Introduction:
According to single institution studies, patients readmitted to the ICU (Intensive Care Unit) following cardiac surgery are at high risk of death. In our study, we primarily aimed to assess the impact of ICU readmission on postoperative results and to identify the independent risk factors of this complication among patients undergoing isolated coronary artery surgery.

Material and methods:
Following exclusions, we analyzed 89,958 consecutive patients in the Polish National Registry of Cardiac Surgical Procedures (KROK Registry), scheduled for isolated coronary artery surgery between January 2010 and December 2019. Variables that independently influenced ICU readmission were identified by means of the multivariable logistic regression. Data of survivors and non-survivors among patients readmitted to the ICU were compared.

Results:
In the analyzed group, 1,003 patients underwent ICU readmission (1.1%). In-hospital mortality among patients readmitted and not readmitted to the ICU was 29.6% and 2.1%, respectively (p<0.001). All postoperative complications were more frequent among patients readmitted to the ICU. Overall, 15 independent predictors of ICU readmission were identified, and conversion to on-pump procedure, age>65 years and preoperative NYHA class III or IV were located on the top of this list. Patients who died following ICU readmission were older, more frequently classified NYHA IV, more frequently underwent non-elective surgery or MIDCAB (Minimally Invasive Coronary Artery Bypass).

Conclusions:
ICU readmission following coronary artery surgery is associated with increased in-hospital mortality and the development of postoperative complications. There are many predictors of ICU readmission. Non-survivors of this complication were older, with more advanced heart failure and more frequently underwent non-elective surgery.