Dagmar I. Keller

Desmosomal gene analysis in arrhythmogenic right ventricular dysplasia/cardiomyopathy: spectrum of mutations and clinical impact in practice

AIMS Five desmosomal genes have been recently implicated in arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) but the clinical impact of genetics remains poorly understood. We wanted to address the potential impact of genotyping. METHODS AND RESULTS Direct sequencing of the five genes (JUP, DSP, PKP2, DSG2, and DSC2) was performed in 135 unrelated patients with ARVD/C. We identified 41 different disease-causing mutations, including 28 novel ones, in 62 patients (46%). In addition, a genetic variant of unknown significance was identified in nine additional patients (7%). Distribution of genes was 31% (PKP2), 10% (DSG2), 4.5% (DSP), 1.5% (DSC2), and 0% (JUP). The presence of desmosomal mutations was not associated with familial context but was associated with young age, symptoms, electrical substrate, and extensive structural damage. When compared with other genes, DSG2 mutations were associated with more frequent left ventricular involvement (P = 0.006). Finally, complex genetic status with multiple mutations was identified in 4% of patients and was associated with more frequent sudden death (P = 0.047). CONCLUSION This study supports the use of genetic testing as a new diagnostic tool in ARVC/D and also suggests a prognostic impact, as the severity of the disease appears different according to the underlying gene or the presence of multiple mutations.

Analyses of a novel SCN5A mutation (C1850S): conduction vs. repolarization disorder hypotheses in the Brugada syndrome.

AIMS Brugada syndrome (BrS) is characterized by arrhythmias leading to sudden cardiac death. BrS is caused, in part, by mutations in the SCN5A gene, which encodes the sodium channel alpha-subunit Na(v)1.5. Here, we aimed to characterize the biophysical properties and consequences of a novel BrS SCN5A mutation. METHODS AND RESULTS SCN5A was screened for mutations in a male patient with type-1 BrS pattern ECG. Wild-type (WT) and mutant Na(v)1.5 channels were expressed in HEK293 cells. Sodium currents (I(Na)) were analysed using the whole-cell patch-clamp technique at 37 degrees C. The electrophysiological effects of the mutation were simulated using the Luo-Rudy model, into which the transient outward current (I(to)) was incorporated. A new mutation (C1850S) was identified in the Na(v)1.5 C-terminal domain. In HEK293 cells, mutant I(Na) density was decreased by 62% at -20 mV. Inactivation of mutant I(Na) was accelerated in a voltage-dependent manner and the steady-state inactivation curve was shifted by 11.6 mV towards negative potentials. No change was observed regarding activation characteristics. Altogether, these biophysical alterations decreased the availability of I(Na). In the simulations, the I(to) density necessary to precipitate repolarization differed minimally between the two genotypes. In contrast, the mutation greatly affected conduction across a structural heterogeneity and precipitated conduction block. CONCLUSION Our data confirm that mutations of the C-terminal domain of Na(v)1.5 alter the inactivation of the channel and support the notion that conduction alterations may play a significant role in the pathogenesis of BrS.

Arrhythmogenic right ventricular cardiomyopathy: diagnostic and prognostic value of the cardiac MRI in relation to arrhythmia-free survival

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a potentially fatal disease, which is often difficult to diagnose. As a non-invasive test cardiac magnetic resonance imaging (CMR) has become an important tool in establishing the diagnosis. The aim of this study was to evaluate the diagnostic and prognostic value of CMR in patients with suspected ARVC and to assess the long-term outcome of patients with CMR-diagnosed ARVC. Thirty-six patients with suspected ARVC (26 male, 10 female, median age 41 years) underwent non-invasive and invasive clinical tests as gold standard for ARVC diagnosis. ARVC was clinically diagnosed in 19 patients and excluded in 17 patients. Both groups underwent CMR, and diagnosis was confirmed by CMR in 16/18 patients with clinically diagnosed ARVC (sensitivity 89%), and correctly excluded in 14/17 of patients with clinically excluded ARVC (specificity 82%). This result indicates a positive predictive value of the CMR of 84%, and a negative predictive value of 88%, respectively (p < 0.0001). Using a scoring system, multiple CMR parameters were compared in the two groups in regard of the clinical diagnosis. By univariate analysis, right ventricular fatty tissue infiltration (p = 0.0003) was predictive for diagnosis. Compared by outcome, 37% of patients with clinically and by CMR-diagnosed ARVC had an arrhythmic event during a mean follow-up of 16 ± 11 months. These data suggest that CMR is a highly sensitive and specific method to diagnose or exclude ARVC, and thus, has an important prognostic impact on predicting arrhythmia free survival.

Prevalence and significance of rare RYR2 variants in arrhythmogenic right ventricular cardiomyopathy/dysplasia: results of a systematic screening.

BACKGROUND Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is a genetic disease predominantly caused by desmosomal gene mutations that account for only ~50% of cases. Ryanodine receptor 2 (RYR2) gene mutations usually cause catecholaminergic polymorphic ventricular tachycardia but have been associated with a peculiar phenotype named ARVC2. OBJECTIVE We aimed to determine the prevalence and phenotype associated with RYR2 mutations in a large ARVC/D population. METHODS We analyzed the whole RYR2 coding sequence by Sanger sequencing in 64 ARVC/D probands without desmosomal gene mutations. RESULTS We have identified 6 rare missense variants: p.P1583S, p.A2213S, p.G2367R, p.Y2932H, p.V3219M, and p.L4670V. It corresponds to a 9% prevalence of rare RYR2 variants in the ARVC/D population (6 of 64 probands), which is significantly higher than the estimated frequency of rare RYR2 variants in controls (Fisher exact test, P = .03). Phenotypes associated with RYR2 variants were similar to desmosome-related ARVC/D, associating typical electrocardiographic abnormalities at rest, frequent monomorphic ventricular tachycardia, right ventricular dilatation, wall motion abnormalities, and fibrofatty replacement when histopathological examination was available. CONCLUSION In this first systematic screening of the whole coding region of the RYR2 gene in a large ARVC/D cohort without mutation in desmosomal genes, we show that putative RYR2 mutations are frequent (9% of ARVC/D probands) and are associated with a conventional phenotype of ARVC/D, which is in contrast with previous findings. The results support the role of the RYR2 gene in conventional ARVC/D.

Emergency physician intershift handover - can a dINAMO checklist speed it up and improve quality?

BACKGROUND Physician intershift handover has been identified as an area of high risk for adverse events, representing a critical step in patient care transition. Due to frequent shift changes and high patient numbers, emergency departments offer an ideal study setting. AIM OF THE STUDY At a tertiary care hospital emergency department we aimed to reduce the time needed for patient handover while maintaining or improving quality of information passed between shifts. METHODS Between 31 March and 20 June 2008 we observed intershift handovers in all non-surgical patients at 8 a.m. between nightshift and dayshift. We collected data on handover characteristics and patient demographics. After the usual clinical rounds following each handover, we asked senior physicians about missing or wrong information and possible implications for patient management. From 31 March to 9 May pre-interventional observation took place. On 13 May the dINAMO checklist with five items and a standardised feedback following each handover was introduced. Post-interventional observation lasted until 20 June. RESULTS 61 handovers totalling 23.4 hours of observation time covered 1011 patients. The intervention using the dINAMO checklist reduced mean handover time by 26% from 99 ± 3.3 to 73 ± 2.8 seconds per individual patient (p <0.0001). This resulted in a reduction of morning handover duration from 30 to 20 minutes. Senior physicians reported insignificant improvement of quality of handover. A significant decline in missing or wrong information from 194 incidents in 496 patients to 78 in 470 patients was recorded. CONCLUSIONS An intervention consisting of a simple checklist of five items (dINAMO) and an immediate feedback on quality not only contributes to a significant shortening of time needed for physician intershift handover in a university hospital emergency department, but simultaneously helps to improve quality of information and therefore patient management.

De novo heterozygous desmoplakin mutations leading to Naxos-Carvajal disease

STUDY/PRINCIPLES Arrythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is an autosomal-dominantly inherited disease caused by mutations in genes encoding desmosomal proteins and is characterised by fibrofatty replacement occurring predominantly in the right ventricle and can result in sudden cardiac death. Naxos and Carvajal syndrome, autosomal recessive forms of ARVC/D, are characterised by involvement of the right and/or left ventricle in association with palmoplantar keratoderma and woolly hair. The aim of the present study has been to screen for mutations in the desmosomal protein genes of two unrelated patients with Naxos-Carvajal syndrome. METHODS AND RESULTS Desmosomal protein genes were screened for mutations by polymerase chain reaction as well as direct sequencing approach. In each patient we identified a single heterozygous de novo mutation in the desmoplakin gene DSP, p.Leu583Pro and p.Thr564Ile, leading to severe combined cardiac/dermatological and cardiac/dermatological/dental phenotypes. The DSP missense mutations are localised in the N terminal domain of desmoplakin. CONCLUSION The identified variations in DSP involve highly conserved residues. Moreover, the variations are de novo mutations and they are localised in critical protein domains that appear to be mutation hot spots. We assume that these heterozygous variations are causal for the mixed Naxos-Carvajal syndrome phenotype in the screened patients.

Value of repeated cardiac magnetic resonance imaging in patients with suspected arrhythmogenic right ventricular cardiomyopathy.

AIM Diagnosis of early stages of arrhythmogenic right ventricular cardiomyopathy (ARVC) with minimal structural abnormalities is challenging. The purpose of this study was to assess the value of repeated cardiac magnetic resonance imaging (CMR) in patients referred for right ventricular arrhythmias and clinical suspicion of ARVC. METHODS AND RESULTS Prospective follow-up study of 18 patients (8 females) studied with CMR for suspected ARVC. Patients with implanted defibrillators (ICD) were excluded. Mean follow-up was 37 +/- 16 (12-59) months. Patients were assigned to 2 categories (ARVC likely or ARVC unlikely) according to a CMR-score based on right ventricular abnormalities. Clinical follow-up revealed no disease progression in 17 patients (94%). In 1 patient, an ICD was implanted because of disease progression. Of 9 patients with initial findings suggestive of ARVC, follow-up CMR remained positive in 3 and was diagnosed as normal in 6, mainly due to the inability to confirm the presence of fatty infiltrates at follow-up (5 of 6 patients). Initially, 9 patients had a normal CMR and 8 of those remained normal during follow-up. CONCLUSION Repeated CMR after an average follow-up of 3 years was normal in 6 of 9 patients with clinical findings consistent with early stages of ARVC at the time of baseline CMR. Thus, CMR diagnosis of early stage ARVC is difficult and should be made with caution.

Elevated high-sensitivity troponin T levels are associated with adverse cardiac remodelling and myocardial fibrosis in hypertrophic cardiomyopathy.

INTRODUCTION Clinical manifestations of hypertrophic cardiomyopathy (HCM) range from asymptomatic disease to early-onset heart failure and sudden cardiac death (SCD). Risk stratification for SCD remains imperfect and novel risk markers are needed. The aim of our study was to evaluate the association of elevated high-sensitivity cardiac troponin T levels (hs-cTnT) with the severity of disease expression and adverse events in patients with HCM. METHODS All patients followed-up at a dedicated HCM clinic at a tertiary care centre between April 2012 and March 2014 were analysed. The clinical care track for these patients includes 12-lead ECG, blood work-up, echocardiography, Holter ECG, exercise stress testing and cardiovascular magnetic resonance imaging (CMR). Clinical data were obtained from medical records. RESULTS Of 91 HCM patients (77% males, mean age at follow up 51 ± 16 years), 46 (51%) had elevated hs-cTnT levels (>0.014 ng/ml). Patients with elevated hs-cTnT levels had greater maximum wall thickness (23 ± 7 mm vs 19 ± 3 mm, p = 0.001), more often had myocardial fibrosis (96% vs 54%, p <0.001), and lower exercise capacity (90% predicted vs 76% predicted, p = 0.002). There was a trend towards lower event-free survival estimates (Kaplan-Meier method, 15% vs 7%, p = 0.16). CONCLUSIONS Elevated hs-cTnT levels in HCM patients are associated with disease severity and, potentially, with more adverse cardiac events. Future studies should test whether integration of hs-cTnT in clinical decision algorithms will improve risk stratification.

A leaky voltage sensor domain of cardiac sodium channels causes arrhythmias associated with dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a structural heart disease that causes dilatation of cardiac chambers and impairs cardiac contractility. The SCN5A gene encodes Nav1.5, the predominant cardiac sodium channel alpha subunit. SCN5A mutations have been identified in patients with arrhythmic disorders associated with DCM. The characterization of Nav1.5 mutations located in the voltage sensor domain (VSD) and associated with DCM revealed divergent biophysical defects that do not fully explain the pathologies observed in these patients. The purpose of this study was to characterize the pathological consequences of a gating pore in the heart arising from the Nav1.5/R219H mutation in a patient with complex cardiac arrhythmias and DCM. We report its properties using cardiomyocytes derived from patient-specific human induced pluripotent stem cells. We showed that this mutation generates a proton leak (called gating pore current). We also described disrupted ionic homeostasis, altered cellular morphology, electrical properties, and contractile function, most probably linked to the proton leak. We thus propose a novel link between SCN5A mutation and the complex pathogenesis of cardiac arrhythmias and DCM. Furthermore, we suggest that leaky channels would constitute a common pathological mechanism underlying several neuronal, neuromuscular, and cardiac pathologies.

Clinical Validation of a Novel High-Sensitivity Cardiac Troponin I Assay for Early Diagnosis of Acute Myocardial Infarction

BACKGROUND Clinical performance of the novel high-sensitivity cardiac troponin I (Siemens-hs-cTnI-Centaur) assay is unknown. We aimed to clinically validate the Siemens-hs-cTnI-Centaur assay and develop 0/1-h and 0/2-h algorithms. METHODS We enrolled patients presenting to the emergency department with symptoms suggestive of acute myocardial infarction (AMI). Final diagnoses were centrally adjudicated by 2 independent cardiologists including all clinical information twice: first, using serial hs-cTnT (Roche-Elecsys, primary analysis); second, using hs-cTnI (Abbott-Architect, secondary analysis) measurements in addition to the clinically applied (hs)-cTn. Siemens-hs-cTnI-Centaur was measured at presentation, 1 h, and 2 h. The primary objective was a direct comparison of diagnostic accuracy, quantified by the area under the ROC curve (AUC), of Siemens-hs-cTnI-Centaur vs the 2 established hs-cTn assays (Roche-hs-cTnT-Elecsys, Abbott-hs-cTnI-Architect). Secondary objectives included the development of Siemens-hs-cTnI-Centaur-specific 0/1-h and 0/2-h algorithms. RESULTS AMI was the final diagnosis in 318 of 1755 (18%) patients (using Roche-hs-cTnT-Elecsys for adjudication). The AUC at presentation for Siemens-hs-cTnI-Centaur was 0.94 (95% CI, 0.92-0.96) and comparable with 0.95 (95% CI, 0.93-0.97) for Roche-hs-cTnT-Elecsys and 0.93 (95% CI, 0.90-0.96) for Abbott-hs-cTnI-Architect. Applying the derived Siemens-hs-cTnI-Centaur 0/1-h algorithm to the validation cohort, 46% of patients were ruled out (sensitivity, 99.1%; 95% CI, 95.3-100), and 18% of patients were ruled in (specificity, 94.1%; 95% CI, 91.8-95.9). The Siemens-hs-cTnI-Centaur 0/2-h algorithm ruled out 55% of patients (sensitivity, 100%; 95% CI, 94.1-100), and ruled in 18% of patients (specificity, 96.0%; 95% CI, 93.1-97.9). Findings were confirmed in the secondary analyses using serial measurements of Abbott-hs-cTnI-Architect for adjudication. CONCLUSIONS Diagnostic accuracy and clinical utility of the novel Siemens-hs-cTnI-Centaur assay are high and comparable with the established hs-cTn assays. ClinicalTrials.gov Identifier: NCT00470587.