Institutional Variation in Mortality After Stroke After Cardiac Surgery: An Opportunity for Improvement

Postoperative stroke remains one of the most devastating complications after cardiac surgery. Variations in stroke rates and ability to rescue from mortality after stroke between surgical centers are not understood. This study evaluated patient risk and institutional factors associated with likelihood of postoperative stroke as well as hospital variation in risk-adjusted stroke and rates of failure to rescue (FTR) after stroke after cardiac surgery.

Patient records from The Society of Thoracic Surgeons' multiinstitutional certified database for cardiac operations (2001 to 2011) were analyzed. The relative contribution of patient- and hospital-related factors to the likelihood of postoperative stroke was assessed by univariate and multivariate analyses. Variations in risk-adjusted stroke and rates of FTR after stroke were compared, and impact of stroke on hospital resource utilization and costs were evaluated.

A total of 57,387 patients was included. Postoperative stroke rate was 1.5%, with significant variation across hospitals (range, 0.8% to 2%, p < 0.001). Stroke patients (versus no stroke patients) presented with more comorbid disease and higher risk profiles (The Society of Thoracic Surgeons predicted risk of mortality, 3% versus 1%, p < 0.001). Mortality was expectedly higher after stroke compared with no stroke (18% versus 2%, p < 0.001). Postoperative stroke was associated with nearly double the total cost of hospitalization. After risk adjustment, individual hospitals demonstrated a strong association with likelihood for stroke (p < 0.001). Furthermore, high-performing hospitals with low stroke rates performed fewer aortic valve operations, more coronary artery bypass graft operations, and accrued longer intensive care unit lengths of stay. Significant hospital variations were observed for risk-adjusted stroke and rates of FTR after stroke (both p < 0.001).

Institutional variation, more so than individual patient risk factors, is highly associated with postoperative stroke and FTR rates after stroke after cardiac surgery. Postoperative stroke remains significantly associated with mortality and morbidity. Institutional practice patterns may confer a disproportionate influence on postoperative stroke independent of case mix. Understanding differences between high and low performing centers is essential to improving outcomes, costs, and hospital quality.