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Implantable cardioverter-defibrillators have aided the prevention of sudden cardiac death in adults. The hope is to provide similar benefits to the pediatric population as the devices become smaller. Herein, we present the case of a 4.9-kg, 5-week-old infant boy who presented with cardiopulmonary arrest. After emergency defibrillation, conventional treatment options included long-term hospitalization for later cardioverter-defibrillator implantation, or installation of an external defibrillator with subsequent home telemetry. On the basis of the infant's body dimensions, we decided that an epicardial implantable cardioverter-defibrillator was feasible and the best option. We performed a median sternotomy and placed a Vitality® implantable cardioverter-defibrillator with a 25-cm defibrillator coil and a 35-cm bipolar ventricular lead. The patient experienced no postoperative morbidity or rhythm disturbances and was discharged from the hospital on postoperative day 5. He was placed on β-blocker therapy and has remained well for 3 years.
Although external devices can be placed in a small patient, we believe that they are too susceptible to lead damage and lead migration, and that the defibrillator thresholds are less reliable. We think that dysrhythmias even in very small children can be treated effectively and safely with use of an epicardial implantable cardioverter-defibrillator. To our knowledge, this 4.9-kg infant is the smallest patient to have undergone a successful implantation of this kind.
Implantable cardioverter-defibrillators (ICDs) have reduced the incidence of sudden cardiac death in the adult population. As these devices become smaller, the hope is to provide their benefits to the pediatric population. However, inappropriate shocks and lead complications may occur as children grow and increase their physical activity.1,2 Furthermore, a patient's size at the time of implantation can make lead and generator placement difficult. Despite these challenges, support has increased for the use of ICDs in children, even as primary prevention.3 In previous reports, the smallest patients to receive an intrathoracic ICD weighed 5.5 and 7 kg.4,5 Herein, we discuss the implantation of an epicardial ICD in a 4.9-kg, 5-week-old infant.
In January 2008, a 5-week-old infant boy with no relevant medical history sustained cardiopulmonary arrest after feeding. In the ambulance, defibrillation was used to terminate ventricular fibrillation. A 15-lead electrocardiogram in our emergency department revealed sinus rhythm with a mildly prolonged QTc interval of 450 ms. Upon correction of the patient's metabolic acidosis, the interval shortened into the upper limits of normal (430–440 ms).
There was no family history of arrhythmias or sudden cardiac death. A transthoracic echocardiogram revealed a structurally normal heart with preserved ventricular function, suggesting a primary rhythm disturbance of unknown cause. Recommended genetic testing, including that for long QT syndrome, was not pursued, because the family's insurance would not cover it. Conventional treatment options for the small patient included long-term hospitalization for later ICD implantation, or discharge from the hospital with an external defibrillator and home telemetry. After a meticulous physical examination of the infant and an evaluation of his body dimensions, we decided that placing an epicardial ICD was feasible and the best option.
At surgery in February 2008, the patient weighed 4.9 kg, he was 64 cm long, and his body surface area was 0.29 m2. A median sternotomy was performed, and a Vitality® ICD (Guidant, part of Boston Scientific Corporation; St. Paul, Minn) was implanted. A 35-cm Transvene® 6937A transvenous superior vena cava coil (Medtronic, Inc.; Minneapolis, Minn) was placed in the transverse sinus as the defibrillator coil, and a 25-cm bipolar pace-sense lead was placed on the right ventricle. To avoid cardiac strangulation, no more than 40% of the heart's circumference was covered and the coil was sewn to the pericardium. A large, left lateral, subfascial generator pocket was created beneath the anterior rectus sheath. The length of the incision was in accord with the width of the generator. The pocket was seated below the left costal margin and extended to the left iliac crest, creating an effective vector for defibrillation. The ventricular lead had excellent sensing with an R wave greater than 30 mV and good capture thresholds of 1.2 V at 0.5 ms. Ventricular fibrillation was induced and successfully terminated by the device with 14 J. The defibrillator lead impedance was 55 W.
The patient tolerated the procedure well. Postoperatively, an echocardiogram showed normal ventricular function with a left ventricular ejection fraction of 0.68, and a chest radiograph showed no pleural effusions or pneumothorax (Fig. 1). The infant had no morbidity or rhythm disturbances and was discharged from the hospital on postoperative day 5, on β-blocker therapy. Follow-up Holter evaluations revealed no arrhythmias. Through June 2011, ongoing interrogation of the ICD revealed stable pacemaker function, good sensing and capture thresholds, stable lead impedances, and no appropriate or inappropriate discharges. The patient was doing well and remained on propranolol therapy.
It is practical to evaluate the body dimensions of a small patient before placing an ICD. A 5-kg child with a wider body may be a better candidate for ICD placement than a heavier child whose body is thinner and longer. Our patient was comparatively short and wide, and he had large amounts of adipose tissue that were conducive to device implantation.
Alternative approaches have been reported. Kriebel and colleagues4 reported the case of a 5.5-kg patient whose completely extrathoracic defibrillation system consisted of transvenous leads implanted subcutaneously, with bipolar epicardial electrodes and an abdominal active-can device (in which the ICD generator is also a defibrillating electrode) as the anode. Thogersen and co-authors5 reported the case of a 7-kg patient who received a defibrillator with an epicardial pace-sense lead and a superior vena cava lead with a subcutaneous defibrillator coil in the posterior left thorax.
Larger series have also reported alternative configurations for defibrillator implantation in pediatric patients with congenital heart disease. These configurations have included subcutaneous arrays and transvenous ICD coils placed epicardially or subcutaneously.6 Radbill and associates7 described a cohort of 39 patients whose implanted defibrillator coils used various nontransvenous modes. However, the survival of those systems was significantly shorter than that of the transvenous systems in the study, and the smallest patient weighed 12 kg. The long-term outlook for our patient is unclear, given the undetermined cause of the rhythm disturbance. If conversion to a transvenous system is required, a minimum weight of 10 kg—ideally, 15 to 20 kg—will be necessary for device implantation. At last examination, our patient weighed 16 kg.
We think that an external device is not optimal for patients who weigh less than 10 kg, because of an increased risk of lead damage or migration, less reliable defibrillator thresholds, and possibly shorter device survival. From our experience, we believe that dysrhythmias even in very small children can be treated effectively and safely with use of an epicardial ICD. To our knowledge, our 4.9-kg patient is the smallest to have undergone this treatment successfully.
Address for reprints: David L.S. Morales, MD, WT19345H, Texas Children's Hospital, 6621 Fannin St., Houston, TX 77030
Dr. Bryant is currently affiliated with the Division of Cardiovascular Surgery at the University of Minnesota Medical Center, Minneapolis, Minnesota.