Programming and Follow-up Surveillance of Permanent Pacemakers

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SAMPLE EXCERPT
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PRE-PROCEDURE
INTRODUCTION

Indications for permanent pacer implantation broadly include sinus node dysfunction, atrioventricular block, neurogenic syncope and carotid sinus hypersensitivity associated with bradycardia, and cardiac resynchronization therapy. Pacing can be completed in the atrium, right ventricle, or left ventricle through the coronary sinus or on the epicardium. Pacemakers are usually programmed in a mode such that they will be inhibited if they sense the underlying electrical signal in the chamber of interest. If there is no native electrical signal, the device will then deliver an output to pace the heart. Sometimes, such as during surgery, the device is programmed to pace asynchronously and ignore the underlying electrical signal. Rate-responsiveness, where the pacing rate increases during physical exertion, may also be a programmable feature. In addition, most pacemakers function as monitoring and recording devices for atrial and/or ventricular arrhythmias. Pacemaker malfunction can occur because of issues with the generator, lead, or drug and electrolyte effects, among many causes.


Initial assessment of a pacemaker should occur immediately after the lead has been attached to the generator at the time of implantation or just after the implantation has been completed. It should be interrogated again within 72 hours after implantation to ensure proper placement and functioning and again in several weeks. Thereafter, assessments can occur in person or remotely on a regular basis every 3 to 12 months. Pacemakers should be routinely checked to confirm normal device and lead function and to assess battery status. In the past, office visits or home trans-telephonic monitoring was required. With new technologies, some devices can be fully analyzed at home using Internet-based services. This procedure describes an in-person pacemaker interrogation.

INDICATIONS
  • Assess for appropriate pacemaker function.
    • Within 72 hours of pacemaker implantation (in person)
    • 2 to 12 weeks after implantation (in person)
    • Every 3 to 12 months (in person or remotely)
    • Annually until battery depletion (in person)
    • Every 1 to 3 months at signs of battery depletion
  • Determine battery longevity and lead integrity.
  • Change programmed settings.
  • Assess frequency of arrhythmias or determine whether symptoms correlate with arrhythmias.
  • Assess pacemaker function after exposure to magnetic resonance imaging or other potential sources of electromagnetic interference.
  • Reprogram settings for perioperative management to avoid electromagnetic interference with important pacemaker functions.
EQUIPMENT
  • Company programmer
  • ECG electrodes
ANATOMY
  • There are three basic configurations of permanent implantable pacemakers. Single-chamber pacemakers have a single lead placed into a chamber of the heart (atrium or ventricle). Dual-chamber pacemakers have two leads placed: one in the right atrium and one in the right ventricle. Biventricular pacemakers have a third lead placed to pace the left ventricle, usually through the coronary sinus. Leads are more frequently placed transvenously through the subclavian, axillary, or cephalic vein but may also be placed epicardially. The generator contains a power source (usually a lithium battery), a sensing circuit, microprocessor, output circuitry, rate-adaptive sensors, and other circuitry and sensors. The outer casing of the generator is usually titanium to minimize inflammatory reactions. The pacemaker generator is most commonly placed below the subcutaneous fat of the chest wall, superficial to the muscles. Subpectoral and, occasionally, abdominal generator placement may be seen, and exact placement is individualized.
  • Each manufacturer uses a different programmer for its devices, and programmers are not interchangeable. Each manufacturer’s generator has a slightly different physical profile. Chest x-ray films (or abdominal films) can usually reveal the manufacturer so that the appropriate programmer can be selected for the device.

Diagnostic testing includes examining several standard tests of pacemaker function.

  • Battery voltage and estimated longevity, including whether the device has reached elective replacement indicator (ERI).
  • Magnet rate: The rate at which the pacemaker will pace the heart asynchronously when a magnet is placed over the generator. This rate varies by manufacturer, but because battery voltage and estimated longevity are provided on most pacemakers, this is rarely used.
  • Sensing: The ability of the device to detect intrinsic cardiac activity
  • Impedance: A test of lead integrity. Sudden or large increases in lead impedance can indicate a fracture in a lead or a loose set screw, while decreases in impedance may indicate a breach of lead insulation.
  • Threshold: The minimum amount of energy in volts and pulse width required to reliably depolarize the chamber being paced by the lead in question. Threshold determination enables proper output settings to establish an appropriate safety margin for reliable pacing, while minimizing unnecessary energy consumption, to prolong battery life.
  • Examination of stored arrhythmic events since the last device interrogation. This may include atrial or ventricular tachyarrhythmias, mode switch events, pacemaker-mediated tachycardia, or sudden bradycardic response. Correlation of recorded events with symptoms may aid in diagnosis.
  • Percentage of time the patient is paced: The pacemaker will read out percentage of time in AS-VS (atrial-sensed, ventricular-sensed), AS-VP (atrial sensed, ventricular paced), AP-VS, and AP-VS modes.

PROCEDURE
Sample excerpt does not include step-by-step text instructions for performing this procedure
The full content of this section includes:
  • Step-by-step text instructions for performing the procedure
  • Clinical pearls providing practical clinical tips from medical experts
  • Patient safety guidelines consistent with Joint Commission and OHSA standards
  • Links to medical evidence and related procedures

POST-PROCEDURE
CARE
  • Dizziness, syncope, fatigue, or palpitations should prompt a repeat pacemaker interrogation.
  • No specific post-procedure care is usually needed.
COMPLICATIONS
  • No studies have examined overall complication rates for pacemaker interrogations/programming sessions.
  • During interrogation, the patient may experience brief symptoms such as palpitations or dizziness (especially during sensing or threshold testing).
  • Care should be taken to properly evaluate final pacing settings because inappropriate changes can lead to incorrect pacing mode or rate.
RESULT ANALYSIS

Common problems seen during interrogation of the pacemaker:

  • Failure to capture is defined as a pacing stimulus without subsequent cardiac depolarization. Pacing outputs should be programmed at least 2× threshold voltage or 3× threshold pulse width. In the setting of ischemia, electrolyte abnormalities, or drug effects, pacing threshold may change significantly.
  • Pacing at a rate not consistent with programmed rate can be due to undersensing or oversensing of myocardial or extracardiac depolarization. Oversensing of physiologic or nonphysiologic signals inhibits delivery of the pacing output. Undersensing can lead to extra pacing stimuli at inappropriate times.
  • High lead impedance suggests lead fracture or loose set screw at the lead connection in the generator. Low impedance suggests insulation breach.
  • Noise—defined as nonphysiologic, noncardiac signal—often represents a lead fracture but can be due to diaphragmatic or pectoralis potentials, electromagnetic interference, loose set screw, or air in the header block, among other causes. Noise should be promptly evaluated.
  • A device at ERI should be replaced within 3 months. A device at end of life (EOL) should be replaced immediately.
  • Nonphysiologic rapid pacing can be due to pacemaker-mediated tachycardia, in which the pacemaker functions as the antegrade limb of an AV reentrant tachycardia. It may also be due to inappropriate sensor-driven pacing or ventricular tracking of atrial tachyarrhythmias.
  • Ideally, P waves are >1.5 mV and R waves are >7 mV. Sensitivity should be programmed for an adequate sensing safety margin.
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