Pacemaker troubleshootingsingle chamber pacemakers Reasons for evaluation • Patient symptomatic – Palpitation – Syncope – presyncope • Pacemaker malfunction suspected – ECG – Telemetry – Ambulatory ECG • Routine pacemaker follow up Patient details • • • • • • • • Indication for pacing Implant operative note Diagnosis Medication –can alter pacing tresholds DC ,MRI,electrocautery Trauma,electrical current exposure Concurrent medical problems-CRF,hyperkalemia Prior ECG,CXR Pacemaker system – manufacturer – Model – current programming – date of implant – special features – Sensing and pacing tresholds – impedance Lead system – manufacturer – model – polarity – Fixation – insulation and date Causes of pacemaker malfunction • Pacing stimuli present with failure to capture • Pacing stimuli present with failure to sense • Pacing stimuli absent – Oversensing – No output • Pseudomalfunction Failure to capture • No evidence of depolarization after pacing artifact Loss of capture Early post device implantation • CXR abnormal – Lead dislodgement • Downward migration of PG • Failure to secure anchoring sleeves properly • Too little or too much slack – Lead perforation • Elevated impedance – Loose set screw – failure to seat lead pin properly in header • Normal CXR,normal impedance – Micro lead dislodgement – Inflammatory response Late post device implantation • • • • • Battery depletion Twiddler s syndrome Abnormal myocardium Insulation failure Conductor failure – Mechanical stress on lead • Anchoring sleeve • Interaction with generator in pocket • b/w clavicle and first rib • Increase the energy in the output pulse – Run a capture threshold test – Adjust the output parameters, if necessary • Pulse amplitude (V) • Pulse width or duration (ms) – It is generally more efficient to increase the pulse amplitude • Investigate possible lead problems • Reprogram device polarity Undersensing • An intrinsic depolarization that is present, yet not seen or sensed by the pacemaker P-wave not sensed Atrial Undersensing • Undersensing occurs when the pacemaker does not detect intrinsic activity that really is there • Undersensing causes the pacemaker to pace more than it should Undersensing May Be Caused By: • Inappropriately programmed sensitivity • Lead dislodgment • Lead failure: – Insulation break; conductor fracture • Lead maturation • Change in the native signal • Functional – Magnet – Noise reversion • Adjust the sensitivity setting – Run a sensing threshold test – Measure the intrinsic signals – Adjust the sensitivity appropriately • To increase sensitivity, decrease the mV setting – Make all changes to sensitivity settings in small steps since large changes may only introduce new sensing problems Oversensing Marker channel shows intrinsic activity... ...Though no activity is present Ventricular Oversensing • The sensing of an inappropriate signal – Can be physiologic or nonphysiologic • Oversensing occurs when the pacemaker inappropriately “thinks” that it sees intrinsic activity that is not there • Oversensing causes the pacemaker to inhibit the pacing output pulse, even though the device should be pacing • Myopotentials – Pectoralis,rectus abdominis,diaphragm – Bipolar leads are less susceptible • Oversensing of normal intracardiac signals – Reduce sensitivity of affected lead to eliminate oversensing • EMI • Provocative maneuvers may be needed if intermittent symptoms • Magnet eliminates pauses-oversensing • Reprogram the sensitivity – Conduct a sensing threshold test – Adjust the sensitivity by making the device less sensitive (increase the mV setting) – Make only small changes • Extend the refractory period 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 No Output May Be Caused By: • • • • Poor connection at connector block Lead failure Battery depletion Circuit failure • Steps to take for possible loss of output – Verify all lead connections – Check lead integrity – Evaluate battery status – Contact the device manufacturer • Loss of output may require the replacement of all or part of the pacing system Pseudomalfunctions Pseudomalfunctions are defined as: Unusual,Unexpected ECG findings that appear to result from pacemaker malfunction but that represent normal pacemaker function • • • • • • Hysteresis Magnet rate rate responsive pacing Noise reversion Rate drop response Sleep rate algorithm Hysteresis • Allows a lower rate between sensed events to occur; paced rate is higher Lower Rate 70 ppm Hysteresis Rate 50 ppm Magnet Operation • Magnet application causes asynchronous pacing at a designated “magnet” rate • Threshold Margin Test (TMT) • Three beats at 100 bpm, followed by a magnet rate of 85 • Third beat has an automatic pulse width decrement of 25% • Elective replacement indicators-change the rate from 85 to 65 • Extended TMT. – TMT is performed at 100 ppm – Pulse width reduced by 25% on 3rd , 50% on 5th , and 75% on 7th Rate Responsive Pacing • An accelerating or decelerating rate may be perceived as anomalous pacemaker behavior VVIR / 60 / 120 Electrical Reset and Battery Depletion • Reset may occur due to exposure to EMI electrocautery, defibrillation, causing reversion to a “backup” mode – Rate and mode changes will occur – Device can usually be reprogrammed to former parameters • Elective replacement indicators (ERI) can resemble back-up mode – Interrogating device will indicate ERI (“Replace Pacer”) A Change in Pacing Modes May Be Caused By: • • • • Battery depletion indicators (ERI/EOL) Electrical reset Mode switching Noise reversion Noise Reversion • Sensing occurring during atrial or ventricular refractory periods will restart the refractory period. Continuous refractory sensing is called noise reversion and will: – Cause pacing to occur at the sensor-indicated rate for rate-responsive modes – Cause pacing to occur at the lower rate for nonrate-responsive modes Noise reversion VT in a patient with VVI-pacing occurs at lower rate due to noise reversion Rate drop response Delivers pacing at high rate when episodic drop in rate occurs Muscle Stimulation May Be Caused By: • Inappropriate electrode placement near diaphragm or nerve plexus • Break in lead insulation • Unipolar pacing Flouro diagnosis 1.ECG shows A.Failure to sense B.Failure to capture C.Hysteresis D.Oversensing 2.ECG shows A.Failure to sense B.Failure to capture C.Hysteresis D.Oversensing 3.ECG shows A.Failure to sense B.Failure to capture C.Hysteresis D.Oversensing • 4.ECG demonstrates a.Failure to sense b.Failure to capture c.Functional non capture d.fusion 5 ECG shows A.Failure to sense B.Failure to capture C.Hysteresis D.Functional non capture 6 ECG shows A.Functional non capture B.Failure to capture C.Hysteresis D.Oversensing 7.possibilities are • A.VVI in VOO mode • B.magnet kept • C.persistent ventricular undersensing • D.Noise reversion • • • • • 8.make and break potentials usually cause A.undersensing B.oversensing C.functional non capture D.failure to capture • 9.elevated pacing threshold and elevated impedance can be caused by • A.lead fracture • B.loose set screw • C.insulation failure • D.battery depletion • 10.elevated threshold with decreased impedance caused by • A.lead fracture • B.loose set screw • C.insulation failure • D.battery depletion 11.What are appropriate in this patient A.sensitivity setting to be adjusted B.lower the programmed rate C.introduce hysteresis D.check capture treshold 12.What is the next step in this patient – A.adjust sensitivity-increase mV setting – B.adjust sensitivity-decrease mV setting – C.pacing treshold test-adjust output parameters – D.activate hysteresis 13.What is appropriate in this patient – A.adjust sensitivity-increase mV setting – B.adjust sensitivity-decrease mV setting – C.pacing treshold test-adjust output parameters – D.activate hysteresis 14.What is appropriate in this patient – A.adjust sensitivity-increase mV setting – B.adjust sensitivity-decrease mV setting – C.pacing treshold test-adjust output parameters – D.activate hysteresis 15.What is appropriate in this patient – A.adjust sensitivity-increase mV setting – B.adjust sensitivity-decrease mV setting – C.pacing treshold test-adjust output parameters – D.activate hysteresis