Autonomic Nerve Function Predicts Risk of Early Death after Discharge in Acute Medical Disease

Abstract

BackgroundHeart rate variability, a marker of autonomic function, has shown promising prognostic results in specific populations, but has not been tested in a general medical population. We hypothesize that heart rate variability identifies high-risk medical patients early after admission to the hospital. MethodA single-center prospective cohort study of acutely admitted medical patients, age ≥18 years old, and life expectancy ≥3 months included between 2019-2023. Unstable patients needing direct admission to the intensive care unit were excluded. Heart rate variability was recorded within 24 hours of admission for 10 minutes. The standard deviation of normal-normal beats (SDNN) was the primary heart rate variability marker. Low SDNN was defined as the lowest tertile (≤22ms). The primary outcome was 30-day all-cause mortality. The secondary outcome was 30-day readmission or mortality. ResultsAmong 721 patients included, low SDNN carried an 8-fold greater risk of 30-day mortality in univariate analysis (HR 8.3, p=0.001); in multivariate analyses a 4-fold greater risk (HR 3.8, p=0.037). Low SDNN was associated with the combined outcome of 30-day mortality or readmission (HR: 1.5, p=0.03) in multivariate analysis. In receiver operating characteristics analyses, low SDNN improved the predictive accuracy of EWS for 30-day mortality or readmission from 0.63 to 0.71 (p=0.008) but did not improve the accuracy for 30-day mortality alone. ConclusionsIn patients admitted due to acute medical illness, low heart rate variability predicted 30-day mortality and readmissions suggesting heart rate variability as a tool to identify patients at high and low risk of relevant endpoints.