Jonathan R. Skinner

A Prospective Study of Sudden Cardiac Death among Children and Young Adults

BACKGROUNDnSudden cardiac death among children and young adults is a devastating event. We performed a prospective, population-based, clinical and genetic study of sudden cardiac death among children and young adults.nnnMETHODSnWe prospectively collected clinical, demographic, and autopsy information on all cases of sudden cardiac death among children and young adults 1 to 35 years of age in Australia and New Zealand from 2010 through 2012. In cases that had no cause identified after a comprehensive autopsy that included toxicologic and histologic studies (unexplained sudden cardiac death), at least 59 cardiac genes were analyzed for a clinically relevant cardiac gene mutation.nnnRESULTSnA total of 490 cases of sudden cardiac death were identified. The annual incidence was 1.3 cases per 100,000 persons 1 to 35 years of age; 72% of the cases involved boys or young men. Persons 31 to 35 years of age had the highest incidence of sudden cardiac death (3.2 cases per 100,000 persons per year), and persons 16 to 20 years of age had the highest incidence of unexplained sudden cardiac death (0.8 cases per 100,000 persons per year). The most common explained causes of sudden cardiac death were coronary artery disease (24% of cases) and inherited cardiomyopathies (16% of cases). Unexplained sudden cardiac death (40% of cases) was the predominant finding among persons in all age groups, except for those 31 to 35 years of age, for whom coronary artery disease was the most common finding. Younger age and death at night were independently associated with unexplained sudden cardiac death as compared with explained sudden cardiac death. A clinically relevant cardiac gene mutation was identified in 31 of 113 cases (27%) of unexplained sudden cardiac death in which genetic testing was performed. During follow-up, a clinical diagnosis of an inherited cardiovascular disease was identified in 13% of the families in which an unexplained sudden cardiac death occurred.nnnCONCLUSIONSnThe addition of genetic testing to autopsy investigation substantially increased the identification of a possible cause of sudden cardiac death among children and young adults. (Funded by the National Health and Medical Research Council of Australia and others.).

Assessment of the predictive accuracy of five in silico prediction tools, alone or in combination, and two metaservers to classify long QT syndrome gene mutations

BackgroundLong QT syndrome (LQTS) is an autosomal dominant condition predisposing to sudden death from malignant arrhythmia. Genetic testing identifies many missense single nucleotide variants of uncertain pathogenicity. Establishing genetic pathogenicity is an essential prerequisite to family cascade screening. Many laboratories use in silico prediction tools, either alone or in combination, or metaservers, in order to predict pathogenicity; however, their accuracy in the context of LQTS is unknown. We evaluated the accuracy of five in silico programs and two metaservers in the analysis of LQTS 1–3 gene variants.MethodsThe in silico tools SIFT, PolyPhen-2, PROVEAN, SNPs&GO and SNAP, either alone or in all possible combinations, and the metaservers Meta-SNP and PredictSNP, were tested on 312 KCNQ1, KCNH2 and SCN5A gene variants that have previously been characterised by either in vitro or co-segregation studies as either “pathogenic” (283) or “benign” (29). The accuracy, sensitivity, specificity and Matthews Correlation Coefficient (MCC) were calculated to determine the best combination of in silico tools for each LQTS gene, and when all genes are combined.ResultsThe best combination of in silico tools for KCNQ1 is PROVEAN, SNPs&GO and SIFT (accuracy 92.7%, sensitivity 93.1%, specificity 100% and MCC 0.70). The best combination of in silico tools for KCNH2 is SIFT and PROVEAN or PROVEAN, SNPs&GO and SIFT. Both combinations have the same scores for accuracy (91.1%), sensitivity (91.5%), specificity (87.5%) and MCC (0.62). In the case of SCN5A, SNAP and PROVEAN provided the best combination (accuracy 81.4%, sensitivity 86.9%, specificity 50.0%, and MCC 0.32). When all three LQT genes are combined, SIFT, PROVEAN and SNAP is the combination with the best performance (accuracy 82.7%, sensitivity 83.0%, specificity 80.0%, and MCC 0.44). Both metaservers performed better than the single in silico tools; however, they did not perform better than the best performing combination of in silico tools.ConclusionsThe combination of in silico tools with the best performance is gene-dependent. The in silico tools reported here may have some value in assessing variants in the KCNQ1 and KCNH2 genes, but caution should be taken when the analysis is applied to SCN5A gene variants.

Utility of Post-Mortem Genetic Testing in Cases of Sudden Arrhythmic Death Syndrome

Background Sudden arrhythmic death syndrome (SADS) describes a sudden death with negative autopsy and toxicological analysis. Cardiac genetic disease is a likely etiology. Objectives This study investigated the clinical utility and combined yield of post-mortem genetic testing (molecular autopsy) in cases of SADS and comprehensive clinical evaluation of surviving relatives. Methods We evaluated 302 expertly validated SADS cases with suitable DNA (median age: 24 years; 65% males) who underwent next-generation sequencing using an extended panel of 77 primary electrical disorder and cardiomyopathy genes. Pathogenic and likely pathogenic variants were classified using American College of Medical Genetics (ACMG) consensus guidelines. The yield of combined molecular autopsy and clinical evaluation in 82 surviving families was evaluated. A gene-level rare variant association analysis was conducted in SADS cases versus controls. Results A clinically actionable pathogenic or likely pathogenic variant was identified in 40 of 302 cases (13%). The main etiologies established were catecholaminergic polymorphic ventricular tachycardia and long QT syndrome (17 [6%] and 11 [4%], respectively). Gene-based rare variants association analysis showed enrichment of rare predicted deleterious variants in RYR2 (p = 5 × 10-5). Combining molecular autopsy with clinical evaluation in surviving families increased diagnostic yield from 26% to 39%. Conclusions Molecular autopsy for electrical disorder and cardiomyopathy genes, using ACMG guidelines for variant classification, identified a modest but realistic yield in SADS. Our data highlighted the predominant role of catecholaminergic polymorphic ventricular tachycardia and long QT syndrome, especially the RYR2 gene, as well as the minimal yield from other genes. Furthermore, we showed the enhanced utility of combined clinical and genetic evaluation.

Physical and Psychological Consequences of Left Cardiac Sympathetic Denervation in Long-QT Syndrome and Catecholaminergic Polymorphic Ventricular Tachycardia

Background—Left cardiac sympathetic denervation reduces risk in long-QT syndrome (LQTS) and catecholaminergic polymorphic ventricular tachycardia. Side effects and patient satisfaction have not been systematically analyzed in patients who underwent left cardiac sympathetic denervation. Aims of this study included documenting physical and psychological consequences and patient satisfaction after left cardiac sympathetic denervation in LQTS or catecholaminergic polymorphic ventricular tachycardia. Methods and Results—Patients with LQTS (N=40) and catecholaminergic polymorphic ventricular tachycardia (N=7) underwent video-assisted thoracoscopic left cardiac sympathetic denervation, with a median follow-up of 29 months (range, 1–67 months). Clinical records were reviewed; 44 patients completed a telephone survey. Of 47 patients (53%), 25 were preoperatively symptomatic (15 syncope, 7 near-drowning, and 3 resuscitated sudden death). Indications for left cardiac sympathetic denervation included &bgr;-blocker intolerance (15; 32%) or nonadherence (10; 21%) and disease factors (18; 38%; catecholaminergic polymorphic ventricular tachycardia [6], near-drowning [2], exertional syncope [1], symptoms on therapy [2], LQT3 [1], QTc>520 ms [6]). Other indications were competitive sports participation (2), family history of sudden death (1), and other (1). Median QTc did not change among patients with LQTS (461±60 to 476±54 ms; P=0.49). Side effects were reported by 42 of 44 (95%). Twenty-nine patients (66%) reported dryness on left side, 26 (59%) a Harlequin-type (unilateral) facial flush, 24 (55%) contralateral hyperhidrosis, 17 (39%) differential hand temperatures, 5 (11%) permanent and 4 (9%) transient ptosis, 5 (11%) thermoregulation difficulties, 4 (9%) a sensation of left arm paresthesia, and 3 (7%) sympathetic flight/fright response loss. Majority of the patients were satisfied postoperatively: 38 (86%) were happy with the procedure, 33 (75%) felt safer, 40 (91%) recommended the procedure to others, and 40 (91%) felt happy with their scar appearance. Conclusions—Despite significant morbidity resulting from left cardiac sympathetic denervation, patients with LQTS and CPVT have high levels of postoperative satisfaction.

Routine ECG screening in infancy and early childhood should not be performed

For all of us working in the field of inherited heart conditions, our ultimate aim is the prevention of sudden cardiac death in young people in our communities. We share the passion and drive to this aim with our colleagues Saul et al, who write to advocate infant screening of infants for LQTS. Although Saul et al aimed to write an unbiased review of the subject, they present data that support screening while underrepresenting evidence against it. Their illustrative Figure 1 is arguably misleading, presenting a graph of freedom from any cardiac event in symptomatic individuals with familial LQTS. We know that 87% of deaths from LQTS occur in those who were previously symptomatic. This discussion, however, is not about symptomatic patients with LQTS; it is about the detection of presymptomatic individuals on a community level. Our aim is to present evidence that has led us to oppose the conclusions and suggestions of their article. Most pediatric cardiologists do not wish to see ECG screening in infancy, and we are among them. Saul et al state that there is sufficient evidence to propose ECG screening in infancy for LQTS. We disagree. We disagree with this view for a number of reasons: (1) The effectiveness of such a program has not been evaluated in terms of outcome. (2) The ECG is an unreliable diagnostic tool with unacceptable reproducibility, specificity, and sensitivity. (3) The adverse effects of overdiagnosing or underdiagnosing LQTS in thousands of individuals have not been evaluated. (4) There are no definitive criterion standard by which LQTS can be excluded once the possibility is raised, and in particular genetic testing is not sensitive or specific enough to do so. (5) There is a paucity of normative ECG and genetic data for non-Whites. We propose what we believe is a more attractive alternative: the detection of LQTS in the community through an active multidisciplinary program to detect probands and screen family members, based around a clinical registry. This has already proven to be effective. If adequately resourced, this method will provide a quicker, more reliable, and more societally acceptable method to detect and manage families at risk, such that it might conceivably render population screening redundant.

High Arrhythmic Burden but Low Mortality during Long-term Follow-up in Arrhythmogenic Right Ventricular Cardiomyopathy

BACKGROUNDnArrhythmogenic right ventricular cardiomyopathy (ARVC) is associated with a high incidence of ventricular tachyarrhythmia and sudden death. The mainstay of management is the implantable cardioverter defibrillator (ICD). A small number of patient cohorts have generated a large number of reports.nnnMETHODSnProspective registry data supplemented with clinical and ICD records of 30 patients with ARVC fulfilling the 2010 modified Task Force Criteria. This cohort has not been reported on previously.nnnRESULTSnMedian age at diagnosis: 46yrs (range 21-68); 20 (80%) male; six (19%) Maori. Duration of follow-up: 7.4yrs (range 1.7-23). Implantable cardioverter defibrillator implantation in 26; three (12%) for resuscitated sudden cardiac death; 17 (65%) for symptomatic ventricular tachyarrhythmia; three (12%) for syncope; and three (12%) for family history of sudden death attributable to ARVC. Two patients died during follow-up, one had an ICD, though died of a carcinoma. Thirteen (50%) experienced appropriate ICD therapy with median time to therapy 12 months, and four (15%) experienced inappropriate shock therapy. Male gender was an independent predictor of appropriate ICD therapy (HR 1.6, 95% CI 1.5-2.7, P=0.01).nnnCONCLUSIONSnThe long-term prognosis of patients with ARVC is favourable although high proportions receive appropriate ICD therapy. Male gender is an independent predictor of appropriate ICD therapy.

Familial mitral valve prolapse associated with short stature, characteristic face, and sudden death

Mitral valve prolapse (MVP) is frequently a familial disorder but in few of these inherited cases it does form a prominent component of a multiple congenital anomaly (MCA) syndrome. We report a family in which eight individuals in four generations were affected by a dominantly inherited disorder involving MVP, short stature, a dolicocephalic face, broad forehead, posteriorly angulated ears, long philtrum, thin upper lip, high arched palate, and a small mandible. The proband presented with infective mastoiditis, bacterial endocarditis, and a supraventricular tachycardia. One other family member also had infective mastoiditis and bacterial endocarditis and both the probands mother and grandmother died suddenly at the age of 30 and 25 years, respectively.

Must every child with long QT syndrome take a beta blocker

Long QT syndrome is the most commonly recognised cause of sudden cardiac death in children. With a prevalence of 1 in 2000, family screening is identifying large numbers of hitherto asymptomatic gene carriers in the community, about a third of whom have a normal QT interval. The mainstay of treatment is long term uninterrupted beta blocker therapy, a treatment with many potential side effects. This article reviews the evidence and suggests a cohort who may, after assessment in a specialised cardiac-genetic clinic, be spared this treatment because of very low baseline risk. These are asymptomatic boys and prepubertal girls with a heart rate corrected QT interval persistently less than 470u2005ms who do not indulge in high risk activities (especially swimming) and do not have a missense mutation in the c-loop region of the KCNQ1 (long QT 1) gene.

Inpatient detection of cardiac-inherited disease: the impact of improving family history taking

Objectives ‘Idiopathic’ cardiac conditions such as dilated cardiomyopathy (DCM) and resuscitated sudden cardiac death (RSCD) may be familial. We suspected that inpatient cardiology services fail to recognise this. Our objective was to compare diagnostic value of family histories recorded by inpatient cardiology teams with a multigenerational family tree obtained by specially trained allied professionals. Methods 2 experienced cardiology nurses working in 2 tertiary adult cardiac units were trained in cardiac-inherited diseases and family history (FHx) taking, and established as regional coordinators for a National Cardiac Inherited Disease Registry. Over 6u2005months they sought ‘idiopathic’ cardiology inpatients with conditions with a possible familial basis, reviewed the FHx in the clinical records and pursued a minimum 3-generation family tree for syncope, young sudden death and cardiac disease (full FHx). Results 37 patients (22 males) were selected: mean age 51u2005years (range 15–79). Admission presentations included (idiopathic) RSCD (14), dyspnoea or heart failure (11), ventricular tachycardia (2), other (10). 3 patients had already volunteered their familial diagnosis to the admitting team. FHx was incompletely elicited in 17 (46%) and absent in 20 (54%). 29 patients (78%) provided a full FHx to the coordinator; 12 of which (41%) were strongly consistent with a diagnosis of a cardiac-inherited disease (DCM 7, hypertrophic cardiomyopathy 3, long QT 1, left ventricular non-compaction 1). Overall, a familial diagnostic rate rose from 3/37(8%) to 12/37 (32%). Conclusions Adult cardiology inpatient teams are poor at recording FHx and need to be reminded of its powerful diagnostic value.

Update on the Diagnosis and Management of Familial Long QT Syndrome

This update was reviewed by the CSANZ Continuing Education and Recertification Committee and ratified by the CSANZ board in August 2015. Since the CSANZ 2011 guidelines, adjunctive clinical tests have proven useful in the diagnosis of LQTS and are discussed in this update. Understanding of the diagnostic and risk stratifying role of LQTS genetics is also discussed. At least 14 LQTS genes are now thought to be responsible for the disease. High-risk individuals may have multiple mutations, large gene rearrangements, C-loop mutations in KCNQ1, transmembrane mutations in KCNH2, or have certain gene modifiers present, particularly NOS1AP polymorphisms. In regards to treatment, nadolol is preferred, particularly for long QT type 2, and short acting metoprolol should not be used. Thoracoscopic left cardiac sympathectomy is valuable in those who cannot adhere to beta blocker therapy, particularly in long QT type 1. Indications for ICD therapies have been refined; and a primary indication for ICD in post-pubertal females with long QT type 2 and a very long QT interval is emerging.