This study was approved by the Institutional Review Board of Seoul National University Hospital (IRB No. 2207-117-134, approved on July 21, 2022). Written informed consent for publication was obtained from the patient.

A 24-year-old male with double-inlet left ventricle underwent pulmonary arterial banding at two weeks and Fontan procedure with epicardial VVI pacemaker implantation for atrioventricular block at 13 months. At the age of 22, generator replacement was performed for battery exhaustion; lead testing showed normal integrity.

Postoperatively, ejection fraction declined from 58% to 41% by Simpson’s biplane method over two years, accompanied by abdominal muscle twitching. Pacemaker testing confirmed abdominal muscle capture unresponsive to setting adjustments. The dysfunction was attributed to atrio-ventricular (AV) dyssynchrony, so we planned to add an atrial lead for DDD pacing and evaluate ventricular lead.

During partial redo-sternotomy, adhesiolysis exposed minor sheath peeling of lead about 10 cm from generator, likely causing insulation failure and abdominal twitching (Figure 1(a)). Further dissection revealed that the previous lead encircled and constricted ventricular apex (Figure 1(b) and (c)). Even after lead removal, a residual fibrotic band maintained apical indentation, which was cautiously released using electrocautery and sharp dissection; in high-risk areas where complete excision was unsafe, the band was fragmented to achieve maximal relief, improving apical wall motion on the transesophageal echocardiography four-chamber view (Figure 1(d)).

Figure 1.

Pictures from the operation. (a) Injured pacemaker lead. (b) White arrows: previous ventricular lead, encircling ventricular apex; black: diaphragm. (c) White dotted: ventricular apex. (d) White triangles: ventricular apical area indentation slightly improved but remained with the fibrotic band even after the removal of the previous ventricular lead.

A bipolar patch-type atrial lead was placed on the right atrial wall, and a new screw-type ventricular lead on the apex. Pacing thresholds were acceptable (0.9 V atrium, 0.7 V ventricle). Postoperative ejection fraction improved to 50.4%, and he had no further abdominal muscle twitching. Follow-up echocardiography confirmed sustained ventricular function recovery. Like other patients with epicardial pacemakers, we followed this patient regularly at 6-month intervals.

Meanwhile, B-type natriuretic peptide was 12 pg/mL two years before generator replacement, increased to 93 five months afterwards, and declined to 48 before conversion and 20 postoperatively.

Discussion

High thresholds are the most common cause of lead failure in epicardial pacemakers.^{Reference Fortescue, Berul, Cecchin, Walsh, Triedman and Alexander1} In our patient, pre- and intra-operative tests revealed no abnormalities, suggesting lead dysfunction at the time of generator change. However, the subsequent operation confirmed insulation break due to sheath damage, which allowed current leakage to adjacent musculature and explained persistent abdominal muscle twitching despite pacemaker reprogramming. The tear may not result from direct surgical injury during prior procedure, as the peeled-off area was surrounded by dense adhesions. It is plausible that minor traction applied to 20-year-old fragile lead sheath during generator replacement caused a small tear, progressively leading to insulation failure and muscle twitching.

Cardiac strangulation caused by pacing wires is rare but potentially fatal, with reported incidence and mortality of 0.016% and 0.004%, respectively.^{Reference Carreras, Duncan, Djurdjev and Campbell2} Carreras et al. recommended minimising wire placement within the pericardial cavity and positioning it anteriorly rather than diaphragmatically. In this patient, X-rays after initial pacemaker implantation at 13 months showed pacing wires loosely encircling heart (Figure 2(a)). As he grew, the wire progressively tightened around heart (Figure 2(b)–(d)), and intraoperative findings confirmed marked apical strangulation (Figure 1). Sudden deaths due to coronary insufficiency or ventricular fibrillation have been reported,^{Reference Carreras, Duncan, Djurdjev and Campbell2–Reference Kwak, Kim and Bae4} so even mild encirclement on X-ray warrants additional imaging to assess possible strangulation.

Figure 2.

Chest X-ray of the patient in chronological order. (a) after inserting the pacemaker at 13 months of age. (b) at age 5 year. (c) at age 17 years. (d) at age 21 years. The position of the pacemaker lead appears to have shifted over time.

Functional improvement after conversion to dual-chamber pacing may have resulted not only from AV synchrony but also from relief of mechanical compression. Because single-ventricle physiology is sensitive to even minor disturbances in hemodynamics, eliminating factors including mechanical compression and lead-related dyssynchrony is essential to restore ventricular function. Given the potential for prolonged asymptomatic progression of cardiac strangulation, routine imaging surveillance in patients with long-standing epicardial leads – particularly those with Fontan physiology – remains crucial for early detection.