Predictive value of the National Institutes of Health Stroke Scale and the Mini-Mental State Examination for neurologic outcome after coronary artery bypass graft surgery

Objective

We intended to define the role of the National Institutes of Health Stroke Scale and the Mini-Mental State Examination in identifying adverse neurologic outcomes in a large international sample of patients undergoing cardiac surgery.

Methods

We evaluated 4707 patients undergoing cardiac surgery with cardiopulmonary bypass at 72 centers in 17 countries between November 1996 and June 2000. Prespecified overt neurologic outcomes were categorized as type I (clinically diagnosed stroke, transient ischemic attack, encephalopathy, or coma) or type II (deterioration of intellectual function). The National Institutes of Health Stroke Scale and Mini-Mental State Examination were administered preoperatively and on postoperative day 3, 4, or 5. Receiver operating characteristic curves were plotted to determine the predictive value of worsening in National Institutes of Health Stroke Scale and Mini-Mental State Examination scores with respect to type I and II outcomes.

Results

The receiver operating characteristic area under the curve for changes in National Institutes of Health Stroke Scale score (n = 4620) was 0.89 for type I outcomes and 0.66 for type II outcomes. A 1-point worsening in National Institutes of Health Stroke Scale score provided excellent discrimination (86% specificity; 84% sensitivity) of type I outcomes. The receiver operating characteristic area under the curve for changes in Mini-Mental State Examination score (n = 4707) was 0.75 for type I outcomes and 0.71 for type II outcomes. A 2-point worsening in Mini-Mental State Examination score provided only fair discrimination (73% specificity; 62% sensitivity) of type II outcomes.

Conclusion

We used baseline controls and postoperative worsening in National Institutes of Health Stroke Scale and Mini-Mental State Examination scores to predict both serious adverse neurologic outcome and deterioration of intellectual function. Our findings provide the only reference for evaluating these tests that are used in cardiac surgical clinical trials.

CTSNet classification: 19, 23

Abbreviations and Acronyms: AUC, area under the curve, CABG, coronary artery bypass grafting, CPB, cardiopulmonary bypass, IREF, Ischemia Research and Education Foundation, MMSE, Mini-Mental State Examination, NIHSS, National Institutes of Health Stroke Scale, ROC, receiver operating characteristic