Browsing by Subject "Long QT syndrome"

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    Calmodulin mutations and life-threatening cardiac arrhythmias: insights from the International Calmodulinopathy Registry
    (Oxford University Press, 2016-06-06) Crotti, Lia; Spazzolini, Carla; Tester, David J; Ghidoni, Alice; Baruteau, Alban-Elouen; Beckmann, Britt-Maria; Behr, Elijah R; Bennett, Jeffrey S; Bezzina, Connie R; Bhuiyan, Zahurul A; Celiker, Alpay; Cerrone, Marina; Dagradi, Federica; De Ferrari, Gaetano M; Etheridge, Susan P; Fatah, Meena; Garcia-Pavia, Pablo; Al-Ghamdi, Saleh; Hamilton, Robert M; Al-Hassnan, Zuhair N; Horie, Minoru; Jimenez-Jaimez, Juan; Kanter, Ronald J.; Kaski, Juan P.; Kotta, Maria-Christina; Lahrouchi, Najim; Makita, Naomasa; Norrish, Gabrielle; Odland, Hans H.; Ohno, Seiko; Papagiannis, John; Parati, Gianfranco; Sekarski, Nicole; Tveten, Kristian; Vatta, Matteo; Webster, Gregory; Wilde, Arthur A. M.; Wojciak, Julianne; George, Alfred L., Jr; Ackerman, Michael J.; Schwartz, Peter J.; Medical and Molecular Genetics, School of Medicine
    Aims Calmodulinopathies are rare life-threatening arrhythmia syndromes which affect mostly young individuals and are, caused by mutations in any of the three genes (CALM 1–3) that encode identical calmodulin proteins. We established the International Calmodulinopathy Registry (ICalmR) to understand the natural history, clinical features, and response to therapy of patients with a CALM-mediated arrhythmia syndrome. Methods and results A dedicated Case Report File was created to collect demographic, clinical, and genetic information. ICalmR has enrolled 74 subjects, with a variant in the CALM1 (n = 36), CALM2 (n = 23), or CALM3 (n = 15) genes. Sixty-four (86.5%) were symptomatic and the 10-year cumulative mortality was 27%. The two prevalent phenotypes are long QT syndrome (LQTS; CALM-LQTS, n = 36, 49%) and catecholaminergic polymorphic ventricular tachycardia (CPVT; CALM-CPVT, n = 21, 28%). CALM-LQTS patients have extremely prolonged QTc intervals (594 ± 73 ms), high prevalence (78%) of life-threatening arrhythmias with median age at onset of 1.5 years [interquartile range (IQR) 0.1–5.5 years] and poor response to therapies. Most electrocardiograms (ECGs) show late onset peaked T waves. All CALM-CPVT patients were symptomatic with median age of onset of 6.0 years (IQR 3.0–8.5 years). Basal ECG frequently shows prominent U waves. Other CALM-related phenotypes are idiopathic ventricular fibrillation (IVF, n = 7), sudden unexplained death (SUD, n = 4), overlapping features of CPVT/LQTS (n = 3), and predominant neurological phenotype (n = 1). Cardiac structural abnormalities and neurological features were present in 18 and 13 patients, respectively. Conclusion Calmodulinopathies are largely characterized by adrenergically-induced life-threatening arrhythmias. Available therapies are disquietingly insufficient, especially in CALM-LQTS. Combination therapy with drugs, sympathectomy, and devices should be considered.
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    Calmodulinopathy in inherited arrhythmia syndromes
    (Wolters Kluwer, 2021-04-14) Tsai, Wen‑Chin; Chen, Peng‑Sheng; Rubart, Michael; Medicine, School of Medicine
    Calmodulin (CaM) is a ubiquitous intracellular calcium sensor that controls and regulates key cellular functions. In all vertebrates, three CaM genes located on separate chromosomes encode an identical 149 amino acid protein, implying an extraordinarily high level of evolutionary importance and suggesting that CaM mutations would be possibly fatal. Inherited arrhythmia syndromes comprise a spectrum of primary electrical disorders caused by mutations in genes encoding ion channels or associated proteins leading to various cardiac arrhythmias, unexplained syncope, and sudden cardiac death. CaM mutations have emerged as an independent entity among inherited arrhythmia syndromes, referred to as calmodulinopathies. The most common clinical presentation associated with calmodulinopathy is congenital long QT syndrome, followed by catecholaminergic polymorphic ventricular tachycardia, both of which significantly increase the possibility of repeated syncope, lethal arrhythmic events, and sudden cardiac death, especially in young individuals. Here, we aim to give an overview of biochemical and structural characteristics of CaM and progress toward updating current known CaM mutations and associated clinical phenotypes. We also review the possible mechanisms underlying calmodulinopathy, based on several key in vitro studies. We expect that further experimental studies are needed to explore the complexity of calmodulinopathy.
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    A Case for Inclusion of Genetic Counselors in Cardiac Care
    (Wolters Kluwer, 2016-03) Arscott, Patricia; Caleshu, Colleen; Kotzer, Katrina; Kreykes, Sarah; Kruisselbrink, Teresa; Orland, Kate; Rigelsky, Christina; Smith, Emily; Spoonamore, Katherine; Larsen Haidle, Joy; Marvin, Monica; Ackerman, Michael J.; Hadi, Azam; Mani, Arya; Ommen, Steven; Cherny, Sara; Department of Medicine, IU School of Medicine
    Recent advances in genetic testing for heritable cardiac diseases have led to an increasing involvement of the genetic counselor in cardiology practice. We present a series of cases collected from a nationwide query of genetics professionals regarding issues related to cost and utilization of genetic testing. Three themes emerged across cases: (1) choosing the most appropriate genetic test, (2) choosing the best person to test, and (3) interpreting results accurately. These cases demonstrate that involvement of a genetic counselor throughout the evaluation, diagnosis, and continuing management of individuals and families with inherited cardiovascular conditions helps to promote the efficient use of healthcare dollars.
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    Clinical presentation of calmodulin mutations: the International Calmodulinopathy Registry
    (Oxford University Press, 2023) Crotti, Lia; Spazzolini, Carla; Nyegaard, Mette; Overgaard, Michael T.; Kotta, Maria-Christina; Dagradi, Federica; Sala, Luca; Aiba, Takeshi; Ayers, Mark D.; Baban, Anwar; Barc, Julien; Beach, Cheyenne M.; Behr, Elijah R.; Bos, J. Martijn; Cerrone, Marina; Covi, Peter; Cuneo, Bettina; Denjoy, Isabelle; Donner, Birgit; Elbert, Adrienne; Eliasson, Håkan; Etheridge, Susan P.; Fukuyama, Megumi; Girolami, Francesca; Hamilton, Robert; Horie, Minoru; Iascone, Maria; Jiménez-Jaimez, Juan; Jensen, Henrik Kjærulf; Kannankeril, Prince J.; Kaski, Juan P.; Makita, Naomasa; Muñoz-Esparza, Carmen; Odland, Hans H.; Ohno, Seiko; Papagiannis, John; Porretta, Alessandra Pia; Prandstetter, Christopher; Probst, Vincent; Robyns, Tomas; Rosenthal, Eric; Rosés-Noguer, Ferran; Sekarski, Nicole; Singh, Anoop; Spentzou, Georgia; Stute, Fridrike; Tfelt-Hansen, Jacob; Till, Jan; Tobert, Kathryn E.; Vinocur, Jeffrey M.; Webster, Gregory; Wilde, Arthur A. M.; Wolf, Cordula M.; Ackerman, Michael J.; Schwartz, Peter J.; Pediatrics, School of Medicine
    Aims: Calmodulinopathy due to mutations in any of the three CALM genes (CALM1-3) causes life-threatening arrhythmia syndromes, especially in young individuals. The International Calmodulinopathy Registry (ICalmR) aims to define and link the increasing complexity of the clinical presentation to the underlying molecular mechanisms. Methods and results: The ICalmR is an international, collaborative, observational study, assembling and analysing clinical and genetic data on CALM-positive patients. The ICalmR has enrolled 140 subjects (median age 10.8 years [interquartile range 5-19]), 97 index cases and 43 family members. CALM-LQTS and CALM-CPVT are the prevalent phenotypes. Primary neurological manifestations, unrelated to post-anoxic sequelae, manifested in 20 patients. Calmodulinopathy remains associated with a high arrhythmic event rate (symptomatic patients, n = 103, 74%). However, compared with the original 2019 cohort, there was a reduced frequency and severity of all cardiac events (61% vs. 85%; P = .001) and sudden death (9% vs. 27%; P = .008). Data on therapy do not allow definitive recommendations. Cardiac structural abnormalities, either cardiomyopathy or congenital heart defects, are present in 30% of patients, mainly CALM-LQTS, and lethal cases of heart failure have occurred. The number of familial cases and of families with strikingly different phenotypes is increasing. Conclusion: Calmodulinopathy has pleiotropic presentations, from channelopathy to syndromic forms. Clinical severity ranges from the early onset of life-threatening arrhythmias to the absence of symptoms, and the percentage of milder and familial forms is increasing. There are no hard data to guide therapy, and current management includes pharmacological and surgical antiadrenergic interventions with sodium channel blockers often accompanied by an implantable cardioverter-defibrillator.
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    Clinician Responses to a Clinical Decision Support Advisory for High Risk of Torsades de Pointes
    (American Heart Association, 2022) Gallo, Tyler; Heise, C. William; Woosley, Raymond L.; Tisdale, James E.; Tan, Malinda S.; Gephart, Sheila M.; Antonescu, Corneliu C.; Malone, Daniel C.; Medicine, School of Medicine
    Background: Torsade de pointes (TdP) is a potentially fatal cardiac arrhythmia that is often drug induced. Clinical decision support (CDS) may help minimize TdP risk by guiding decision making in patients at risk. CDS has been shown to decrease prescribing of high‐risk medications in patients at risk of TdP, but alerts are often ignored. Other risk‐management options can potentially be incorporated in TdP risk CDS. Our goal was to evaluate actions clinicians take in response to a CDS advisory that uses a modified Tisdale QT risk score and presents management options that are easily selected (eg, single click). Methods and Results: We implemented an inpatient TdP risk advisory systemwide across a large health care system comprising 30 hospitals. This CDS was programmed to appear when prescribers attempted ordering medications with a known risk of TdP in a patient with a QT risk score ≥12. The CDS displayed patient‐specific information and offered relevant management options including canceling offending medications and ordering electrolyte replacement protocols or ECGs. We retrospectively studied the actions clinicians took within the advisory and separated by drug class. During an 8‐month period, 7794 TdP risk advisories were issued. Antibiotics were the most frequent trigger of the advisory (n=2578, 33.1%). At least 1 action was taken within the advisory window for 2700 (34.6%) of the advisories. The most frequent action taken was ordering an ECG (n=1584, 20.3%). Incoming medication orders were canceled in 793 (10.2%) of the advisories. The frequency of each action taken varied by drug class (P<0.05 for all actions). Conclusions: A modified Tisdale QT risk score–based CDS that offered relevant single‐click management options yielded a high action/response rate. Actions taken by clinicians varied depending on the class of the medication that evoked the TdP risk advisory, but the most frequent was ordering an ECG.
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    Human Nav1.5 F1486 deletion associated with long-QT syndrome leads to deficiency in inactivation and reduces lidocaine sensitivity
    (2012-03-19) Song, Weihua; Shou, Weinian; Cummins, Theodore R.; Chen, Peng-Sheng; Hudmon, Andrew; Nass, Richard; Khanna, Rajesh
    The cardiac voltage-gated sodium channel α subunit Nav1.5 generates the cardiac sodium current, which is essential for the initiation and propagation of the cardiac action potentials. Mutations of SCN5A, the gene that encodes Nav1.5, have been well documented to cause long-QT syndrome (LQTs) by disrupting channel inactivation and increasing late sodium current. Previous studies have revealed the importance of the intracellular loop region between transmembrane domain III and IV of sodium channel α subunit in regulating the fast inactivation. A recent clinical case study reported an infant patient with LQTs carrying a phenylalanine (F) deletion at amino acid 1486 of the Nav1.5 channel. This study reported that the patient showed severe cardiac arrhythmia reflected as LQTs and subsequent ventricular tachycardia, which was refractory to antiarrhythmic drug lidocaine treatment. Therefore, it was hypothesized that the deletion of F1486 on Nav1.5 would substantially alter electrophysiological properties of the channel and reduce the potency of lidocaine on sodium channel. Using HEK293 cells and neonatal rat cardiomyocytes, the F1486del channel was functionally characterized by whole-cell patch clamp techniques. Studies revealed that the deletion of F1486 causes a combination of changes including a loss-of-function alteration reflected as a substantial reduction of peak current density and a number of gain-of-function alterations including reduced channel inactivation, substantial augmentation of late sodium current, and an increase in ramp current. In addition, lidocaine sensitivity was dramatically reduced. By contrast, the voltage for half maximal activation (V1/2) and the time constant for channel deactivation for the F1486del channel were identical to the wild type channels. Using neonatal rat cardiomyocytes, we were able to study the functional consequence of F1484del on action potential duration (APD). Cardiomyocytes expressing F1486del channel have substantial APD prolongation and prominent spontaneous early afterdepolarizations, which likely underlie the subsequent LQTs in the patient. Taken together, despite the reduction in peak current density, the substantial gain-of-function changes are sufficient to cause the APD prolongation, which is a prominent characteristic of LQTs. These findings provide knowledge for understanding the relationships between sodium channel structure, pharmacology and the physiological consequence of sodium channel mutations that underlie LQT3.
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    Incidence of Corrected QT Prolongation With Concomitant Methadone and Atypical Antipsychotics in Critically Ill Children
    (Allen Press, 2021) Hughes, Kaitlin M.; Thorndyke, Anne; Tillman, Emma M.; Pediatrics, School of Medicine
    Objective: To evaluate the safety of the combination of methadone and an atypical antipsychotic in PICU patients. Methods: This was a retrospective observational cohort pilot study in a single-center PICU in an academic children's hospital. Children 1 month to 18 years of age were included if they received methadone, were then initiated on an atypical antipsychotic (i.e., quetiapine or risperidone), and had EKG monitoring before and after medication initiation. Results: Prolongation of the corrected QT (QTc) interval occurred in 5 of the 34 included patients when an atypical antipsychotic was added to methadone. Of the 5 patients who had a prolonged QTc interval, 4 (80%) were older than 12 years and had a median weight of 91.3 kg. There were statistical differences between age and weight when comparing patients who experienced QTc prolongation, but no differences in sex, ethnicity, electrolyte deficiencies, number of additional QTc-prolonging medications, and number of additional drug-drug interactions were identified. When comparing atypical antipsychotics, 9.5% of patients receiving risperidone had a prolonged QTc interval, versus 23% of patients receiving quetiapine (p = 0.04). The net change in QTc interval after initiation of methadone was 0.19 milliseconds (IQR: -3, 15), which increased after atypical antipsychotic initiation to 4 milliseconds (IQR: -16, 15). Conclusions: Our pilot trial suggests there is no clinically significant difference in incidence of QTc prolongation with addition of atypical antipsychotics to methadone.
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    Maternal mosaicism in long QT syndrome due to a pathogenic variant in KCNH2
    (Elsevier, 2020-11-16) Sawyer, Briana L.; Tristani-Firouzi, Martin; Wells, Layne E.; Vatta, Matteo; Etheridge, Susan P.; Medical and Molecular Genetics, School of Medicine