Impact of increasing degrees of renal impairment on outcomes of coronary artery bypass grafting: the off-pump advantage

Abstract

OBJECTIVES Increasing degrees of renal impairment are associated with higher rates of morbimortality after coronary artery bypass grafting (CABG). This incremental risk has not been well studied in off-pump procedures (OPCAB). We assessed its impact on OPCAB and on-pump CABG (ONCAB).

METHODS A total of 1769 patients undergoing primary CABG (January 1995 through June 2011) had complete data on glomerular filtration rate (eGFR). 930 patients had Stage 2 renal insufficiency, 330 Stage 3, 27 Stage 4 and 465 normal renal function (Stage 1). Seventeen patients with end-stage disease (Stage 5) were excluded. The OPCAB technique was selectively used in 350 high-risk patients. Preoperative variables and postoperative outcomes were compared among eGFR subgroups and between matched and unmatched OPCAB vs ONCAB groups.

RESULTS Stages 3–4 patients were older (P < 0.0001), with higher prevalence of diabetes (36.8, 35.0, 39.7 and 74.1%, P < 0.01, 1–4 eGFR groups) peripheral arteriopathy (6.0, 9.0, 15.8 and 29.6%, P < 0.0001) and lower left ventricular ejection fraction (LVEF) (GFR-LVEF correlation: Pearson: 0.12, P < 0.0001). On-pump GFR groups had increasingly higher in-hospital mortality (1.0, 1.2, 3.5 and 15.4%, P < 0.0001), but no differences were observed in OPCAB (5.5, 4.8, 5.4 and 7.1%, P = 0.97). Similar trends on in-hospital morbidity were observed in ONCAB vs OPCAB groups: low cardiac output (P < 0.01), pneumonia (P < 0.01) and stroke (P < 0.05). GFR only predicted mortality in ONCAB patients (odds ratio (OR): 0.96, 95% CI: 0.94–0.98; P < 0.01). Patients with higher eGFR stages had statistically more reduced long-term survival, and this pattern was similar in the three treatment groups, also including the OPCAB group, who had the lowest survival in patients with eGFR stage 4.

CONCLUSIONS Patients with low GFR (Stages 3–4) undergoing ONCAB were at increased risk of early morbimortality. In contrast, there were no significant differences in operative morbimortality among eGFR groups in OPCAB patients. This ‘off-pump advantage’ on early outcomes was not observed at the long-term follow-up.