Maximal tachycardia and high cardiac strain during night shifts of emergency physicians

To compare tachycardia and cardiac strain between 24-hour shifts (24hS) and 14-hour night shifts (14hS) in emergency physicians (EPs), and to investigate key factors influencing tachycardia and cardiac strain. We monitored heart rate (HR) with Holter-ECG in a shift-randomized trial comparing a 24hS, a 14hS, and a control day, within a potential for 19 EPs. We also measured 24-h HR the third day (D3) after both shifts. We measured perceived stress by visual analog scale and the number of life-and-death emergencies. The 17 EPs completing the whole protocol reached maximal HR (180.9 +/- 6.9 bpm) during both shifts. Minutes of tachycardia > 100 bpm were higher in 24hS (208.3 +/- 63.8) than in any other days (14hS: 142.3 +/- 36.9; D3/14hS: 64.8 +/- 31.4; D3/24hS: 57.6 +/- 19.1; control day: 39.2 +/- 11.6 min, p < .05). Shifts induced a cardiac strain twice higher than in days not involving patients contact. Each life-and-death emergency enhanced 26 min of tachycardia ae<yen>100 bpm (p < .001), 7 min ae<yen> 110 bpm (p < .001), 2 min ae<yen> 120 bpm (p < .001) and 19 min of cardiac strain ae<yen>30% (p = .014). Stress was associated with greater duration of tachycardia ae<yen>100, 110 and 120 bpm, and of cardiac strain ae<yen>30% (p < .001). We demonstrated several incidences of maximal HR during shifts combined with a high cardiac strain. Duration of tachycardia were the highest in 24hS and lasted several hours. Such values are comparable to those of workers exposed to high physical demanding tasks or heat. Therefore, we suggest that EPs limit their exposure to 24hS. We, furthermore, demonstrated benefits of HR monitoring for identifying stressful events.