Background: Vasoactive-inotrope score (VIS) has recently been proposed as a surrogate marker of illness severity after cardiac surgery for pediatric patients with congenital heart disease (CHD). However, it has not been validated in an exclusively pediatric population as a robust outcome predictor in the early postoperative period. Furthermore, as a result of advances in the treatment of CHD, the majority of these children now survive to adulthood when they will require additional surgical intervention. However, there are no risk prediction tools for these adult patients with CHD; and pediatric and adult non-CHD cardiac risk scores perform poorly in this population. A simple yet robust risk prediction tool is crucial to support clinical decision making and optimize quantity and quality of life for both pediatric and adult CHD patients undergoing cardiac surgery.
Objectives: This research aims to 1) externally validate VIS risk predictive performance of early outcome in pediatric CHD patients after cardiac surgery; 2) propose a simplified VIS Index model with robust predictive performance of early postoperative mortality and morbidity by incorporating both the magnitude and duration of inotrope support required for pediatric CHD patients after cardiac surgery; 3) evaluate whether the proposed VIS Index has strong discriminative performance of early mortality and morbidity outcome for adult CHD patients after cardiac surgery. Methods: Automated data capture of the electronic medical record (EMR) system was utilized in conjunction with retrospective clinical chart review. A total number of 244 infant CHD patients and 243 adult CHD patients undergoing cardiac surgery at the Mayo Clinic Rochester, MN were included in the study. Inotrope and vasoactive dose values were collected at 15-minute intervals for the first 96 hours after cardiac Intensive Care Unit (ICU) admission. Demographic and clinical data were collected from both Mayo Clinic institutional Society of Thoracic Surgeons database and clinical chart review. Maximum vasoactive inotrope support (maxVIS) values were calculated and VIS postoperative temporal characteristics were further assessed to evaluate their relationship with early mortality and morbidity. The logistic regression model with generalized estimating equation methodology was applied to address the correlated outcomes from the same patient. The maxVIS model was validated on pediatric CHD patients. A simplified VIS index model incorporating both the magnitude and duration of inotrope support was developed with superior predictive performance of early mortality and morbidity for both pediatric and adult CHD patients following cardiac surgery. The area under the curve (AUC) of the receiver operating characteristic (ROC) curves was used to evaluate the discriminative performance; Hosmer-Lemeshow (H-L) test was used to assess the goodness of fit of the model.
Results: The maxVIS model proposed by recent research was externally validated in our institution to exhibit good predictive ability (H-L test, P = 0.791) and discriminate reasonably well between CHD patients with high- and low-risk for early mortality and morbidity (AUC = 0.77, 95% CI: 0.72 to 0.82). The new VIS index risk prediction model shows superior discriminative performance over the existing maxVIS model for pediatric CHD patients undergoing cardiac surgery (AUC = 0.84, 95% CI: 0.78 to 0.88; H-L tests, P = 0.725). A high VIS index is strongly associated with a poor clinical outcome compared to a low VIS index. Patients with a VIS index of 6 have an estimated risk of 98% (95% CI: 85% to 100%) of having a poor outcome after cardiac surgery, compared with a risk of 20% (95% CI: 11% to 34%) for patients with a VIS index of 1. Furthermore, both maxVIS model and VIS index model presents robust predictive performance for adult CHD patients after cardiac surgery with the VIS index model consistently showing superior discriminative performance over the maxVIS model for early postoperative mortality and morbidity (MaxVIS model AUC = 0.82, 95% CI: 0.76 to 0.88; VIS index model AUC = 0.88, 95% CI: 0.82 to 0.93). Adult CHD patients with a VIS index of 6 have an estimated risk of 95% (95% CI: 72 % to 99%) of experiencing a poor clinical outcome during early postoperative period, compared with a risk of 6% (95% CI: 3% to 11%) for patients with a VIS index of 1.
Conclusions: The maxVIS model is a strong predictive tool of early mortality and morbidity for CHD patients undergoing cardiac surgery. The VIS index we proposed is a more robust, yet much simpler tool to predict early postoperative mortality and morbidity for both pediatric and adult CHD patients after cardiac surgery. More importantly, this is the first analysis evaluating the correlation between VIS and poor clinical outcomes in adult CHD patients undergoing cardiac surgery. The findings of this research will facilitate earlier detection of high risk patients to direct clinical interventions and preventative measures that will improve outcome for pediatric and adult CHD patients after cardiac surgery.
University of Minnesota Ph.D. dissertation. May 2013. Major: Health Informatics. Advisor:Professor Stuart Speedie. 1 computer file (PDF); xi, 121 pages.
Golden, Adele Wen.
A simplified risk prediction model using electronic medical record data for pediatric and adult patients with congenital heart disease undergoing cardiac surgery.
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