Faculty Bibliography

Continued research into the identification of mutated genes that cause inherited arrhythmogenic diseases has helped forward understanding into their pathophysiology. Over the last two decades the progress that has been made in the realm of genetic arrhythmias has made it possible not only for symptomatic patients to improve their outcomes, but also family members to better understand their risks and allow them in conjunction with their care providers to make the best decisions for their care. With this continued progress, significant changes will continue to occur in clinical practice. The advances in technology coupled with the improving understanding of genetically determined arrhythmias assists in earlier recognition of potentially fatal diseases, which leads to earlier implementation of treatment. It is the aim of this article to abridge the current knowledge of the genetic background of inherited arrhythmogenic diseases, namely long QT syndrome, short QT syndrome, Brugada syndrome and catecholaminergic polymorphic ventricular tachycardia. Pathogenesis and genotype-phenotype correlations are also discussed

Informatics for Integrating Biology and the Bedside (i2b2) is an initiative funded by the NIH that aims at building an informatics infrastructure to support biomedical research. The University of Pavia has recently integrated i2b2 infrastructure with a registry of inherited arrhythmogenic diseases. Within this project, the authors created a novel i2b2 cell, named R Engine Cell, which allows the communication between i2b2 and the R statistical software. As survival analyses are routinely performed by cardiology researchers, the authors have first concentrated on making Kaplan-Meier analyses available within the i2b2 web interface. To this aim, the authors developed a web-client plug-in to select the patient set on which to perform the analysis and to display the results in a graphical, intuitive way. R Engine Cell has been designed to easily support the integration of other R-based statistical analyses into i2b2

Although clinical trial results and the implementation of current guidelines appear to have encouraged progress in the treatment of arrhythmias, great discrepancies still exist between European Society of Cardiology (ESC) member countries. Guidelines are not adhered to for a variety of reasons. This cannot be explained only by economic factors, although these obviously play a substantial role. Other factors responsible for adequate guideline implementation appear to be the lack of trained personnel, the lack of infrastructure, or different health insurance systems. In this complex scenario, the data based on European registries are useful for creating standards and harmonizing the treatment of arrhythmias. Moreover, a summary of registry data, such as presented in the European Heart Rhythm Association (EHRA) White Book, can provide the opportunity to share and exchange information among ESC member countries on specific needs for improvements, reimbursement policy, and training issues

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmogenic disease occurring in patients with a structurally normal heart: the disease is characterized by life-threatening arrhythmias elicited by stress and emotion. In 2001, the ryanodine receptor was identified as the gene that is linked to CPVT; shortly thereafter, cardiac calsequestrin was implicated in the recessive form of the same disease. It became clear that abnormalities in intracellular Ca(2+) regulation could profoundly disrupt the electrophysiological properties of the heart. In this article, we discuss the molecular basis of the disease and the pathophysiological mechanisms that are impacting clinical diagnosis and management of affected individuals. As of today, the interaction between basic scientists and clinicians to understand CPVT and identify new therapeutic strategies is one of the most compelling examples of the importance of translational research in cardiology

OBJECTIVES: We aimed to identify risk factors for recurrent syncope in children and adolescents with congenital long QT syndrome (LQTS). BACKGROUND: Data regarding risk assessment in LQTS after the occurrence of the first syncope episode are limited. METHODS: The Prentice-Williams-Peterson conditional gap time model was used to identify risk factors for recurrent syncope from birth through age 20 years among 1,648 patients from the International Long QT Syndrome Registry. RESULTS: Multivariate analysis demonstrated that corrected QT interval (QTc) duration (>/=500 ms) was a significant predictor of a first syncope episode (hazard ratio: 2.16), whereas QTc effect was attenuated when the end points of the second, third, and fourth syncope episodes were evaluated (hazard ratios: 1.29, 0.99, 0.90, respectively; p < 0.001 for the null hypothesis that all 4 hazard ratios are identical). A genotype-specific subanalysis showed that during childhood (0 to 12 years), males with LQTS type 1 had the highest rate of a first syncope episode (p = 0.001) but exhibited similar rates of subsequent events as other genotype-sex subsets (p = 0.63). In contrast, in the age range of 13 to 20 years, long QT syndrome type 2 females experienced the highest rate of both first and subsequent syncope events (p < 0.001 and p = 0.01, respectively). Patients who experienced >/=1 episodes of syncope had a 6- to 12-fold (p < 0.001 for all) increase in the risk of subsequent fatal/near-fatal events independently of QTc duration. Beta-blocker therapy was associated with a significant reduction in the risk of recurrent syncope and subsequent fatal/near-fatal events. CONCLUSIONS: Children and adolescents who present after an episode of syncope should be considered to be at a high risk of the development of subsequent syncope episodes and fatal/near-fatal events regardless of QTc duration

OBJECTIVES: We investigated whether increased Ca(2+)/calmodulin-dependent kinase II (CaMKII) activity aggravates defective excitation-contraction coupling and proarrhythmic activity in mice expressing R4496C mutated cardiac ryanodine receptors (RyR2). BACKGROUND: RyR2 dysfunction is associated with arrhythmic events in inherited and acquired cardiac disease. METHODS: CaMKIIdeltac transgenic mice were crossbred with RyR2(R4496C+/-) knock-in mice. RESULTS: Heart weight-to-body weight ratio in CaMKIIdeltac/RyR2(R4496C) and CaMKIIdeltac mice was similarly increased approximately 3-fold versus wild-type mice (p < 0.05). Echocardiographic data showed comparable cardiac dilation and impaired contractility in CaMKIIdeltac/RyR2(R4496C) and CaMKIIdeltac mice. Sarcoplasmic reticulum Ca(2+) content in isolated myocytes was decreased to a similar extent in CaMKIIdeltac/RyR2(R4496C) and CaMKIIdeltac mice. However, relaxation parameters and Ca(2+) decay at 1 Hz were prolonged significantly in CaMKIIdeltac mice versus CaMKIIdeltac/RyR2(R4496C) mice. Sarcoplasmic reticulum Ca(2+) spark frequency and characteristics indicated increased sarcoplasmic reticulum Ca(2+) leak in CaMKIIdeltac/RyR2(R4496C) versus CaMKIIdeltac myocytes (p < 0.05), most likely because of increased RyR2 phosphorylation. Delayed afterdepolarizations were significantly more frequent with increased amplitudes in CaMKIIdeltac/RyR2(R4496C) versus CaMKIIdeltac mice. Increased arrhythmias in vivo (67% vs. 25%; p < 0.05) may explain the increased mortality in CaMKIIdeltac/RyR2(R4496C) mice, which died prematurely with only 30% alive (vs. 60% for CaMKIIdeltac, p < 0.05) after 14 weeks. CONCLUSIONS: CaMKIIdeltac overexpression in RyR2(R4496C+/-) knock-in mice increases the propensity toward triggered arrhythmias, which may impair survival. CaMKII contributes to further destabilization of a mutated RyR2 receptor