Sudden cardiac death due to ARVC in the young: molecular autopsy by whole exome sequencing of DNA from dried blood spots (DBS) collected at birth

Funding Acknowledgements

Type of funding sources: Public hospital(s). Main funding source(s): Uppsala University Hospital (ALF) and Marcus Börgström Foundation

Background

The post-mortem investigation of cases with sudden cardiac death (SCD) is critical for risk stratification and adequate care of surviving relatives. Genetic testing is limited by access to DNA from the proband, as blood samples are not routinely collected at the time of death, or DNA of poor quality obtained from formalin-fixed paraffin-embedded (FFPE) tissues. Whole exome sequencing (WES) on minute amounts of DNA has opened up for the possibility to use DNA from Dried Blood Spots (DBS).

Purpose

To evaluate the feasibility of WES on DNA from archived DBS collected at the time of newborn screening in cases of SCD. 

Methods

Through National Health Databases and Registries, we identified all cases of SCD in the young (<35 y.o.a.) in Sweden with a post-mortem diagnosis of ARVC between 2000 and 2010 (n = 22). Clinical records, medical and family histories, and autopsy findings were collected. Surviving parents were invited to participate. DNA was extracted from samples in National Biobanks such as DBS collected at birth (n = 19), formalin-fixed paraffin-embedded (FFPE) heart tissues (n = 8) from autopsies, and frozen blood samples (n = 3). Patient and parental DNA samples (when available) underwent WES. DNA- and sequencing-quality check (QC) metrics were compared between two different sequencing platforms and specimen types. We analysed 392 cardiomyopathy and arrhythmia genes and variants were classified as pathogenic or likely pathogenic according to the criteria from the American College of Medical Genetics.

Results

A higher quality but a lower yield of DNA (7.3 – 140 ng) was obtained from DBS when compared to FFPE samples (515 – 3065 ng). However, 100% of DBS vs. 62,5% of FFPE samples passed QC before sequencing. The average mean target depth for DBS samples (160X) was similar to that in blood samples (155X) and higher than FFPE (82X). Furthermore, >97% of target regions were covered with read depths >30X in DNA from DBS and blood compared to 88% for FFPE samples (Min 63%; Max 97%). Analysis of WES data uncovered clinically relevant variants in 12 out of 19 families (63%), of which four were located in ARVC genes. In six cases, the molecular autopsy identified another arrhythmogenic syndrome. Additionally, we identified one SCD with hemochromatosis and one with myotonic dystrophy as a possible contributing cause. In two additional families, variants of unknown significance fulfilled criteria for further segregation analysis. The concordance of positive results between different tissue samples was 100%.

Conclusions

DNA obtained from DBS has a quality comparable to that of blood and is a reliable source for WES-based molecular autopsy that may improve the diagnostic yield in cases of SCD. In a proportion of cases diagnosed post-mortem with ARVC, our molecular autopsy analysis pointed to a different diagnosis, highlighting its importance for the correct medical care of surviving relatives.

QRS dispersion using 252-leads Body Surface Mapping (BSM) – an explorative study of a novel diagnostic tool for Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)

Background

The diagnosis of ARVC is complex and challenging requiring multiple investigational tools, most of which include the demonstration of depolarization/conduction abnormalities, described in recent HRS consensus documents 2019. A simple and user friendly diagnostic tool is warranted.

Purpose

The purpose of our study was therefore to explore whether the analysis of QRS dispersion obtained from 252-leads recorded by a Body Surface Mapping (BSM) system can be used to identify ARVC patients as compared to the traditional ECG criteria including QRS dispersion measured by conventional 12 lead surface ECG.

Methods

12 definite ARVC patients (10/12 with known pathogenic mutation) (Group 1) and 8 healthy family members tested negative for the family mutation served as controls (Group 0), were included. All patients underwent 12-lead ECG (50mm/sec), Signal-averaged ECG for late potentials and 252 lead BSM recordings. The QRS duration was measured in each of the 12 ECG leads manually with digital caliper. The QRS duration from the BSM leads were manually analyzed in Matlab by two observers unaware of the diagnosis. For each lead, the mean value of three randomly chosen beats was calculated. The QRS dispersion was calculated as the difference between the minimum and maximum value for both the 12 lead ECG and the BSM recordings.

Results

The mean age was 49,6 and 38,8 years in ARVC patients and controls, respectively. The number of males in the two groups were 8/12 and 5/8, respectively. Epsilon waves and Terminal Activation Duration (TAD) >55msec were detected in 6/12 and 8/12 ARVC patients, respectively, but in no controls. Late potentials were detected in 11/12 ARVC patients and in 2 controls. The QRS duration and QTc duration was not statistically different in the two Groups.

The ECG-QRS dispersion was significantly more pronounced in Group 1 (42 ms ± 15, range 20–70 ms) than in Group 0 (26 ms ± 8, range 16–36 ms) (p=0.013). The BSM-QRS dispersion was significantly longer in Group 1 (68 ms ± 17, range 29–90ms) than in Group 0 (30 ms ± 7, range 22–41ms) (p=0.001). Only one ARVC patient had a BSM-QRS dispersion <50 msec, whereas none of the controls had a QRS dispersion over 50 msec (Fig. 1).

Conclusion

BSM-QRS dispersion, specifically using the cut off <50 ms, can potentially be a more sensitive and specific method than other ECG related techniques for diagnosing ARVC patients versus non-ARVC patients. Larger patient cohorts and further studies are required to confirm our findings.

Figure 1. ECG and BSM-QRS dispersion

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): Selanders Stiftelse

The repolarization pattern of ARVC patients, healthy gene carriers and controls as analyzed with a 252-leads Body Surface Mapping Vest

Background

Repolarization abnormalities have a central role on the diagnosis of ARVC according to recent HRS consensus document from 2019 stating that T wave inversion in the right precordial leads is a major criteria if it appears in V1-V3 or a minor criteria if it appears in only V1-V2.

Purpose

The aim of our study was to investigate whether repolarization patterns as recorded by a Body Surface Mapping (BSM) system consisting of a vest with 252 ECG leads, could differentiate ARVC patients and even gene carriers from normal individuals. Our hypothesis is that the method can potentially identify repolarization disturbances earlier or better than conventional 12-lead ECG.

Method

12 definite ARVC patients, 20 healthy gene carriers and 8 family members who tested negative for the family mutation (controls) were included. All patients underwent 12-lead ECG, including right precordial leads (V4R) and BSM recordings. Repolarization (T-wave polarity and concordance with QRS complex vector) was analyzed qualitatively in all BSM recordings, the results of which were displayed on a color code map (fig.1).

Results

The mean age was 49.6, 43.6 and 38.8 years in ARVC patients, healthy gene carriers and controls, respectively. The number of males in the three groups were 8/12, 8/20 and 5/8, respectively.

All 8 controls had similar repolarization patterns with negative and concordant T waves on the right back panel, and T waves that successively changed from negative concordant (green) to positive disconcordant (red) and finally positive concordant (blue) on the left front panel (pattern 1). All 12 ARVC patients had different repolarization patterns as compared to the controls. Two of these patients had no apparent repolarization changes on conventional 12 lead ECG. The pattern type 2 repolarization, as defined by same pattern as the controls at the right back panel but different pattern at the front left panel was seen in 3/12 ARVC patients. The remaining 9 ARVC patients had different repolarization patterns both on the front and on the back panel (pattern 3). Among gene carriers, 15 had a normal repolarization pattern (pattern 1) and 5 demonstrated an abnormal repolarization pattern (4 had pattern type 2 and one pattern 3) despite normal surface ECG.

Conclusions

Using BSM recordings, abnormal repolarization patterns can be detected in all ARVC patients, even in those without repolarization changes on conventional surface ECG. The observation that 25% of gene carriers had divergent repolarization patterns, may indicate an early stage of the disease, and be used as an early diagnostic marker of the disease. Further and larger studies are warranted to confirm these observations.

Repolarisation patterns recorded by BSM

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): Selanders Stiftelse

1270The epidemiological and phenotypic characteristics of SCD victims with ARVC in Sweden between 2000-2010: a Nationwide study

Background

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is autosomal dominant inherited, and associated with a significant risk of sudden cardiac death (SCD) due to a progressive fibrofatty replacement of the myocardium predisposing for ventricular arrhythmias. It is a main cause of SCD in individuals younger than 40 years of age. The prevalence of ARVC in young individuals with SCD in Sweden has recently been approximated to 4 %, but the characteristics of these patients have not been described before.

Purpose

To study the patient characteristics, physical activity level, medical history, family history and symptoms prior death in subjects who died due to ARVC.

Methods

A retrospective study of all subjects aged 1-35 years who died a SCD due to ARVC in Sweden between 1 January 2000 and 31 December 2010. The diagnosis ARVC was based on data from a forensic or clinical autopsy and a histological examination. We also collected data from the police report, medical records, as well as through interviews with family members.

Results

A total of 552 individuals died from SCD during the study period. The study population consists of 22 cases with autopsy verified ARVC. In our cohort there were included 14 males and 8 females. The mean age was 23.7 years old (min age: 13, max age: 35).

Two subjects were diagnosed with ARVC prior to the SCD. In addition, one subject had survived a cardiac arrest a few years before, and got diagnosed with Long QT Syndrome. Another subject was diagnosed with myocarditis just a few months before death. Further, four subjects had a history of ventricular tachycardia, and three subjects had a history of seizures.

Fifteen of the subjects had experienced cardiac symptoms before SCD

nine had a history of syncope, presyncope or both; six subjects had experienced chest discomfort; nine subjects had a history of palpitations. In total, eight of fifteen subjects had sought medical care prior to SCD because of cardiac symptoms.

The majority of the cases were physically active, five participated in competitive sports and 12 in recreational activities. Regarding the type of physical activity, 15/22 participated in a high dynamic physical activity.

Twelve subjects had a positive family history of SCD. In 10 cases, there was a family history of SCD, but only in two in a first degree relative. Three family members had ICD. In four cases there was a family history of cardiomyopathy (one case with Hypertrophic Cardiomyopathy, one with myocarditis, and two with ARVC). CPVT was also diagnosed in one family prior to SCD. 

Conclusions

In this nationwide study of SCD in the young, only two of the 22 subjects had a clinical diagnosis of ARVC prior to death, despite that, most of the individuals had either a history of ventricular arrhythmias or had experienced cardiac symptoms.

Acetabular labrum of hip joint in osteoarthritis: A qualitative original study and short review of the literature

PURPOSE

Histological architecture of normal acetabular labrum regarding free nerve endings (FNEs) and mechanoreceptors (MRs) has been satisfactorily described in the literature. However, the presence of FNEs and MRs in acetabular labrum of hip joint has been analyzed only once in patients with osteoarthritis (OA). Aim of this article is to report histological distribution pattern of FNEs and MRs in acetabular labrum of patients with severe OA, at the same time conducting a comparison with normal acetabular labrum described in the literature.

METHODS

Seven patients with severe hip OA were enrolled in this study. Patient selection was assisted by the utilization of specific clinical scales delineated by the American College of Rheumatology. After successful total hip arthroplasty, tissue samples of acetabular labra of seven patients were histologically processed and stained with the gold standard chloride method, which was subsequently examined under a compound microscope.

RESULTS

FNEs and MRs constituted the major histological structures. Identified MRs included Pacini corpuscles, Ruffini corpuscles, and Golgi-Mazzoni corpuscles. The presence of FNEs was predominant in the middle part of the acetabular labrum, featuring a remarkable decrease in peripheral parts. In contrast, MRs were detected basically in peripheral parts and less in the middle part.

CONCLUSIONS

Differentiation of the distribution pattern of MRs and FNEs in acetabular labrum of hip joint is remarkable between normal patients and patients with severe OA. The abundance of FNEs in the middle part of the pathologic labrum is mainly responsible for the observed discrimination. A "conversion" of MRs to FNEs may occur during OA progression, modulating therefore this pattern as well as the upcoming clinical manifestations.