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The Emergence of Order in Space
Published in Pier Luigi Gentili, Untangling Complex Systems, 2018
A recent study (Nitsan et al. 2016) has demonstrated that the communication among the cardiac cells is not based only on electrochemical signals. In fact, there is also a mechanical communication that is essential for converting electrical pacing into synchronized beating. As mechanical coupling depends on the elastic properties of tissue, disruption of the normal mechanical environment can impair this interaction. For example, if there exists even a small region with disordered features, heterogeneities or defects, such as an unexcitable tissue, the excitation waves may be perturbed in passing through that region, and they may break apart (Glass 2001). When an excitation wave breaks, it leaves two free ends. These ends tend to curl up into spirals. Spiral waves have a larger speed (remember the eikonal equation [9.46]). Eventually, the heart tissue will oscillate at a higher frequency. This effect is thought to cause a heart disorder known as “paroxysmal tachycardia,” when the frequency of the heartbeat increases by a factor of ten (Cross and Hohenberg 1993). Another cardiac pathology, fibrillation, is thought to involve an inhomogeneous excitable medium in which an excitation target wave breaks up to form many spirals. The net result is the presence of many different structures vibrating asynchronously in a chaotic way.
Health problems among Swedish ambulance personnel: long-term risks compared to other professions in Sweden – a longitudinal register study
Published in International Journal of Occupational Safety and Ergonomics, 2022
Kåre Karlsson, Salmir Nasic, Lars Lundberg, Jan Mårtensson, Anders Jonsson
Table 2 shows in closer detail for ‘Diseases of the circulatory system’ (I00–I99) that AP has significantly higher risk for ‘Hypertensive diseases’ (I10–I15) than OP in cohort 2001. In ‘Other forms of heart disease’ (I30–I52), there is a significant risk in cohort 2008 for AP vs both HCW and OP but not in cohort 2001. In more detail, there is a significant risk for ‘Paroxysmal tachycardia, atrial fibrillation and flutter, other cardiac arrhythmias’ (I47–I49) for AP vs both HCW and OP in both cohort 2001 and cohort 2008. In ‘Hernia, noninfective enteritis and colitis, other diseases of intestines, diseases of peritoneum’ (K40–K67) we found a significant risk for AP vs OP in cohort 2001. In ‘Diseases of the musculoskeletal system and connective tissue’ (M00–M99), there was a significant risk for ‘Arthropathies’ (M00–M25) for AP vs OP in cohort 2001 and AP vs HCW and OP in cohort 2008. For ‘Gonarthrosis [arthrosis of knee]’ (M17), this was true for AP vs HCW and OP in cohort 2001 and AP vs OP in cohort 2008. For ‘Dorsopathies’ (M40–M54), risk was significant for AP vs HCW and OP in cohort 2001 and AP vs OP in cohort 2008. ‘Other intervertebral disc disorders’ (M51) was significant for AP vs HCW and OP in both cohort 2001 and cohort 2008. ‘Soft tissue disorders’ (M60–M79) was significant for AP vs OP in cohort 2008 (Table 2).