensitivity setting while observing EGM. The sensitivity value at which sensing is lost on the EGM is the sensing threshold. Sensitivity threshold safety is twice the attained valve. Sensitivity Slew rate Atrium 1-2mv(0.5mv) > 0.5 v/s ventricle 2-3mv > 0.75 v/s
  12. 12. Electrical Testing Of Pacemaker3. Pulse generator timing circuit : a. Lower rate limit (LRL) b. Hysteresis rate c. Refractory and blanking periods d. Ventricular safety pacing interval . e. Upper rate response .
  13. 13. Electrical Testing Of Pacemaker3.Pulse generator timing circuit : Lower rate interval - lowest rate that the pacemaker will pace . A paced or non-refractory sensed event restarts the rate timer at the programmed rate.
  14. 14. Electrical Testing Of Pacemaker3. Pulse generator timing circuit :Condition LRL (beats/mt)Infrequent pauses 40-50Chronic persistent bradycardia 60-70Relative bradycardia detrimental (long QT) 70-80Detrimental fast heart rates (angina) 50-60VVI 60-70
  15. 15. Electrical Testing Of Pacemaker3. Pulse generator timing circuit : Hysteresis : Hysteresis allows the rate to drop below the programmed pacing LRL. Advantages of hysteresis : 1. Encourages native rhythm – maintain AV sync in VVI , prolong battery life 2. Prevent retrograde conduction – avoids pacemaker syndrome
  16. 16. Electrical Testing Of Pacemaker3. Pulse generator timing circuit :  AV delay (AVI) – pacemaker equivalent of PR interval.  Sensed vs paced AVI – paced AVI is programmed at 125-200ms , sensed AV interval is programmed at 20-50ms shorter than paced.  Dynamic AV delay allow pacemaker to respond to exercise sAVI – 150ms pAVI – 200ms
  17. 17. Electrical Testing Of Pacemaker3. Pulse generator timing circuit : AV delay (AVI) Longer AVI :  Good AV conduction – maintains AV synchrony , long battery life  Achieved by following methods :Programming longer AVI , managed ventricular pacing , AV delay hysteresis . Shorter AVI:  HOCM – RV apical pacing decreases HOCM gradient  CRT – usually 80-120ms , for 100%ventricular pacing and optimize CO  Physiological response to faster heart rates can be answered
  18. 18. Electrical Testing Of Pacemaker3. Pulse generator timing circuit :  Refractory and blanking periods :  Refractory period – sensing present but no action  Blanking period - sensing absent and hence no action
  19. 19. Electrical Testing Of Pacemaker3. Pulse generator timing circuit :  Blanking periods :Blanking period Time ImportanceAtrial blanking period 50-100ms Non programmable , Avoid atrial sensing of its own paced beatPost ventricular atrial 220ms Avoid sensing of ventricular beatblanking period Long PVAB decreases detection of AF,AFLVentricular blanking 50-100ms Non programmable,period Avoid ventricular sensing of its paced beatPost atrial ventricular 28ms if the PAvB period is too long, R on T -blanking period ventricular tachyarrhythmia.
  20. 20. Electrical Testing Of Pacemaker3. Pulse generator timing circuit :  Refractory period: Refractory period Importance Ventricular refractory period (VRP) Prevent sensing of T wave . Atrial refractory period (ARP) AVI (120-200ms) . Post ventricular atrial refractory period Avoid sensing retrograde P waves (PMT) , far field R waves .
  21. 21. Electrical Testing Of Pacemaker 3. Pulse generator timing circuit :Ventricular safety pacing/ventriculartriggered period/cross talk sensing window : Atrial pacing in DDD Trigger ventricular sensing PAVB - pAVI False inhibition of ventricular pacing circuit Asystole
  22. 22. Electrical Testing Of Pacemaker4. Pulse generator rate responsive pacing: Rate responsive pacing refer to ability of pacemaker to increase its lower rate in response to physiological stimulus Sinus node dysfunction , AF patients – fail to increase heart rates HRR should start with in 10s of exercise , peak at 90 – 120s and should return to baseline with in 60 – 120s after exercise. Fastest rate at which pacemaker will pace upper rate response. If intrinsic atrial rate exceeds URR then wenckebach or 2:1 AVB Choosing URR : young patients (150b/mt) , old angina (<110b/mt). Various sensors (activity , minute ventilation , QT)
  23. 23. Electrical Testing Of Pacemaker4. Pulse generator rate responsive pacing: Wenckebach 2:1 AVB
  24. 24. Electrical Testing Of Pacemaker4. Pulse generator modes:
  25. 25. Electrical Testing Of Pacemaker5. Pulse generator modes switching: DDD / VDD Atrial tachyarrythmias Sensed atrial events DDIR / Trigger fast ventricular rates VVIR Palpitations. Dyspnoea. And Fatigue.
  26. 26. Electrical Testing Of Pacemaker5. Pulse generator modes switching: Programming mode switching Mode switching occurs when the sensed atrial rate exceeds a programmed atrial tachycardia detection rate. By definition, this value must be faster than the URL (maximum tracking rate). Atrial tachycardia detection is typically programmed to 175-l88bpm or thereabouts.AMS base rate is higher than LRI.
  27. 27. Electrical Testing Of PacemakerPacemaker follow up guidelines: Transtelephonic monitoring guidelines Medicare guidelines Single chambered pacing Dual chambered pacing 1st month q 2 week 1st month q 2 weeks 2nd -48th month q 12 week 2nd – 30th month q 12weeks 49th – 72nd month q 8 week 31st – 48th month q 8 weeks 73rd month and later q 4 weeks 49th month and later q 4week NASPE guidelines Single or dual pacing 1st visit 6 – 8 week post implant , if symptomatic prior to this 5th month From 6th month q 3month Battery wear present q 1month
  28. 28. Electrical Testing Of PacemakerPacemaker complications
  29. 29. Pacemaker complications Pacemaker complicationsPocket complications Lead dislodgementPocket hematoma Pneumothorax /air embolismInfection Cardiac perforationErosion Extracardiac stimulationWound pain Venous thrombosisAllergic reactions Coronary sinus dissection Twidller syndrome Pacemaker malfunction
  30. 30. Pacemaker complicationsPocket hematoma : The risk of haematoma is increased in patients taking antithrombotic or anticoagulant drugs (Goldstein et al., 1998). Most small hematomas can be managed conservatively with cold compress and withdrawal of antiplatelet or antithrombotic agents. Occasionally, large hematomas that compromise the suture line or skin integrity may have to be surgically evacuated. Needle aspiration increases risk of infection and should not be done.
  31. 31. Pacemaker complicationsPocket hematoma : In patients requiring oral anticoagulants (warfarin), to take INR of about 2.0 at the time of implantation is safe (Belott & Reynolds, 2000). Unfractionated heparin or low-molecular-weight heparin are always discontinued prior to device implant and ideally avoided for a minimum of 24 hours post implantation. Administration of anticoagulants can be resumed within 48-72 h after implantation if there is no evidence of substantial hematoma formation.
  32. 32. Pacemaker complicationsDevice-related infections : The reported incidence of pacemaker-related infection ranges from 0.5% to 6% in early series The use of prophylactic antibiotics and pocket irrigation with antibiotic solutions has decreased the rate of acute infections following pacemaker implantations to <1 to 2 percent in most series The mortality of persistent infection when infected leads are not removed can be as high as 66%. DM, malignancy, operator inexperience, advanced age, corticosteroid use, anticoagulation, recent device manipulation, CRF, and bacteremia from a distant focus of infection.
  33. 33. Pacemaker complicationsDevice related infection : Device infection is defined as either:  (a) deep infection - infection involving the generator pocket and/or the intravenous portion of the leads, with bacteremia, requiring device extraction or  (b) superficial infection - characterized by local inflammation, involving the skin but not the generator pocket, and treated with oral antibiotics.
  34. 34. Pacemaker complicationsDevice related infection : 2007;49;1851-1859 J. Am. Coll. Cardiol.
  35. 35. Pacemaker complicationsDevice related infection : 2007;49;1851-1859 J. Am. Coll. Cardiol.
  36. 36. Pacemaker complicationsDevice related infection : 2007;49;1851-1859 J. Am. Coll. Cardiol.
  37. 37. Pacemaker complicationsWound pain : Infection , Pacemaker implanted too superficially , Pacemaker implanted too laterally , Pacemaker allergy .Skin erosion : Incidence has been estimated around 0.8% .Old age , infection. Surgical revision of pocket and reimplantation .Allergic reactions : Always rule out infection before coming to diagnosis of allergy
  38. 38. Pacemaker complicationsLead dislodgement: Relatively common – 5-10% of patients(ICD database 2001) Atrial more common than ventricular(2-3% vs. 1%) Micro dislodgement , macro dislodgement Increased pacing threshold , failure to pace and sense Active fixation (decreases risk)
  39. 39. Pacemaker complicationsPneumothorax , : Uncommon complication – 1.6-2.6% During or 48 hrs after procedure Inadvent puncture and laceration of subclavian vein , artery or lung Related to operator experience and underlying anatomy Avoided by 1. Venogram – flouroscpic puncture 2. Axillary venous access (Martin etal’96) 3. One way mechanism sheath
  40. 40. Pacemaker complicationsCardiac Perforation : Uncommon but potentially serious complication - lower than 1%. Acute (<5 days) , subacute(5d-1month) , chronic (>1month) Increasing stimulation threshold , RBBB pattern for RV pacing, intercostal muscle or diaphragmatic contraction, friction rub, and pericarditis, pericardial effusion, or cardiac tamponade. CXR , ECHO , CT Lead withdrawal and repositioning ; surgical back up
  41. 41. Pacemaker complicationsCardiac Perforation :
  42. 42. Pacemaker complicationsExtracardiac stimulation The diaphragm or pectoral or intercostal muscles Diaphragmatic stimulation - direct stimulation of the diaphragm (left) or stimulation of the phrenic nerve (right). Early postimplantation period , dislodgment of the pacing lead. MC in patients with LV coronary vein branch lead placement for CRT Output pacing importance (testing and treatment) Pectoral stimulation - incorrect orientation of the pacemaker or a current leak from a lead insulation failure or exposed connector.
  43. 43. Pacemaker complicationsVenous thrombosis : Venous thrombosis occurs in 30% to 50% of patients and only 1-3% of patients become symptomatic. Manifestations vary from usually asymptomatic, acute symptomatic thrombosis, and even SVCS . Early or late after pacemaker implantation. Predictors of severe stenosis are multiple pacemaker leads , previous pacing , double coils , hormone therapy . Asymptomatic (no treatment) , symptomatic (anticoagulants – endovascular stents – surgical correction ).
  44. 44. Pacemaker complicationsTwiddler syndrome: Obese women with loose, fatty subcutaneous tissue Small size of the implanted generator with a large pocket Twisting of pulse generator in long axis Lead dislodgement and lead fracture Failure to capture
  45. 45. Pacemaker complications Twiddler syndrome: The prevelance of this syndrome is 0.07% (Gungor et al., 2009) Rotated along the transverse axis it is referred by us as the reel syndrome. Pocket should be revised. Avoid by Limit the pocket size,  Suture the device to the fascia  The patients not to manipulate their device pocket
  46. 46. Pacemaker malfunction Failure to capture Failure to output Sensing abnormalities(under and over sensing) Specific mode complications 1. Pacemaker related tachycardia 2. Pacemaker syndrome
  47. 47. Pacemaker malfunctionFailure to capture: Pacing artifact present but no evoked potential . Causes 1. Lead dislodgement or perforation 2. Lead maturation(inflammation/fibrosis)(exit block) 3. Battery depletion 4. Circuit failure(coil fracture , insulation defect) 5. Capture management algorithm failure 6. Inappropriate programming 7. Pseudo malfunction 8. Functional non capture 9. Metabolic , drugs , cardiomyopathies
  48. 48. Pacemaker malfunction Failure to capture:Electrocardiographic tracing from a patient with a DDDR pacemaker. All ventricular pacing artifacts but one failed to result in ventricular depolarization— that is, failure to capture
  49. 49. Pacemaker malfunction Failure to capture: Pacing threshold Normal Increased Dislodgement Normal Exit blockBattery depletionFunctional non capture Impedance Insulation Decreased failure/break Lead fracture Increased Loose screw
  50. 50. Pacemaker malfunctionFailure to output: Absence of pacing stimuli and hence no capture . Causes 1. Pseudo malfunction - hysteresis , PMT termination , sleep rate 2. Over sensing - EMI ; T P R over sensing ; Myopotential/diaphragmatic ; Cross talk ; Make break signals 3. Open circuit - lead fracture , loose screw , air in the pocket , incompatible lead . 4. Battery depletion 5. Recording artifact.
  51. 51. Pacemaker malfunction  Failure to output: VVIR pacemaker This patient had a pacemaker programmed to a unipolar sensing configuration. The sensing of myopotentials led to symptomaticpauses, and reprogramming the pacemaker to a bipolar sensing configuration prevented subsequent myopotential over sensing.
  52. 52. Pacemaker malfunction Failure to output: Application of magnet Eliminates pauses Pauses persistentOver sensing Normal Battery depletionPseudo malfunction Impedance Insulation Decreased failure/break Lead fracture Increased Loose screw
  53. 53. Pacemaker malfunctionBattery depletion : Elective replacement indicators (ERI) 1. Low voltage(2.1-2.4) 2. Low pacing rate on magnet application 3. Elevated battery impedance 4. Increased pulse width duration 5. Restricted programmability 6. Change to simpler pacing mode End of life (EOL) 1. Low voltage(≤2.1vol)
  54. 54. Pacemaker malfunctionPacemaker undersensing : Pacing artifact present but no sensing(sensed beat doesn’t reset cycle) Causes are 1. Defect in signal production – scar /fibrosis , BBB , ectopic , cardioversion , defibrillation , metabolic. 2. Defect in signal transmission – lead fracture /dislodgement , insulation failure , partial open circuit. 3. Defect in pacemaker – battery depletion , sensing circuit abnormalities , committed DVI.
  55. 55. Pacemaker malfunctionPacemaker undersensing : VVI pacemaker
  56. 56. Pacemaker malfunctionPacemaker over sensing : Cross talk : Present as failure to pace High atrial output Causes High ventricular sensitivity 1. EMI Low VBP 2. T , P , R over sensing . 3. Cross talk Ventricular sensing of 4. Myopotential (unipolar) paced atrial impulse 5. Make break signals Pts with Poor AV conduction – Ventricular Asystole
  57. 57. Pacemaker malfunction  Electromagnetic interference :Source Pacer Inhibition Rate Asynchronous Uni/ damage increase noise bipolarCardioversion/ Y N N N U/BDefibrillationAnit theft devices / N Y N N UWeapon detectorPhone (cell/cordless) N Y Y Y U/BAblation Y Y Y N U/BDiathermy/ Y Y Y Y U/BlithotripsyFM radio N Y N Y UTV transmitterMRI/PET Y Y(N) Y(N) Y(N) U/B
  58. 58. Pacemaker malfunctionPacemaker syndrome : Seen in 20% of PPI (5% severe symptomatic) VVI/DDD/AAI Pulsations in neck , fatigue , cough ,chest fullness , headache , chocking sensation , PND , confusion , syncope , pulmonary edema. Rx : VVI – program hysteresis , or change to DDD ; DDD –atrial lead reprogrammed or changed
  59. 59. Pacemaker malfunctionPacemaker mediated tachycardia :  Dual chamber  VPC , intact retrograde conduction , PVARP<VA .  Px , Rx : 1. PVARP > VA 2. Long PVARP after VPC 3. Absent atrial sensing after VPC
  60. 60. Pacemaker Testing
  61. 61. Pacemaker Testing
  62. 62. Pacemaker Testing
  63. 63. Thank you
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