Effects of beta-blockers on ventricular repolarization documented by 24-hour electrocardiography in long QT syndrome type 2

Peer reviewe

Replicated evidence for aminoacylase 3 and nephrin gene variations to predict antihypertensive drug responses

Peer reviewe

Genealogy and clinical course of catecholaminergic polymorphic ventricular tachycardia caused by the ryanodine receptor type 2 P2328S mutation

Background Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a severe inherited arrhythmic disease associated with a risk of syncope and sudden cardiac death (SCD).Aims We aimed at identifying RYR2 P2328S founder mutation carriers and describing the clinical course associated with the mutation.Methods The study population was drawn from the Finnish Inherited Cardiac Disorder Research Registry, and from the present genealogical study. Kaplan-Meier graphs, log-rank test and Cox regression model were used to evaluate the clinical course.Results Genealogical study revealed a common ancestor couple living in the late 17(th) century. A total of 1837 living descendants were tested for RYR2 P2328S mutation unveiling 62 mutation carriers aged mean 3923 years old. No arrhythmic deaths were documented among genotyped subjects, but 11 SCDs were detected in non-genotyped family members since 1970. Three genotyped patients (5%) suffered an aborted cardiac arrest (ACA), and 15 (25%) had a syncope triggered by exercise or stress. Rate of cardiac events was higher among patients who in exercise stress test showed a maximum rate of premature ventricular contractions >30/min (68% vs 17%, p<0.01; hazard ratio = 7.1, p = 0.02), in comparison to patients without the respective finding. A cardioverter-defibrillator (ICD) was implanted to 13 (22%) patients, with an appropriate ICD shock in four (31%) subjects. All ICD shocks, one ACA, and one syncope occurred during -blocker medication.Conclusions Previously undiagnosed CPVT patients may be identified by well-conducted genealogical studies. The RYR2 P2328S mutation causes a potentially severe phenotype, but its expression is variable, thus calling for additional studies on modifying factors

Clinical and molecular genetic risk determinants in adult long QT syndrome type 1 and 2 patients

Background: Long QT syndrome (LQTS) is an inherited cardiac disorder predisposing to sudden cardiac death (SCD). We studied factors affecting the clinical course of genetically confirmed patients, in particular those not receiving beta-blocker treatment. In addition, an attempt was made to associate risk of events to specific types of KCNQ1 and KCNH2 mutations. Methods: A follow-up study covering a mean of 18.6 +/- 6.1 years was conducted in 867 genetically confirmed LQT1 and LQT2 patients and 654 non-carrier relatives aged 18-40 years. Cox regression models were used to evaluate the contribution of clinical and genetic risk factors to cardiac events. Results: In mutation carriers, risk factors for cardiac events before initiation of beta-blocker included LQT2 genotype (hazard ratio [HR] = 2.1, p = 0.002), female gender (HR = 3.2, p = 500 ms (vs G and other KCNQ1 mutation carriers after adjusting for gender, QTc duration, and cardiac events before age 18. KCNH2 c. 453delC, L552S and R176W mutations associated with lower risk (HR = 0.11-0.23, p <0.001) than other KCNH2 mutations. Conclusions: LQT2 (compared to LQT1), female gender, a cardiac event before age 18, and long QT interval increased the risk of cardiac events in LQTS patients aged 18 to 40 years. The nature of the underlying mutation may be associated with risk variation in both LQT1 and LQT2. The identification of high-risk and low-risk mutations may enhance risk stratification.Peer reviewe

An actionable KCNH2 Long QT Syndrome variant detected by sequence and haplotype analysis in a population research cohort

The Viking Health Study Shetland is a population-based research cohort of 2,122 volunteer participants with ancestry from the Shetland Isles in northern Scotland. The high kinship and detailed phenotype data support a range of approaches for associating rare genetic variants, enriched in this isolate population, with quantitative traits and diseases. As an exemplar, the c.1750G > A; p.Gly584Ser variant within the coding sequence of the KCNH2 gene implicated in Long QT Syndrome (LQTS), which occurred once in 500 whole genome sequences from this population, was investigated. Targeted sequencing of the KCNH2 gene in family members of the initial participant confirmed the presence of the sequence variant and identified two further members of the same family pedigree who shared the variant. Investigation of these three related participants for whom single nucleotide polymorphism (SNP) array genotypes were available allowed a unique shared haplotype of 1.22 Mb to be defined around this locus. Searching across the full cohort for this haplotype uncovered two additional apparently unrelated individuals with no known genealogical connection to the original kindred. All five participants with the defined haplotype were shown to share the rare variant by targeted Sanger sequencing. If this result were verified in a healthcare setting, it would be considered clinically actionable, and has been actioned in relatives ascertained independently through clinical presentation. The General Practitioners of four study participants with the rare variant were alerted to the research findings by letters outlining the phenotype (prolonged electrocardiographic QTc interval). A lack of detectable haplotype sharing between c.1750G > A; p.Gly584Ser chromosomes from previously reported individuals from Finland and those in this study from Shetland suggests that this mutation has arisen more than once in human history. This study showcases the potential value of isolate population-based research resources for genomic medicine. It also illustrates some challenges around communication of actionable findings in research participants in this context.Peer reviewe

Is Symptomatic Long QT Syndrome Associated with Depression in Women and Men?

We examined whether long QT syndrome (LQTS) mutation carrier status or symptomatic LQTS are associated with depression, and whether there are sex differences in these potential relationships. The sample comprised 782 participants (252 men). Of the 369 genetically defined LQTS mutation carriers, 169 were symptomatic and 200 were asymptomatic. The control group consisted of 413 unaffected relatives. Depression was assessed using the Beck Depression Inventory-II (BDI-II). No association was found for LQTS mutation carrier status with depression. The multinomial logistic regression showed that LQTS mutation carrier men with arrhythmic events scored higher on depression compared with the control group, even when adjusting for age, beta-blockers, antidepressants, and social support (OR = 1.09, 95 % CI [1.02, 1.15], p = .007). The binary logistic regression comparing symptomatic and asymptomatic LQTS mutation carriers showed that symptomatic LQTS was associated with depression in men (OR = 1.10, 95 % CI [1.03, 1.19], p = .009). The results were unchanged when additionally adjusted for education. These findings suggest that symptomatic LQTS is associated with depression in men but not in women. Overall, however, depression is more frequent in women than men. Thus, regular screening for depression in LQTS mutation carriers and their unaffected family members can be important.Peer reviewe

Genealogy and clinical course of catecholaminergic polymorphic ventricular tachycardia caused by the ryanodine receptor type 2 P2328S mutation

Background Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a severe inherited arrhythmic disease associated with a risk of syncope and sudden cardiac death (SCD). Aims We aimed at identifying RYR2 P2328S founder mutation carriers and describing the clinical course associated with the mutation. Methods The study population was drawn from the Finnish Inherited Cardiac Disorder Research Registry, and from the present genealogical study. Kaplan-Meier graphs, log-rank test and Cox regression model were used to evaluate the clinical course. Results Genealogical study revealed a common ancestor couple living in the late 17(th) century. A total of 1837 living descendants were tested for RYR2 P2328S mutation unveiling 62 mutation carriers aged mean 3923 years old. No arrhythmic deaths were documented among genotyped subjects, but 11 SCDs were detected in non-genotyped family members since 1970. Three genotyped patients (5%) suffered an aborted cardiac arrest (ACA), and 15 (25%) had a syncope triggered by exercise or stress. Rate of cardiac events was higher among patients who in exercise stress test showed a maximum rate of premature ventricular contractions >30/min (68% vs 17%, p-blocker medication. Conclusions Previously undiagnosed CPVT patients may be identified by well-conducted genealogical studies. The RYR2 P2328S mutation causes a potentially severe phenotype, but its expression is variable, thus calling for additional studies on modifying factors.Peer reviewe