European Heart Rhythm Association (EHRA)/Heart Rhythm Society (HRS)/Asia Pacific Heart Rhythm Society (APHRS)/Latin American Heart Rhythm Society (LAHRS) Expert Consensus Statement on the state of genetic testing for cardiac diseases.

Genetic testing has advanced significantly since the publication of the 2011 HRS/EHRA Expert Consensus Statement on the State of Genetic Testing for the Channelopathies and Cardiomyopathies.1 In addition to single-gene testing, there is now the ability to perform whole-exome sequencing (WES) and whole-genome sequencing (WGS). There is growing appreciation of oligogenic disorders,2,3 the role of modifier genes,2 and the use of genetic testing for risk stratification, even in common cardiac diseases such as coronary artery disease or atrial fibrillation (AFib), including a proposal for a score awaiting validation.4 This document reviews the state of genetic testing at the present time, and addresses the questions of what tests to perform and when to perform them. It should be noted that, as articulated in a 1999 Task Force Document by the European Society of Cardiology (ESC) on the legal value of medical guidelines,5 ‘The guidelines from an international organization, such as the ESC, have no specific legal territory and have no legally enforcing character. Nonetheless, in so far as they represent the state-of-the-art, they may be used as indicating deviation from evidence-based medicine in cases of questioned liability’. In the case of potentially lethal and treatable conditions such as catecholaminergic polymorphic ventricular tachycardia (CPVT) or long QT syndrome (LQTS), it is the responsibility of the physician, preferably in conjunction with an expert genetics team, to communicate to the patient/family the critical importance of family screening, whether this be facilitated by cascade genetic testing or by broader clinical family screenin

A mutation in the beta 3 subunit of the cardiac sodium channel associated with Brugada ECG phenotype

Brugada syndrome, characterized by ST-segment elevation in the right precordial ECG leads and the development of life-threatening ventricular arrhythmias, has been associated with mutations in 6 different genes. We identify and characterize a mutation in a new gene. A 64-year-old white male displayed a type 1 ST-segment elevation in V1 and V2 during procainamide challenge. Polymerase chain reaction-based direct sequencing was performed using a candidate gene approach. A missense mutation (L10P) was detected in exon 1 of SCN3B, the beta 3 subunit of the cardiac sodium channel, but not in any other gene known to be associated with Brugada syndrome or in 296 controls. Wild-type (WT) and mutant genes were expressed in TSA201 cells and studied using whole-cell patch-clamp techniques. Coexpression of SCN5A/WT+SCN1B/WT+SCN3B/L10P resulted in an 82.6% decrease in peak sodium current density, accelerated inactivation, slowed reactivation, and a -9.6-mV shift of half-inactivation voltage compared with SCN5A/WT+SCN1B/WT+SCN3B/WT. Confocal microscopy revealed that SCN5A/WT channels tagged with green fluorescent protein are localized to the cell surface when coexpressed with WT SCN1B and SCN3B but remain trapped in intracellular organelles when coexpressed with SCN1B/WT and SCN3B/L10P. Western blot analysis confirmed the presence of Na(V)beta 3 in human ventricular myocardium. Our results provide support for the hypothesis that mutations in SCN3B can lead to loss of transport and functional expression of the hNa(v)1.5 protein, leading to reduction in sodium channel current and clinical manifestation of a Brugada phenotyp

Relevancia biológica y clínica del inmunofenotipaje celular en la leucemia linfoide aguda del niño Biological and clinical importance of the cellular immunophenotyping in acute lymphocytic leukemia in children

Se estudiaron las características biológicas y clínicas de 238 niños con leucemia linfoide aguda (LLA) en un período de 13 años. El inmunofenotipaje celular de muestras procedentes de la médula ósea se realizó mediante un ultramicrométodo inmunocitoquímico. Del total de LLA estudiadas 81,4 % fueron de fenotipo B y 18,5 % de fenotipo T. El 48,4 % de los niños con LLA de fenotipo B se encontraron en edades comprendidas entre 2-5 años, mientras que el 65,9 % con LLA-T presentaron 6 o más años de edad. No se encontraron diferencias estadísticamente significativas cuando se analizaron el sexo y el color de la piel en relación con el fenotipo celular leucémico. Al diagnóstico de la enfermedad, el 59,3 % de los pacientes con LLA-B mostraron cifras de leucocitos en sangre periférica < 20 x 10(9)/L y en el 61,4 % con LLA-T cifras superiores a 50 x 10(9)/L. Se observó una mayor incidencia de organomegalia, adenopatías mediastinales, manifestaciones hemorrágicas e infiltración inicial del sistema nervioso central en enfermos con LLA-T en relación con los de LLA-B, con diferencias altamente significativas. Estos resultados demuestran que el fenotipo leucémico en la LLA del niño pudiera considerarse como un factor pronóstico positivo o negativo de la enfermedad.<br>The biological and clinical characteristics of 238 children with acute lymphocytic leukemia (ALL) were studied for 13 years. The cellular immunophenotyping of samples from the bone marrow was performed by an immunocytochemical ultramicromethod. Of the total of studied ALL, 81.4 % were phenotype B and 18.5 % phenotype T. 48.4 % of the children with B-ALL were 2-5 years old, whereas 65.9 % with T-ALL were 6 or over. No statistically significant differences were found when sex and colour of the skin were analyzed in relation to the cellular leukemic phenotype. On diagnosing the disease, 59.3 % of the patients with B-ALL showed figures of leukocytes in peripheral blood < 20x109/L, whereas in 61.4 % with T-ALL, the figures were higher than 50x109/L. It was observed a greater incidence of organomegaly, mediastinal adenopathies, hemorrhagic manifestations and initial infiltration of the central nervous system in patients with T-ALL compared with those suffering B-ALL. The differences were highly significant. These results proved that the leukemic phenotype in ALL in children could be considered as a positive or negative prognostic factor of the disease

Functional effects of KCNE3 mutation and its role in the development of Brugada syndrome

INTRODUCTION: The Brugada Syndrome (BrS), an inherited syndrome associated with a high incidence of sudden cardiac arrest, has been linked to mutations in four different genes leading to a loss of function in sodium and calcium channel activity. Although the transient outward current (I(to)) is thought to play a prominent role in the expression of the syndrome, mutations in I(to)-related genes have not been identified as yet. METHODS AND RESULTS: One hundred and five probands with BrS were screened for ion channel gene mutations using single strand conformation polymorphism (SSCP) electrophoresis and direct sequencing. A missense mutation (R99H) in KCNE3 (MiRP2) was detected in one proband. The R99H mutation was found 4/4 phenotype positive and 0/3 phenotype-negative family members. Chinese hamster ovary (CHO)-K1 cells were co-transfected using wild-type (WT) or mutant KCNE3 and either WT KCND3 or KCNQ1. Whole-cell patch clamp studies were performed after 48 hours. Interactions between Kv4.3 and KCNE3 were analyzed in co-immunoprecipitation experiments in human atrial samples. Co-transfection of R99H-KCNE3 with KCNQ1 produced no alteration in current magnitude or kinetics. However, co-transfection of R99H KCNE3 with KCND3 resulted in a significant increase in the I(to) intensity compared to WT KCNE3+KCND3. Using tissues isolated from left atrial appendages of human hearts, we also demonstrate that K(v)4.3 and KCNE3 can be co-immunoprecipitated. CONCLUSIONS: These results provide definitive evidence for a functional role of KCNE3 in the modulation of I(to) in the human heart and suggest that mutations in KCNE3 can underlie the development of BrS

Loss-of-Function Mutations in the Cardiac Calcium Channel Underlie a New Clinical entity characterized by ST-segment elevation, short QT interval and sudden cardiac death

BACKGROUND: Cardiac ion channelopathies are responsible for an ever-increasing number and diversity of familial cardiac arrhythmia syndromes. We describe a new clinical entity that consists of an ST-segment elevation in the right precordial ECG leads, a shorter-than-normal QT interval, and a history of sudden cardiac death. METHODS AND RESULTS: Eighty-two consecutive probands with Brugada syndrome were screened for ion channel gene mutations with direct sequencing. Site-directed mutagenesis was performed, and CHO-K1 cells were cotransfected with cDNAs encoding wild-type or mutant CACNB2b (Ca(v beta2b)), CACNA2D1 (Ca(v alpha2delta1)), and CACNA1C tagged with enhanced yellow fluorescent protein (Ca(v)1.2). Whole-cell patch-clamp studies were performed after 48 to 72 hours. Three probands displaying ST-segment elevation and corrected QT intervals < or = 360 ms had mutations in genes encoding the cardiac L-type calcium channel. Corrected QT ranged from 330 to 370 ms among probands and clinically affected family members. Rate adaptation of QT interval was reduced. Quinidine normalized the QT interval and prevented stimulation-induced ventricular tachycardia. Genetic and heterologous expression studies revealed loss-of-function missense mutations in CACNA1C (A39V and G490R) and CACNB2 (S481L) encoding the alpha1- and beta2b-subunits of the L-type calcium channel. Confocal microscopy revealed a defect in trafficking of A39V Ca(v)1.2 channels but normal trafficking of channels containing G490R Ca(v)1.2 or S481L Ca(v beta2b)-subunits. CONCLUSIONS: This is the first report of loss-of-function mutations in genes encoding the cardiac L-type calcium channel to be associated with a familial sudden cardiac death syndrome in which a Brugada syndrome phenotype is combined with shorter-than-normal QT intervals