Pediatric Pulmonology 22:319-321 (1996)

Case Reports -

Diaphragmatic Pacemaker Failure In Congenital Central Hypoventilation Syndrome: A Tale of Two Twiddlers

Dominic Fitzgerald, MBBS, PhD, FRAcP,’ G. Michael Davis, MB, chB, FRACP,’ Ronald Gottesman, MD, FRCP(C)? Annie Fecteau, MD, FRCS(C),~ and Frank Guttman, MD, FRCS(C)~

Summary. Two patients with congenital central hypoventilation syndrome (CCHS) experienced phrenic nerve pacer failure due to deliberate manipulation of the internal receiver implant (”twid- dling“). The patients, aged 7 and 12 years, presented with repeated episodes of pacer failure associated with local pain over a period of 18 months. They had progressively coiled the pacing wires to the point of breakage, which only became apparent at surgey The breaks were not recognized radiologically, although in retrospect progressive twisting of the wires was evident on serial chest radiographs. Both patients required replacement of the internal receivers under general anesthesia. We recommend that the chest radiograph that is undertaken to investigate the cause of pacer dysfunction include the internal receiver. A plain chest radiograph that demonstrates progressive coiling of the subcutaneous pacing wire should raise suspicion of pacer wire breakage regardless of the patient‘s age. Pediatr Pulmonol. 1996; 22:319-321. 0 1996 Wiley-Liss, Inc.

Key words: Diaphragmatic pacemaker failure; internal receiver manipulation; pacing wire breakage; twiddler’s syndrome.

INTRODUCTION CASE REPORTS

Over the last 30 years diaphragmatic pacing has be- come an increasingly popular therapy in patients with hypoventilation secondary to high quadraplegia or con- genital central alveolar hypoventilation syndrome (CCHS).’ The exact number of patients with diaphrag- matic pacers worldwide is not known, and it has been estimated that less than 20% of patients in North America with diaphragmatic pacers are children.* Pacing wire breakage is recognized as a cause of pacemaker failure, and previous reports have emphasized the utility of the chest radiograph in diagnosing this c~mplication.~ Delib- erate manipulation of the implanted receiver [“twiddler’s syndrome”] is recognized in adults with cardiac pace- maker dysfunctionM and has been reported in one child with unilateral diaphragmatic pacer f a i l ~ r e . ~ Given the increased use of diaphragm pacing in children, we de- scribe in detail two cases of diaphragmatic pacemaker failure due to twisting of the phrenic nerve wires follow- ing manipulation of the implanted receivers.

Case 1 B.B. was diagnosed with CCHS in the neonatal period,

was ventilated via tracheostomy from 4 months of age, and underwent initial bilateral phrenic nerve pacemaker insertion (S-232- 1, Avery Laboratories, New York) at 16 months of age. While awake he was managed with synchronous bilateral pacing, and when asleep by me- chanical ventilation. At 10 years of age, repeated transient episodes of left-sided chest pain with occasional radiation

From the Departments of Respiratory Medicine,’ Pediatric Intensive Care: and S ~ g e r y , ~ Montreal Children’s HospitallMcGill University, 2300 Tupper, Montreal, Quebec, Canada, H3H 1P3.

Received February 21, 1996; (revision) accepted for publication May 25. 1996.

Address correspondence and reprint requests to Dominic Fitzgerald, Respiratory Medicine, Suite D-380, Montreal Children’s Hospital, 2300 Tupper, Montreal, Quebec, Canada, H3H 1P3.

0 1996 Wiley-Liss, Inc.

320 Fitzgerald et al.

Fig. 1. Lateral chest radiograph demonstrating the normal posi- tion of internal wiring. The arrow indicates the normal position of the wires prior to manipulation (“twiddling”).

to the ipsilateral shoulder tip were reported in association with unexplained variable left-sided pacemaker dysfunc- tion. These problems were initially self-limited. Subse- quently, he required increased pacing parameters until complete failure of transmission occurred at 12 years of age. During this 2 year period serial chest radiographs failed to demonstrate wire breakage. Toward the end of the 2 year period the right-sided pacemaker had also begun to behave erratically. Given that the implants were now more than 7 years old, bilateral pacemaker replace- ment was performed.

During the initial surgical approach it became apparent that the left cathode wire was tightly twisted and coiled upon itself. Once surgically dissected and mobilized, the wire was found to be functioning normally when tested with an 1-110 system (Avery Laboratories). The right

Abbreviations

CCHS Congenital central hypoventilation syndrome

Fig. 2. Lateral chest radiograph incorporating the top of the internal receiver, demonstrated pacing wire coiling (arrowed).

cathode wire was also tightly coiled yet functioned satis- factorily after untwisting. On both sides there was a dis- continuity in the wires between the receiver and the nerve- electrode connection. After the operation the patient admitted twiddling with both subcutaneous implants. Six months later, the replacement implants continue to function perfectly.

Case 2 M.L. was born after a 27 week gestation and was

diagnosed with CCHS at 8 weeks of age following unex- plained, prolonged ventilator dependence. Her awake ventilation remained normal until 5 years of age when Atrostim Jukka (Tampere, Finland) phrenic nerve pacers were inserted subcutaneously (with the cathode wires apposed to the intrathoracic phrenic nerves bilaterally) because spontaneous ventilation was no longer sufficient. Post-operatively, the system functioned well, and she was maintained with daytime diaphragmatic pacing and me- chanical ventilation via tracheostomy when sleeping. A post-operative lateral chest radiograph demonstrate satis- factory internal connections (Fig. 1).

Intermittent non-specific abdominal pain and localized pain over the subcutaneous implants were reported within

Pacer Failure in CCHS 321

6 months. Lumbar back pain was reported periodically during the following months and was noted to be worse when the child was lying in the left lateral position. In- creasing stimulation thresholds for the left-sided pace- maker capture were required with repeated transient epi- sodes of left-sided pacemaker failure. A lateral chest radiograph (Fig. 2) demonstrated that both pacing wires were coiled tightly around themselves, although there was no evidence of wire breakage. Testing of the right- sided pacemaker revealed adequate function in only 2 of the 4 electrodes. At 73/i2 years a thoracotomy was performed and the left-sided pacemaker and pacing wires were replaced. At operation it became apparent that 2 of the 4 left-sided wires were broken. Replacement of the right-sided device was deferred as it was still functional. Post-operatively, the patient admitted rolling the skin overlying the internal receiver between her fingers. The patient was discharged 10 days after the thoracotomy with daytime pacing and nocturnal ventilation via trache- ostomy as before.

DISCUSSION

This paper reports an uncommon type of diaphragmatic pacer wire damage in two school-aged children with CCHS, leading to failure of the implanted devices. The cause of equipment failure was not initially suspected, despite the possibility that accidental wire breakage is more likely in active children than in ad~lts.~,’ The extent of the damage was only apparent at surgery. Importantly, serial chest radiographs, as recommended to screen for wire damage or di~ruption,2.~ did not aid in making the diagnosis pre-operatively. On review of previous films after surgery, the progressive coiling of the wires was apparent when the field of the chest radiograph included the receiver (Fig. 2).

In retrospect, the children may have rotated the receiver implant within the subcutaneous pocket, albeit as an inno- cent habit. It is understandable that curiosity might en- courage children (and adults) to explore alterations in their body image. Rotation of a subcutaneous implant may have been associated with some discomfort given that it would necessitate stretching of the overlying tis- sues. Spontaneous rotation of the internal receiver within a generous subcutaneous pouch in an adult with a cardiac pacemake? and in a child with CCHS3 has been reported previously. Unlike these cases, there was nothing to sug- gest an inappropriately large subcutaneous pocket in ei- ther of the patients reported here. In our cases, there was a lengthy delay between insertion of the internal receivers and the reporting of dysfunction, suggesting that this complication was not related to surgical technique.*

For both cases, the parents were not aware of the chil- dren’s behavior, although the children admitted the activ- ity when directly questioned following surgery. The con-

sequences of the boy’s (B.B.) behavior were minor, involving only replacement of the subcutaneous implant. The consequences were more serious in the second case (M.L.), as she required a thoracotomy for unilateral sys- tem replacement. Moreover, there is evidence that M.L.’s contralateral system had also been “twiddled” with (Fig. 1) and was partially dysfunctional, suggesting a hairline fracture of the wire not radiographically apparent. At operation, bilateral thoracotomies were considered once the true cause of pacemaker dysfunction was known, but the second procedure was deferred because of the morbidity associated with elective replacement of a func- tional unit.

Strategies to avoid this unusual complication include implanting the internal components out of the patients’ reach, such as over the posterior ribcage. However, this would be unacceptable for the patient when sleeping su- pine. Alternatively, incorporation of adhesive pads (as with central venous catheters) or wings secured with non- resorbable sutures to prevent torsion (as with sub-cutane- ous vascular access “ports”) may become necessary. Ide- ally, implantation of the receiver within the thoracic cavity (extra-pleurally) would obviate the opportunity to “twid- dle.” However, the only alternative at present is continued vigilance of traditionally sited components. Therefore, we recommend that the chest radiographs that are under- taken to investigate diaphragmatic pacemaker dysfunc- tion include the internal implant. As these cases illustrate, the chest radiograph will not necessarily demonstrate a reason for dysfunction of the pacemaker, although pacing wire coiling on a radiograph should suggest wire disconti- nuity from twiddling as a likely cause of pacemaker failure.

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