Shrunken Pore Syndrome is associated with a sharp rise in mortality in patients undergoing elective coronary artery bypass grafting

Shrunken Pore Syndrome was recently suggested for the pathophysiologic state in patients characterized by an estimation of their glomerular filtration rate (GFR) based upon cystatin C, which is lower or equal to 60% of their estimated GFR based upon creatinine, i.e. when eGFR(cystatin C) ≤ 60% of eGFR(creatinine). Not only the cystatin C level, but also the levels of other low molecular mass proteins are increased in this condition. The preoperative plasma levels of cystatin C and creatinine were measured in 1638 patients undergoing elective coronary artery bypass grafting. eGFR(cystatin C) and eGFR(creatinine) were calculated using two pairs of estimating equations, CAPA and LMrev, and CKD-EPI(cystatin C) and CKD-EPI(creatinine), respectively. The Shrunken Pore Syndrome was present in 2.1% of the patients as defined by the CAPA and LMrev equations and in 5.7% of the patients as defined by the CKD-EPI(cystatin C) and CKD-EPI(creatinine) equations. The patients were studied over a median follow-up time of 3.5 years (2.0–5.0 years) and the mortality determined. Shrunken Pore Syndrome defined by both pairs of equations was a strong, independent, predictor of long-term mortality as evaluated by Cox analysis and as illustrated by Kaplan-Meier curves. Increased mortality was observed also for the subgroups of patients with GFR above or below 60 mL/min/1.73 m(2). Changing the cut-off level from 60 to 70% for the CAPA and LMrev equations increased the number of patients with Shrunken Pore Syndrome to 6.5%, still displaying increased mortality.