Figure 5.

Illustration of the causes of the higher number of arrhythmic events in the afternoon. According to the circadian pattern, sympathetic tone (along with the heart rate and blood pressure) is higher in the early morning and in the late afternoon and lower during the evening and the night [32]. Desmosomal remodelling causes sodium channel and calcium handling alterations, with electromechanical alterations [26,31] that are part of the arrhythmic substrate. Ion channels and calcium handling are also circadian-regulated [19]. Their alteration causes a circadian rhythm malfunction with a further increase in sympathetic tone [28]. The threshold for arrhythmic events is, therefore, lower. Moreover, in the afternoon, the level of physical activity is higher than in the morning [33,34,35,36]. Therefore, increased physical activity may act as a trigger for ventricular arrhythmia in the afternoon. Free clip art from https://creazilla.com (accessed on 9 February 2022) and https://smart.servier.com (accessed on 9 February 2022).