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Background: Symptomatic children with catecholaminergic polymorphic ventricular tachycardia (CPVT) are at risk for recurrent arrhythmic events. Beta-blockers (BBs) decrease this risk, but studies comparing individual BBs in sizeable cohorts are lacking. We aimed to assess the association between risk for arrhythmic events and type of BB in a large cohort of symptomatic children with CPVT. Methods: From two international registries of patients with CPVT, RYR2 variant-carrying symptomatic children (defined as syncope or sudden cardiac arrest prior to BB initiation and age at start of BB therapy

AIMS: Atrial fibrillation (AF) and heart failure (HF) are two growing epidemics that frequently co-exist. We aimed to gain insights into underlying pathophysiological pathways in HF patients with AF by comparing circulating biomarkers using pathway overrepresentation analyses. METHODS AND RESULTS: From a panel of 92 biomarkers from different pathophysiological domains available in 1,620 patients with HF, we first tested which biomarkers were dysregulated in patients with HF and AF (n = 648) compared with patients in sinus rhythm (n = 972). Secondly, pathway overrepresentation analyses were performed to identify biological pathways linked to higher plasma concentrations of biomarkers in patients who had HF and AF. Findings were validated in an independent HF cohort (n = 1,219, 38\% with AF). Patient with AF and HF were older, less often women, and less often had a history of coronary artery disease compared with those in sinus rhythm. In the index cohort, 24 biomarkers were upregulated in patients with AF and HF. In the validation cohort, 8 biomarkers were upregulated, which all overlapped with the 24 biomarkers found in the index cohort. The strongest up-regulated biomarkers in patients with AF were spondin-1 (fold change 1.18, p = 1.33x10-12), insulin-like growth factor-binding protein-1 (fold change 1.32, p = 1.08x10-8), and insulin-like growth factor-binding protein-7 (fold change 1.33, p = 1.35x10-18). Pathway overrepresentation analyses revealed that the presence of AF was associated with activation amyloid-beta metabolic processes, amyloid-beta formation, and amyloid precursor protein catabolic processes with a remarkable consistency observed in the validation cohort. CONCLUSION: In two independent cohorts of patients with HF, the presence of AF was associated with activation of three pathways related to amyloid-beta. These hypothesis-generating results warrant confirmation in future studies. TRANSLATIONAL PERSPECTIVE: Using an unbiased approach, we identified and validated dysregulation of three amyloid-beta related pathways in patients who had heart failure (HF) with concomitant atrial fibrillation (AF). Amyloid-beta depositions are a hallmark of Alzheimer's disease, but might also play a role in pathophysiological processes outside the central nervous system. Biopsy studies are needed to confirm the pathophysiological role of amyloid-beta in patients with AF and HF. Diagnostic and therapeutic implications should be investigated in the light of potential pathophysiological overlap between the three aging-related epidemics: Alzheimer's disease, AF and HF.