A risk score for predicting 30-day mortality in heart failure patients undergoing non-cardiac surgery

Background: Heart failure is an established risk factor for poor outcomes in patients undergoing non-cardiac surgery, yet risk stratification remains a clinical challenge. We developed an index for 30-day mortality risk prediction in this particular group.

Methods and results: All individuals with heart failure undergoing non-cardiac surgery between October 23 2004 and October 31 2011 were included from Danish administrative registers (n = 16 827). In total, 1787 (10.6%) died within 30 days. In a simple risk score based on the variables from the revised cardiac risk index, plus age, gender, acute surgery, and body mass index category the following variables predicted mortality (points): male gender (1), age 56-65 years (2), age 66-75 years (4), age 76-85 years (5), or age >85 years (7), being underweight (4), normal weight (3), or overweight (1), undergoing acute surgery (5), undergoing high-risk procedures (intra-thoracic, intra-abdominal, or suprainguinal aortic) (3), having renal disease (1), cerebrovascular disease (1), and use of insulin (1). The c-statistic was 0.79 and calibration was good. Mortality risk ranged from <2% for a score <5 to >50% for a score ≥20. Internal validation by bootstrapping (1000 re-samples) provided c-statistic of 0.79. A more complex risk score based on stepwise logistic regression including 24 variables at P < 0.05 performed only slightly better, c-statistic = 0.81, but was limited in use by its complexity.

Conclusions: For patients with heart failure, this simple index can accurately identify those at low risk for perioperative mortality.