Pacemaker troubleshooting-single 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 CorePace Module 4: Troubleshooting 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 CorePace Module 4: Troubleshooting Failure to capture No evidence of depolarization after pacing artifact loss of atrial capture, followed by a scheduled ventricular pace. Following , the marker channel recorded an intrinsic P-wave. 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

CorePace Module 4: Troubleshooting Undersensing An intrinsic depolarization that is present, yet not seen or sensed by the pacemaker An 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 “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. 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: CorePace Module 4: Troubleshooting 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 Insulation breaks may cause undersensing if the insulation break results in the: Reduction of intrinsic beats at the sense amplifier Inability of the amplitude to meet the sensitivity requirement Conductor fracture may cause an open circuit. If intrinsic signals cannot cross the conductor fracture, undersensing will occur. The primary cause of conductor fracture is the chronic stress imposed on the lead as a result of its placement in the subclavian region, and may be reflected in increased impedance readings. During the first week following lead implantation, the amplitude and slew rate may abruptly decline; these values increase to approach implantation values after about 6-8 weeks as the lead matures.1 (Steroid-eluting leads may eliminate the reduction in sensitivity by minimizing the growth of fibrotic tissue near the electrode). Lead dislodgment usually occurs early in the life of the pacemaker before the lead has fibrosed to endocardial tissue. The primary causes of lead dislodgment are: Inadequate initial positioning Patient movement (bringing arms overhead, etc.) Secondary intervention rates for lead dislodgement should be below 2% for ventricular leads and 3% for atrial leads.2 One recent clinical trial reported a lead dislodgement rate of 2.2%.2 Changes in the native signal may be caused by: Myocardial infarction Change in medications (not common) Electrolyte imbalance Undersensing may be caused by an inappropriately programmed setting. 1Hayes DH. Cardiac Pacing and Defibrillation: A Clinical Approach. Armonk, NY: Futura Publishing Company; 2000. Page 453. 2Link MS et al. Complications of dual chamber pacemaker implantation in the elderly. Pacemaker Selection in the Elderly (PASE) Investigators. J Interv Card Electrophysiol. 2:175-179, 1998.

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 The sensing of an inappropriate signal CorePace Module 4: Troubleshooting Oversensing ...Though no activity is present Marker channel shows intrinsic activity... Ventricular Oversensing If a pacemaker is oversensing, you will see signals on the marker channel that do not correspond to the ECG pattern. In this example, the pacemaker recorded a ventricular pulse on the marker channel. However, no activity was demonstrated on the ECG strip. Pauses or intervals longer than the programmed lower rate will occur in single chamber systems. Dual chamber systems may show tracking at the upper rate with atrial oversensing. Lead insulation failure (a decrease in lead impedance will be seen) Make-and-break fracture A lead connection problem Insulation failure—a common cause of oversensing—occurs when myopotentials are detected at the site of the insulation break. Lead fracture is another common cause of oversensing. As the frayed ends of conductor wires “make and break” contact, the pacemaker senses these “make and break” signals, which results in oversensing. Oversensing may also occur if the lead is loose in the connector block. 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

Oversensing of normal intracardiac signals 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

CorePace Module 4: Troubleshooting No Output Pacemaker artifacts do not appear on the ECG; rate is less than the lower rate When 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

No Output May Be Caused By: CorePace Module 4: Troubleshooting No Output May Be Caused By: Poor connection at connector block Lead failure Battery depletion Circuit failure A poor connection at the connector block can result in a lack of output, which can prevent the pacemaker from delivering a pacing pulse. In addition to lead dislodgment, lead perforation should be considered with acute implants as a potential cause of noncapture. Battery depletion can result in a lack of output, which can prevent the pacemaker from delivering a pacing pulse. At generator replacement procedures, (and sometimes at initial implants) the pacemaker pocket may be malformed or too large to accommodate the pacemaker. Air can get trapped in the pocket which, with unipolar devices, will not allow appropriate grounding. No output can result. Circuit failure—more commonly referred to as “pacemaker malfunction”—is very rare.

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: CorePace Module 4: Troubleshooting Pseudomalfunctions Pseudomalfunctions are defined as: Unusual,Unexpected ECG findings that appear to result from pacemaker malfunction but that represent normal pacemaker function Pseudomalfunctions should be ruled out as the cause(s) of an anomalous ECG strip before corrective measures are taken.

Hysteresis Magnet rate rate responsive pacing Noise reversion Rate drop response Sleep rate algorithm

CorePace Module 4: Troubleshooting Hysteresis Allows a lower rate between sensed events to occur; paced rate is higher Hysteresis 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. Hysteresis Rate 50 ppm Lower Rate 70 ppm

CorePace Module 4: Troubleshooting Magnet Operation Magnet application causes asynchronous pacing at a designated “magnet” rate Magnet operation varies within different product lines and from manufacturer to manufacturer, but will usually involve a rate change when the magnet is applied. The Threshold Margin Test (TMT) is part magnet operation for most of Medtronic’s devices. The following operation describes magnet operation and TMT for most Medtronic devices: Three beats at 100 bpm, followed by a magnet rate of 85 The third beat has an automatic pulse width decrement of 25% (loss of capture would indicate that the stimulation safety margin is inadequate) Dual chamber devices will shorten the AV delay to 100 ms Elective replacement indicators will change the rate from 85 to 65 and the mode from dual to single chamber pacing It is important to remember that magnet modes vary from manufacturer to manufacturer, and from device to device. While recent Medtronic devices use the above rule of thumb, many older devices used the programmed lower rate as the magnet rate, or would decrease the rate by a certain percentage as a battery depletion indicator. Kappa devices have a feature called Extended TMT. Extended TMT is a programmable feature and will operate as follows: TMT is performed at 100 ppm with the pulse width reduced by 25% on the third pulse, 50% on the fifth pulse, and 75% on the seventh pulse. This type of operation is extremely useful in assessing adequate safety margins, by simply using a magnet.

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 CorePace Module 4: Troubleshooting Rate Responsive Pacing An accelerating or decelerating rate may be perceived as anomalous pacemaker behavior If a patient is active it is easy to equate rate increases with rate responsive pacing. Some patients may experience “false positive” increases in rate from their sensors. In the case of a piezoelectric crystal, the pacemaker may begin pacing at a faster rate if, for example, the patient is either lying on the side that the pacemaker is implanted on or experiencing a bumpy car ride. Minute ventilation sensors measure the change in respiration rate and tidal volume. If a patient experiences rapid respiration resulting from a cause other than exercise (e.g., hyperventilation), the pacemaker may begin pacing at a faster rate. VVIR / 60 / 120

Electrical Reset and Battery Depletion CorePace Module 4: Troubleshooting Electrical Reset and Battery Depletion Reset may occur due to exposure to EMI electrocautery, defibrillation, causing reversion to a “back-up” 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”) Electrical reset, or “back-up,” modes are usually exhibited by a rate change and often by a mode change. a pacemaker may interpret the radiofrequency signal as an intrinsic event, which would result in inappropriate inhibition of a pacing pulse and could cause the pacemaker to revert to a back-up mode. Defibrillation may damage both the pulse generator and cardiac tissue because it delivers a large amount of electrical energy in the vicinity of the pacemaker. If the pacemaker’s protective mechanisms are overwhelmed by defibrillation, the back-up mode will be activated. Elective replacement indicators are often similar to back-up modes.

A Change in Pacing Modes May Be Caused By: CorePace Module 4: Troubleshooting A Change in Pacing Modes May Be Caused By: Battery depletion indicators (ERI/EOL) Electrical reset Mode switching Noise reversion The Elective replacement indicator (ERI) is designed to alert the clinician at least three months before the battery voltage drops to a level at which noncapture or inconsistent pacing would result. The end of life (EOL) indication is designed to give the patient and physician adequate time to replace the device. Battery depletion may necessitate a mode switch prior to battery failure. For example, the mode may be switched from DDD to VVI or from DOO to VOO.

CorePace Module 4: Troubleshooting 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 non- rate-responsive modes The portion of the refractory period after the blanking period ends is commonly called the “noise sampling period.” A sensed event in the noise sampling period will initiate a new refractory period and blanking period.

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: CorePace Module 4: Troubleshooting Muscle Stimulation May Be Caused By: Inappropriate electrode placement near diaphragm or nerve plexus Break in lead insulation Unipolar pacing Diaphragmatic stimulation may occur because of inappropriate lead

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 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