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Andersen-Tawil syndrome is an autosomal dominant condition characterized by dysmorphic features, periodic paralysis, and ventricular arrhythmias. Twiddler syndrome is characterized by intentional or inadvertent manipulation of implanted devices in the pacemaker pocket. We describe an unusual case of an 8-year-old girl who had both syndromes.
Andersen-Tawil syndrome is an autosomal dominant disorder that is characterized by dysmorphic features, periodic paralysis, and ventricular arrhythmias.1,2 Nearly two thirds of all cases of Andersen-Tawil syndrome are caused by mutations in the KCNJ2 gene, which encodes for Kir2.1, the inwardly rectifying potassium ion channel.3 This mutation results in abnormal ventricular repolarization and in prolongation of the QT interval.3 Patients with Andersen-Tawil syndrome may have polymorphic ventricular tachycardia that necessitates implantation of an automatic internal cardioverter-defibrillator (ICD). In patients with a pacemaker or ICD, twisting of the device within the implantation pocket, known as Twiddler syndrome, results in dislocation of 1 or more leads and pacemaker or ICD dysfunction.4,5 Here, we describe the case of a pediatric patient who had both Andersen-Tawil syndrome and Twiddler syndrome. To our knowledge, this is the 1st such case to be reported in the medical literature.
An 8-year-old girl with no history of cardiac disorder came to our institution's emergency room because of a syncopal event. The patient had experienced 2 previous syncopal events, which had occurred at school on 2 different days. Her family history included 2 miscarriages on the part of her mother, which were a result of mutations in the KCNJ2 gene. In addition, the patient's mother, maternal grandmother, and 2 maternal cousins had histories of arrhythmias that had necessitated ICD implantation.
Physical findings were unremarkable except that, like her mother and maternal grandmother, the patient had a small mandible, which resulted from Andersen-Tawil syndrome. The patient's muscle strength and tone were normal. She was admitted to the hospital and underwent electrocardiography, echocardiography, and Holter monitoring. The electrocardiogram showed frequent ventricular ectopy and a corrected QT interval of approximately 670 ms (Fig. 1). On echocardiography, the heart was structurally normal, with normal biventricular systolic function. Holter monitoring revealed frequent episodes of nonsustained polymorphic ventricular tachycardia and frequent polymorphic premature ventricular contractions. A genetics specialist evaluated the patient and diagnosed Andersen-Tawil syndrome, but the patient's family refused genetics testing.
We prescribed atenolol to the patient and, because of her family history and ventricular tachycardia, implanted an ICD. After hospital discharge, the patient returned for follow-up evaluation. Examination of the ICD revealed that it had not discharged. However, chest radiography revealed that the device had been twisted and that there was less slack than normal in the ventricular lead. These findings were consistent with Twiddler syndrome (Fig. 2). On follow-up, the patient continues to do well clinically and has shown no signs of defibrillator discharge.
Andersen-Tawil syndrome is a rare disease characterized by dysmorphic features, periodic paralysis, and ventricular arrhythmias with a wide phenotypic spectrum.3 The full triad of these features is present in 58% to 78% of patients with known genetic mutations, whereas 2 of the 3 findings are present in 32% to 81% of such patients.6,7 Most cases are due to mutations in the KCNJ2 gene that cause loss of function. This gene is responsible for encoding the Kir2.1 inward-rectifier potassium channel, a component of the inward-rectifier potassium current IK1. The IK1 current is important in the repolarization phase of the cardiac potential. The reduction in Kir2.1 results in a prolonged terminal phase of the action potential, delayed afterdepolarizations, and spontaneous arrhythmias.6 In the setting of Andersen-Tawil syndrome, clinical arrhythmias include premature ventricular contractions, bigeminy, and polymorphic ventricular tachycardia. The clinical incidence of nonsustained tachycardia is high,8 but deterioration into lethal ventricular arrhythmias is uncommon in adults.9
Patients with pacemakers or ICDs may intentionally or inadvertently manipulate or “twiddle” the pacing generator, causing the battery to roll upward in the pocket of the device.4,5,10 This complication, referred to as Twiddler syndrome, was described initially in 1968.11 The syndrome results in the dislocation of 1 or more of the leads and in the consequent dysfunction of the pacemaker or ICD.4,5 On chest radiography, the leads are seen to be bent, dislocated, or fractured.10 Because children have thin subcutaneous tissues, they may be at a heightened risk when they twiddle the generator; however, few pediatric cases have been reported.12 Patients should be advised not to manipulate the pocket of the device. If necessary, a new pocket can be created, and the leads can be placed beneath the fascia of the pectoralis muscle.
Our case involves a rare patient with both Andersen-Tawil syndrome and Twiddler syndrome. This case shows the importance of device observation by means of chest radiography in children.
Address for reprints: John L. Jefferies, MD, Pediatric Cardiology, Texas Children's Hospital, 6621 Fannin, MC 19345-C, Houston, TX 77030