Preoperative risk factors in 10 418 patients with prior myocardial infarction and 5241 patients with prior unstable angina undergoing elective coronary artery bypass graft surgery.

BACKGROUND

The EuroSCORE associates coronary artery bypass graft (CABG) surgery with higher perioperative risk in the first 3 months after a myocardial infarction (MI). The optimal scheduling of CABG surgery after unstable angina (UA) is unknown. We investigated the preoperative predictors of adverse outcomes in patients undergoing CABG with prior MI or UA and investigated the importance of time interval between the cardiac event and CABG.

METHODS

The Hospital Episode Statistics database (April 2006-March 2010) was analysed for elective admissions for CABG. Independent preoperative patient factors influencing length of stay, readmission rates, and mortality, were identified by logistic regression and presented as adjusted odds ratios (ORs).

RESULTS

A total of 10 418 patients with prior MI (mortality 1.8%) and 5241 patients with prior UA (mortality 2.2%) were included in the respective cohorts. Multiple risk factors were identified in each population including liver disease and renal failure. The time interval from cardiac event (MI or UA) to elective CABG surgery did not influence perioperative outcomes when analysed as a continuous measure or using the arbitrary 3-month threshold [MI, OR 1.1 (0.78-1.57) and UA, OR 0.65 (0.39-1.09)].

CONCLUSIONS

Our hypothesis generating data suggest that the increased risk currently allocated in the EuroSCORE for an interval of 3 months between MI and CABG should be critically re-evaluated. Furthermore, prior MI should not be discounted as a risk factor if it is more than 3 months old.