Published online June 30, 2006
PEDIATRICS
Vol. 118
No. 2
August 2006, pp.
e526-e529
(doi:10.1542/peds.2006-0129)
Successful Parental Use of an Automated External Defibrillator for an Infant With Long-QT Syndrome
Abhay Divekar, MBBS, MD and
Reeni Soni, MD
Section of Pediatric Cardiology, Department of Pediatrics, Health Sciences Center, University of Manitoba, Winnipeg, Manitoba, Canada
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ABSTRACT
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Congenital long-QT syndrome with 2:1 atrioventricular block presenting in the perinatal period is rare, has a poor prognosis, and leads to high risk for lethal ventricular arrhythmic events. An implantable cardioverter-defibrillator seems to be the most effective treatment in the prevention of arrhythmic sudden cardiac death in patients with long-QT syndrome. Technical limitations and risks associated with implantable cardioverter-defibrillators in asymptomatic infants is considered too great to justify use for primary prophylaxis against sudden cardiac death. In this case report we describe the first successful parental use of an automated external defibrillator prescribed for primary prophylaxis against sudden cardiac death in an infant with long-QT syndrome.
Key Words: automated external defibrillator • long-QT syndrome • sudden cardiac death
Abbreviations: LQTS, long-QT syndrome • AED, automated external defibrillator • SCD, sudden cardiac death • QTc, corrected QT interval • EKG, electrocardiogram • ICD, implantable cardioverter-defibrillator
Congenital long-QT syndrome (LQTS) with 2:1 atrioventricular block presenting in the perinatal period is rare and has a poor prognosis.1 Parental use of commercially available automated external defibrillators (AEDs) has been reported for 2 children.2,3 In this case report we describe the first successful parental use of a configured AED with a weight-appropriate defibrillation dose for an infant with LQTS prescribed for primary prophylaxis against sudden cardiac death (SCD).
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CASE REPORT
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An 8-month-old, 8.6-kg girl first presented antenatally with recurrent fetal tachycardia. She was treated with maternal digoxin for a presumptive diagnosis of supraventricular tachycardia. Subsequent assessment showed normal rhythm. Postnatal evaluation showed a prolonged corrected QT interval (QTc) of 600 milliseconds with intermittent 2:1 atrioventricular block (no digoxin was administered). There was no structural heart disease, and left ventricular systolic function was normal. Initially, she had multiple sustained runs of torsade de pointes without hemodynamic compromise preceded by 2:1 atrioventricular block (Fig 1). T-wave morphology (Fig 2) on a resting 12-lead electrocardiogram (EKG) was consistent with the LQT3 genotype.4 Diagnostic challenge for sodium channelopathy (SCN 5A) with 1 mg/kg of lidocaine followed by continuous infusion of 30 µg/kg per minute resulted in shortening of the QTc to 424 milliseconds, restoration of normal sinus rhythm, and suppression of torsade de pointes. Genetic testing is pending.
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FIGURE 1 EKG recording illustrating nonsustained torsade de pointes preceded by 2:1 atrioventricular block.
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FIGURE 2 Twelve-lead resting EKG showing prolonged QTc late-onset narrow and peaked T waves and a long ST segment. This T-wave morphology is consistent with the LQT3 genotype.
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She had no family history of LQTS, consanguinity, or SCD. Screening EKGs in both parents were normal. Mexiletine was initiated at 2 mg/kg per dose 3 times a day; the lidocaine infusion was discontinued after 4 doses of mexiletine. A final dose of 4 mg/kg per dose was required to achieve full suppression of torsade de pointes before discharge from the hospital; the QTc ranged from 424 to 450 milliseconds.
Potential high risk for life-threatening ventricular arrhythmias identified several issues related to discharge planning. Local emergency medical services protocol precluded defibrillation of children <1 year of age except by advanced paramedics. The risk/benefit ratio for an implantable cardioverter-defibrillator (ICD) in an asymptomatic infant with good control on medical therapy was considered to be too high to justify prescription for primary prophylaxis.
To address these issues in the face of malignant natural history for life-threatening ventricular arrhythmias, several precautionary steps were undertaken. The parents and grandparents completed a formal course in cardiopulmonary resuscitation. All 911 calls from their residence were "red-flagged" to include dispatch of advanced paramedics. Attempts to improve early access to defibrillation prompted an innovative approach. Zoll Canada (Mississuaga, Ontario, Canada) agreed to configure an M-series defibrillator with a weight-appropriate defibrillation dose and the functionality of an AED. A PCMCIA card allowed data storage. Extensive education related to use of the AED was completed before the girl was discharged from the hospital and reinforced during follow-up visits, including the need to have the AED available at all times. The family was instructed to confirm nonresponsiveness before discharge of the defibrillation dose. They were informed of the rationale and experimental use of this innovative approach.
Frequent follow-up was maintained to increase the dose of mexiletine for weight gain. Resting 12-lead EKGs showed normal sinus rhythm with a QTc that varied from 424 to 450 milliseconds, normal left ventricular function, and surveillance 24-hour ambulatory Holter monitoring showed good arrhythmia control with only isolated ventricular ectopy.
When the girl was 8 months old, her mother went to check on her, half an hour before her nightly scheduled mexiletine dose, after hearing an abnormal cry. She was found nonresponsive and cyanosed with labored respiration. The father brought the defibrillator and activated 911. Her mother attached the self-adhesive pads and activated the unit. Downloaded data from the PCMCIA card (Fig 3) showed that rhythm analysis using the configured AED's standard diagnostic algorithm appropriately identified and advised therapy for ventricular fibrillation. The third defibrillation dose converted ventricular fibrillation to perfusing junctional rhythm at 60/minute followed by sinus tachycardia. She regained color and responsiveness. Analysis during sinus rhythm correctly identified nonshockable rhythm.
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FIGURE 3 Data downloaded from the PCMCIA card at the time of successful parental resuscitation. A, Rhythm at the time of activating the AED. B, Appropriate recognition of the patient's rhythm as shockable. C, Voice prompt advising the parents to check the patient after advice to deliver the third defibrillation dose was not acted on. D, Successful conversion from ventricular fibrillation to perfusing junctional rhythm. E, Appropriate recognition of perfusing sinus rhythm with a "no shock advised" prompt.
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She was admitted to the ICU for monitoring. A 12-lead EKG showed normal sinus rhythm with a QTc of 454 milliseconds. Echocardiography demonstrated normal left ventricular function. Her serum electrolyte levels were normal. She had not missed any doses of her medication. She was clinically stable and neurologically intact. Approximately 15 hours after admission, half an hour before her mexiletine dose, she had another episode of ventricular fibrillation from which she was successfully defibrillated. The frequency of mexiletine administration was increased from every 8 to every 6 hours.
In view of 2 episodes of resuscitated SCD, the patient underwent successful ICD implantation for secondary prophylaxis at 8 months.
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DISCUSSION
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Prescription of an AED was felt to be the safest practical way to provide defibrillation for all witnessed life-threatening events in our high-risk patient. Concerns regarding the defibrillation dose (the lowest defibrillation dose for any commercially available unit is 50 J) prompted configuration of a commercially available defibrillator for the patient's needs (the commercial M-series unit does not deliver an age-appropriate dose and is not an AED). The patient's rhythm (torsade de pointes; Fig 1) was tested against the unit's standard adult algorithm and appropriately recognized it as a shockable rhythm. Parenteral education, mock rehearsals, and motivation were part of ongoing follow-up.
The data downloaded during the event are instructive at many levels. The defibrillator's standard adult algorithm correctly identified both shockable and nonshockable rhythms. Successful early defibrillation before emergency medical services arrival and intact neurologic recovery reiterates the need for prompt and early access to defibrillation even in children. "Layperson" education allows successful use of AEDs.
ICDs are thought to be the most effective treatment in the prevention of arrhythmic SCD in a variety of clinical disorders including LQTS.5 In patients with LQTS, ICD implantation for secondary prevention of SCD is a class I indication; all other high-risk patients have a class IIb indication.6 Neonates with LQTS with 2:1 atrioventricular block and an LQT3 genotype are recognized as being at high risk for lethal ventricular arrhythmic events.7 AEDs have been theoretically suggested, citing technical limitations and risks associated with ICD implantation in asymptomatic infants awaiting growth.7
AEDs have dramatically improved resuscitation rates and outcomes in adults by providing early access to defibrillation.8 The role of AEDs in infants and children is evolving.8 Two reports have described successful parental use of commercially available AEDs in children.2,3 Successful use of AEDs in children by health care professionals has also been reported.9 The major limitation/concern for use of AEDs in young children is rhythm recognition based on adult algorithms and the safety of adult defibrillation doses.9,10 Published data in children show that adult algorithms have high specificity (99%–100%) for nonshockable rhythms and high sensitivity (94%–96%) for ventricular fibrillation.8 Thus, the likelihood of inappropriate shock is exceedingly low.8
AEDs may be the safest practical modality for providing prophylaxis against SCD in individualized high-risk patients such as neonates with LQTS and 2:1 atrioventricular block. The ability to configure any commercial unit to deliver a weight-appropriate defibrillation dose should allow use of this technology while awaiting the verdict on an appropriate defibrillation dose on a case-by-case basis. This and similar case reports should help emphasize the need for early access to defibrillation in children. A voice prompt to confirm nonresponsiveness before discharge of the defibrillation dose may minimize the likelihood of inappropriate shock.
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ACKNOWLEDGMENTS
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We and the family are indebted to Mr Neil Johnston, Ms Helen Turner, and technical engineers at Zoll Canada for donating the M-series defibrillator free of cost and analyzing the event from the PCMCIA card. We also thank Dr R. Grierson (Medical Director of Fire Paramedic Services, Winnipeg, Manitoba) for arranging dispatch of advanced paramedics for 911 calls from the patient's residential number.
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FOOTNOTES
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Accepted Feb 2, 2006.
Address correspondence to Abhay Divekar, MBBS, MD, Pediatric Cardiology, University of Manitoba, Variety Children's Heart Center, Health Sciences Center, FE-241, 685 William Ave, Winnipeg, Manitoba, Canada R3E 0Z2. E-mail: adivekar{at}exchange.hsc.mb.ca
The authors have indicated they have no financial relationships relevant to this article to disclose.
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PEDIATRICS (ISSN 1098-4275). ©2006 by the American Academy of Pediatrics
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