Combined gating and trafficking defect in Kv11.1 manifests as a malignant long QT syndrome phenotype in a large Danish p.F29L founder family.

BACKGROUND: Congenital long QT syndrome (LQTS) is a hereditary cardiac channelopathy characterized by delayed ventricular repolarization, syncope, torsades de pointes and sudden cardiac death. Thirty-three members of five apparently 'unrelated' Danish families carry the KCNH2:c.87C> A; p.F29L founder mutation. METHODS AND RESULTS: Linkage disequilibrium mapping with microsatellites around KCNH2 enabled us to estimate the age of the founder mutation to be approximately 22 generations, corresponding to around 550 years. Neighbouring-Joining analysis disclosed one early and three later nodes. The median QTc time of the carriers was 490 ms (range: 415-589 ms) and no difference was seen between the different branches of the family. The mutation is malignant with a penetrance of 73%. Ten F29L carriers received implantable defibrillators (ICDs) (median age at implant 20 years), and of those four individuals experienced eight appropriate shocks. Patch-clamp analysis in HEK 293 cells, performed at 34°C disclosed a loss-of-function phenotype with fast deactivation, reduced steady-state inactivation current density and a positive voltage shift in inactivation. Western blotting of HEK 293 cells transfected with KCNH2:WT and KCNH2:c.87C> A revealed a reduced fraction of fully glycosylated hERG:p.F29L suggesting that this mutation results in defective trafficking. CONCLUSION: The altered channel gating kinetics in combination with defective trafficking of mutated channels is expected to result in reduced repolarizing current density and, thus, a LQTS phenotype.

Management of patients with Arrhythmogenic Right Ventricular Cardiomyopathy in the Nordic countries.

OBJECTIVES: Diagnostics of patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) are complex, and based on the 2010 Task Force document including different diagnostic modalities. However, recommendations for clinical management and follow-up of patients with ARVC and their relatives are sparse. This paper aims to give a practical overview of management strategies, risk stratification, and selection of appropriate therapies for patients with ARVC and their family members. DESIGN: This paper summarizes follow-up and treatment strategies in ARVC patients in the Nordic countries. The author group represents cardiologists who are actively involved in the Nordic ARVC Registry which was established in 2009, and contains prospectively collected clinical data from more than 590 ARVC patients from Denmark, Norway, Sweden, and Finland. RESULTS: Different approaches of management and follow-up are required in patients with definite ARVC and in genetic-mutation-positive family members. Furthermore, ARVC patients with and without implantable cardioverter defibrillators (ICDs) require different follow-up strategies. CONCLUSION: Careful follow-up is required in patients with ARVC diagnosis to evaluate the need of anti-arrhythmic therapy and ICD implantation. Mutation-positive family members should be followed regularly for detection of early disease and risk stratification of ventricular arrhythmias.

Rare cause of ventricular tachycardia: Pheochromocytoma.

Pheochromocytoma is known from a wide range of clinical manifestations and can mimic other disorders which can lead to delay in diagnosis. We report a case of a young female presenting with chest pain, electrocardiographic changes, and episodes of ventricular tachycardia, finally diagnosed with this catecholamine-producing tumor. .

[The genome and cardiology].

Several cardiac diseases are autosomal dominantly inherited. This includes cardiomyopathies, primary arrhythmias (channelopathies), dyslipidaemias, premature ischaemic heart diseases and diseases of the thoracic aorta. Sudden cardiac death in the young is also often due to one of the inherited cardiac diseases. Clinical and genetic cascade family screening of the relatives to patients with inherited cardiac diseases is now organized in a national network of centres of cardiology, sharing pedigrees, clinical and genetic information. This gives unique opportunities for offering focused prophylaxis in the group of high-risk relatives.

The diagnostic performance of imaging methods in ARVC using the 2010 Task Force criteria.

AIMS: This study evaluates the agreement between echocardiographic and cardiac magnetic resonance (CMR) imaging data, and the impact a discrepancy between the two may have on the clinical diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC). METHODS AND RESULTS: From the Nordic ARVC Registry, 102 patients with definite ARVC who had undergone both echocardiography and CMR were included (median age 42 ± 16 years, 36% female, 78% probands). Patients were divided into two groups according to CMR-positive or -negative criteria, and the echocardiographic data were compared between the two. There were 72 CMR-positive patients. They had significantly larger RV dimensions and lower fractional area change on echocardiography compared with CMR-negative patients; parasternal long-axis right ventricular outflow tract (RVOT) 37 ± 7 vs. 32 ± 5 mm, parasternal short-axis RVOT 38 ± 7 vs. 32 ± 6 mm, fractional area shortening 31 ± 9 vs. 39 ± 9% (P < 0.003 for all). Only 36 (50%) of the CMR-positive patients fulfilled ARVC criteria by echocardiography, hence the diagnostic performance was low; sensitivity 50% and specificity 70%, positive predictive value 80% and negative predictive value 37%. Individuals with regional wall abnormalities on CMR were more likely to have ventricular arrhythmias (77 vs. 57%, P = 0.047). CONCLUSION: A significant proportion of patients with imaging-positive ARVC by CMR did not fulfil echocardiographic ARVC 2010 criteria. These findings confirm that echocardiographic evaluation of subtle structural changes in the right ventricle may be unreliable, and the diagnostic performance of CMR compared with echocardiography should be reflected in the guidelines.

Mutations in Danish patients with long QT syndrome and the identification of a large founder family with p.F29L in KCNH2.

BACKGROUND: Long QT syndrome (LQTS) is a cardiac ion channelopathy which presents clinically with palpitations, syncope or sudden death. More than 700 LQTS-causing mutations have been identified in 13 genes, all of which encode proteins involved in the execution of the cardiac action potential. The most frequently affected genes, covering > 90% of cases, are KCNQ1, KCNH2 and SCN5A. METHODS: We describe 64 different mutations in 70 unrelated Danish families using a routine five-gene screen, comprising KCNQ1, KCNH2 and SCN5A as well as KCNE1 and KCNE2. RESULTS: Twenty-two mutations were found in KCNQ1, 28 in KCNH2, 9 in SCN5A, 3 in KCNE1 and 2 in KCNE2. Twenty-six of these have only been described in the Danish population and 18 are novel. One double heterozygote (1.4% of families) was found. A founder mutation, p.F29L in KCNH2, was identified in 5 "unrelated" families. Disease association, in 31.2% of cases, was based on the type of mutation identified (nonsense, insertion/deletion, frameshift or splice-site). Functional data was available for 22.7% of the missense mutations. None of the mutations were found in 364 Danish alleles and only three, all functionally characterised, were recorded in the Exome Variation Server, albeit at a frequency of < 1:1000. CONCLUSION: The genetic etiology of LQTS in Denmark is similar to that found in other populations. A large founder family with p.F29L in KCNH2 was identified. In 48.4% of the mutations disease causation was based on mutation type or functional analysis.

Long pacing pulses reduce phrenic nerve stimulation in left ventricular pacing.

INTRODUCTION: Phrenic nerve stimulation is a major obstacle in cardiac resynchronization therapy (CRT). Activation characteristics of the heart and phrenic nerve are different with higher chronaxie for the heart. Therefore, longer pulse durations could be beneficial in preventing phrenic nerve stimulation during CRT due to a decreased threshold for the heart compared with the phrenic nerve. We investigated if long pulse durations decreased left ventricular (LV) thresholds relatively to phrenic nerve thresholds in humans. METHODS AND RESULTS: Eleven patients, with indication for CRT and phrenic nerve stimulation at the intended pacing site, underwent determination of thresholds for the heart and phrenic nerve at different pulse durations (0.3-2.9 milliseconds). The resulting strength duration curves were analyzed by determining chronaxie and rheobase. Comparisons for those parameters were made between the heart and phrenic nerve, and between the models of Weiss and Lapicque as well. In 9 of 11 cases, the thresholds decreased faster for the LV than for the phrenic nerve with increasing pulse duration. In 3 cases, the thresholds changed from unfavorable for LV stimulation to more than a factor 2 in favor of the LV. The greatest change occurred for pulse durations up to 1.5 milliseconds. The chronaxie of the heart was significantly higher than the chronaxie of the phrenic nerve (0.47 milliseconds vs. 0.22 milliseconds [P = 0.029, Lapicque] and 0.79 milliseconds vs. 0.27 milliseconds [P = 0.033, Weiss]). CONCLUSION: Long pulse durations lead to a decreased threshold of the heart relatively to the phrenic nerve and may prevent stimulation of the phrenic nerve in a clinical setting.

The role of CAV3 in long-QT syndrome: clinical and functional assessment of a caveolin-3/Kv11.1 double heterozygote versus caveolin-3 single heterozygote.

BACKGROUND: Mutations in CAV3, coding for caveolin-3, the major constituent scaffolding protein of cardiac caveolae, have been associated with skeletal muscle disease, cardiomyopathy, and most recently long-QT syndrome (LQTS) and sudden infant death syndrome. We examined the occurrence of CAV3 mutations in a large cohort of patients with LQTS. METHODS AND RESULTS: Probands with LQTS (n=167) were screened for mutations in CAV3 using direct DNA sequencing. A single proband (0.6%) was found to be a heterozygous carrier of a previously described missense mutation, caveolin-3:p.T78M. The proband was also a heterozygous carrier of the trafficking-deficient Kv11.1:p.I400N mutation. The caveolin-3:p.T78M mutation was found isolated in 3 family members, none of whom had a prolonged QTc interval. Coimmunoprecipitations of caveolin-3 and the voltage-gated potassium channel subunit (Kv11.1) were performed, and the electrophysiological classification of the Kv11.1 mutant was carried out by patch-clamp technique in human embryonic kidney 293 cells. Furthermore, the T-wave morphology was assessed in mutation carriers, double mutation carriers, and nonmutation carriers by applying a morphology combination score. The morphology combination score was normal for isolated caveolin-3:p.T78M carriers and of LQT2 type in double heterozygotes. CONCLUSIONS: Mutations in CAV3 are rare in LQTS. Furthermore, caveolin-3:p.T78M did not exhibit a LQTS phenotype. Because no association has ever been found between LQTS and isolated CAV3 mutations, we suggest that LQTS9 is considered a provisional entity.

Cascade screening in families with inherited cardiac diseases driven by cardiologists: feasibility and nationwide outcome in long QT syndrome.

OBJECTIVES: We assessed the outcome of cascade screening of families with congenital long QT syndrome (LQTS) in Danish heart centers. METHODS: Affected family members were identified through systematic family screening. RESULTS: In total, 228 affected relatives were identified from 90 families. A disease-causing mutation useful for presymptomatic genetic testing was found in 82% of probands. Two-thirds of affected relatives fulfilled electrocardiographic criteria for the diagnosis, whereas diagnosis was based on genetic findings in only one-third. The majority of affected relatives were asymptomatic. Symptomatic relatives and probands most often presented with syncope, followed by aborted cardiac arrest and sudden cardiac death. A serious cardiac event (SCE, such as syncope, aborted cardiac arrest or cardiac arrest) was reported by 32% of affected relatives and 87% of probands (p < 0.0001). Fifty-two percent of affected relatives were on ß-blockers and 11% had an implantable cardioverter defibrillator (ICD), as compared to 88 and 49% of probands (p < 0.0001). Appropriate ICD therapy was given to 13% of affected relatives and to 27% of probands (p = 0.1). CONCLUSIONS: Clinically driven cascade screening of Danish LQTS families identified 2-3 affected relatives per proband. Affected relatives had milder disease courses, but SCEs in a subset strongly support screening. Danish cardiologists have adopted cascade screening of LQTS families according to specific Danish guidelines.

Low disease prevalence and inappropriate implantable cardioverter defibrillator shock rate in Brugada syndrome: a nationwide study.

AIMS: Brugada syndrome (BrS) is an inherited channelopathy that predisposes to malignant ventricular arrhythmias and thereby syncope and sudden cardiac death. Prior studies characterizing BrS patients have used highly selected referral populations from tertiary centres and prevalence estimates have been carried out using electrocardiogram (ECG) surveys only. We aimed to identify and characterize all diagnosed BrS patients in Denmark (population 5.4 million). METHODS AND RESULTS: Brugada syndrome patients were identified using several modalities including identification in all Danish tertiary referral centres, search in public health registries, contact to all cardiology departments in Denmark, and searching in a pedigree database for inherited heart disease used nationwide in Denmark. We identified 43 definite diagnosed BrS patients and 25 possible BrS patients, corresponding to a prevalence of 1.1 definite BrS cases per 100 000 inhabitants. Most definite BrS patients were men (86%) and the median age at diagnosis was 48 years. A total of 35 definite BrS patients (81%) had an implantable cardioverter defibrillator (ICD) implanted and of these 9 (26%) experienced appropriate shocks and 3 (8%) experienced inappropriate shocks during a median follow-up of 47 months. No patient died or experienced aborted sudden cardiac death during follow-up. CONCLUSIONS: We report the first nationwide study of BrS patients. We found a low incidence of diagnosed definite BrS compared with estimates from ECG surveys. Follow-up data show a lower rate of inappropriate therapies in ICD carriers than that reported in previous studies.

[Radiotherapy in patients with a pacemaker or an implantable cardioverter defibrillator]. / Stråleterapi hos patienter med pacemakere og implanterbare kardioverterdefibrillatorer.

With an ageing population an increasing number of patients with a pacemaker or implantable cardioverter defibrillator will present at radiotherapy units due to malignancy. Two separate questionnaires concerning routines of departments treating this population were sent to Danish implanting cardiology centers and to radiotherapy departments. Differences in the handling of these patients were found. Removal of the devices and monitoring of the patients is assessed on a highly individual basis. In the absence of updated official guidelines, departments treating these patients should produce local instructions.

Adhesion molecules and C-reactive protein are associated to adverse events in angina pectoris.

OBJECTIVES: To examine the prognostic value of soluble cellular adhesion molecules (CAMs) and highly sensitive C reactive protein (hsCRP) on long-term outcome for patients with stable angina pectoris (SAP). DESIGN: In a prospective study, 291 patients referred for coronary angiography due to clinically suspected SAP had serum level of soluble intercellular adhesion molecule-1 (sICAM-1), vascular adhesion molecule-1 (sVCAM-1), sP-selectin and hsCRP determined at baseline. The primary outcome was predefined as death from any cause, myocardial infarction or stroke during a mean follow-up of 7.1 years. RESULTS: Thirty four patients experienced the primary outcome. Hazard ratios and 95% confidence intervals for the primary outcome were: sVCAM-1: 2.4 [1.1-4.9], sICAM-1: 3.3 [1.5-7.2], sP-selectin: 1.2 [0.6-2.6] and hs-CRP: 3.1 [1.5-6.3], when comparing patients in the 4th quartile with those in lower quartiles in a multivariable model. Higher risk of adverse outcome was observed in patients having levels of both hsCRP and sICAM-1 (HR 4.7 [1.7-9.9]) or hsCRP and sVCAM-1 (HR 4.2 [1.7-9.9]) in the 4th quartile. CONCLUSIONS: sVCAM-1, sICAM-1 and hsCRP were significantly associated with long term outcomes of patients with SAP beyond the risk associated with traditional risk factors. Risk predictions were improved when combining information about sCAMs and hsCRP.

Cellular Adhesion Molecules in Healthy Subjects: Short Term Variations and Relations to Flow Mediated Dilation.

The objective was primarily to describe short term intra-individual variation in serum levels of soluble adhesion molecules (sCAMs: E-selectin, P-selectin, intercellular adhesion molecule-1(sICAM-1) and vascular cellular adhesion molecule-1(sVCAM-1)) in healthy subjects. Secondly, sCAMs were correlated to brachial artery flow mediated vasodilation (FMD).Forty healthy subjects aged 24-66 years had sCAMs measured twice with 4 week intervals and short-term intra-individual variation was estimated as variation in the paired measurements after correcting for the analytical precision of the used method. At baseline, brachial FMD was measured.No difference was observed in mean sCAMs in the whole study group. Estimated intra-subject variations in sCAMs were 7.6-11.3%. In a regression analysis, significant negative association was found between sE-selectin and FMD after controlling for possible confounders (p < 0.04) while no significant correlation could be demonstrated between the other sCAMs and FMD.In conclusion, short term intra-individual variations in sCAMs were 7.6-11.3% in healthy subjects. We also found a significant negative association between sE-selectin and FMD, indicating an possible association between inflammation and dysfunction of the vascular endothelium; however further studies are required to confirm this preliminary finding.

Soluble adhesion molecules and marine n-3 fatty acids in patients referred for coronary angiography.

OBJECTIVE: To investigate the relationship between soluble cellular adhesion molecules (sCAMs) and the extent of coronary artery disease (CAD) in patients with stable angina pectoris. METHODS AND RESULTS: Two hundred and ninety-one subjects had fasting levels of circulating intercellular adhesion molecule-1(sICAM-1), vascular cellular adhesion molecule-1 (sVCAM-1), sP-selectin and contents of n-3 polyunsaturated fatty acids (n-3 PUFA) in granulocyte membranes and adipose tissue determined before undergoing elective coronary angiography. Levels of soluble VCAM-1 (983+/-216 versus 893+/-196 ng/l, p<0.001), ICAM-1 (318+/-140 versus 290+/-75 ng/l, p<0.05) and P-selectin (90+/-27 versus 80+/-23 ng/l, p<0.01) were significantly increased in subjects with significant CAD compared to subjects with no significant stenoses. In a linear regression analysis, both sVCAM-1 and sP-selectin, but not sICAM-1, correlated to the presence and the severity of CAD. Both sICAM-1 and sP-selectin were significantly correlated to current smoking status and a history of myocardial infarction. The content of total n-3 PUFA and docosahexaenoic acid in adipose tissue was marginally, but significant positively correlated to VCAM-1. CONCLUSION: sVCAM-1 and sP-selectin may serve as markers of CAD in patients with stable angina pectoris. Only sVCAM-1 was weakly correlated to n-3 PUFA in adipose tissue.