Scholarly article on topic 'A novel de novo calmodulin mutation in a 6-year-old boy who experienced an aborted cardiac arrest'

A novel de novo calmodulin mutation in a 6-year-old boy who experienced an aborted cardiac arrest Academic research paper on "Clinical medicine"

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{Arrhythmia / Calmodulin / "Long QT" / "Catecholaminergic polymorphic VT" / "Sudden cardiac arrest"}

Academic research paper on topic "A novel de novo calmodulin mutation in a 6-year-old boy who experienced an aborted cardiac arrest"

Author's Accepted Manuscript

A novel de novo calmodulin mutation in a 6-year-old boy who experienced an aborted cardiac arrest

Kazuhiro Takahashi, Taisuke Ishikawa, Naomasa Makita, Kiyotaka Takefuta, Taisuke Nabeshima, Mami Nakayashiro

Heart Rhythm

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PII: S2214-0271(16)30109-9

DOI: http ://dx.doi. org/ 10.1016/j. hrcr.2016.09.004

Reference: HRCR294

To appear in: HeartRhythm Case Reports

Received date: 21 June 2016 Revised date: 23 August 2016 Accepted date: 13 September 2016

Cite this article as: Kazuhiro Takahashi, Taisuke Ishikawa, Naomasa Makita, Kiyotaka Takefuta, Taisuke Nabeshima and Mami Nakayashiro, A novel de novo calmodulin mutation in a 6-year-old boy who experienced an aborted cardiac arrest, HeartRhythm Case Reports,

http ://dx.doi. org/ 10.1016/j. hrcr.2016.09.004

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Case Report

A novel de novo calmodulin mutation in a 6-year-old boy who experienced an aborted cardiac arrest

Short Title: Novel calmodulin mutation in cardiac arrest

Kazuhiro Takahashia, MD, PhD: bigkaz@mua.biglobe.ne.jp Taisuke Ishikawab, DVM, PhD: ishitai@nagasaki-u.ac.jp Naomasa Makitab, MD, PhD: makitanaomasa@gmail.com Kiyotaka Takefutaa, MD: africa.de.etamono.priceless@gmail.com Taisuke Nabeshimaa, MD: nabedonwalker@hotmail.co.jp Mami Nakayashiroa, MD: maminak@gmail.com

a. Department of Pediatric Cardiology, Okinawa Nanbu and Children's Medical Center, Okinawa, Japan

b. Department of Molecular Physiology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan

Corresponding Author: Kazuhiro Takahashi, MD, PhD Pediatric Cardiology, Okinawa Children's Medical Center 118-1 Arakawa, Haebaru-chou, Okinawa, 901-1193, Japan Phone: +81-98-888-0123 Fax: +81-98-888-6400 Email: bigkaz@mua.biglobe.ne.jp

Conflicts of Interest: None Financial Support: None

Keywords: arrhythmia; calmodulin; long QT; catecholaminergic polymorphic VT; sudden cardiac arrest

Key teaching points :

• Mutations in the human calmodulin genes (CALM1, CALM2, and CALM3) are associated with life-threatening conditions in childhood, such as idiopathic VF, LQTS, and CPVT.

• An LQTS-specific "calmodulinopathy" phenotype associated with CALM mutations has been described with an early onset of the disease.

• Genetic testing for CALM mutations should be performed in children with QT prolongation, especially in those who have experienced an aborted cardiac arrest and who have a negative family history.

Introduction

Mutations in the human calmodulin genes (CALM1, CALM2, and CALM3) are associated with life-threatening conditions in childhood, such as idiopathic ventricular fibrillation

(IVF) and long-QT syndrome (LQTS). - Furthermore, CALM1 mutations and an arrhythmia syndrome was in a catecholaminergic polymorphic ventricular tachycardia (CPVT)-like phenotype.4 Sudden unexplained death in the young can be the first clinical manifestation of an underlying arrhythmogenic disorder such as IVF.5,6 After an aborted cardiac arrest, determining the diagnosis begins with a systematic clinical evaluation. Subsequently, targeted genetic testing may be considered for genetic confirmation and

family screening, , although in the absence of a significant family history or electrocardiographic abnormalities, identification of the disease etiology should be limited to previously recognized conditions.9

Here we report a novel de novo missense mutation in CALM1 associated with a phenotype compatible with LQTS in a child who experienced an aborted first-episode cardiac arrest.

Case Report

The patient was a 6-year-old, otherwise healthy boy (the proband) born to seemingly healthy parents. He had a mild pervasive developmental disorder, with hyperactivity and mild bronchial asthma. His five siblings were healthy, and there was no family history of syncope or sudden death.

After a breakfast at his home, the boy suddenly lost consciousness, collapsed, and was unresponsive. His mother called for an ambulance. On arrival, the emergency medical staff confirmed cardiopulmonary arrest and performed cardiopulmonary resuscitation (CPR). The automated external defibrillator showed ventricular fibrillation (VF), and the patient was successfully cardioverted. He was intubated and taken to the local community hospital. Arterial blood gas analysis showed combined respiratory and metabolic acidosis thought to be related to the CPR. An infusion of dopamine induced premature ventricular contractions, singly and in bidirectional couplets, which responded to xylocaine (Figure 1A). He was then transferred to our hospital for further evaluation and treatment. VF recurred on arrival at our hospital's emergency room. A direct current shock and 150 mg of amiodarone were administered, and he was transferred to the pediatric intensive care unit. Blood samples taken at the time of admission showed normal biochemistry, including normal troponin T and creatinine kinases. Transthoracic echocardiography was normal, with good left ventricular systolic function. A resting baseline 12-lead electrocardiogram (ECG) did not indicate any abnormality such as LQTS or Brugada syndrome. At midnight, he developed polymorphic ventricular tachycardia, which degenerated to VF with remarkable QT prolongation (Figure 1B). When the patient awoke the next day, torsade de pointes recurred with an increasing heart rate, despite the continuous infusion of xylocaine (1 mg/kg/h) (Figure 1C). An additional continuous infusion of propranolol (0.01 mg/kg/h) and mexiletine (0.5 mg/kg/h) was commenced. The triple regimen of xylocaine, propranolol, and mexiletine was markedly effective. The patient was successfully extubated and administered oral medication of propranolol and mexiletine. He experienced no further episodes of syncope or seizure on

the regimen of beta-blockers and mexiletine. His exercise test on the regimen did not reach a definitive result due to his intolerance to the test. Invasive electrophysiological testing was not performed. An implantable cardioverter defibrillator (ICD) was not recommended because of the risk of inappropriate shocks, which could provoke more severe anxiety and possible ICD storms.

Genetic testing

Using the candidate gene approach, we initially screened the authentic long-QT syndrome genes KCNQ1, KCNH2, SCN5A, and KCNE1 but found no mutation in them. When screening for other candidate genes, we identified a novel missense variation c.A314>C in exon 5 of CALM1. This nucleotide change predicts the substitution of a conserved glutamic acid residue with alanine (p.E105A) within the third EF-hand calcium-binding motif in the C-terminal domain of the encoded calmodulin protein (Figure 2). This variation is not registered in any public DNA variation databases, including the NHLBI GO Exome Sequencing Project, 1000 Human Genome Project, Exome Aggregation Consortium, and Japanese exome database HGVD (http://www.genome.med.kyoto-u.ac.jp/SnpDB/. Accessed June 2016). In silico variant effect prediction programs Polyphen2 and SIFT gave the results "deleterious" (score 0) and "probably damaging" (score 0.997), respectively.

Clinical evaluation and genetic testing of family members

The patient had four siblings, three sisters and one brother, aged 8-15 years. None had any known cardiac diseases or symptoms. The parents and siblings had normal ECG indices, including normal QTc intervals. Both parents turned out to be non-carriers of

CAML1-E105A, demonstrating that this is a de novo mutation; therefore, we did not further investigate the siblings.

Discussion

Here we described a case of aborted cardiac arrest in a seemingly healthy preschool boy who exhibited profound QT prolongation with an increasing heart rate before the recurrence of polymorphic ventricular tachycardia at a pediatric ICU.

Therapy for a cardiac arrest survivor largely depends on the underlying diagnosis, typically combining condition-specific medication with an ICD. The management of the patient's family is driven by the outcome of a thorough evaluation of the index cardiac arrest survivor. Therefore, every effort should be made to determine the underlying pathophysiology in order to clarify the prognosis and establish the appropriate therapy. Genetic arrhythmia disorders require further investigation of family members who may be at risk.

As is characteristic of calmodulin gene mutations, the patient had a negative family history of heart disease, and his parents' ECGs were normal. A cascade gene study was conducted on the index case and his parents, and the results were filtered to include a novel sporadic variant in the proband. Similar to other calmodulin mutations reported so far, E105A is located at the acidic residues located at the EF-hands. It is speculated that E105A results in a substantial reduction of Ca affinity, thereby disrupting the ability to

transduce intracellular Ca signals and leading to lethal arrhythmias, including severe catecholaminergic QT prolongation and torsade de pointes. It is difficult to identify individuals susceptible to lethal arrhythmias during neonatal ECG screening.

The patient also exhibited a developmental delay and mild bronchial asthma as an extra-cardiac manifestation. Although channelopathies in the brain are similar to the cardiac channelopathies in some inherited arrhythmia disorders,10 the cause of the patient's cognitive delay is unknown.

Although the follow-up thus far has been short term (18 months), this patient has successfully responded to beta-blockade, the primary first line treatment for this disease. Mexiletine therapy was added for the arrhythmia control in the present case as well as in the previous cases published by Crotti et al.11 However, CALM-related calcium channel dysfunction was proposed for the pathophysiological mechanism in calmodulionopathy.12-4 Therefore calcium antagonist may be a more beneficial treatment of the choice. If the patient continues to have syncope or arrhythmias on medication, he should be strongly considered for ICD implantation or cardiac sympathetic denervation to prevent life-threatening arrhythmias because of his history of bronchial asthma.

Conclusions

We report a novel de novo CALM1 missense mutation associated with a phenotype compatible with LQTS in a child who experienced an aborted first-episode cardiac arrest. Genetic testing for CALM mutations should be performed in children with QT prolongation, especially in those who have experienced an aborted cardiac arrest and who have a negative family history.

References

1. Makita N, Yagihara N, Crotti L, et al. Novel calmodulin mutations associated with congenital arrhythmia susceptibility. Circ Cardiovasc Genet 2014;7:466-474.

2. Marsman RF, Barc J, Beekman L, Alders M, Dooijes D, van den Wijngaard A, Ratbi I, Sefiani A, Bhuiyan ZA, Wilde AA, Bezzina CR. A mutation in CALM1 encoding calmodulin in familial idiopathic ventricular fibrillation in childhood and adolescence. J Am Coll Cardiol 2014;63:259-266.

3. Boczek NJ, Gomez-Hurtado N, Ye D, et al. Spectrum and prevalence of CALM1 -, CALM2-, and CALM3-encoded calmodulin variants in long QT syndrome and functional characterization of a novel long QT syndrome-associated calmodulin missense variant, E141G. Circ Cardiovasc Genet 2016;9:136-146.

4. Nyegaard M, Overgaard MT, Sondergaard MT, et al. Mutations in calmodulin cause ventricular tachycardia and sudden cardiac death. Am J Hum Genet. 2012;91:703-12.

5. Wong LC, Behr ER. Sudden unexplained death in infants and children: the role of undiagnosed inherited cardiac conditions. Europace 2014;16:1706-1713.

6. Ackerman M, Atkins DL, Triedman JK. Sudden cardiac death in the young. Circulation. 2016;133:1006-1026.

7. Ackerman MJ, Priori SG, Willems S, et al. HRS/EHRA expert consensus statement on the state of genetic testing for the channelopathies and cardiomyopathies: this document was developed as a partnership between the

Heart Rhythm Society (HRS) and the European Heart Rhythm Association (EHRA). Europace 2011;13:1077-1109.

8. Schwartz PJ, Ackerman MJ, George AL Jr, Wilde AA. Impact of genetics on the clinical management of channelopathies. J Am Coll Cardiol 2013;62:169-180.

9. Semsarian C, Ingles J, Wilde AA. Sudden cardiac death in the young: the molecular autopsy and a practical approach to surviving relatives. Eur Heart J 2015;36:1290-1296.

10. Takano K, Liu D, Tarpey P, Gallant E, Lam A, Witham S, Alexov E, Chaubey A, Stevenson RE, Schwartz CE, Board PG, Dulhunty AF. An X-linked channelopathy with cardiomegaly due to a CLIC2 mutation enhancing ryanodine receptor channel activity. Hum Mol Genet 2012;21:4497-4507.

11. Crotti L, Johnson CN, Graf E, et al. Calmodulin mutations associated with recurrent cardiac arrest in infants. Circulation. 2013;127:1009-17.

12. Yin G, Hassan F, Haroun AR, et al. Arrhythmogenic calmodulin mutations disrupt intracellular cardiomyocyte Ca2+ regulation by distinct mechanisms. J Am Heart Assoc. 2014;3:e000996.

13. Marie-A. Chaix, Tamara T. Koopmann, Philippe Goyette, et al. Novel CALM3 mutations in pediatric long QT syndrome patients support a CALM3-specific calmodulinopathy. HeartRhythm Case Reports 2016.

14. Gomez-Hurtado N, Boczek NJ, Kryshtal DO, et al. Novel CPVT-associated

calmodulin mutation in CALM3 (CALM3-A103V) activates arrhythmogenic Ca waves and sparks. Circ Arrhythm Electrophysiol. 2016;9. pii: e004161.

Figure legends Figure 1

A: Initial 12-lead ECG shows bidirectional premature ventricular beats. B: QT prolongation during sinus bradycardia at night. C: Torsades de pointes with increasing heart rate.

Figure 2. A novel CALM1 mutation E105A.

Upper panel indicates the sequence pherogram of the novel CALM1 missense mutation E105A. Lower panel shows schematic representations of the Ca2+ binding loops in the N-terminal (I and II) and C-terminal (III and IV) and the locations of mutations. Red circle represents the CALM1-E105A identified in our present study and green symbols represents CALM1 and CALM2 mutations previously reported mutations.