Mutation analysis of cases of sudden unexplained death, 15 years after death: Prompt genetic evaluation after resuscitation can save future lives

The role of genetic testing in the prevention, diagnosis, and prognosis of sudden cardiac arrest in children

BACKGROUND

Determining the pathogenesis of sudden cardiac arrest (SCA) in children is crucial for its management and prognosis. Our aim is to analyze the role of broad genetic testing in the prevention, diagnosis, and prognosis of SCA in Children.

METHODS

ECG, 12-lead holter, exercise testing, cardiac imaging, familial study, and genetic testing were used to study 29 families, in whom a child experienced SCA.

RESULTS

After a thorough clinical and genetic evaluation a positive diagnosis was reached in 24/29 (83%) families. Inherited channelopathies (long QT syndrome and catecholaminergic polymorphic ventricular tachycardia) were the most prevalent 20/29 (69%) diagnosis, followed by cardiomyopathy 3/29 (10%). Broad genetic testing was positive in 17/24 (71%) cases. Using the Mann-Whitney test, we found that genetic testing (effect size = 0.625, p = 0.003), ECG (effect size = 0.61, p = 0.009), and exercise test (effect size = 0.63, p = 0.047) had the highest yield in reaching the final diagnosis. Genetic testing was the only positive test available for five (17%) families. Among 155 family members evaluated through cascade screening, 73 (47%) had a positive clinical evaluation and 64 (41%) carried a pathologic mutation. During 6 ± 4.8 years of follow-up, 58% of the survived children experienced an arrhythmic event. Of nine family members who had an ICD implant for primary prevention, four experienced appropriate ICD shock.

CONCLUSIONS

The major causes of SCA among children are genetic etiology, and genetic testing has a high yield. Family screening has an additional role in both the diagnosis and preventing of SCA.

European Resuscitation Council Guidelines 2021: Epidemiology of cardiac arrest in Europe

In this section of the European Resuscitation Council Guidelines 2021, key information on the epidemiology and outcome of in and out of hospital cardiac arrest are presented. Key contributions from the European Registry of Cardiac Arrest (EuReCa) collaboration are highlighted. Recommendations are presented to enable health systems to develop registries as a platform for quality improvement and to inform health system planning and responses to cardiac arrest.

Upgraded molecular models of the human KCNQ1 potassium channel

The voltage-gated potassium channel KCNQ1 (K_V7.1) assembles with the KCNE1 accessory protein to generate the slow delayed rectifier current, I_KS, which is critical for membrane repolarization as part of the cardiac action potential. Loss-of-function (LOF) mutations in KCNQ1 are the most common cause of congenital long QT syndrome (LQTS), type 1 LQTS, an inherited genetic predisposition to cardiac arrhythmia and sudden cardiac death. A detailed structural understanding of KCNQ1 is needed to elucidate the molecular basis for KCNQ1 LOF in disease and to enable structure-guided design of new anti-arrhythmic drugs. In this work, advanced structural models of human KCNQ1 in the resting/closed and activated/open states were developed by Rosetta homology modeling guided by newly available experimentally-based templates: X. leavis KCNQ1 and various resting voltage sensor structures. Using molecular dynamics (MD) simulations, the capacity of the models to describe experimentally established channel properties including state-dependent voltage sensor gating charge interactions and pore conformations, PIP2 binding sites, and voltage sensor–pore domain interactions were validated. Rosetta energy calculations were applied to assess the utility of each model in interpreting mutation-evoked KCNQ1 dysfunction by predicting the change in protein thermodynamic stability for 50 experimentally characterized KCNQ1 variants with mutations located in the voltage-sensing domain. Energetic destabilization was successfully predicted for folding-defective KCNQ1 LOF mutants whereas wild type-like mutants exhibited no significant energetic frustrations, which supports growing evidence that mutation-induced protein destabilization is an especially common cause of KCNQ1 dysfunction. The new KCNQ1 Rosetta models provide helpful tools in the study of the structural basis for KCNQ1 function and can be used to generate hypotheses to explain KCNQ1 dysfunction.

Genetic screening in sudden cardiac death in the young can save future lives

Background

Autopsy of sudden cardiac death (SCD) in the young shows a structurally and histologically normal heart in about one third of cases. Sudden death in these cases is believed to be attributed in a high percentage to inherited arrhythmogenic diseases. The purpose of this study was to investigate the value of performing post-mortem genetic analysis for autopsy-negative sudden unexplained death (SUD) in 1 to 35 year olds.

Methods and results

From January 2009 to December 2011, samples from 15 cases suffering SUD were referred to the Department of Clinical Genetics, Umeå University Hospital, Sweden, for molecular genetic evaluation. PCR and bidirectional Sanger sequencing of genes important for long QT syndrome (LQTS), short QT syndrome (SQTS), Brugada syndrome type 1 (BrS1), and catecholaminergic polymorphic ventricular tachycardia (CPVT) (KCNQ1, KCNH2, SCN5A, KCNE1, KCNE2, and RYR2) was performed. Multiplex ligation-dependent probe amplification (MLPA) was used to detect large deletions or duplications in the LQTS genes. Six pathogenic sequence variants (four LQTS and two CPVT) were discovered in 15 SUD cases (40 %). Ten first-degree family members were found to be mutation carriers (seven LQTS and three CPVT).

Conclusion

Cardiac ion channel genetic testing in autopsy-negative sudden death victims has a high diagnostic yield, with identification of the disease in 40 % of families. First-degree family members should be offered predictive testing, clinical evaluation, and treatment with the ultimate goal to prevent sudden death.

Sudden cardiac death in the young: how can disease recognition and prevention in family members be improved?

Sudden cardiac death (SCD) in young patients (<45 years of age) is a rare event. However, it is particularly tragic as it affects active and often otherwise healthy individuals. Furthermore, SCD may unmask an underlying congenital structural disease or channelopathy. The leading cause of SCD is coronary artery disease; however, the likelihood of an underlying congenital cardiac disease is higher in young individuals. Each SCD should therefore initiate a thorough work-up of an underlying cardiac cause, which should ideally include a molecular autopsy. Familial screening should also be initiated if a physician is years later confronted with a history of SCD in a young patient. The common aim is to prompt identification of affected family members, to include the patient in regular cardiological follow-up and if indicated to initiate prophylactic therapy to prevent further SCD. This current issue on hereditary cardio(myo)pathy will cover the main topics on familial diseases. In addition the role of molecular autopsy and molecular genetic screening is discussed.