Missense and Non-Missense Lamin A/C Gene Mutations Are Similarly Associated with Major Arrhythmic Cardiac Events: A 20-Year Single-Centre Experience.

Arrhythmic risk stratification in patients with Lamin A/C gene (LMNA)-related cardiomyopathy influences clinical decisions. An implantable cardioverter defibrillator (ICD) should be considered in patients with an estimated 5-year risk of malignant ventricular arrhythmia (MVA) of ≥10%. The risk prediction score for MVA includes non-missense LMNA mutations, despite their role as an established risk factor for sudden cardiac death (SCD) has been questioned in several studies. The purpose of this study is to investigate cardiac features and find gene-phenotype correlations that would contribute to the evidence on the prognostic implications of non-missense vs. missense mutations in a cohort of LMNA mutant patients. An observational, prospective study was conducted in which 54 patients positive for a Lamin A/C mutation were enrolled, and 20 probands (37%) were included. The median age at first clinical manifestation was 41 (IQR 19) years. The median follow-up was 8 years (IQR 8). The type of LMNA gene mutation was distributed as follows: missense in 26 patients (48%), non-frameshift insertions in 16 (30%), frameshift deletions in 5 (9%), and nonsense in 7 (13%). Among the missense mutation carriers, two (8%) died and four (15%) were admitted onto the heart transplant list or underwent transplantation, with a major adverse cardiovascular event (MACE) rate of 35%. No statistically significant differences in MACE prevalence were identified according to the missense and non-missense mutation groups (p value = 0.847). Our data shift the spotlight on this considerable topic and could suggest that some missense mutations may deserve attention regarding SCD risk stratification in real-world clinical settings.

VINYL: Variant prIoritizatioN bY survivaL analysis.

MOTIVATION: Clinical applications of genome re-sequencing technologies typically generate large amounts of data that need to be carefully annotated and interpreted to identify genetic variants potentially associated with pathological conditions. In this context, accurate and reproducible methods for the functional annotation and prioritization of genetic variants are of fundamental importance. RESULTS: In this article, we present VINYL, a flexible and fully automated system for the functional annotation and prioritization of genetic variants. Extensive analyses of both real and simulated datasets suggest that VINYL can identify clinically relevant genetic variants in a more accurate manner compared to equivalent state of the art methods, allowing a more rapid and effective prioritization of genetic variants in different experimental settings. As such we believe that VINYL can establish itself as a valuable tool to assist healthcare operators and researchers in clinical genomics investigations. AVAILABILITY AND IMPLEMENTATION: VINYL is available at http://beaconlab.it/VINYL and https://github.com/matteo14c/VINYL. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Targeted next-generation sequencing detects novel gene-phenotype associations and expands the mutational spectrum in cardiomyopathies.

Cardiomyopathies are a heterogeneous group of primary diseases of the myocardium, including hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), and arrhythmogenic right ventricular cardiomyopathy (ARVC), with higher morbidity and mortality. These diseases are genetically diverse and associated with rare mutations in a large number of genes, many of which overlap among the phenotypes. To better investigate the genetic overlap between these three phenotypes and to identify new genotype-phenotype correlations, we designed a custom gene panel consisting of 115 genes known to be associated with cardiomyopathic phenotypes and channelopathies. A cohort of 38 unrelated patients, 16 affected by DCM, 14 by HCM and 8 by ARVC, was recruited for the study on the basis of more severe phenotypes and family history of cardiomyopathy and/or sudden death. We detected a total of 142 rare variants in 40 genes, and all patients were found to be carriers of at least one rare variant. Twenty-eight of the 142 rare variants were also predicted as potentially pathogenic variants and found in 26 patients. In 23 out of 38 patients, we found at least one novel potential gene-phenotype association. In particular, we detected three variants in OBSCN gene in ARVC patients, four variants in ANK2 gene and two variants in DLG1, TRPM4, and AKAP9 genes in DCM patients, two variants in PSEN2 gene and four variants in AKAP9 gene in HCM patients. Overall, our results confirmed that cardiomyopathic patients could carry multiple rare gene variants; in addition, our investigation of the genetic overlap among cardiomyopathies revealed new gene-phenotype associations. Furthermore, as our study confirms, data obtained using targeted next-generation sequencing could provide a remarkable contribution to the molecular diagnosis of cardiomyopathies, early identification of patients at risk for arrhythmia development, and better clinical management of cardiomyopathic patients.

Clinical and functional characterization of a novel mutation in lamin a/c gene in a multigenerational family with arrhythmogenic cardiac laminopathy.

Mutations in the lamin A/C gene (LMNA) were associated with dilated cardiomyopathy (DCM) and, recently, were related to severe forms of arrhythmogenic right ventricular cardiomyopathy (ARVC). Both genetic and phenotypic overlap between DCM and ARVC was observed; molecular pathomechanisms leading to the cardiac phenotypes caused by LMNA mutations are not yet fully elucidated. This study involved a large Italian family, spanning 4 generations, with arrhythmogenic cardiomyopathy of different phenotypes, including ARVC, DCM, system conduction defects, ventricular arrhythmias, and sudden cardiac death. Mutation screening of LMNA and ARVC-related genes PKP2, DSP, DSG2, DSC2, JUP, and CTNNA3 was performed. We identified a novel heterozygous mutation (c.418_438dup) in LMNA gene exon 2, occurring in a highly conserved protein domain across several species. This newly identified variant was not found in 250 ethnically-matched control subjects. Genotype-phenotype correlation studies suggested a co-segregation of the LMNA mutation with the disease phenotype and an incomplete and age-related penetrance. Based on clinical, pedigree, and molecular genetic data, this mutation was considered likely disease-causing. To clarify its potential pathophysiologic impact, functional characterization of this LMNA mutant was performed in cultured cardiomyocytes expressing EGFP-tagged wild-type and mutated LMNA constructs, and indicated an increased nuclear envelope fragility, leading to stress-induced apoptosis as the main pathogenetic mechanism. This study further expands the role of the LMNA gene in the pathogenesis of cardiac laminopathies, suggesting that LMNA should be included in mutation screening of patients with suspected arrhythmogenic cardiomyopathy, particularly when they have ECG evidence for conduction defects. The combination of clinical, genetic, and functional data contribute insights into the pathogenesis of this form of life-threatening arrhythmogenic cardiac laminopathy.

Head-up tilt testing for diagnosing vasovagal syncope: a meta-analysis.

BACKGROUND: A systematic evaluation focused on sensitivity and specificity of head-up tilt testing (HUT) for diagnosing vasovagal syncope has not been previously performed. We conducted a meta-analysis of studies comparing HUT outcome between patients with syncope of unknown origin and control subjects without previous syncope. METHODS: We searched Pubmed and Embase databases for all English-only articles concerning case-control studies estimating the diagnostic yield of HUT, and selected 55 articles, published before March 2012, including 4361 patients and 1791 controls. The influence of age, test duration, tilt angle, and nitroglycerine or isoproterenol stimulation on tilt testing outcome was analyzed. RESULTS: Head-up tilt testing demonstrated to have a good overall ability to discriminate between symptomatic patients and asymptomatic controls with an area under the summary receiver-operating characteristics curve of 0.84 and an adjusted diagnostic odds ratio of 12.15 (p<0.001). A significant inverse relationship between sensitivity and specificity of tilt testing for each study was observed (p<0.001). At multivariate analysis, advancing age and a 60° tilt angle showed a significant effect in reducing sensitivity and increasing specificity of the test. Nitroglycerine significantly raised tilt testing sensitivity by maintaining a similar specificity in comparison to isoproterenol. CONCLUSIONS: The results from this meta-analysis show the high overall performance of HUT for diagnosing vasovagal syncope. Our findings provide useful information for evaluating clinical and instrumental parameters together with pharmacological stressors influencing HUT accuracy. This could allow the drawing of tilt testing protocols tailored on the diagnostic needs of each patient with unexplained syncope.

Altered two-dimensional strain measures of the right ventricle in patients with Brugada syndrome and arrhythmogenic right ventricular dysplasia/cardiomyopathy.

AIMS: Brugada syndrome (BrS) is an inherited channelopathy that can be characterized by mild right ventricular (RV) abnormalities that are not detectable with conventional echocardiography. The aim of this study was to evaluate the presence of RV abnormalities in BrS patients when compared with controls and a group of patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) using two-dimensional (2D) strain analysis. METHODS AND RESULTS: We enrolled 25 BrS, 15 ARVD/C patients, and 25 controls. Right and left ventricular dimension and systo-diastolic function were evaluated by conventional echocardiography. Longitudinal systolic strain (sS) peak, systolic and early diastolic strain rate of lateral RV segments were evaluated by 2D speckle tracking analysis. Left ventricle global and segmental strain measures were also evaluated. A reduced basal or mid-RV lateral sS were the parameters mostly associated with both BrS and ARVD/C. In BrS patients the minimum sS observed in these segments was significantly lower than that of controls (-28.9±3.2% vs. -32.3±3.2%, P: 0.002) but significantly greater than that evaluated in ARVD/C patients (-24.6±6.7%, P<0.001 both vs. BrS and controls). No differences were found between the BrS and the control group when left ventricular strain measures were analysed. CONCLUSION: By 2D strain technique it is possible to observe mild abnormalities in RV systolic and diastolic function of BrS patients that are less pronounced than those observed in ARVD/C patients. These results help to better define the phenotypic characteristics of BrS patients and represent the basis for future studies aimed at testing their clinical usefulness in BrS patients.

Independent role of reduced arterial baroreflex sensitivity during head-up tilt testing in predicting vasovagal syncope recurrence.

AIMS: The involvement of arterial baroreflex function in the pathophysiology of vasovagal syncope (VVS) is controversial, and there are no published data supporting its clinical usefulness. The aim of this study was to evaluate the role of arterial baroreflex sensitivity (BRS) at baseline and during head-up tilt testing (HUT) in predicting the recurrence of VVS. METHODS AND RESULTS: The study involved otherwise healthy patients with a history of unexplained syncope who underwent diagnostic HUT by being tilted to 70 degrees after 10 min supine rest; the test was potentiated by the administration of 300 microg of nitroglycerine (NTG) after 20 min. Beat-to-beat heart rate and systolic blood pressure were continuously recorded, and the sequence method was used to measure arterial baroreflex control of heart rate. The 190 enrolled patients were followed up for 18 +/- 6 months, during which 34 experienced a total of 90 episodes of syncope recurrence. In a stepwise multivariate analysis, female gender [hazard ratio (HR): 2.74; P = 0.008], the presence of >or=3 syncope events before HUT (HR: 3.36; P = 0.004), and BRS below median value after the start of HUT or after the administration of NTG (HR: 3.79; P = 0.006) were significantly and independently associated with the recurrence of syncope. Moreover, when a BRS value of less than the median was added to the other independent factors in a stepwise model, a significant increase in discrimination (C-index: 0.77) and model fitting (P = 0.001) was observed. CONCLUSION: Reduced BRS during HUT has independent and incremental value in predicting the recurrence of syncope, thus supporting its potential usefulness in the clinical management of patients.

Nitrate-potentiated head-up tilt testing in older patients: outcomes, hemodynamic responses and prodrome recognition.

BACKGROUND: To compare head-up tilt testing (HUT) outcomes and hemodynamic responses, and the prevalence and correlates of prodromes, in elderly and younger patients with suspected vasovagal syncope (VVS). METHODS: Consecutive outpatients with a history of recurrent unexplained syncope underwent HUT by being tilted to 70°; the test was potentiated by the administration of 300 µg of nitroglycerine after 20 minutes. Occurrence of VVS and hemodynamic responses during passive and nitroglycerine phases of HUT were evaluated; symptoms preceding HUT-induced syncope were recorded, together with heart rate and arterial blood pressure values. RESULTS: Four hundred and sixty of the 743 patients were HUT positive: 156 fainted during the unmedicated phase and 304 after nitroglycerine administration. The patients aged ≥65 years (n = 102) experienced VVS more frequently during the pharmacological stage of HUT; the overall rate of positive results was similar to that observed in the patients aged 36-64 years (n = 329) and only slightly lower than that observed in those aged ≤ 35 years (n = 312). In the older patients, who experienced fewer and mainly prodrome-free spontaneous syncopal episodes, HUT increased the number of premonitory symptoms, and there were no significant age-related differences in symptom prevalence or timing or the patients' hemodynamic characteristics. CONCLUSIONS: The rate of VVS induced by nitroglycerine-potentiated HUT is similar in elderly and younger patients. In the former, nitroglycerine-potentiated HUT significantly increases the prevalence of prodromes in comparison with spontaneous episodes, which suggests that it may be useful not only for diagnosis but also for patient counseling.

Lack of association between genetic polymorphisms affecting sympathetic activity and tilt-induced vasovagal syncope.

Although the pathophysiology of vasovagal syncope is not completely understood, the involvement of sympathetic nervous system alterations has been suggested. Since predisposition to fainting during orthostatic challenge may be associated with genetic variations, we sought to explore the role of genetic polymorphisms affecting sympathetic nervous system function in the susceptibility to tilt-induced vasovagal syncope. We genotyped 129 subjects with recurrent unexplained syncope who underwent tilt testing, and investigated the recurrence of syncope. The analysed polymorphisms were Arg492Cys (ADRA1A gene), Ser49Gly and Arg389Gly (ADRB1), Arg16Gly and Gln27Glu (ADRB2), 825C/T (GNB3), -1021C/T (DBH) and S/L (SLC6A4). No association of the aforementioned genetic variants with both tilt test outcomes and new syncopal episodes during follow-up was found. None of the considered polymorphisms influencing sympathetic activity is a major risk factor for vasovagal syncope in Italian patients.

Clinical predictors of head-up tilt test outcome during the nitroglycerin phase.

OBJECTIVES: Nitrate-stimulated head-up tilt testing (HUT) is currently recommended to confirm the diagnosis of vasovagal syncope in subjects with syncope of unknown origin. Given the few data currently available, the aim of this study was to assess correlations between nitrate-induced HUT outcomes and the clinical characteristics of patients. METHODS: Two hundred and thirty consecutive, otherwise healthy subjects with a history of recurrent unexplained syncope underwent HUT. After 10 min supine rest, they were tilted to 70 degrees , and the test was potentiated by the administration of 300 microg of nitroglycerin after 20 min. RESULTS: Out of 178 subjects who underwent nitroglycerin administration during HUT, 95 fainted. At univariate Cox regression analysis, a reduced probability of VVS occurrence after nitrates was associated with greater systolic blood pressure and body mass index values, to male gender and smoking. At multivariate Cox regression analysis, only male gender (HR = 0.61; P = 0.039) and smoking (HR = 0.18; P = 0.001) remained significantly associated with HUT outcomes during the pharmacological phase of the test. INTERPRETATION: Smokers and males are less likely to faint after nitrate administration during HUT than non-smokers and females. Further studies should clarify the possibility of improving the diagnostic power of HUT in these patients.

Prevalence, timing, and haemodynamic correlates of prodromes in patients with vasovagal syncope induced by head-up tilt test.

AIMS: To evaluate the prevalence, timing, and haemodynamic characteristics of prodromal symptoms in patients experiencing vasovagal syncope (VVS) during a head-up tilt test (HUT) potentiated with nitroglycerin, and their relationships with those reported before spontaneous episodes. METHODS AND RESULTS: Symptoms preceding HUT-induced syncope were recorded, together with heart rate (HR) and arterial blood pressure (BP) values, in 149 otherwise healthy and drug-free subjects with recurrent unexplained syncope. Head-up tilt test significantly increase the number of patients capable of recognizing the premonitory symptoms of VVS than before spontaneous episodes (96 vs. 79%; P<0.001). The nine most frequent symptoms were stratified into three groups on the basis of their characteristics: headache, hot flashes, and palpitations occurred more than 3 min before syncope, with a very slight reduction in BP; nausea, asthenia, diaphoresis, vertigo, and epigastric discomfort preceded syncope by 1-3 min and were associated with a slight reduction in BP; and blurred vision appeared the last minute before syncope and was characterized by the lowest BP and HR values. CONCLUSION: In comparison with spontaneous syncopal episodes, HUT allows the more frequent recognition of prodromes also providing useful information in terms of timing and haemodynamic characteristics of symptoms that may allow more tailored patient counselling.

Endothelin system polymorphisms in tilt test-induced vasovagal syncope.

INTRODUCTION: Genetics may be involved in the pathophysiology of vasovagal syncope. The 3A/4A polymorphism of the EDN1 gene affects the expression of endothelin-1, and the H323H T/C polymorphism of the EDNRA gene encoding for the endothelin type A receptor has been associated with cardiovascular pathologies. As the endothelin system participates in the regulation of cardiovascular homeostasis, the aim of this study was to analyse the role of these genetic variants in influencing tilt-induced vasovagal syncope. MATERIALS AND METHODS: We recorded the cardiovascular parameters of 107 otherwise healthy subjects with recurrent unexplained syncope who underwent a head-up tilt test; 58 (54%) fainted. RESULTS: In terms of the EDNRA polymorphism, eight subjects (8%) had the T/T genotype, 41 were heterozygous (38%) and 58 homozygous (54%) for the C allele. Sixty subjects (56%) carried homozygosis for the 3A allele of the EDN1 polymorphism and 47 were heterozygous (44%). The 4A allele was significantly more frequent in the patients who responded positively to the tilt test than in those who did not: the relative odds ratios and confidence intervals at univariate and multivariate analyses were respectively 2.37 (1.07-5.26) and 2.41 (1.05-5.49). Comparisons with a control group further supported these data. Among the tilt-positive patients, the carriers of the 4A allele were more likely to have a vasodepressive pattern than those who were homozygous for the 3A variant. CONCLUSION: In conclusion, the 3A/4A polymorphism of the EDN1 gene affects susceptibility to syncope, and the 4A variant associated with increased endothhelin-1 expression may promote vasodepressive hemodynamic responses during tilt testing.

Endothelin system polymorphisms in tilt test-induced vasovagal syncope.

OBJECTIVES: As the endothelin system participates in the regulation of cardiovascular homeostasis, the aim of this study was to analyse the role of endothelin system polymorphisms in influencing tilt-induced vasovagal syncope. METHODS: We evaluated 107 otherwise healthy subjects with recurrent unexplained syncope who underwent a head-up tilt test. All subjects were genotyped for the 3A/4A polymorphism of the EDN1 gene and the H323H T/C polymorphism of the EDNRA gene. RESULTS: Fifty-eight patients (54%) fainted. In terms of the EDNRA polymorphism, eight subjects (8%) had the T/T genotype, 41 were heterozygous (38%) and 58 homozygous (54%) for the C allele. Sixty subjects (56%) carried homozygosis for the 3A allele of the EDN1 polymorphism and 47 were heterozygous (44%). The 4A allele was significantly more frequent in the patients who responded positively to the tilt test than in those who did not: the relative odds ratios and confidence intervals at univariate and multivariate analyses were respectively 2.37 (1.07-5.26) and 2.41 (1.05-5.49). Comparisons with a control group further supported these data. Among the tilt-positive patients, the carriers of the 4A allele were more likely to have a vasodepressive pattern than those who were homozygous for the 3A variant. INTERPRETATION: The 3A/4A polymorphism of the EDN1 gene affects susceptibility to syncope, and the 4A variant associated with increased endothelin-1 expression may promote vasodepressive hemodynamic responses during tilt testing.

Impaired arterial baroreflex function before nitrate-induced vasovagal syncope during head-up tilt test.

AIMS: The aim of this study was to evaluate arterial baroreflex control of heart rate immediately before head-up tilt test (HUT)-induced vasovagal syncope (VVS). METHODS AND RESULTS: We enrolled 97 otherwise healthy subjects with recurrent unexplained syncope. After 10 min of rest in supine position, they underwent a passive HUT potentiated with nitroglycerin administration after 20 min. Beat-to-beat heart rate and systolic blood pressure were continuously recorded. Sequence method was used to measure two complementary parameters reflecting arterial baroreflex control of heart rate: the baroreflex sensitivity (BRS) and the baroreflex effectiveness index (BEI). Twenty-one patients fainted before nitrate administration (HUT+) and 37 after nitrate administration (NTG+). Immediately before syncope, the NTG+ patients showed significantly lower BRS values than those observed at the end of the test in the patients without syncope (5.5 +/- 2.8 vs. 7.7 +/- 3.4 ms/mmHg; P = 0.004) and a significantly lower BEI (30 +/- 20% vs. 53 +/- 24%; P < 0.001). The HUT+ patients did not show any significant differences in BRS and BEI before syncope from the values observed during the corresponding tilt period in the other groups. CONCLUSION: A significant depression in BRS and BEI occurs immediately before syncope in patients who faint after nitrate administration, thus suggesting that arterial baroreflex dysfunction plays a role in mediating nitrate-induced VVS.

The 212A variant of the APJ receptor gene for the endogenous inotrope apelin is associated with slower heart failure progression in idiopathic dilated cardiomyopathy.

BACKGROUND: Idiopathic dilated cardiomyopathy (IDC) has multiple genetic and acquired causes. Apelin is an endogenous peptide that increases cardiac inotropism through his APJ receptor. No data are available concerning the APJ gene mutations responsible for IDC or on the role of APJ receptor gene variants in predicting heart failure (HF) progression. METHODS AND RESULTS: We prospectively evaluated 202 consecutive patients with IDC and 202 matched controls: 90 were screened for APJ gene mutations and all 202 were genotyped for G212A and A445C APJ receptor polymorphisms. No mutations were found within the coding or untranslated regions of the APJ receptor, and no differences in allelic or genotype frequencies were observed comparing patients with a healthy control population. The correlations between APJ receptor polymorphisms and HF progression were assessed. During a median follow-up of 37 months, 35 patients experienced HF progression. Univariate analysis showed that patients carrying at least 1 copy of 212A had a significantly lower risk for HF-related events than those who were homozygous for the G212 variant, and multivariate analysis confirmed that it was significantly related to a more favorable prognosis. CONCLUSIONS: APJ is unlikely to be a gene causing IDC, but the independent correlation between the 212A allele and a better prognosis suggests that it might act as a modifier gene.

Beta1- and beta2-adrenergic receptor polymorphisms affect susceptibility to idiopathic dilated cardiomyopathy.

OBJECTIVE: Beta1- and beta2-adrenergic receptors (ARs) play a pivotal role in myocardial function. We investigated whether functionally relevant polymorphisms within the genes encoding for these receptors indicate susceptibility to idiopathic dilated cardiomyopathy (DCM). METHODS: This case-control association study involved 189 patients with DCM and 378 gender- and age-matched control subjects. All of the subjects were characterised by polymerase chain reaction-restriction fragment length polymorphism analysis in terms of Ser49Gly and Arg389Gly polymorphisms in the beta1-AR, and the 5' leader cistron Arg19Cys, Arg16Gly, Gln27Glu, and Thr164Ile polymorphisms in the beta2-AR. Genotype, allele and haplotype frequencies were analysed. RESULTS: Univariate analysis showed that the distribution of genotype and allele frequencies of the beta1-Ser49Gly, beta1-Arg389Gly and beta2-Arg16Gly polymorphisms was significantly different between the patients and controls, and the beta1-Gly49/beta1-Arg389 haplotype was significantly more represented in the patients. Multivariate analysis showed that only the beta1-Gly49 variant (odds ratio 1.91; 95% confidence interval 1.24-2.95; P = 0.003) and beta2-Gly16Gly genotype (odds ratio 1.58; 95% confidence interval 1.10-2.26; P = 0.013) carriers were at significantly higher risk of developing DCM. CONCLUSIONS: In our population from southern Italy, the Gly49 allele of the beta1-AR and the Gly16Gly genotype of the beta2-AR were significantly and independently associated with the DCM phenotype, thus suggesting their role in favouring susceptibility to the disease.

Ventricular repolarization dynamicity provides independent prognostic information toward major arrhythmic events in patients with idiopathic dilated cardiomyopathy.

OBJECTIVES: The purpose of this work was to evaluate whether ventricular repolarization dynamicity predicts major arrhythmic events in patients with idiopathic dilated cardiomyopathy (DCM). BACKGROUND: Arrhythmic risk stratification in patients with DCM is still an open issue. Ventricular repolarization analysis should provide relevant information, but QT interval and QT dispersion failed in predicting arrhythmic risk. METHODS: The following parameters were evaluated in 179 consecutive DCM patients without history of sustained ventricular tachycardia (VT) and/or ventricular fibrillation (VF) at enrollment: QRS duration, QT interval corrected for heart rate, and QT dispersion at electrocardiogram (ECG); left ventricular ejection fraction (LVEF) and left ventricular end-diastolic diameter at echocardiogram; and nonsustained ventricular tachycardia (NSVT), heart rate variability (standard deviation of RR intervals), and ventricular repolarization dynamicity as measured by means of 24-h ECG monitoring, by calculating the slope of linear regression analysis of QT end and RR intervals (QTe-slope) and the value of mean QT end corrected for heart rate. RESULTS: During a mean follow-up of 39 months, 9 patients died suddenly and 15 experienced VT and/or VF. At multivariate analysis, LVEF (p = 0.047), NSVT (p = 0.022), and QTe-slope (p = 0.034) were significantly associated with arrhythmic events. Among the patients with a low LVEF, NSVT and/or steeper QTe-slope identified a subgroup at highest arrhythmic risk. CONCLUSIONS: In patients with DCM, QT dynamicity is independently associated with the occurrence of major arrhythmic events and improves the predictive accuracy of stratifying arrhythmic risk of these patients.

SCN5A polymorphism restores trafficking of a Brugada syndrome mutation on a separate gene.

BACKGROUND: Brugada syndrome is associated with a high risk of sudden cardiac death and is caused by mutations in the cardiac voltage-gated sodium channel gene. Previously, the R282H-SCN5A mutation in the sodium channel gene was identified in patients with Brugada syndrome. In a family carrying the R282H-SCN5A mutation, an asymptomatic individual had a common H558R-SCN5A polymorphism and the mutation on separate chromosomes. Therefore, we hypothesized that the polymorphism could rescue the mutation. METHODS AND RESULTS: In heterologous cells, expression of the mutation alone did not produce sodium current. However, coexpressing the mutation with the polymorphism produced significantly greater current than coexpressing the mutant with the wild-type gene, demonstrating that the polymorphism rescues the mutation. Using immunocytochemistry, we demonstrated that the R282H-SCN5A construct can traffic to the cell membrane only in the presence of the H558R-SCN5A polymorphism. Using fluorescence resonance energy transfer and protein fragments centered on H558R-SCN5A, we demonstrated that cardiac sodium channels preferentially interact when the polymorphism is expressed on one protein but not the other. CONCLUSIONS: This study suggests a mechanism whereby the Brugada syndrome has incomplete penetrance. More importantly, this study suggests that genetic polymorphisms may be a potential target for future therapies aimed at rescuing specific dysfunctional protein channels.

Alpha- and beta-adrenergic receptor polymorphisms in hypertensive and normotensive offspring.

BACKGROUND: The offspring of hypertensive families are characterized by higher arterial blood pressure values and a depressed autonomic control of heart rate. The present study aimed to verify whether these differences are associated with a different genotype distribution of functionally relevant polymorphisms of the alpha- and beta-adrenergic receptor (AR) genes. METHODS: We selected 109 age- and sex-matched young normotensive subjects with (FH+, n = 56) and without (FH-, n = 53) a family history of hypertension who underwent evaluation of arterial pressure; 24-h electrocardiogram monitoring to assess time-domain parameters of autonomic heart rate control [i.e. mean RR interval (NN), SD of RR intervals (SDNN) and mean square root of the differences of consecutive RR intervals (rMSSD)]; spectral baroreflex sensitivity measurement; and echo-Doppler to assess diastolic function and left ventricular mass. They were also characterized for the following polymorphisms by means of polymerase chain reaction-restriction fragment polymorphism analysis: Arg492Cys in the alpha1a-AR; Del301-303 in the alpha2b-AR; Ser49Gly and Arg389Gly in the beta1-AR; and the 5' leader cistron Arg19Cys, Arg16Gly and Gln27Glu in the beta2-AR. RESULTS: FH+ individuals showed a higher systolic pressure, a lower SDNN and a greater isovolumic relaxation time compared to normotensive offspring. No differences were found between the two groups when genotype distribution of the studied polymorphisms was considered. Subjects carrying alpha1a-AR Cys492 allelic variant showed lower values of NN, SDNN and rMSSD, independent of age, gender and body mass index. CONCLUSIONS: The functionally relevant polymorphisms of alpha2b-, beta1- and beta2-AR genes are not associated with a family history of essential hypertension. The Arg492Cys polymorphism of the alpha1a-AR gene, although not associated with a family history of hypertension, was strongly related to autonomic control of heart rate.