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Aims: It is unknown whether cardiac syncope, and possibly also other syncope aetiologies exhibit circadian, weekly, seasonal, and temperature-dependent patterns., Methods and Results: We prospectively recorded the exact time, date, and outside temperature of syncope of patients >40 years old presenting with syncope to the emergency department in a diagnostic multicentre study. Two independent cardiologists/emergency physicians adjudicated the final diagnosis based on all information becoming available during clinical work-up including 1-year follow-up. Among 1230 patients, the adjudicated aetiology was cardiac in 14.6%, reflex in 39.2%, orthostatic in 25.7%, other non-cardiac in 9.7%, and unknown in 10.8% of patients. All syncope aetiologies occurred much more frequently during the day when compared with the night (P < 0.01). While reflex and orthostatic syncope showed a broad peak of prevalence with 80.9% of these events occurring between 4 am and 4 pm, cardiac syncope showed a narrow peak of prevalence with 70.1% of all events occurring between 8 am and 2 pm. A weekly pattern was present for most syncope aetiologies, with events occurring mainly from Monday to Friday (P < 0.01). Reflex syncope displayed a seasonal rhythm and was more common in winter (P < 0.01), while cardiac syncope stayed constant over the year. Syncope occurred most often when the outside temperature was coldest. Overall the patterns observed for cardiac syncope were similar to the patterns observed for its differential diagnosis., Conclusion: Syncope aetiologies in patients >40 years old display circadian, weekly, seasonal, and temperature-dependent patterns. Unfortunately, these patterns do not allow to reliably differentiate cardiac syncope from other aetiologies., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2018. For permissions, please email: journals.permissions@oup.com.)

Background: Combining 2 signals of cardiomyocyte injury, cardiac troponin I (cTnI) and T (cTnT), might overcome some individual pathophysiological and analytical limitations and thereby increase diagnostic accuracy for acute myocardial infarction with a single blood draw. We aimed to evaluate the diagnostic performance of combinations of high-sensitivity (hs) cTnI and hs-cTnT for the early diagnosis of acute myocardial infarction., Methods: The diagnostic performance of combining hs-cTnI (Architect, Abbott) and hs-cTnT (Elecsys, Roche) concentrations (sum, product, ratio, and a combination algorithm) obtained at the time of presentation was evaluated in a large multicenter diagnostic study of patients with suspected acute myocardial infarction. The optimal rule-out and rule-in thresholds were externally validated in a second large multicenter diagnostic study. The proportion of patients eligible for early rule-out was compared with the European Society of Cardiology 0/1 and 0/3 hour algorithms., Results: Combining hs-cTnI and hs-cTnT concentrations did not consistently increase overall diagnostic accuracy as compared with the individual isoforms. However, the combination improved the proportion of patients meeting criteria for very early rule-out. With the European Society of Cardiology 2015 guideline recommended algorithms and cut-offs, the proportion meeting rule-out criteria after the baseline blood sampling was limited (6% to 24%) and assay dependent. Application of optimized cut-off values using the sum (9 ng/L) and product (18 ng 2 /L 2 ) of hs-cTnI and hs-cTnT concentrations led to an increase in the proportion ruled-out after a single blood draw to 34% to 41% in the original (sum: negative predictive value [NPV] 100% [95% confidence interval (CI), 99.5% to 100%]; product: NPV 100% [95% CI, 99.5% to 100%]) and in the validation cohort (sum: NPV 99.6% [95% CI, 99.0-99.9%]; product: NPV 99.4% [95% CI, 98.8-99.8%]). The use of a combination algorithm (hs-cTnI <4 ng/L and hs-cTnT <9 ng/L) showed comparable results for rule-out (40% to 43% ruled out; NPV original cohort 99.9% [95% CI, 99.2-100%]; NPV validation cohort 99.5% [95% CI, 98.9-99.8%]) and rule-in (positive predictive value [PPV] original cohort 74.4% [95% Cl, 69.6-78.8%]; PPV validation cohort 84.0% [95% Cl, 79.7-87.6%])., Conclusions: New strategies combining hs-cTnI and hs-cTnT concentrations may significantly increase the number of patients eligible for very early and safe rule-out, but do not seem helpful for the rule-in of acute myocardial infarction., Clinical Trial Registration: URL (APACE): https://www.clinicaltrial.gov . Unique identifier: NCT00470587. URL (ADAPT): www.anzctr.org.au . Unique identifier: ACTRN12611001069943.