MULTIPLE CASE REPORT
Implantable diagnostic and therapeutic
devices in children
T-N. Le, S.C. Gouw, T.M. Hoornte, N. Sreeram
Many advances have been made in the use of implantable diagnostic and therapeutic devices in adults. In children the indications for and diagnostic and therapeutic value of these devices still have to be determined. Our aim is to provide an overview of the clinical use of diagnostic and therapeutic devices in children. The role of implantable loop recorders (ILR), the feasibility and safety of transvenous pacing in neonates, the value of permanent pacing in children with recurrent syncope or reflex anoxic seizures and the role of implantable cardioverter defibrillator devices are highlighted with relevant case histories. (NethHeartJ2002;10:462-6.) Key words: children, implantable devices, paediatrics
there has been a revolution in the use ofimplantable devices for diagnostic and therapeutic purposes, primarily in adults. The indications for, and diagnostic or therapeutic yield of some ofthese devices in children remain to be defined. In this report we review the role of implantable devices in children. Particular attention will be paid to implantable Holter recorders, transvenous pacemakers in neonates, and implantable cardioverter defibrillator devices (ICDs) in infants and children in current clinical practice. Implantable loop recorder (ILR) Children with infrequently occurring probably arrhythmic events present a diagnostic challenge. The conventional investigation of such patients involves short-term ECG monitoring (standard Holter T-N. Le. S.C. Gouw. T.M. Hoomtje. N. Sreeram. Department of Cardiology, Wilhelmina Children's Hospital, KG 01 319.0, P0 Box 85090, 3508 AB Utrecht. Address for correspondence: N. Sreeram. E-mail:
[email protected]
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monitoring or patient- or parent-operated externally applied ambulatory Holter recordings), provocative testing with head-up tilt and electrophysiological testing. Despite these techniques, a symptom-rhythm correlation is often difficult to obtain during spontaneous episodes because of their sporadic, infrequent and unpredictable nature.' Thus, in these cases continuous ECG recording over prolonged periods is required for diagnosis. In children, the ILR device can be implanted subcutaneously in the abdomen or in the left infraclavicular region. The ILR measures 61 x 19 x 8 mm. It can continuously record the subcutaneous electrogram for a period of approximately 14 months. When a clinical event occurs the electrocardiograms during the event can be stored and subsequently read out using an external activator. The memory loop of the ILR can be pre-programmed to read out the electrocardiogram for a maximum duration of 40 minutes prior to and two minutes following the clinical event. Various combinations of automated and patient-activated events can be recorded, depending on how the ILR has been programmed. Case reports Case 1 A 14-month-old boy presented at the age of three months with recurrent apparently life-threatening events (episodes of cyanosis and briefloss of consciousness) requiring cardiopulmonary resuscitation. Following a ten-day continuous in-hospital Holter recording and an invasive electrophysiological study, a cause could not be revealed, so an ILR (Medtronic BV, the Netherlands) was inserted. Three months later an ECG recording was obtained during a syncopal event. It showed an abrupt onset of sinus tachycardia (230 beats/min for three minutes) and then a junctional bradycardia developed suddenly (32 beats/min) with ST-segment depression. These findings were suggestive of suffocation. After further questioning, the mother confessed that she had suffocated her son with a pillow. A diagnosis of Munchausen's syndrome by proxy was made.2 Netherlands Heart Joumal, Volume 10, Number 11, Novrember 2002
Implantable diagnostic and therapeutic devices in children
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Figure la and b. Spontaneous onset ofventricular tachycardia during sleep in Case 2, recorded by the ILR device. Two time points in the same day are shown.
Case 2 This boy presented when he was six years old with a skull fracture resulting from falling down the stairs. In the intensive care unit transient supraventricular arrhythmias and ventricular tachycardia were detected, but a 24-hour Holter recording thereafter showed no arrhythmias. Two years later he had an attack of loss of consciousness and incontinence. The diagnosis of epilepsy could not be confirmed by EEG recordings. On cardiac evaluation monomorphic ventricular ectopy was demonstrated during ambulatory Holter monitoring. On exercise testing the grade of arrhythmia increased, but the patient remained without symptoms. Despite 5-blocker medication (propanolol) he had intermittent episodes of dizziness. Under general anaesthesia, an invasive electrophysiology study was performed, but no ventricular ectopy or arrhythmia was inducible. Subsequently, an ILR was implanted when he was nine years of age and the medication was stopped. During follow-up, the patient has had periodic pre-syncopal symptoms while awake, always associated with a monomorphic ventricular ectopic beat in a bigeminal rhythm, but with relatively low ventricular rates (120 beats/min). In addition, he has recurrent spontaneous sustained monomorphic ventricular tachycardia (rate 200 beats/min, lasting between 30 and 60 seconds) during sleep, almost on a daily basis, but without symptoms (figures la and b). He is awaiting an electrophysiology study and catheter ablation, without the use of general anaesthesia. Case 3 This 19-year-old patient underwent surgical repair of Ebstein's anomaly at the age of two years. She presented with recurrent syncope not associated with palpitations, and not observed by a third party. The 12-lead electrocardiogram and outpatient ambulatory Holter recording were normal. Following implantation of an ILR, the patient had no symptoms during a fourmonth follow-up (although she had several events per
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month in the preceding interval). These findings suggest a diagnosis of attention-seeking behaviour, for which fiurther referral to the psychologist may be appropriate.
Case 4 This girl presented at the age of eight with two syncopal episodes. She had undergone anatomical repair of transposition of the great arteries in the neonatal period, with a good result and an uneventfuil followup until the present complaints. An exercise test revealed monomorphic ventricular ectopic beats at rest, but no ventricular ectopy during exercise. During invasive electrophysiology study, no sustained arrhythmia was inducible. An ILR was therefore implanted. During follow-up she had an episode of asystole lasting 3.6 seconds during sleep. Should these episodes be shown to recur at regular intervals, a permanent pacemaker can be implanted. Discussion The ILR is an effective means for diagnosing or excluding potentially life-threatening arrhythmias in children. The small dimensions ofthe device also make it suitable for use in young patients.
Neonatal transvenous pacing Endocardial pacing is the method of choice in adult patients who require pacemaker therapy. Many concerns existwith regard to permanent transvenous pacing in neonates (technical difficulties in gaining venous access, lead stretch caused by rapid somatic growth, and risk ofvenous thrombosis in the long term). However, transvenous pacemaker implantation has several advantages such as better performance of endocardial electrodes, and a lower incidence ofexit block as a result of dislodgment or fracture when compared with epicardial electrodes.3 We describe five consecutive patients who received a transvenous pacemaker in the neonatal period during the period 1997-2001.
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Implantable diagnostic and therapeutic devices in children
Patients Five consecutive neonates, two girls and three boys with a median weight of 3.4 kg (range 2.3 to 5 kg) compared with the average body weight of a 4-yearold child of 15 kg - and a median age of 2 days (range 1 to 4 days) underwent permanent transvenous pacemaker implantation. Three of them had congenital complete atrioventricular block, the other two had congenital long-QT syndrome associated with a high degree of atrioventricular block. Technique
Under general anaesthesia, venous access was gained by percutaneous puncture of the left subclavian vein. Via a 7F peel-away introducer, a 7F unipolar or 6F bipolar steroid-eluting active fixation lead (Medtronic BV, the Netherlands) was introduced and fixed in the apex ofthe right ventricle. After confirmation of good lead thresholds, the extravascular portion of the lead was tunnelled subcutaneously to the anterior abdominal wall (bodyweight
