Pacemaker Malfunction

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• Failure to capture:

  • – Pacing spike is not followed by a depolarization

• Oversensing:

  • – Typically, the T wave or skeletal muscle potentials are sensed as depolarization, and a pacing spike is not initiated

• Pacemaker-mediated tachycardia:

  • – Pacing at or near the programmed upper tracking rate limit secondary to retrograde conduction of the ventricular complex to the atrium, which is sensed as a P wave

• Lead fracture is suspected when there is high lead impedance

• Lead insulation failure leads to low lead impedance

• Electromagnetic interference (eg, MRI scanners) may interfere with pacemaker function

GENERAL CONSIDERATIONS

• Component failure can be intermittent, and a complete evaluation may not identify the problem initially

• Activity before the clinical event is useful and should be sought

• Pacemaker interrogation is critical in the evaluation

• A complete evaluation includes history, examination, indication for pacemaker insertion, and review of imaging studies

• Medications influence the pacing thresholds and should be examined

• Lead dislodgement usually occurs soon after implantation

• Exit block is a chronic problem, presumably related to fibrosis disturbing the electrode–myocardium interface (reduced by steroid-eluting leads)

• Perforation and metabolic alteration (including medication) may raise pacing thresholds

• Air in the pocket may result in pacing failure of unipolar pacemaker

• Loose set screw manifests as failure to pace or capture

• Overall, pacemakers are extraordinarily reliable; component failure is rare

• Diaphragmatic stimulation is rare but may occur, in particular with biventricular devices

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• Dizziness

• Syncope

• Fatigue

• Palpitations secondary to excessive response from a sensor-driven pacemaker

PHYSICAL EXAM FINDINGS

• Usually no change in findings

• Myopotential oversensing can be brought on by isometric maneuver

• Diaphragmatic pacing may be observed

DIFFERENTIAL DIAGNOSIS

• Lead dislodgement

• Loose connection between the lead and the pulse generator

• Metabolic abnormalities such as hyperkalemia

• Antiarrhythmic medication adverse effects

DIAGNOSTIC EVALUATION

LABORATORY TESTS

• Cardiac biomarker if undersensing is an issue and is not explained by other conditions

• Basic metabolic panel to evaluate the causes of undersensing or failure to capture

ELECTROCARDIOGRAPHY

• ECG with rhythm strip to identify the problem

IMAGING STUDIES

• Echocardiogram may be useful when there is an intervening event such as myocardial infarction

• Chest x-ray may help in evaluating lead fracture and definitely macrodislodgement

• CT scan and echocardiogram may be helpful in cardiac perforation

DIAGNOSTIC PROCEDURES

• Device interrogation

TREATMENT

CARDIOLOGY REFERRAL

• Electrophysiologic evaluation is recommended for all patients

HOSPITALIZATION CRITERIA

• Depends on underlying problem

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