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Aims: The relationship between caffeine consumption and the occurrence of arrhythmias remains controversial. Despite this lack of scientific evidence, counselling to reduce caffeine consumption is still widely advised in clinical practice. We conducted a systematical review and meta-analysis of interventional studies of the caffeine effects on ventricular arrhythmias., Methods and Results: The search was performed on Pubmed, Embase, and Cochrane database, and terms related to coffee, caffeine, and cardiac arrhythmias were used. Methodological quality was assessed based on The Cochrane Collaboration recommendations and the ARRIVE guidelines. There were 2016 citations retrieved on the initial research. After full-text assessment, seven human and two animal studies were included in the meta-analysis. In animal studies, the main outcome reported was the ventricular fibrillation threshold. We observed a significant mean difference of -2.15 mA (95% CI -3.43 to -0.87; I(2) 0.0%, P for heterogeneity = 0.37). The main outcome evaluated in human studies was the rate of ventricular premature beats (VPBs). The overall relative risk for occurrence of VPBs in 24 h attributed to caffeine exposure was 1.00 (95% CI 0.94-1.06; I(2) 13.5%, P for heterogeneity = 0.32). Sensitivity analysis for caffeine dose, different designs, and subject profile was performed and no major differences were observed., Conclusion: Our meta-analysis demonstrates that data from human interventional studies do not show a significant effect of caffeine consumption on the occurrence of VBPs. The effects observed in animal studies are most probably the result of very high caffeine doses that are not regularly consumed in a daily basis by humans., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2015. For permissions please email: journals.permissions@oup.com.)

Objective: To evaluate the seasonal variation of ventricular arrhythmias and its correlation with ambient temperature in patients submitted to 24-hour Holter monitoring in the city of Porto Alegre, southern Brazil., Methods: Holter monitoring reports of 3,034 patients from 1996 to 2002 were analyzed. Ventricular tachycardia (VT) was defined as the presence of 3 or more consecutive ventricular beats, at a rate equal to or higher than 100 beats per minute. Percentage distribution of patients presenting VT by seasons and its correlation with ambient temperature were analyzed., Results: Mean age was 59.2 +/- 17.4 years, with a predominance of the female sex (61.9%). Patient distribution by season of the year was: 561 (18.5%) in summer, 756 (24.9%) in fall, 843 (27.8%) in winter and 874 (28.8%) in spring. Fifty-two patients (9.3%) presented VT episodes in summer, 39 (5.2%) in autumn, 56 (6.6%) in winter and 60 (6.9%) in spring (p = 0.035). There was a 40% relative increase in the proportion of patients presenting VT during summer in comparison to winter. There was a trend of increase in the proportion of patients presenting VT with rising temperatures (r = 0.57; p = 0.052)., Conclusion: The occurrence of VT presents seasonal variations in southern Brazil, with a higher proportion of episodes occurring in summer. There is an association trend between VT and temperature increase.