Prevalence of Renal Artery Disease and Its Prognostic Significance in Patients Undergoing Coronary Bypass Grafting

• The presence of renal artery stenosis (10%) is frequent in patients undergoing coronary artery bypass grafting (CABG). Also, 9% present an elevated renal index, a marker of renal arterial resistance.
• The presence of renal artery stenosis is not associated with postoperative outcomes.
• The presence of an elevated renal index is predictive of 30-day cardiovascular outcomes and acute kidney injury after CABG.
• Preoperative renal arterial duplex assessment is useful to stratify the postoperative cardiovascular and renal outcomes in patients undergoing CABG.

Several studies demonstrated the prognostic importance of renal failure and peripheral artery disease in patients undergoing coronary artery bypass grafting (CABG), but data regarding the prognostic value of renal artery disease in this context are scarce. We aimed to study the prevalence and prognostic value of renal artery disease in patients undergoing CABG. We assessed by duplex ultrasound the renal arteries of 429 consecutive patients who underwent CABG, of whom 401 had satisfactory imaging quality to detect >60% renal artery stenosis (RAS) and/or an elevated resistive index (ERI >0.80). Of the 401 subjects included (age 68 ± 10 years, 83% men), 40 (10%) had RAS and 35 (9%) had ERI. Nine patients (2.2%) had both conditions. Patients were followed up for 12.4 ± 7.0 months. The primary outcome was composite, including 30-day death, stroke, and/or myocardial infarction. In a multivariate model adjusted for age, gender, cardiovascular (CV) risk factors, renal function, chronic obstructive pulmonary disease, the use of off-pump CABG, CV co-morbidities, and drugs, the presence of ERI was strongly associated with the occurrence of the composite outcome (odds ratio 4.3, 95% confidence interval 1.7 to 9.9, p = 0.0006). Similarly, ERI, not RAS, was significantly associated with the 30-day acute kidney disease and the midterm mortality, as well as fatal and nonfatal CV events. In conclusion, regardless of renal function and other factors, the renal resistive index is a strong predictor of CV and renal events after CABG. Renal duplex ultrasound can identify a subgroup of patients at high risk of CABG.