Laboratory Studies
The following laboratory studies may be useful in cases of pacemaker malfunction:
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Troponin level: Elevated in myocardial injury and cardiac trauma
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Coagulation panel: Required to prevent bleeding complications during invasive procedures
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Electrolyte levels: To exclude electrolyte abnormalities that may affect pacing thresholds
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Thyroid functions tests: Hypothyroidism or hyperthyroidism can affect the underlying cardiac rhythm
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Drug levels: For drugs such as digoxin and antiarrhythmics (particularly flecainide [4] ) that may alter pacing thresholds
Imaging Studies
The following imaging studies may be considered in cases of pacemaker malfunction:
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Chest radiography: Overpenetrated film helps to evaluate lead position, fracture, and the set-screws. Specific markers on pulse generator are useful for identification.
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Fluoroscopy: To evaluate common sites of lead fracture such as an area of acute angulation or compression by real-time imaging while applying gentle traction on the lead.
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Echocardiogram: It has limited use in the diagnosis of pacing system malfunction. Inappropriate lead position (ie, left ventricle, left atrium, or pericardial space), pericardial effusion/tamponade, or lead fracture may be observed on 2-dimensional echocardiogram.
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Computed tomography: CT scanning of the chest helps to evaluate lead position, especially in patients with suboptimal radiograph and echocardiogram results. Preprocedural ECG-gated multidetector CT scanning may aid clinicians in identifying patients at high risk for mechanical complications and significant perforation during lead extraction for lead malfunction, class I lead advisories, and infection. [11]
Other Tests
Several other studies may be indicated in cases of pacemaker malfunction. Consider the following:
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Pacemaker interrogation: Evaluation of thresholds, lead impedance, and battery voltage, as well as review of histograms, mode switch episodes, and stored electrograms.
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Magnet application: After magnet application, pacemaker goes to asynchronous pacing mode at a programmed rate that is unique to that model. This is helpful in the diagnosis of loss of capture and battery depletion.
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12-lead electrocardiogram: This simple bedside test is useful to diagnose undersensing, oversensing, and capture loss.
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Telemetry monitoring: This is useful in early recognition of loss of sensing and capture from lead dislodgment in the immediate postimplant period.
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Holter monitoring: This 24-48-hour simple test is helpful in the diagnosis of atrial and ventricular arrhythmias and abnormal sensing or capture. Sometimes, an event monitor may be required to diagnose intermittent pacemaker dysfunction.
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Transtelephonic monitoring: Periodic transtelephonic monitoring is very useful in early recognition of battery depletion based on the magnet rate, which is unique to each pacemaker model.
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Fluoroscopy is useful to evaluate lead fracture, especially during provocative maneuvers.
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Pacemaker Malfunction. Atrial undersensing. The rhythm strip shows an atrial pacing artifact after the intrinsic P wave.
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Pacemaker Malfunction. Ventricular undersensing. The rhythm strip shows ventricular pacing artifacts despite normal underlying ventricular activity.
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Pacemaker Malfunction. Atrial lead dislodgment. The chest radiograph film detail shows a dislodged atrial lead with the tip in the right ventricular cavity.
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Pacemaker Malfunction. Ventricular noncapture. The rhythm strip shows atrial (P wave) sensing followed by a ventricular spike, which failed to capture the ventricle.
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Pacemaker Malfunction. Loss of atrial capture. The rhythm strip shows intermittent loss of atrial capture.
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Pacemaker Malfunction. Pacemaker-mediated tachycardia. The rhythm strip shows ventricular pacing at 110 beats per minute (programmed maximal track rate).
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Pacemaker Malfunction. Termination of pacemaker-mediated tachycardia (PMT). Automatic postventricular atrial refractory period (PVARP) extension terminated the PMT.
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Pacemaker Malfunction. This image shows an artifact due to monitor malfunction or a loose limb lead connection. An abrupt loss of a portion of the QRS complex followed by a flat line can be observed. If R-R intervals are matched, two QRS complexes are missing during the pause. If the artifact is due to a dislodged lead, a pacing artifact with no capture should be observed.
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Pacemaker Malfunction. This is a typical example of ventricular oversensing with inhibition of ventricular pacing. In ventricular noncapture, a ventricular pacing artifact should be present after the third P wave.
