Cardiovascular Risk Scores to Predict Perioperative Stroke in Noncardiac Surgery

Abstract

Background and Purpose- Perioperative stroke is associated with significant morbidity and mortality. Conventional cardiovascular risk scores have not been compared to predict acute stroke after noncardiac surgery. Methods- Patients undergoing noncardiac surgery between 2009 and 2010 were identified from the US National Surgical Quality Improvement Program (n=540 717). Patients were prospectively followed for 30 days postoperatively for the primary outcome of stroke. Established cardiovascular and perioperative risk scores (CHADS₂, CHA₂DS₂-VASc, Revised Cardiac Risk Index, Mashour et al risk score, Myocardial Infarction or Cardiac Arrest risk score, and National Quality Improvement Project American College of Surgeons surgical risk calculator) were assessed to predict perioperative stroke. Results- Stroke occurred in the perioperative period of 1474 noncardiac surgeries (0.27%). Patients with perioperative stroke were older, more frequently male, had lower body mass index, and were more likely to have undergone vascular surgery or neurosurgery than patients without stroke (P<0.001 for each comparison). All risk prediction models were associated with increased risk of perioperative stroke (C statistic [AUC] range, 0.743-0.836). The Myocardial Infarction or Cardiac Arrest risk score (AUC, 0.833) and American College of Surgeons surgical risk calculator (AUC, 0.836) had the most favorable test characteristics and a greater ability to discriminate perioperative stroke when compared with Revised Cardiac Risk Index, CHADS₂, CHA₂DS₂-VASc, and Mashour risk scores (P for comparison, <0.001; Delong). Risk scores did not provide consistent discriminative ability across surgery types and were least predictive in vascular surgery (AUC range, 0.588-0.672). Conclusions- The Myocardial Infarction or Cardiac Arrest risk score and American College of Surgeons surgical risk calculator surgical risk scores provide excellent risk discrimination for perioperative stroke in most patients undergoing noncardiac surgery. Stroke prediction was less optimal in patients undergoing vascular surgery.

Keywords: forecasting; humans; male; preoperative care; stroke.

Figure 1.. Frequency of Perioperative Stroke by Non-Cardiac Surgical Subtype

Stroke, defined as development of an embolic, thrombotic, or hemorrhagic vascular accident or stroke with motor, sensory, or cognitive dysfunction (e.g., hemiplegia, hemiparesis, aphasia, sensory deficit, impaired memory) that persists for 24 or more hours, per 100,000 surgery.

Figure 2.. Risk Model Receiver Operating Characteristic Curves to Predict Perioperative Stroke

C-statistics, calculated using the sensitivity and specificity of each risk score for the outcome of perioperative stroke, are displayed within the figure. Risk scores between 0.5-0.7 were considered poorly discriminative, between 0.7-0.8 were considered moderately discriminative, and >0.8 were considered highly discriminative.^, ROC: Receiver Operating Characteristics RCRI: Revised Cardiac Risk Index MICA: Myocardial Infarction or Cardiac Arrest MASHOUR: Mashour et al. risk score for perioperative stroke ACS-SRC: American College of Surgeons Surgical Risk Calculator

Figure 3.. Prediction of Perioperative Stroke by Risk Model and Surgery Type. C-statistics with 95%confidence intervals are shown.

C-statistics and 95% confidence intervals are displayed by surgery type, defined by specialty of the operating surgeon. A c-statistic of greater than 0.7 (vertical line) indicates a model with acceptable accuracy in discriminating patients at risk for stroke. RCRI: Revised Cardiac Risk Index MICA: Myocardial Infarction or Cardiac Arrest MASHOUR: Mashour et al. risk score for perioperative stroke ACS-SRC: American College of Surgeons Surgical Risk Calculator