Nanna Sveinsdóttir¹

Sunna Rún Heiðarsdóttir¹

Árni Steinn Steinþórsson¹

Hera Jóhannesdóttir²

Alexandra Aldís Heimisdóttir²

Tómas Þór Kristjánsson²

Þórir Einarsson Long³

Ingibjörg Guðmundsdóttir^1,4

Martin Ingi Sigurðsson^1,5

Tómas Guðbjartsson^1,2

¹Faculty of Medicine, University of Iceland, ²Departments of Cardiothoracic Surgery, ³Nephrology, ⁴Cardiology and ⁵Anesthesia and Intensive Care, Landspitali University Hospital.

Correspondence: Tómas Guðbjartsson,
tomasgud@landspitali.is

Key words: Coronary artery bypass grafting (CABG), reduced kidney function, chronic kidney disease, short-term, complications, outcome

INTRODUCTION: Impaired renal function as seen in chronic kidney disease (CKD) is a known risk factor for coronary artery diseases and has been linked to inferior outcome after myocardial revascularization. Studies on the outcome of coronary bypass grafting (CABG) in CKD-patients are scarce. We aimed to study this subgroup of patients following CABG in a well defined whole-nation cohort, focusing on short term complications and 30 day mortality.

MATERIALS AND METHODS: A retrospective study on 2300 consecutive patients that underwent CABG at Landspítali University Hospital 2001-2020. Patients were divided into four groups according to preoperative estimated glomerular filtration rate (GFR), and the groups compared. GFR 45–59 mL/mín/1.73m², GFR 30-44 mL/mín/1.73m², GFR <30 mL/mín/1.73m² and controls with normal GFR (≥60 mL/mín/1.73m²). Clinical information was gathered from medical records and logistic regression used to estimate risk factors of 30-day mortality.

RESULTS: Altogether 429 (18.7%) patients had impaired kidney function; these patients being more than six years older, having more cardiac symptoms and a higher mean EuroSCORE II (5.0 vs. 1.9, p<0.001) compared to controls. Furthermore, their left ventricular ejection fraction was also lower, their median hospital stay extended by two days and major short-term complications more common, as was 30 day mortality (24.4% vs. 1.4%, p<0.001). In multivariate analysis advanced age, ejection fraction <30% and GFR <30 mL/min/1.73m² were independent predictors of higher 30-day mortality (OR=10.4; 95% CI: 3.98-25.46).

CONCLUSIONS: Patients with impaired renal function are older and more often have severe coronary artery disease. Early complications and 30-day mortality were much higher in these patients compared to controls and advanced renal failure and the strongest predictor of 30-day mortality.

Figure I. The division of the 2300 patients into four groups based on GFR (mL/min/1,73m²).

 

Control group: GFR > 60 mL/min/1,73m²

 

Table I. Comparison of background factors between the GFR groups (ml/min/1,73m²).

Mean + standard deviation or number of cases (%) are shown.

Table II. Comparison between GFR groups (ml/min/1.73m²) of primary risks of coronary artery disease. Number of cases (%) are shown.

Table III. Comparison of operation related factors and hospital stay according to GFR. Mean + standard deviation or number of cases (%) are shown, except median + range for hospital stay.

GFR level, ml/min/1.73m²

Figure II. Incidence of early complications, minor and major, and 30-day mortality. The incidence of all the factors increased significantly as GFR decreased.

GFR level, ml/min/1.73m²

Control group: GFR > 60 mL/min/1,73m²

Table IV. Comparison of short term complications and 30-day mortality. Number of cases (%) are shown. Patients may have more than one complication at a time.
GFR level, ml/min/1.73m²

Table V. Predictive factors for 30 day postoperative mortality. Raw and adjusted odds ratio (OR) for 30 day mortality with 95% confidence interval.