Familial Long QT Syndrome and Late Development of Dilated Cardiomyopathy in a Child with a KCNQ1 Mutation: a Case Report

Familial long QT syndrome and late development of dilated cardiomyopathy in a child with a KCNQ1 mutation: A case report Kiona Y. Allen, MD, Victoria L. Vetter, MD, MPH, Maully J. Shah, MBBS, Matthew J. O’Connor, MD From the Division of Cardiology, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania. Introduction and nadolol thereafter. Throughout this time he was clin- Congenital long QT syndrome (LQTS) is an inherited ically well, without palpitations, syncope, or documented cardiac channelopathy characterized by prolongation of the arrhythmias, although his QTc remained prolonged on serial QT interval on electrocardiogram (ECG), and is associated ECG evaluations. He underwent formal exercise testing at 7 with an increased risk of life-threatening ventricular arrhyth- years of age, which was notable for a prolonged QTc mias. Mutations in over a dozen distinct genes have been throughout exercise and recovery. There were no arrhyth- implicated in the pathogenesis of this group of disorders.1 mias and he had a normal oxygen consumption of 40.5 mL/ LQTS type 1 (LQT1), the most prevalent LQTS subtype, is kg/min. He was active in multiple recreational sports, including basketball, lacrosse, and baseball; an automated characterized by a heterozygous loss-of-function mutation in fi the KCNQ1 gene, which codes for the α-subunit of the external de brillator was available for emergency use. delayed rectifier inward potassium ion channel. The associ- Repeat exercise testing was performed at 8 years of age, ation of LQTS with dilated cardiomyopathy (DCM) is rare which again demonstrated a prolonged QTc without ven- but has been reported in the presence of sodium channel gene tricular ectopy. Oxygen consumption was not measured, but mutations, as seen in LQTS type 3. In this case report, we his physical working capacity was described as low (work describe a patient with familial LQT1 (KCNQ1 mutation) rate 67 watts). identified in infancy who was subsequently diagnosed with At 9 years of age, the patient was admitted to the hospital severe DCM later in childhood. complaining of several days of diffuse abdominal pain, vomiting, diarrhea, and fatigue. He was admitted to the general pediatric service with a presumed diagnosis of viral Case report gastroenteritis and discharged home the following day after A 2-day-old male infant underwent cardiology evaluation receiving intravenous hydration. He presented to the emer- owing to a family history of LQTS. Evaluation of the gency room 1 week later with continued gastrointestinal extended family had previously been remarkable for multiple symptoms, as well as worsening fatigue and dyspnea. The family members, including his mother, having a prolonged initial physical examination was notable for tachypnea and ’ QTc on ECG screening. The patient s ECG demonstrated a intermittent retractions. On auscultation, a 1/6 holosystolic QTc of 495 msec and abnormal T-wave morphology murmur was heard at the apex, with no other abnormalities. (Figure 1A). He was admitted to the hospital for initiation Hepatomegaly with tenderness to palpation was present. The of propranolol. Genetic testing of the patient and multiple initial laboratory evaluation was notable for an elevated fi fi rst- and second-degree maternal relatives identi ed the B-type natriuretic peptide of 8578 pg/mL. A chest radio- presence of a deleterious genetic mutation, KCNQ1 Ser 349 graph showed increased interstitial markings without pulmo- ’ Ter, consistent with LQT1. The patient s older brother, who nary edema or cardiomegaly. His ECG showed new T wave had previously been thought to be unaffected, was also found changes and voltage criteria for left ventricular (LV) hyper- to be positive for the mutation and started on medication. The trophy, but no evidence of arrhythmia (Figure 1B). A patient was maintained on propranolol until 4 years of age, transthoracic echocardiogram was performed and demonstrated severely diminished LV ejection with a markedly KEYWORDS Familial long QT syndrome; Dilated cardiomyopathy; KCNQ1; dilated left atrium, a mildly dilated left ventricle, and Voltage-gated potassium channel; Genetics (Heart Rhythm Case Reports 2016;2:128–131) moderate to severe mitral regurgitation. The LV ejection ’ Address reprint requests and correspondence: Dr Kiona Y. Allen, The fraction (EF), as estimated by Simpson s rule (biplane), was Children’s Hospital of Philadelphia, 3401 Civic Center Blvd, Philadelphia, 15%. Right ventricular (RV) ejection was decreased as well, PA 19104. E-mail address: [email protected]. but not as markedly as that of the left ventricle. There was 2214-0271 B 2016 Heart Rhythm Society. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). http://dx.doi.org/10.1016/j.hrcr.2015.10.011 Allen et al Case Report of Dilated Cardiomyopathy in Long QT Syndrome 129 fl fl KEY TEACHING POINTS chain reaction assays for adenovirus, in uenza, parain uenza, metapneumovirus, rhinovirus, enterovirus, cytomegalovirus, An association between long QT syndrome and HHV-6, parechovirus, parvovirus B19, Epstein-Barr virus, dilated cardiomyopathy has been previously and stool polymerase chain reaction assays for common described in the presence of SCN5A mutations and gastrointestinal pathogens were all negative) or systemic fl o may represent a sodium channel “overlap in ammation (C-reactive protein 0.5 mg/dL, erythrocyte syndrome” between channelopathies and sedimentation rate 0 mm/h) and the troponin I was 0.01 ng/ mL. He was treated with 2 g/kg of intravenous immunoglo- cardiomyopathies. bulin, without improvement. It is possible that molecular interaction between A metabolic evaluation (lactate, pyruvate, acylcarnitine potassium channel mutations and other mutations profile, blood and urine carnitine levels, plasma amino acids, in the cardiac sarcomere and mitochondria may urine organic acid, and creatine kinase) was negative. Com- lead to a phenotypic overlap syndrome between mercial genetic testing consisting of DNA sequencing for 51 long QT syndrome and cardiomyopathy. known cardiomyopathy genes was performed by the Labora- tory for Molecular Medicine (Boston, MA) and was notable Additional screening for cardiomyopathy may be for a variant of unknown significance in the titin gene warranted in patients with a variety of genetic (p.Asn18096Lys). A Combined Mito Genome Plus Mito 140 channelopathies. Nuclear Gene Panel (GeneDx, Gaithersburg, MD) was also performed and showed heterozygosity for a variant of unknown echocardiographic evidence of elevated pulmonary artery significance in the ACO2 gene (p.Arg142Gln) and hetero- pressures with an RV pressure estimate of 38 mm Hg above zygosity for a variant of unknown significance in the central venous pressure and a pulmonary artery end-diastolic NDUFA10 gene (p.Arg337His). Cardiac magnetic resonance pressure estimated at 15 mm Hg using the modified Bernoulli imaging (MRI) was obtained and demonstrated moderate to equation (Figure 2). An infectious evaluation failed to show severe LV dilation (end-diastolic volume 165 mL/m2), severely any evidence of active viral infection (blood polymerase diminished LV ejection (EF 21%), and moderately diminished Figure 1 A: Twelve-lead electrocardiogram obtained at 2 days of life showing a corrected QT interval of 495 msec and nonspecific T wave abnormalities. B: Twelve-lead electrocardiogram obtained at time of presentation with heart failure at 9 years of age demonstrating new T wave changes and voltage criteria for left ventricular hypertrophy. 130 Heart Rhythm Case Reports, Vol 2, No 2, March 2016 Figure 2 Transthoracic echocardiogram showing severe dilation and systolic dysfunction of the left ventricle. RV ejection (EF 32%) without dilation or hypertrophy. MRI 14 mm Hg, and normal pulmonary vascular resistance. Based tissue characterization was limited owing to myocardial thin- on these findings and clinical status, the patient was listed for ning, but the Lake Louise criteria for MRI diagnosis of heart transplantation. He recently underwent an uncomplicated myocarditis were not met.2 Basedonthesefindings, a diagnosis orthotopic heart transplant. Gross pathologic examination of the of idiopathic DCM was made. Upon clinical improvement, explanted heart was consistent with the diagnosis of DCM, with milrinone was discontinued and he was transitioned to an oral scattered myocyte hypertrophy on microscopic examination. regimen of enalapril, digoxin, nadolol, and enteral diuretics. The patient’s older brother, who also has the LQT1 mutation, Owing to his lack of arrhythmias and relative small size, was evaluated with screening echocardiography and has normal placement of a primary prevention implantable cardioverter- cardiac chamber size and systolic function. No other family defibrillator was deferred. He was discharged home after members have been diagnosed with cardiomyopathy (Figure 3). approximately 4 weeks, but required readmission for reinitia- tion of milrinone approximately 1 month later owing to recurrent symptoms of congestive heart failure. A cardiac Discussion catheterization was performed during that admission and was To our knowledge, this is the first report in the medical notable for preserved cardiac index of 3.6 L/min/m2 (on literature of an association between LQT1 and DCM. Our milrinone), elevated pulmonary capillary wedge pressure of patient is unique, as he carries genotypic and phenotypic Figure 3 Family pedigree demonstrating

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