Complexity of preoperative blood pressure dynamics: possible utility in cardiac surgical risk assessment
Complexity measures are intended to assess the cardiovascular system’s capacity to respond to stressors. We sought to determine if decreased BP complexity is associated with increased estimated risk as obtained from two standard instruments: the Society of Thoracic Surgeons’ (STS) Risk of Mortality and Morbidity Index and the European System for Cardiac Operative Risk Evaluation Score (EuroSCORE II). In this observational cohort study, preoperative systolic, diastolic, mean (MAP) and pulse pressure (PP) time series were derived in 147 patients undergoing cardiac surgery. The complexity of the fluctuations of these four variables was quantified using multiscale entropy (MSE) analysis. In addition, the traditional time series measures, mean and standard deviation (SD) were also computed. The relationships between time series measures and the risk indices (after logarithmic transformation) were then assessed using nonparametric (Spearman correlation, rs) and linear regression methods. A one standard deviation change in the complexity of systolic, diastolic and MAP time series was negatively associated (p < 0.05) with the STS and EuroSCORE indices in both unadjusted (21–34%) and models adjusted for age, gender and SD of the BP time series (15–31%). The mean and SD of BP time series were not significantly associated with the risk index except for a positive association with the SD of the diastolic BP. Lower preoperative BP complexity was associated with a higher estimated risk of adverse cardiovascular outcomes and may provide a novel approach to assessing cardiovascular risk. Future studies are needed to determine whether dynamical risk indices can improve current risk prediction tools.
KeywordsBlood pressure complexity STS EuroSCORE Risk Multiscale entropy
This research was supported in part by a grant from the National Institutes of Health (5R01GM098406 and 5R01GM104987), as well as grants from the G. Harold and Leila Y. Mathers Charitable Foundation and James S. McDonnell Foundation.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no competing interests.
- 16.Zong W, Heldt T, Moody GB, Mark RG. An open-source algorithm to detect onset of arterial blood pressure pulses. Comput Cardiol 2003;2003:259–62.Google Scholar
- 20.Roques F, Nashef SAM, Michel P, Gauducheau E, De Vincentiis C, Baudet E, Cortina J, David M, Faichney A, Gavrielle F, Gams E, Harjula A, Jones MT, Pinna-Pintor P, Salamon R, Thulin L. Risk factors and outcome in European cardiac surgery: analysis of the EuroSCORE multinational database of 19030 patients. Eur J Cardiothorac Surg. 1999;15(6):816–23.CrossRefPubMedGoogle Scholar
- 25.Piazza N, Wenaweser P, van Gameren M, Pilgrim T, Tsikas A, Otten A, Nuis R, Onuma Y, Cheng JM, Kappetein AP, Boersma E, Juni P, de Jaegere P, Windecker S, Serruys PW. Relationship between the logistic EuroSCORE and the Society of Thoracic Surgeons Predicted Risk of Mortality score in patients implanted with the CoreValve ReValving system—a Bern-Rotterdam Study. Am Heart J 2010;159(2):323–29.CrossRefPubMedGoogle Scholar
- 26.Ad N, Henry L, Hunt S. Comparison of the New EuroSCORE II with the Original EuroSCORE and the Society of Thoracic Surgeons Risk Score. Circulation. 2012;126:A18614.Google Scholar
- 28.Team RC. R: A language and environment for statistical computing. Vienna: R Foundation for Statistical Computing; 2013.Google Scholar