Long QT Syndrome in Children in the Era of Implantable Defibrillators
Susan P. Etheridge, MD, FACC*,*,
Shubhayan Sanatani, MD ,
Mitchell I. Cohen, MD, FACC ,
Cecilia A. Albaro, MD*,
Elizabeth V. Saarel, MD, FACC* and
David J. Bradley, MD, FACC*
* University of Utah, Salt Lake City, Utah
University of British Columbia, Vancouver, British Columbia, Canada
Phoenix Children's Hospital and Arizona Pediatric Consults/Pediatrix, Phoenix, Arizona
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Figure 1 Reason for Diagnosis of LQTS
The diagnosis of long QT syndrome (LQTS) was most often made because of a family history and an abnormal electrocardiogram (ECG) obtained as a screening tool. As shown here in blue, 53% of our patients were diagnosed as a result of family screening. In red are the patients diagnosed after presentation with syncope. Sudden death or resuscitated sudden death was present in only 3% of patients, and 17% were diagnosed because of an abnormal ECG in the absence of symptoms or a family history of LQTS.
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Figure 2 Genetic Diagnoses in Those With Available Genetic Data
Genetic testing results are known in 51 patients. The KCNQ1 mutation was most common. There was a single patient with both the SCN5A mutation and the KCNQ1 mutation who is listed in both groups.
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Figure 3 Indications for Device Implantation
The most common indication for device implantation was syncope despite beta-blocker therapy. There were 13 patients in this group. Devices were placed in 4 patients with documented torsades de pointes (TdP) or ventricular tachycardia (VT) and in 3 who presented with resuscitated sudden death. A family history of sudden death caused by long QT syndrome (LQTS) was the sole indication in 3 additional patients. A pacemaker was placed in an infant with LQTS and 2:1 atrioventricular block (AVB), and an implantable cardioverter-defibrillator (ICD) was placed in an asymptomatic patient with an SCN5A mutation. A device was placed in 1 patient with syncope and a QTc interval of >600 ms who was later identified as a compound heterozygote having both SCN5A and KCNQ1 mutations. BB = beta-blockers; FH = positive family history of long QT syndrome; SD = sudden death.
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Figure 4 Outcomes in Pacemaker and ICD Patients
There were 8 patients in whom a pacemaker was initially implanted. In this group there was 1 death, and 4 patients underwent upgrade to an implantable cardioverter-defibrillator (ICD), 3 after documented ventricular tachycardia (VT) or ventricular fibrillation (VF). A single asymptomatic patient underwent an upgrade to an ICD at the time of a generator change because of concerns about compliance with beta-blocker therapy. There were 19 patients who underwent an ICD implantation as initial device therapy. Appropriate shocks have occurred in 5 patients, and inappropriate shocks in 4 patients. Sixteen ICD patients have not had a shock.
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Figure 5 Kaplan-Meier Survival Curve of Patients With and Without a Device
A shown in this Kaplan-Meier graph, survival was not different in patients with and without devices. The 15-year survival was >90% in both groups.
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Figure 6 Genetic Diagnoses in Patients With and Without a Device
Genetic testing results are known in 51 patients, and the KCNQ1 mutation is the most common finding. A single patient was identified with a compound mutation of KCNQ1 and SCN5A and is represented in both columns. This is the only patient with a device in the group with a known KCNQ1 mutation.
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