Thoracic impedance during national holidays

Abstract Background Several studies have observed increased incidence of myocardial infarctions during Christmas and national holidays. Emotional stress, overindulgence in food and alcohol have been suggested as potential underlying mechanisms. Monitoring of thoracic impedance (TI) by cardiac implantable electronic devices (CIED) has been proposed as a tool for detection of fluid accumulation. We aimed to assess the relationship between TI and national holidays in patients treated with CIED with and without reduced left ventricular ejection fraction (LVEF). Method Consecutive patients with CIED capable of TI monitoring enrolled in the remote monitoring program at a tertiary care hospital in Sweden were screened. Full disclosure remote CIED monitoring database containing daily measurements of TI and device therapy delivery was accessed as the source of information for this retrospective cohort study. Patients were included if they had the monitoring data for at least one holiday (Christmas, New Year or Midsummer) between June 2015 and January 2020. TI during the holiday was compared with baseline values, defined as a mean value of three days preceding Christmas Eve and Midsummer. Clinical characteristics, LVEF, medical treatment and possible contact with healthcare during the holidays or the following week were obtained from medical records. A linear mixed model was used since dependent observations existed. Result In total, 96 patients (82 % men, age 69±10 years, 92 % ICD, 78 % CRT, 72 % with LVEF<40%) were included, which provided data for 255 patient-holidays. TI decreased by mean 1.3 Ohm (95% CI -1.9 to -0.6, p< 0.001) on the Christmas Day, 0.6 Ohm (95 % CI -1.4 to 0.1, p = 0.08) on New Years Day and 1.0 Ohm (95 %CI -1.7 to -0.3, p=0.005) on Midsummer Day. These TI changes were not related to age and did not differ between men and women. Holiday-related TI drop was observed regardless of LVEF: mean decrease on Christmas Day 1,1 vs 1,4 Ohm, New Years Day 0,2 vs 0,4 Ohm and Midsummer Day 1,2 vs 1,0 Ohm for LVEF <40% and >40% respectively. By the third day after a holiday, TI had reached the baseline level. Only one ventricular tachycardia event requiring shock therapy and hospital admission was documented. No other patients were seeking care during the holidays or the days afterwards. Conclusion A significant transient decrease in thoracic impedance was evident during Christmas Day and Midsummer Day in CIED treated patients with reduced and preserved LVEF. These holidays are therefore associated with both decrease in thoracic impedance and incidence of myocardial infarction and it is possible that decrease in thoracic impedance could contribute to the increased incidence of myocardial infarction during holidays.