Relative tachycardia at admission as a predictor of mortality in severe and critical COVID-19, a tertiary centre study

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: None. BACKGROUND: Relative tachycardia is the phenomenon of disproportionate tachycardia in response to fever, originally described in the context of systemic inflammatory response syndrome (SIRS) (1). Systemic COVID-19 has shown similarities to SIRS, as well as arrhythmogenic effects and other cardiovascular complications. Relative tachycardia is associated with increased mortality in SIRS, however currently there is no data on effects of relative tachycardia in COVID-19. PURPOSE: Our goal was to determine whether relative tachycardia impacted clinical outcomes of COVID-19 patients. METHODS: We retrospectively analyzed data on 3490 COVID patients hospitalized at our institution from March 2020 to June 2021. Inclusion criteria were age over 18 and positive polymerase chain reaction test to SARS-CoV-2 virus. Exclusion criteria were beta blocker use and atrial fibrillation. We stratified our patients into four quartiles according to their heart rate to body temperature ratio at admission. We defined the fourth quartile as relative tachycardia. RESULTS: Most patients were male (57.5%), median age was 69 years, median Charlson comorbidity index was 3, 69% had severe COVID and 15% had critical COVID at admission. Median heart rate was 90 beats per minute, median body temperature was 38 degrees Celsius and median pulse-to-temperature radio was 2.36 at admission. Patients whose heart rate-to-fever ratio at admission indicated relative tachycardia were significantly more likely to require mechanical ventilation (OR 1.48, CI 1,22-1,80), be transferred to an intensive care unit (OR 1.62, CI 1.36 to 1.93), to experience venous thromboembolisms (OR 1.50, CI 1.12-1.99) and increased intrahospital mortality (OR 1.63, CI 1.39-1.92) compared to those in first three quartiles. After adjustment for age (OR 1.04, CI 1.03-1.05), sex (OR 1.36, CI 1.14-1.61), Charlson comorbidity index (OR 1.24, CI 1.19-1.29) and COVID severity (OR 28.81, CI 14.68-56.55), death during hospitalization was significantly higher in the relative tachycardia group (OR 1.86, CI 1.47-2.35). CONCLUSIONS: COVID patients with excessive tachycardic response to fever at admission seem to have lower chances of survival. Further research is necessary to establish a cut-off value for this easily measured clinical parameter.