UNASSIGNED: Brugada syndrome is an inheritable arrhythmia condition that is associated with rare, loss-of-function variants in SCN5A. Interpreting the pathogenicity of SCN5A missense variants is challenging, and ≈79% of SCN5A missense variants in ClinVar are currently classified as variants of uncertain significance. Automated patch clamp technology enables high-throughput functional studies of ion channel variants and can provide evidence for variant reclassification.
UNASSIGNED: An in vitro SCN5A-Brugada syndrome automated patch clamp assay was generated and independently studied at Vanderbilt University Medical Center and Victor Chang Cardiac Research Institute. The assay was calibrated according to ClinGen Sequence Variant Interpretation recommendations using high-confidence variant controls (n=49). Normal and abnormal ranges of function were established based on the distribution of benign variant assay results. Odds of pathogenicity values were derived from the experimental results according to ClinGen Sequence Variant Interpretation recommendations. The calibrated assay was then used to study SCN5A variants of uncertain significance observed in 4 families with Brugada syndrome and other arrhythmia phenotypes associated with SCN5A loss-of-function.
UNASSIGNED: Variant channel parameters generated independently at the 2 research sites showed strong correlations, including peak INa density (R2=0.86). The assay accurately distinguished benign controls (24/25 concordant variants) from pathogenic controls (23/24 concordant variants). Odds of pathogenicity values yielded 0.042 for normal function and 24.0 for abnormal function, corresponding to strong evidence for both American College of Medical Genetics and Genomics/Association for Molecular Pathology benign and pathogenic functional criteria (BS3 and PS3, respectively). Application of the assay to 4 clinical SCN5A variants of uncertain significance revealed loss-of-function for 3/4 variants, enabling reclassification to likely pathogenic.
UNASSIGNED: This validated high-throughput assay provides clinical-grade functional evidence to aid the classification of current and future SCN5A-Brugada syndrome variants of uncertain significance.

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Calmodulin (CaM) is a ubiquitous, small cytosolic calcium (Ca2+)-binding sensor that plays a vital role in many cellular processes by binding and regulating the activity of over 300 protein targets. In cardiac muscle, CaM modulates directly or indirectly the activity of several proteins that play a key role in excitation-contraction coupling (ECC), such as ryanodine receptor type 2 (RyR2),  l-type Ca2+ (Cav1.2), sodium (NaV1.5) and potassium (KV7.1) channels. Many recent clinical and genetic studies have reported a series of CaM mutations in patients with life-threatening arrhythmogenic syndromes, such as long QT syndrome (LQTS) and catecholaminergic polymorphic ventricular tachycardia (CPVT). We recently showed that four arrhythmogenic CaM mutations (N98I, D132E, D134H, and Q136P) significantly reduce the binding of CaM to RyR2. Herein, we investigate in vivo functional effects of these CaM mutations on the normal zebrafish embryonic heart function by microinjecting complementary RNA corresponding to CaMN98I, CaMD132E, CaMD134H, and CaMQ136P mutants. Expression of CaMD132E and CaMD134H mutants results in significant reduction of the zebrafish heart rate, mimicking a severe form of human bradycardia, whereas expression of CaMQ136P results in an increased heart rate mimicking human ventricular tachycardia. Moreover, analysis of cardiac ventricular rhythm revealed that the CaMD132E and CaMN98I zebrafish groups display an irregular pattern of heart beating and increased amplitude in comparison to the control groups. Furthermore, circular dichroism spectroscopy experiments using recombinant CaM proteins reveals a decreased structural stability of the four mutants compared to the wild-type CaM protein in the presence of Ca2+. Finally, Ca2+-binding studies indicates that all CaM mutations display reduced CaM Ca2+-binding affinities, with CaMD132E exhibiting the most prominent change. Our data suggest that CaM mutations can trigger different arrhythmogenic phenotypes through multiple and complex molecular mechanisms.

BACKGROUND: Factors associated with cardiovascular complications of COVID-19 remain understudied.
OBJECTIVE: Here we investigate the occurrence and risk factors of arrythmias, myocardial infarction and/or stroke, and thromboembolism in the course of COVID-19.
METHODS: We have performed an observational study with prospectively designed data collection. Data of patients diagnosed with COVID-19 who were admitted from March 6th 2020 to November 30th 2021 in our Hospital were analyzed. Logistic regression was used to identify variables associated with the odds of early hospital death due to COVID-19.
RESULTS: Fourteen-point three percent of 1964 patients had cardiovascular complications, 6.36 % arrhythmias, 5.5 % thromboembolic events and 2.39 % myocardial infarction and/or stroke. Factors independently increasing the odds of arrhythmia were older age (OR=1.49 [95 % CI: 1.17-1.92], p = 0.02), longer time between admission and the first onset of symptoms (1.02 [0.99-1.05], p = 0.049), concomitant atrial fibrillation/flutter (2.84 [1.37-5.70], p = 0.004), nicotinism (2.49 [1.37-4.49], p = 0.002), and eGFR<60 ml/min/1.73m2 (2.44 [1.08-5.59], p = 0.033). Factors independently increasing the odds of myocardial infarction and/or stroke were dementia (4.55 [0.97-19.3], p = 0.044), hemiplegia (12.67 [3.12-46.1], p < 0.001), nicotinism (3.36 [1.30-10.4], p = 0.013) and higher C-reactive protein concentration (1.01 [1.00-1.01], p = 0.040). Factors independently increasing the odds of thromboembolic events were longer hospitalization (1.08 [1.05-1.10], p < 0.001) and higher d-dimers (1.04 [1.02-1.05], <0.001).
CONCLUSIONS: The risk of cardiovascular complications was especially pronounced in patients with older age, pre-existing cardiovascular disease and more sever pneumonia at presentation to care. This underlines the importance of close and careful clinical follow-up in the course of COVID-19 for specific patients\' populations, including a pro-active approach in diagnosis.

OBJECTIVE: Guidelines recommend insertable cardiac monitor (ICM) in the early phases of the evaluation of unexplained syncope (US) syncope, when an arrhythmic etiology is suspected. We examined the diagnostic yield of the last generation ICM (LG-ICM) to establish the causes of US, by assessing in the clinical practice the incidence of: relevant arrhythmia diagnosis, syncope recurrences and CM-guided cardiac electronic device (CIED) implantation. We investigated also baseline patient characteristics associated to an increased risk of relevant arrhythmias and of syncope recurrence.
METHODS: Data prospectively collected from consecutive patients receiving LG-ICM for investigation of US or presyncope in our institution between November 2020 and January 2023 were analyzed.
RESULTS: A total of 109 patients (mean age 64.4 ± 16.1 years, 40.4% women) with US or pre-syncope episodes underwent implantation of the LG-ICM. During a mean follow-up of 11.7 ± 8.1 months, LG-ICM diagnostic yield was 42% . In particular, LG-ICM detected cardiac arrhythmias in 29 (27%) patients (in 6 out of them during a syncope recurrence) and to exclude the arrhythmic origin of the syncope in additional 19 (17%) patients. LG-ICM guided the implantation of a CIED in 16 (15%) US patients, due to the diagnosis of asystole or severe bradycardia. Age ≥ 65 years (p = 0.012) and atrial arrhythmia history (p = 0.004) are significant independent predictors of arrhythmic diagnoses performed by LG-ICM, while CAD is predictor of syncope recurrence (bordering on statistical significance, p = 0.056).
CONCLUSIONS: The diagnostic yield of LG-ICM in US syncope is comparable to those of ILR and previous generation ICM. The advantages of LG-ICM should be sought in lower hospital workload necessary to manage ICM data. Age ≥ 65 years and atrial arrhythmia history are independent predictors of significant ICM-detected arrhythmias.

UNASSIGNED: Patients with congenital heart disease (CHD) have a higher incidence of arrhythmias during pregnancy, yet the utility of mobile cardiac telemetry (MCT) to predict adverse outcomes is unknown.
UNASSIGNED: The purpose of this study is to determine whether arrhythmias on screening MCT correlate with adverse pregnancy outcomes.
UNASSIGNED: Patients with CHD prospectively enrolled in the Standardized Outcomes in Reproductive Cardiovascular Care initiative underwent 24-hour MCT (within 18 months prior to pregnancy). Positive findings on MCT were defined as episodes of bradyarrhythmia, symptomatic atrioventricular block, ectopic atrial or ventricular activity, and supraventricular or ventricular tachycardia. Clinically significant arrhythmia events (CSAEs) were those requiring medical or device intervention or an emergency room visit. Clinical events during the antepartum, intrapartum, and postpartum periods were compared using Fisher\'s exact test. Analyses were performed using Stata version 16.
UNASSIGNED: In 141 pregnancies in 118 patients with CHD, MCT detected positive findings in 17%. Adverse cardiac outcomes occurred in 11% of pregnancies, of which CSAE occurred in 3.5%. Positive MCT was significantly associated with subsequent CSAE (21% vs 0%, P < 0.001) and cumulative adverse maternal cardiac outcomes (33% vs 7%, P = 0.001) but did not correlate with obstetric (46% vs 41%, P = 0.660) or neonatal outcomes (33% vs 31%, P = 0.810). Of the patients with CSAE, 75% had ≥moderate CHD complexity.
UNASSIGNED: Patients with CHD had a high rate of positive MCT findings. This was associated with CSAE and adverse maternal cardiac outcomes. Patients with ≥moderate CHD complexity may benefit from screening MCT to improve preconceptual counseling and planning.

Tuberous sclerosis is a rare genetic disorder involving mainly the nervous and cardiovascular systems. The early recognition of the cardiovascular manifestations by the pediatrician allows an appropriate management and therefore enhances the quality of life of the affected children. Cardiac rhabdomyomas and the associated arrhythmias are the first cardiac features and they might represent a diagnosis challenge given their wide spectrum of clinical manifestations. We aimed to provide the paediatric practitioners with current knowledge regarding the cardiovascular complications in children with tuberous sclerosis. We overviewed the antenatal and postnatal evolution of cardiovascular manifestations, the systematic screening and long-term follow-up strategy of cardiac rhabdomyomas and arrhythmias in children with tuberous sclerosis.

Flecainide is a medication used to treat supraventricular and ventricular tachyarrhythmias. Cases of overdoses are rare, however, can lead to significant cardiac effects. In previous cases of flecainide toxicity, treatment with sodium bicarbonate, intravenous lipid emulsion and amiodarone have been reported to be effective in preventing cardiovascular collapse and reestablishing baseline rhythm. Here, we present a case of a man in his 40s presented with flecainide overdose with wide-complex tachycardia that was treated with intravenous sodium bicarbonate following failure of amiodarone to normalise QRS interval.

OBJECTIVE: To assess congenital fetal bradyarrhythmias with regard to etiological causes, features, risk factors, and prognosis.
METHODS: This retrospective study involved fetuses with fetal bradyarrhythmias. All fetuses were evaluated by ultrasonography. Parental ECGs and family histories were obtained, and maternal autoantibodies were measured. Gestational age at diagnosis, fetal atrial and ventricular rates at presentation, type of bradyarrhythmias, the presence or absence of a congenital heart defect (CHD), fetal hydrops, fetal myocardial dysfunction, extra-cardiac abnormalities, maternal autoimmune diseases, maternal autoantibodies as well as prenatal treatment, and neonatal outcome were collected.
RESULTS: Of the 40 fetuses included in the study, 11 had maternal rheumatologic disease, 16 had complex cardiac anomalies such as left and right isomerism. Fetuses with CHD significantly differed from those without CHD with increased rates of extra-cardiac anomalies, hydrops, fetal deaths and shorter survival after 28 days (p<0.05). Survival was significantly better in fetuses with maternal rheumatic disease as compared with those with no maternal rheumatic disease (p<0.05). Maternal anti-arrhythmic therapy was administered in 11 fetuses. In utero maternal treatment resulted in no significant difference in the course of arrhythmia or hydrops in fetuses with or without maternal rheumatic disease (p<0.05). In regression analysis, the absence of fetal hydrops was the only independent factor associated with survival (p=0.04).
CONCLUSIONS: The course of bradyarrhythmias, along with survival, seems to be more favorable in fetuses with maternal rheumatic disease than in those with CHD, especially left and right isomerism. Hydrops was the sole independent factor associated with poor survival.

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