The Breakdown of Fractal Heart Rate Dynamics Predicts Prolonged Postoperative Myocardial Ischemia Timo T. Laitio, MD*, Heikki V. Huikuri, MD, Timo H. Ma ¨kikallio, MD, Jouko Jalonen, MD*, Erkki S. H. Kentala, MD*, Hans Helenius, MSc‡, Olar Pullisaar, MD†, Jaakko Hartiala, MD†, and Harry Scheinin, MD§ From the Departments of *Anesthesiology and Intensive Care, and †Clinical Physiology, Turku University Hospital, Turku, Finland; the Departments of ‡Biostatistics, and §Pharmacology and Clinical Pharmacology, and Turku PET Centre, University of Turku, Turku, Finland; Division of Cardiology, Department of Medicine, Oulu University Hospital, Oulu, Finland Patients with myocardial ischemia after noncardiac surgery have a three- to ninefold increased risk of adverse cardiac events. In this study we tested the hypothesis that altered preoperative heart rate variability (HRV) predicts postoper- ative prolonged myocardial ischemia ( 10 min) in elderly surgical patients. Thirty-two patients, age 60 yr or older, ad- mitted to hospital for surgical repair of a traumatic hip frac- ture with preoperative night and daytime Holter recordings were included. Holter monitoring was initiated at arrival at hospital and continued until the third postoperative morn- ing. Conventional HRV measures along with analysis of short-term fractal scaling exponent (  1 ) of RR intervals were assessed for night (from 2 am to 5 am) and day (7 am to 12 am) periods in each patient. Preoperative  1 was signifi- cantly lower (i.e., increased randomness in HRV) during the nighttime compared with daytime (mean  sem; 0.92  0.08 versus 1.03  0.06; P = 0.002) in patients with postoperative myocardial ischemia. Patients without ischemia had no such difference. In stepwise multivariate logistic regression anal- ysis, increased preoperative night-day difference of  1 was the only independent predictor of postoperative prolonged ischemia. The odds ratio for an increase of 0.16 U in night- day difference of  1 (corresponding to interquartile range) was 7.7 (95% confidence interval, 1.9 –51.4; P = 0.0018). Breakdown of fractal-like heart rate dynamics is predictive for postoperative prolonged myocardial ischemia in elderly patients having emergency surgery for traumatic hip fracture. (Anesth Analg 2004;98:1239 –44) P atients with myocardial ischemia after nonvas- cular and noncardiac vascular surgery have a three- to ninefold risk of adverse cardiac events, respectively, and cardiac complications account for more than half of the deaths (1–3). Especially, pro- longed ischemia over 10 min is a strong predictor for postoperative death and myocardial infarction (4). The prevalence of perioperative myocardial ischemia in unselected hip fracture patients has been reported to be more than 30% (2). Complications are mainly at- tributable to ischemic events, pneumonia, and lung embolism. The 3-year mortality rate is more than 30%, and almost half of those who survive are permanently institutionalized (5). The American Heart Association has issued guidelines to identify patients at increased risk for postoperative adverse cardiac outcome preop- eratively but diagnostic tools with better performance in risk stratification are still needed (6). The autonomic nervous system plays a significant role in the pathophysiology of perioperative ischemia (7). There is evidence that sympathetic activation has an important role in the onset of adverse cardiac events (7). Adrenergic activity and plasma catechol- amine levels change considerably in the postoperative period, which may predispose to myocardial ischemia by altering the relationship between myocardial oxy- gen demand and supply (1). Furthermore, increased sympathetic activation during rapid eye movement (REM) sleep has been suggested to be associated with the circadian pattern of ischemia occurring most fre- quently during early morning hours (8,9). Heart rate variability (HRV) measures from ambulatory electro- cardiograph (ECG) recordings are widely used in the assessment of cardiovascular autonomic regulation. Recent studies suggest that newer measures of HRV, such as fractal analysis methods, can complement the Supported, in part, by an unrestricted study grant from the In- strumentarium Science Foundation, Helsinki, Finland. Accepted for publication November 26, 2003. Address correspondence and reprint requests to Timo Laitio, MD, Department of Anesthesiology and Intensive Care, Turku Univer- sity Hospital, Turku, Finland. POB 52, FIN-20521 Turku, Finland. Address email to timo.laitio@tyks.fi. DOI: 10.1213/01.ANE.0000112311.94466.F1 ©2004 by the International Anesthesia Research Society 0003-2999/04 Anesth Analg 2004;98:1239–44 1239