Sara Partemi

State of the art in forensic investigation of sudden cardiac death.

The sudden death of a young person is a devastating event for both the family and community. Over the last decade, significant advances have been made in understanding both the clinical and genetic basis of sudden cardiac death. Many of the causes of sudden death are due to genetic heart disorders, which can lead to both structural (eg, hypertrophic cardiomyopathy) and arrhythmogenic abnormalities (eg, familial long QT syndrome, Brugada syndrome). Most commonly, sudden cardiac death can be the first presentation of an underlying heart problem, leaving the family at a loss as to why an otherwise healthy young person has died. Not only is this a tragic event for those involved, but it also presents a great challenge to the forensic pathologist involved in the management of the surviving family members. Evaluation of families requires a multidisciplinary approach, which should include cardiologists, a clinical geneticist, a genetic counselor, and the forensic pathologist directly involved in the sudden death case. This multifaceted cardiac genetic service is crucial in the evaluation and management of the clinical, genetic, psychological, and social complexities observed in families in which there has been a young sudden cardiac death. The present study will address the spectrum of structural substrates of cardiac sudden death with particular emphasis given to the possible role of forensic molecular biology techniques in identifying subtle or even merely functional disorders accounting for electrical instability.

Coexistence of epilepsy and Brugada syndrome in a family with SCN5A mutation

Cardiac arrhythmias are associated with abnormal channel function due to mutations in ion channel genes. Epilepsy is a disorder of neuronal function also involving abnormal channel function. It is increasingly demonstrated that the etiologies of long QT syndrome and epilepsy may partly overlap. However, only a few genetic studies have addressed a possible link between cardiac and neural channelopathies. We describe a family showing the association between Brugada syndrome and epilepsy in which a known mutation in the SCN5A gene (p.W1095X, c.3284G>A) was identified. We suggest that this mutation can be responsible for cardiac and brain involvement, probably at different developmental age in the same individual. This observation confirms the possibility that SCN5A mutations may confer susceptibility for recurrent seizure activity, supporting the emerging concept of a genetically determined cardiocerebral channelopathy.

Genetics of arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy is a rare clinical entity characterised by fibro-fatty replacement of myocardium, mainly involving right ventricular free wall, leading to malignant electrical instability and sudden cardiac death. The disease is inherited in up to 50% of cases, with incomplete penetrance and variable phenotypic expression. To date, more than 300 pathogenic mutations have been identified in 12 genes, mainly with autosomal dominant inheritance. Here, we focus on recent advances in the genetics of arrhythmogenic right ventricular cardiomyopathy. Despite continuous improvements, current genotype–phenotype studies have not contributed yet to establish a genetic risk stratification of the disease.

Negative autopsy and sudden cardiac death.

Forensic medicine defines the unexplained sudden death as a death with a non-conclusive diagnosis after autopsy. Molecular diagnosis is being progressively incorporated in forensics, mainly due to improvement in genetics. New genetic technologies may help to identify the genetic cause of death, despite clinical interpretation of genetic data remains the current challenge. The identification of an inheritable defect responsible for arrhythmogenic syndromes could help to adopt preventive measures in family members, many of them asymptomatic but at risk of sudden death. This multidisciplinary translational research requires a specialized team.

Analysis of mRNA from human heart tissue and putative applications in forensic molecular pathology

The usefulness of post-mortem mRNA analysis and its potential applications in forensic casework is currently of interest, especially because of several factors affecting the quality of RNA samples that are not practically predictable. In fact, post-mortem RNA degradation is a complex process that has not been studied systematically. The purpose of this work is to establish whether RNA analysis from post-mortem heart tissue could be used as a forensic tool to investigate the cause of death, with special regard to those cases where a cardiac disease is suspected as the manner of death. We analysed heart tissue from 16 individuals with normal cardiac function, 9 with long post-mortem intervals (L-PMI) and 7 from organ donors with very short PMIs (S-PMIs). Right ventricle tissue was homogenised, and the RNA was isolated and reverse transcribed. The resulting cDNA was used in real-time PCR reactions to quantify the gene expression of beta-glucuronidase (GUSB), Nitric Oxide Synthase 3 (NOS3), Collagen 1 (COL1A1) and Collagen 3 (COL3A1). The percentage of samples with high-quality RNA was higher in samples with S-PMI (7 out of 7) than in samples with L-PMI (4 out of 9, p<0.05). No differences in PMI time or cause of exitus were found between samples with degraded or non-degraded RNA in the L-PMI group. When comparing mRNA levels in samples with non-degraded RNA, we found similar values between the L-PMI and S-PMI groups for GUSB, COL1A1 and COL3A1. The NOS3 gene expression in the L-PMI subgroup was less than half that in the S-PMI. These results suggest that high-quality mRNA can be extracted from post-mortem human hearts only in some cases. Moreover, our data show that mRNA levels are independent from the PMI, even though there are mRNAs in which the expression levels are very susceptible to ischemia times. Clear knowledge about the relationship between mRNA integrity and expression and PMI could allow the use of several mRNAs as forensic tools to contribute to the determination of the cause of death with special regard to cardiovascular diseases.

Loss-of-function KCNH2 mutation in a family with long QT syndrome, epilepsy, and sudden death

There has been increased interest in a possible association between epilepsy channelopathies and cardiac arrhythmias, such as long QT syndrome (LQTS). We report a kindred that features LQTS, idiopathic epilepsy, and increased risk of sudden death. Genetic study showed a previously unreported heterozygous point mutation (c.246T>C) in the KCNH2 gene. Functional studies showed that the mutation induces severe loss of function. This observation provides further evidence for a possible link between idiopathic epilepsy and LQTS.

Further evidence of the association between LQT syndrome and epilepsy in a family with KCNQ1 pathogenic variant

PURPOSE Ion channels are expressed both in the heart and in the brain, being advocated as responsible for sudden unexpected death in epilepsy but few pathogenic mutations have been identified. We aim to identify a novel gen associated with channelopathies and epilepsy in a family. METHODS We assessed a family showing epilepsy concomitant with LQTS. Index case showed prolonged QT interval. His father suffers of LQT and epilepsy. We performed a direct sequencing analysis of KCNQ1, KCNH2, KCNE1, KCNE2 and SCN5A genes. RESULTS We identified a non-synonymous heterozygous missense pathogenic mutation (p.L273F) in exon 6 of the KCNQ1 gene. All clinically affected relatives carried the same mutation. CONCLUSION We report, for a first time, a KCNQ1 mutation in a family suffering of both phenotypes, suggesting that KCNQ1 genetic variations may confer susceptibility for recurrent seizure activity increasing the risk or lead to sudden death.

Autopsy investigation and Bayesian approach to coronary artery disease in victims of motor-vehicle accidents

BACKGROUND Each year, 1.2 million people die worldwide as a result of motor-vehicle accidents (MVA), representing a tremendous burden to healthcare. The aim of this study was to define the prevalence of coronary disease and its possible role in motor-vehicle accidents. METHODS AND RESULTS We examined consecutive cases of non-hospital sudden death autopsies in the area of West Quebec during the period of 2002-2006, and we focused on those victims of MVA. Severe coronary artery disease (CAD) was defined as a narrowing of ≥ 75% of a cross-sectional area or the presence of acute plaque events in major epicardial coronary arteries. From a total cohort of 1260 autopsies, MVA were responsible for 123 deaths, 100 of whom were men and 23 were women. Significant CAD was documented in approximately 37% of these cases. In individuals older than 60 years, the prevalence of significant CAD and ischemia were 86.2% and 19.8%, respectively. A percentage of 40% of the coronary patients showed erratic driving before the accident, as observed by witnesses. Statistical analysis showed that an individual affected by CAD has 9% probability of suffering a motor-vehicle accident. CONCLUSIONS The prevalence of severe CAD and acute myocardial ischemia is very high among individuals who have suffered a MVA. Our data suggest the hypothesis that acute CAD could be the cause of accidents in a large group of the drivers affected by coronary disease. For these reasons CAD could be investigated in drivers above 50 years old, as a possible preventive measure and determinant of individual risk stratification.

Mild beckwith-wiedemann and severe long-QT syndrome due to deletion of the imprinting center 2 on chromosome 11p.

We report on a young woman admitted to our Cardiology Unit because of an episode of cardiac arrest related to a long-QT syndrome (LQTS). This manifestation was part of a broader phenotype, which was recognized as a mild form of Beckwith-Wiedemann syndrome (BWS). Molecular analysis confirmed the diagnosis of BWS owing to a maternally inherited deletion of the centromeric imprinting center, or ICR2, an extremely rare genetic mechanism in BWS. The deletion interval (198 kb) also included exons 11–16 of the KCNQ1 gene, known to be responsible for LQTS at locus LQT1. No concomitant mutations were found in any other of the known LQT genes. The proposita’s mother carries the same deletion in her paternal chromosome and shows manifestations of the Silver-Russell syndrome (SRS). This report describes the smallest BWS-causing ICR2 deletion and provides the first evidence that a paternal deletion of ICR2 leads to a SRS-like phenotype. In addition, our observation strongly suggests that in cases of LQTS due to mutation of the KCNQ1 gene (LQT1), an accurate clinical genetic evaluation should be done in order to program the most appropriate genetic tests.

Genetic analysis, in silico prediction, and family segregation in long QT syndrome

The heritable cardiovascular disorder long QT syndrome (LQTS), characterized by prolongation of the QT interval on electrocardiogram, carries a high risk of sudden cardiac death. We sought to add new data to the existing knowledge of genetic mutations contributing to LQTS to both expand our understanding of its genetic basis and assess the value of genetic testing in clinical decision-making. Direct sequencing of the five major contributing genes, KCNQ1, KCNH2, SCN5A, KCNE1, and KCNE2, was performed in a cohort of 115 non-related LQTS patients. Pathogenicity of the variants was analyzed using family segregation, allele frequency from public databases, conservation analysis, and Condel and Provean in silico predictors. Phenotype-genotype correlations were analyzed statistically. Sequencing identified 36 previously described and 18 novel mutations. In 51.3% of the index cases, mutations were found, mostly in KCNQ1, KCNH2, and SCN5A; 5.2% of cases had multiple mutations. Pathogenicity analysis revealed 39 mutations as likely pathogenic, 12 as VUS, and 3 as non-pathogenic. Clinical analysis revealed that 75.6% of patients with QTc≥500 ms were genetically confirmed. Our results support the use of genetic testing of KCNQ1, KCNH2, and SCN5A as part of the diagnosis of LQTS and to help identify relatives at risk of SCD. Further, the genetic tools appear more valuable as disease severity increases. However, the identification of genetic variations in the clinical investigation of single patients using bioinformatic tools can produce erroneous conclusions regarding pathogenicity. Therefore segregation studies are key to determining causality.