Worldwide, the Brugada syndrome has been recognized as an important cause of sudden cardiac death in individuals at a relatively young age. Importantly, many drugs have been reported to induce the ...characteristic Brugada syndrome-linked ECG abnormalities and/or (fatal) ventricular tachyarrhythmias.
The purpose of this study was to review the literature on the use of drugs in Brugada syndrome patients, to make recommendations based on the literature and on expert opinion regarding drug safety, and to ensure worldwide online and up-to-date availability of this information to all physicians who treat Brugada syndrome patients.
We performed an extensive review of the literature, formed an international expert panel to produce a consensus recommendation to each drug, and initiated a website (www.brugadadrugs.org).
The literature search yielded 506 reports for consideration. Drugs were categorized into one of four categories: (1) drugs to be avoided (n = 18); (2) drugs preferably avoided (n = 23); (3) antiarrhythmic drugs (n = 4); and (4) diagnostic drugs (n = 4). Level of evidence for most associations was C (only consensus opinion of experts, case studies, or standard-of-care) as there are no randomized studies and few nonrandomized studies in Brugada syndrome patients.
Many drugs have been associated with adverse events in Brugada syndrome patients. We have initiated a website (www.brugadadrugs.org) to ensure worldwide availability of information on safe drug use in Brugada syndrome patients.
L-type calcium channel (LTCC) mutations have been associated with Brugada syndrome (BrS), short QT (SQT) syndrome, and Timothy syndrome (LQT8). Little is known about the extent to which LTCC ...mutations contribute to the J-wave syndromes associated with sudden cardiac death.
The purpose of this study was to identify mutations in the α1, β2, and α2δ subunits of LTCC (Ca(v)1.2) among 205 probands diagnosed with BrS, idiopathic ventricular fibrillation (IVF), and early repolarization syndrome (ERS). CACNA1C, CACNB2b, and CACNA2D1 genes of 162 probands with BrS and BrS+SQT, 19 with IVF, and 24 with ERS were screened by direct sequencing.
Overall, 23 distinct mutations were identified. A total of 12.3%, 5.2%, and 16% of BrS/BrS+SQT, IVF, and ERS probands displayed mutations in α1, β2, and α2δ subunits of LTCC, respectively. When rare polymorphisms were included, the yield increased to 17.9%, 21%, and 29.1% for BrS/BrS+SQT, IVF, and ERS probands, respectively. Functional expression of two CACNA1C mutations associated with BrS and BrS+SQT led to loss of function in calcium channel current. BrS probands displaying a normal QTc had additional variations known to prolong the QT interval.
The study results indicate that mutations in the LTCCs are detected in a high percentage of probands with J-wave syndromes associated with inherited cardiac arrhythmias, suggesting that genetic screening of Ca(v) genes may be a valuable diagnostic tool in identifying individuals at risk. These results are the first to identify CACNA2D1 as a novel BrS susceptibility gene and CACNA1C, CACNB2, and CACNA2D1 as possible novel ERS susceptibility genes.
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.
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.
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.
Zusammenfassung
Die molekulargenetische Untersuchung ist mittlerweile elementarer Bestandteil der Diagnostik bei Verdacht auf angeborene Ursachen für maligne Arrhythmien, Kardiomyopathien oder den ...plötzlichen Herztod. Die Ergiebigkeit der molekulargenetischen Untersuchung variiert zwischen den einzelnen Erkrankungen. Für die wichtigsten Ionenkanalerkrankungen und Kardiomyopathien besteht mittlerweile eine Klasse-I-Indikation zur Durchführung einer genetischen Testung. Das Gendiagnostikgesetz (GenDG) regelt die Zulassungen und Zuständigkeiten für die verschiedenen Schritte der Untersuchung (von der Veranlassung der Untersuchung bis zur humangenetischen Beratung und Befundmitteilung). Im klinischen Alltag stellt die Koordination der verschiedenen Beteiligten eine gewisse Herausforderung dar. Die Hinzuziehung von Humangenetikspezialisten mit fachspezifischer Kenntnis kardiologischer Erkrankungen ist unbedingt notwendig. Für die sog. „prädiktive genetische Untersuchung“ ist sowohl bei der Veranlassung der Untersuchung als auch bei der erforderlichen humangenetischen Beratung vor und nach der Untersuchung humangenetische Facharztkompetenz bzw. die Zusatzqualifikation für die fachgebundene humangenetische Beratung unerlässlich. In Bezug auf die zuverlässige Beurteilung einer genetischen Variante wird in regelmäßigen Abständen die Kausalität zwischen genetischer Veränderung und Phänotyp überprüft. Dies führt in einigen Fällen, insbesondere bei Varianten mit unklarer Signifikanz (VUS; ACMG American College of Medical Genetics and Genomics Klasse 3) zur Neubewertung der Pathogenität einzelner Varianten.
Adenosine triphosphate (ATP)-sensitive potassium cardiac channels consist of inward-rectifying channel subunits Kir6.1 or Kir6.2 (encoded by KCNJ8 or KCNJ11) and the sulfonylurea receptor subunits ...SUR2A (encoded by ABCC9).
To examine the association of mutations in KCNJ8 with Brugada syndrome (BrS) and early repolarization syndrome (ERS) and to elucidate the mechanism underlying the gain of function of ATP-sensitive potassium channel current.
Direct sequencing of KCNJ8 and other candidate genes was performed on 204 BrS and ERS probands and family members. Whole-cell and inside-out patch-clamp methods were used to study mutated channels expressed in TSA201 cells.
The same missense mutation, p.Ser422Leu (c.1265C>T) in KCNJ8, was identified in 3 BrS and 1 ERS probands but was absent in 430 alleles from ethnically matched healthy controls. Additional genetic variants included CACNB2b-D601E. Whole-cell patch-clamp studies showed a 2-fold gain of function of glibenclamide-sensitive ATP-sensitive potassium channel current when KCNJ8-S422L was coexpressed with SUR2A-wild type. Inside-out patch-clamp evaluation yielded a significantly greater half maximal inhibitory concentration for ATP in the mutant channels (785.5 ± 2 vs 38.4 ± 3 μM; n = 5; P <.01), pointing to incomplete closing of the ATP-sensitive potassium channels under normoxic conditions. Patients with a CACNB2b-D601E polymorphism displayed longer QT/corrected QT intervals, likely owing to their effect to induce an increase in L-type calcium channel current (I(Ca-L)).
Our results support the hypothesis that KCNJ8 is a susceptibility gene for BrS and ERS and point to S422L as a possible hotspot mutation. Our findings suggest that the S422L-induced gain of function in ATP-sensitive potassium channel current is due to reduced sensitivity to intracellular ATP.
Genetic testing and counselling has become a fundamental part of the diagnostic work-up and risk stratification in ion channel diseases. The diagnostic yield varies among the different entities. For ...the most common diseases, there is a class I recommendation for the initiation of genetic testing and counseling. The German law for genetic diagnostics defines all steps of the pathway in detail. In clinical practice, coordination of the different levels of clinical guidance and genetic diagnostics and testing poses a logistic challenge. Involving human geneticists in the procedure is mandatory. For predictive genetic testing, human genetic counseling is mandatory before initiation of the testing and after obtaining the results. As far as causality of genetic variants for the arrhythmic phenotypes is concerned, repeated curations are undertaken to avoid misinterpretation and overdiagnosis.
Objectives Our purpose was to evaluate the efficacy of antiarrhythmic drugs (AADs) in recurrent ventricular fibrillation (VF) associated with inferolateral early repolarization pattern on the ...electrocardiogram. Background Although an implantable cardioverter-defibrillator is the treatment of choice, additional AADs may be necessary to prevent frequent episodes of VF and reduce implantable cardioverter-defibrillator shock burden or as a lifesaving therapy in electrical storms. Methods From a multicenter cohort of 122 patients (90 male subjects, age 37 ± 12 years) with idiopathic VF and early repolarization abnormality in the inferolateral leads, we selected all patients with more than 3 episodes of VF (multiple) including those with electrical storms (≥3 VF in 24 h). The choice of AAD was decided by individual physicians. Follow-up data were obtained for all patients using monitoring with implantable defibrillator. Successful oral AAD was defined as elimination of all recurrences of VF with a minimal follow-up period of 12 months. Results Multiple episodes of VF were observed in 33 (27%) patients. Electrical storms (34 ± 47 episodes) occurred in 16 and were unresponsive to beta-blockers (11 of 11), lidocaine/mexiletine (9 of 9), and verapamil (3 of 3), while amiodarone was partially effective (3 of 10). In contrast, isoproterenol infusion immediately suppressed electrical storms in 7 of 7 patients. Over a follow-up of 69 ± 58 months, oral AADs were poorly effective in preventing recurrent VF: beta-blockers (2 of 16), verapamil (0 of 4), mexiletine (0 of 4), amiodarone (1 of 7), and class 1C AADs (2 of 9). Quinidine was successful in 9 of 9 patients, decreasing recurrent VF from 33 ± 35 episodes to nil for 25 ± 18 months. In addition, quinidine restored a normal electrocardiogram. Conclusions Multiple recurrences of VF occurred in 27% of patients with early repolarization abnormality and may be life threatening. Isoproterenol in acute cases and quinidine in chronic cases are effective AADs.
Brugada syndrome is an arrhythmogenic disease characterized by an ECG pattern of ST-segment elevation in the right precordial leads and augmented risk of sudden cardiac death. Little is known about ...the clinical presentation and prognosis of this disease in children.
Thirty children affected by Brugada syndrome who were <16 years of age (mean, 8+/-4 years) were included. All patients displayed a type I ECG pattern before or after drug provocation challenge. Diagnosis of Brugada syndrome was made under the following circumstances: aborted sudden death (n=1), syncope of unexplained origin (n=10), symptomatic supraventricular tachycardia (n=1), suspicious ECG (n=1), and family screening for Brugada syndrome (n=17). Syncope was precipitated by fever in 5 cases. Ten of 11 symptomatic patients displayed a spontaneous type I ECG. An implantable cardioverter-defibrillator was implanted in 5 children; 4 children were treated with hydroquinidine; and 1 child received a pacemaker because of symptomatic sick sinus syndrome. During a mean follow-up of 37+/-23 months, 1 child experienced sudden cardiac death, and 2 children received an appropriate implantable cardioverter-defibrillator shock; all of them were symptomatic and had manifested a type I ECG spontaneously. One child had a cardioverter-defibrillator infection that required explantation of the defibrillator.
In the largest population of children affected by Brugada syndrome described to date, fever represented the most important precipitating factor for arrhythmic events, and as in the adult population, the risk of arrhythmic events was higher in previously symptomatic patients and in those displaying a spontaneous type I ECG.
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