| 1. |
- Lahrouchi, Najim, et al.
(författare)
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Transethnic Genome-Wide Association Study Provides Insights in the Genetic Architecture and Heritability of Long QT Syndrome
- 2020
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Ingår i: Circulation. - : Lippincott Williams & Wilkins. - 0009-7322 .- 1524-4539. ; 142:4, s. 324-338
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Tidskriftsartikel (refereegranskat)abstract
- Background: Long QT syndrome (LQTS) is a rare genetic disorder and a major preventable cause of sudden cardiac death in the young. A causal rare genetic variant with large effect size is identified in up to 80% of probands (genotype positive) and cascade family screening shows incomplete penetrance of genetic variants. Furthermore, a proportion of cases meeting diagnostic criteria for LQTS remain genetically elusive despite genetic testing of established genes (genotype negative). These observations raise the possibility that common genetic variants with small effect size contribute to the clinical picture of LQTS. This study aimed to characterize and quantify the contribution of common genetic variation to LQTS disease susceptibility. Methods: We conducted genome-wide association studies followed by transethnic meta-analysis in 1656 unrelated patients with LQTS of European or Japanese ancestry and 9890 controls to identify susceptibility single nucleotide polymorphisms. We estimated the common variant heritability of LQTS and tested the genetic correlation between LQTS susceptibility and other cardiac traits. Furthermore, we tested the aggregate effect of the 68 single nucleotide polymorphisms previously associated with the QT-interval in the general population using a polygenic risk score. Results: Genome-wide association analysis identified 3 loci associated with LQTS at genome-wide statistical significance (P<5x10(-8)) nearNOS1AP,KCNQ1, andKLF12, and 1 missense variant inKCNE1(p.Asp85Asn) at the suggestive threshold (P<10(-6)). Heritability analyses showed that approximate to 15% of variance in overall LQTS susceptibility was attributable to common genetic variation (h2SNP0.148; standard error 0.019). LQTS susceptibility showed a strong genome-wide genetic correlation with the QT-interval in the general population (r(g)=0.40;P=3.2x10(-3)). The polygenic risk score comprising common variants previously associated with the QT-interval in the general population was greater in LQTS cases compared with controls (P<10-13), and it is notable that, among patients with LQTS, this polygenic risk score was greater in patients who were genotype negative compared with those who were genotype positive (P<0.005). Conclusions: This work establishes an important role for common genetic variation in susceptibility to LQTS. We demonstrate overlap between genetic control of the QT-interval in the general population and genetic factors contributing to LQTS susceptibility. Using polygenic risk score analyses aggregating common genetic variants that modulate the QT-interval in the general population, we provide evidence for a polygenic architecture in genotype negative LQTS.
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| 2. |
- Dahlberg, Pia, et al.
(författare)
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QT correction using Bazett's formula remains preferable in long QT syndrome type 1 and 2
- 2021
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Ingår i: Annals of Noninvasive Electrocardiology. - : John Wiley & Sons. - 1082-720X .- 1542-474X. ; 26:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: The heart rate (HR) corrected QT interval (QTc) is crucial for diagnosis and risk stratification in the long QT syndrome (LQTS). Although its use has been questioned in some contexts, Bazett's formula has been applied in most diagnostic and prognostic studies in LQTS patients. However, studies on which formula eliminates the inverse relation between QT and HR are lacking in LQTS patients. We therefore determined which QT correction formula is most appropriate in LQTS patients including the effect of beta blocker therapy and an evaluation of the agreement of the formulae when applying specific QTc limits for diagnostic and prognostic purposes.Methods: Automated measurements from routine 12-lead ECGs from 200 genetically confirmed LQTS patients from two Swedish regions were included (167 LQT1, 33 LQT2). QT correction was performed using the Bazett, Framingham, Fridericia, and Hodges formulae. Linear regression was used to compare the formulae in all patients, and before and after the initiation of beta blocking therapy in a subgroup (n = 44). Concordance analysis was performed for QTc >= 480 ms (diagnosis) and >= 500 ms (prognosis).Results: The median age was 32 years (range 0.1-78), 123 (62%) were female and 52 (26%) were children <= 16 years. Bazett's formula was the only method resulting in a QTc without relation with HR. Initiation of beta blocking therapy did not alter the result. Concordance analyses showed clinically significant differences (Cohen's kappa 0.629-0.469) for diagnosis and prognosis in individual patients.Conclusion: Bazett's formula remains preferable for diagnosis and prognosis in LQT1 and 2 patients.
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| 3. |
- Diamant, Ulla-Britt, 1955-, et al.
(författare)
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Electrophysiological phenotype in the LQTS mutations Y111C and R518X in the KCNQ1 gene
- 2013
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Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 115:10, s. 1423-1432
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Tidskriftsartikel (refereegranskat)abstract
- Long QT syndrome is the prototypical disorder of ventricular repolarization (VR), and a genotype-phenotype relation is postulated. Furthermore, although increased VR heterogeneity (dispersion) may be important in the arrhythmogenicity in long QT syndrome, this hypothesis has not been evaluated in humans and cannot be tested by conventional electrocardiography. In contrast, vectorcardiography allows assessment of VR heterogeneity and is more sensitive to VR alterations than electrocardiography. Therefore, vectorcardiography was used to compare the electrophysiological phenotypes of two mutations in the LQT1 gene with different in vitro biophysical properties, and with LQT2 mutation carriers and healthy control subjects. We included 99 LQT1 gene mutation carriers (57 Y111C, 42 R518X) and 19 LQT2 gene mutation carriers. Potassium channel function is in vitro most severely impaired in Y111C. The control group consisted of 121 healthy subjects. QRS, QT, and T-peak to T-end (Tp-e) intervals, measures of the QRS vector and T vector and their relationship, and T-loop morphology parameters were compared at rest. Apart from a longer heart rate-corrected QT interval (QT heart rate corrected according to Bazett) in Y111C mutation carriers, there were no significant differences between the two LQT1 mutations. No signs of increased VR heterogeneity were observed among the LQT1 and LQT2 mutation carriers. QT heart rate corrected according to Bazett and Tp-e were longer, and the Tp-e-to-QT ratio greater in LQT2 than in LQT1 and the control group. In conclusion, there was a marked discrepancy between in vitro potassium channel function and in vivo electrophysiological properties in these two LQT1 mutations. Together with previous observations of the relatively low risk for clinical events in Y111C mutation carriers, our results indicate need for cautiousness in predicting in vivo electrophysiological properties and the propensity for clinical events based on in vitro assessment of ion channel function alone.
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| 4. |
- Diamant, Ulla-Britt, 1955-
(författare)
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Long QT syndrome : studies of diagnostic methods
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: The Long QT Syndrome (LQTS) is a hereditary heart disease with risk of malignant ventricular arrhythmia and sudden cardiac death. Despite our increased knowledge about genotype and phenotype correlation we still rely on the 12-lead ECG for assessment of the QT interval and the T-wave morphology for diagnosis and risk stratification. Intra- and -inter individual variability in manually QT measurement and, e.g., difficulties in defining the end of the T-wave may impair the diagnosis of LQTS. Increased heterogeneity in ventricular repolarization (VR) may be an important factor in the arrhythmogenicity in cases of LQTS. In a LQTS founder population the same mutation is carried by numerous individuals in many families which provide a unique opportunity to study diagnostic methods, risk assessment, VR and the correlation between genotype and phenotype.Methods: Resting 12-lead ECG and vectorcardiogram (VCG) were recorded in 134 LQTS mutation carriers and 121 healthy controls, to investigate the capability and precision in measuring the QT interval. For assessment of the VR, VCG was compared in individuals with mutations in the KCNQ1 and KCNH2 gene. Genealogical and geographic studies were performed in 37 index cases and their relatives to determine if Swedish carriers of the Y111C mutation in the KCNQ1 gene constitute a founder population. To confirm kinship, haplotype analysis was performed in 26 of the 37 index cases. The age and prevalence of the Y111C mutation were calculated in families sharing a common haplotype.Results: VCG by automatic measurement of the QT interval provided the best combination of sensitivity (90%) and specificity (89%) in the diagnosis of LQTS. VCG showed no consistent pattern of increased VR heterogeneity among KCNQ1 and KCNH2 mutation carriers. Living carriers of the Y111C mutation shared a common genetic (haplotype), genealogic and geographic origin. The age of the Y111C mutation was approximately 600 years. The prevalence of living carriers of the Y111C mutation in the mid-northern Sweden was estimated to 1:1,500-3,000.Conclusion: We have shown that VCG provides a valuable contribution to the diagnosis and risk assessment of LQTS in adults and children. No consistent pattern of increased VR heterogeneity was found among the LQTS mutation carriers. The identified Swedish LQTS founder population will be a valuable source to future LQTS research and may contribute to increase our understanding of LQTS and the correlation of phenotype, genotype and modifying factors.
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| 5. |
- Diamant, Ulla-Britt, et al.
(författare)
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LQTS founder population in Northern Sweden – the natural history of a potentially fatal inherited cardiac disorder
- 2021
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Ingår i: Biodemography and Social Biology. - : Routledge. - 1948-5565 .- 1948-5573. ; 66:3-4, s. 191-207
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Tidskriftsartikel (refereegranskat)abstract
- Long QT Syndrome (LQTS) is an autosomal dominant inherited cardiac disorder associated with life-threatening arrhythmias. In northern Sweden, a LQTS founder mutation (p.Y111C, KCNQ1 gene) was verified by genetic haplotype analysis and genealogical studies, and a common ancestor couple was identified. Clinical studies of this population revealed an apparent mild phenotype. However, due to early commencement of prophylactic treatment, the natural history of this disorder cannot be properly assessed based only on clinical data. By using the family tree mortality ratio method (FTMR), we assessed the natural history of the untreated LQTS founder population. The principle of FTMR is to compare the age-specific mortality rates in a historic population harboring an inherited disorder with the corresponding mortality rates in an unaffected control population.Initially, we used the general Swedish population during the same period for comparison and observed an apparent increased longevity in the p.Y111C study population. However, when using a control population born in the same area, we observed no differences regarding overall mortality. Moreover, patterns suggesting age- and sex-stratified excess mortality, in accordance with previous LQTS studies, were evident.This study shows the importance of being aware of historical demographic patterns to avoid misinterpreting when comparing historical data.
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| 6. |
- Diamant, Ulla-Britt, et al.
(författare)
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Two automatic QT algorithms compared with manual measurement in identification of long QT syndrome
- 2010
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Ingår i: Journal of Electrocardiology. - : Elsevier BV. - 0022-0736 .- 1532-8430. ; 43:1, s. 25-30
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Long QT syndrome (LQTS) is an inherited disorder that increases the risk of syncope and malignant ventricular arrhythmias, which may result in sudden death.METHODS: We compared manual measurement by 4 observers (QT(manual)) and 3 computerized measurements for QT interval accuracy in the diagnosis of LQTS: 1. QT measured from the vector magnitude calculated from the 3 averaged orthogonal leads X, Y, and Z (QTVCG) and classified using the same predefined QTc cut-points for classification of QT prolongation as in manual measurements; 2. QT measured by a 12-lead electrocardiogram (ECG) program (QTECG) and subsequently classified using the same cut-points as in (1) above; 3. The same QT value as in (2) above, automatically classified by a 12-lead ECG program with thresholds for QT prolongation adjusted for age and sex (QTinterpret). The population consisted of 94 genetically confirmed carriers of KCNQ1 (LQT1) and KCNH2 (LQT2) mutations and a combined control group of 28 genetically confirmed noncarriers and 66 unrelated healthy volunteers.RESULTS: QT(VCG) provided the best combination of sensitivity (89%) and specificity (90%) in diagnosing LQTS, with 0.948 as the area under the receiver operating characteristic curve. The evaluation of QT measurement by the 4 observers revealed a high interreader variability, and only 1 of 4 observers showed acceptable level of agreement in LQTS mutation carrier identification (kappa coefficient >0.75).CONCLUSION: Automatic QT measurement by the Mida1000/CoroNet system (Ortivus AB, Danderyd, Sweden) is an accurate, efficient, and easily applied method for initial screening for LQTS.
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| 7. |
- Diamant, Ulla-Britt, et al.
(författare)
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Vectorcardiographic recordings of the Q-T interval in a pediatric long Q-T syndrome population
- 2013
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Ingår i: Pediatric Cardiology. - : Springer Science and Business Media LLC. - 0172-0643 .- 1432-1971. ; 34:2, s. 245-249
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of the Q-T interval are less reliable in children than in adults. Identification of superior diagnostic tools is warranted. This study aimed to investigate whether a vectorcardiogram (VCG) recorded from three orthogonal leads (X, Y, Z) according to Frank is superior to a 12-lead electrocardiogram (ECG) in providing a correct long Q-T syndrome (LQTS) diagnosis in children. This LQTS group consisted of 35 genetically confirmed carriers of mutations in the KCNQ1 (n = 29) and KCNH2 (n = 6) genes. The control group consisted of 35 age- and gender-matched healthy children. The mean age was 7 years in the LQTS group and 6.7 years in the control group (range, 0.5-16 years). The corrected Q-T interval (QT(c)) was measured manually (QT(man)) by one author (A.W.). The 12-lead ECG automatic measurements (QT(ECG)) and interpretation (QT(Interpret)) of QT(c) were performed with the Mac5000 (GE Medical System), and the VCG automatic measurements (QT(VCG)) were performed with the Mida1000, CoroNet (Ortivus AB, Sweden). By either method, a QT(c) longer than 440 ms was considered prolonged and indicative of LQTS. Of the 35 children with genetically confirmed LQTS, 30 (86 %) received a correct diagnosis using QT(VCG), 29 (82 %) using QT(man), 24 (69 %) using QT(ECG), and 17 (49 %) using QT(Interpret). Specificity was 0.80 for QT(VCG), 0.83 for QT(man), 0.77 for QT(ECG), and 0.83 for QT(Interpret). The VCG automatic measurement of QT(c) seems to be a better predictor of LQTS than automatic measurement and interpretation of 12-lead ECG.
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| 8. |
- Mörner, Stellan, et al.
(författare)
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Ärftliga hjärt–kärlsjukdomar – ett multidisciplinärt arbetssätt krävs : [Experiences from a multidisciplinary cardiogenetic clinic]
- 2021
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Ingår i: Läkartidningen. - : Läkartidningen Förlag AB. - 0023-7205 .- 1652-7518. ; 118:40
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Tidskriftsartikel (refereegranskat)abstract
- Comprehensive genetic and clinical care of families with monogenic cardiovascular diseases requires competences from different medical specialties. Genetic assessment, cascade screening, risk estimation, treatment and follow-up is difficult to cover. Fourteen years ago, a center for cardiovascular diseases was created in our hospital, to improve the care of families with monogenic cardiovascular diseases. At our center, clinical geneticists, cardiologists, angiologists, pediatric cardiologists and genetic counselors work together in a seamless organization, while still having different clinic affiliations. A key feature of this organization are the family outpatient clinics, where the proband and his/her relatives at genetic risk are invited to take part. When the family or relatives live in other parts of the country, they are invited to participate through video conference. In this paper we report our experiences and working routines from more than 300 families and 2000 individuals.
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| 9. |
- Nilsson, Ulf, et al.
(författare)
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The prevalence of prolonged QTc by spirometric classification in a populationbased cohort : normal lung function, restrictive pattern and airway obstruction
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Background Prolonged QT (corrected for heart rate, QTc) is associated with malignantarrhythmias. Cardiovascular comorbidity contributes to the increased mortality in COPD, butthe role of QTc is unclear.Aim The aim of this population-based study was to estimate the prevalence of QTcprolongation among subjects with normal lung function (NLF), airway obstruction (fixedratio, GOLD-COPD and Lower Limit of Normal, LLN-COPD) and restrictive spirometricpattern (RSP). Furthermore, to evaluate the prognostic impact of QTc prolongation.Method After re-examination of population-based cohorts in 2002-04, all individuals (n=993)with airway obstruction were identified together with age and sex-matched referents withoutairway obstruction. In 2005, the study-population was invited to examination includingspirometry, structured interview and 12-lead ECG, and QTc was calculated. Mortality datawere collected until December 31st, 2010.Results The study-population included NLF (n=734), RSP (n=175) and GOLD-COPD(n=571) whereof 299 LLN-COPD. RSP had longer mean QTc and higher prevalence ofprolonged QTc than NLF. GOLD-COPD, LLN-COPD and NLF had similar mean QTc andprevalence of prolonged QTc. In GOLD-COPD and LLN-COPD, the prevalence of prolongedQTc increased by GOLD-grade (test for trend p=0.002 and 0.043) and the cumulativemortality was higher in subjects with borderline and prolonged QTc in both groups, comparedto normal QTc. This was not the case in NLF or RSP.Conclusion The prevalence of prolonged QTc was higher in RSP than NLF, while it wassimilar in COPD and NLF, but increased by GOLD-grade in COPD. QTc prolongation wasassociated with increased mortality in GOLD-COPD and LLN-COPD but not in NLF or RSP.
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| 10. |
- Nilsson, Ulf, et al.
(författare)
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The prevalence of prolonged QTc increases by GOLD stage, and is associated with worse survival among subjects with COPD
- 2019
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Ingår i: Heart & Lung. - : Elsevier BV. - 0147-9563 .- 1527-3288. ; 48:2, s. 148-154
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Tidskriftsartikel (refereegranskat)abstract
- Background: The role of QTc-prolongation, in relation to the increased mortality in COPD, is unclear. Objectives: To estimate the prevalence and prognostic impact, assessed as mortality, of QTc-prolongation in COPD, restrictive spirometric pattern (RSP), and normal lung function (NLF), respectively. Methods: All individuals (n = 993) with COPD and age- and sex-matched non-obstructive referents were identified from well-defined population-based cohorts examined in Northern Sweden in 2002-04. In 2005, the study-sample was invited to re-examination including ECG; QTc was calculated and mortality data collected until 31st December 2010. Results: The prevalence of QTc-prolongation was higher among people with RSP than among those with NLF and, although similar in NLF and COPD, the prevalence increased by COPD-severity. Among participants with COPD, those with QTc prolongation had higher mortality than those with normal QTc, while no such differences were found among participants with NLF or RSP. Conclusion: Among participants with COPD, the prevalence of QTc-prolongation increased by disease-severity and was associated with mortality. (C) 2018 Elsevier Inc. All rights reserved.
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