The Clinical Picture

A broken pacemaker lead in a 69-year-old woman

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A 69-year-old woman presented with fatigue, cough, and lightheadedness. She had a history of atrial fibrillation and complete heart block, for which she had a pacemaker (dual-pacing, dual-sensing, dual-response, and rate-adaptive mode) inserted in 2005. Her heart rate was 30 beats per minute.

Figure 1. Posterior-anterior chest radiograph showed discontinuity of a lead wire, consistent with complete lead fracture.

A chest radiograph showed a fractured right ventricular pacemaker lead (Figure 1). Electrocardiography showed sinus rhythm with a high-grade atrioventricular block (Figure 2). Pacemaker interrogation confirmed the diagnosis of lead fracture. A new lead was placed, and the old lead was abandoned.

HOW LEADS BREAK

Figure 2. The patient’s electrocardiogram showed sinus rhythm, high-grade atrioventricular block, reflected by the atrioventricular dissociation with intermittent conduction (asterisk), and pacemaker spikes (arrows) with loss of capture, reflected by the absence of QRS waves following the pacemaker spikes.

The rate of lead fracture ranges from 0.1% to 4.2% per patient-year, and the annual failure rate increases progressively with time after implantation.1,2

Extrinsic pressure on the lead can eventually break it. This can happen between the first rib and clavicle, in “subclavian crush” injury, or with any anatomical abnormality that narrows the thoracic outlet. Typically, classic subclavian crush results from entrapment of the pacemaker leads by the subclavius muscle or the costoclavicular ligament as the lead follows the needle course of the antecedent access puncture of the subclavian vein. This results in intermittent flexing of the lead and potential lead fracture3 and was likely the cause of lead fracture in our patient.

The risk of fracture is higher in patients under the age of 50, those who perform intense physical activity, women, and patients with greater left ventricular ejection fraction.4,5 Certain leads are prone to fracture due to design flaws. One of these was the Medtronic Sprint Fidelis cardioverter defibrillator lead, which was recalled in 2007.5

DETECTING LEAD FRACTURE

Symptoms of lead fracture vary, depending on the patient’s pacemaker-dependency and on the degree of loss of capture (ie, the degree to which the heart fails to respond to the pacemaker’s signals), and may include lightheadedness, syncope, and extracardiac stimulation.

The electrical integrity of a lead can be tested by measuring the circuit impedance, which normally ranges from 300 to 1,000 ohms.6 An insulation failure results in very low impedance, while a disrupted circuit due to lead fracture commonly causes a sudden rather than gradual increase in impedance.6

Simple imaging studies such as chest radiography or fluoroscopy may establish the diagnosis of lead fracture. One should carefully trace every lead along its entire course and look for any conductor discontinuity, kinks, or sharp bends.6

REMOVE THE OLD LEAD, OR LEAVE IT IN PLACE?

The treatment for lead fracture is usually to put in a new lead, with or without extracting the old one.

In view of the potential complications of lead removal such as cardiac perforation or vascular tear, lead abandonment with placement of a new lead may be performed.7 There are no controlled clinical studies comparing lead abandonment vs lead extraction.8 However, extraction is currently recommended only in patients in whom the old lead causes life-threatening arrhythmias, interferes with the operation of implanted cardiac devices, interferes with radiation therapy or needed surgery, or, due to its design or failure, poses an immediate threat to the patient if left in place.7 Lead removal is reasonable in patients who require specific imaging studies such as magnetic resonance imaging with no available imaging alternative for the diagnosis.7

In our patient, a new lead was placed without removing the fractured lead, with no complications. Afterward, the patient’s heart rhythm was observed to be appropriately paced, and she was discharged home the following day.

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