Slightly to moderately elevated CRP levels in patients undergoing CABG surgery: Implications

A new study published in the March issue of Anesthesiology raises awareness for an additional risk category for patients undergoing routine coronary artery bypass surgery - low to moderate levels of inflammation.

C-reactive protein (CRP) is a recognized marker of systemic inflammation, routinely measured in patients to assess their risk for heart attack. CRP has emerged as a predictor of adverse cardiac events in healthy, non-surgical patients along with the more universally recognized cardiac risk factors of high cholesterol, high blood pressure, diabetes, smoking and obesity.

In this new study, research on CRP levels has been extended to the cardiac surgical population; investigating CRP levels as additional predictors for adverse events and increased mortality in otherwise healthy patients undergoing coronary artery bypass surgery.

"Based on previous research, we knew that patients who present for CABG surgery with high levels of circulating CRP are at risk for increased adverse outcomes, including extended hospital stays and elevated mortality rates, compared to patients with normal or very low CRP levels. These risks are increased if high CRP levels are associated with ongoing myocardial ischemia or infarction," said study author Tjorvi E. Perry, M.D., MMSc. "What was not known were the implications of slightly to moderately elevated CRP levels in low-acuity patients undergoing routine CABG surgery."

Dr. Perry and colleagues from Brigham and Women's Hospital in Boston and Baylor College of Medicine Division of Cardiovascular Anesthesia, Texas Heart Institute, St. Luke's Episcopal Hospital in Houston, studied 914 patients undergoing routine, non-emergency CABG surgery to determine whether circulating preoperative CRP levels in patients could help predict hospital length of stay and long-term postoperative survival.

Patients were stratified to four categories based on preoperative CRP levels; <1mgL, 1-3mgL, 3-10 mg/L and >10 mg/L. Excluding patients with increased CRP levels due to infections, autoimmune disease or ongoing myocardial ischemia or infarction, researchers examined the association between the stratified CRP categories and mortality (death) after CABG surgery.

A total of 87 patients (9.5 percent) died over a mean postoperative follow-up period of 4.8+/-1.5 years. Using a proportional-hazards regression model, results revealed that the 3-10 mg/L CRP group and the >10mg/L CRP group were associated with extended hospital lengths of stay and increased long-term mortality.

"The findings confirm that patients with circulating CRP levels >10 mg/L are at greater risk for adverse events when compared with patients in the lowest preoperative CRP level (< 1mg/L)," said Dr. Perry. "Of great interest is the finding that patients with preoperative levels as low as even 3 mg/L required a longer hospital stay and were at significant risk for increased mortality up to five years after surgery."

Dr. Perry suggested that his findings indicate not only that CRP levels are an important predictor of adverse outcomes in otherwise low-risk cardiac surgical patients undergoing routine CABG surgery, but also that CRP levels may be a target for perioperative therapeutic intervention to reduce the risk for adverse events after surgery."