Elevated heart rate after non-cardiac surgery: post-hoc analysis of a prospective observational cohort study

Background Elevated heart rate (HR) is associated with accelerated mortality and independently predicts poorer outcomes in patients discharged from hospital after myocardial infarction and/or heart failure. We examined whether resting HR measured within 24 hours of hospital discharge following elective non-cardiac surgery was elevated compared to preoperative values. We also investigated the relationship between changes in HR with and/or autonomic function associated with morbidity after surgery. Methods We conducted a post-hoc analysis of HR data obtained in a prospective observational cohort study of patients ≥18years in whom serial Holter-based measurements of cardiac autonomic activity were made before, and for 48h after, surgery. The primary outcome was absolute discharge HR (beats minute -1 ), recorded at rest before hospital discharge. We examined the association between quartiles of discharge HR and autonomic measures (time/frequency domain heart rate variability) associated with morbidity (defined by Postoperative morbidity survey). Results In 157 patients (66 (42%) male; age 67(9) years), HR at hospital discharge (range: 53-122) increased by 5 beats minute -1 (95%CI:3–7;p<0.001) compared to preoperative values. Patients in the upper quartile of discharge HR (≥85bpm) were more likely to sustain pulmonary (odds ratio (OR):2.18 (95%CI:1.07-4.44);p=0.03) and infectious (OR:2.31 (95%CI:1.13-4.75);p=0.02) morbidity within seven days of surgery, compared to lower quartiles. Pulmonary/infectious morbidity was associated with loss of cardiac vagal activity. Conclusions Heart rate on discharge from hospital following major elective non-cardiac surgery is frequently elevated and is promoted by morbidity associated with reductions in cardiac vagal activity.