Association between lipoprotein levels and outcomes after coronary artery bypass grafting surgery: a systematic review and meta-analysis

INTRODUCTION: Lipoprotein(a) (Lp[a]) is a variant of low-density lipoprotein (LDL) and has been associated with increased risk of vascular inflammation and thrombosis. Coronary artery bypass grafting (CABG) has been associated with local inflammation of the myocardium. It is plausible, therefore, that patients with elevated baseline Lp(a) may be prone to unfavorable clinical outcomes following CABG. We evaluate differences in outcomes between CABG patients with high and low serum Lp(a) in this meta-analysis. EVIDENCE ACQUISITION: A comprehensive literature search was performed to identify studies reporting outcomes in CABG patients stratified by preoperative Lp(a) level. When possible, the outcomes were pooled in a meta-analysis. We assessed post-operative mortality, major cardiovascular events, stroke occurrence and saphenous graft occlusion. EVIDENCE SYNTHESIS: Eight studies involving 8681 patients were included. Articles used varying cut-offs for high versus low Lp(a), and outcomes varied. In the three studies evaluating mortality, two showed no statistically significant difference between groups while one reported increased mortality associated with high Lp(a) level. Both studies investigating major adverse cardiovascular events reported higher risk in patients with high Lp(a). A study-level meta-analysis of four studies reporting saphenous vein graft occlusion incidence after CABG was performed. High (≥30 mg/dL) preoperative Lp(a) was not associated with an increased risk of graft occlusion compared with low (<30 mg/dL) preoperative Lp(a) (OR=1.88, 95% CI: 0.66-5.36; P=0.15). CONCLUSIONS: Studies evaluating the impact of Lp(a) on outcomes in CABG patients are few, with heterogenous cut-offs and outcomes. In the limited published studies, Lp(a) level was not associated with graft occlusion.