The investigators conducted a prospective observational pilot study to explore the incidence of peri-operative covert strokes (detected by brain MRI) and the potential impact on delirium and cognitive decline in post-operative cardiac surgery patients at the Hamilton General Hospital. This pilot study assessed the feasibility of a larger prospective international cohort study exploring this objective.

Delirium and cognitive decline are common following cardiac surgery and increase the burden on patients and health care resources. Covert (sub-clinical) strokes are associated with these complications. The investigators conducted a prospective cohort pilot study enrolling consecutive cardiac surgery patients to receive a post-operative brain MRI and a series of questionnaires to assess for changes in cognition, physical function and delirium. Regional cerebral oxygen saturation (rSO2) was recorded during surgery with the use of near-infrared spectroscopy (NIRS) sensors placed on the patients' forehead. The primary aim was to determine the feasibility of conducting a larger study to establish an association between covert stroke and long-term cognitive decline in cardiac surgery patients.

Inclusion Criteria:

1. Male or female ≥ 21 years old

2. Provide written informed consent

3. Scheduled to undergo isolated CABG through a median sternotomy approach

4. Have at least one of the following risk factors:

   1. Peripheral vascular disease (previous peripheral arterial bypass, amputation due to ischemia, ABPI <0.9, or previous AAA repair)
   2. Cerebrovascular disease (history of stroke, TIA, or carotid stenosis >70%)
   3. Renal insufficiency (eGFR <60 mL/min/1.73m2)
   4. Diabetes mellitus (on oral hypoglycemic agent(s) and/or insulin replacement)
   5. Urgent CABG (in-patient awaiting revascularization for ACS or MI)
   6. Recent smoker (within the last year)
   7. Left ventricular ejection fraction <35%

Exclusion Criteria:

1. Concomitant cardiac procedure with CABG Prior enrolment in this study
2. Emergency CABG surgery (immediate revascularization for hemodynamic instability)
3. Redo CABG
4. Circulatory arrest planned during the cardiac operation
5. Diagnosed dementia of any types
6. Contra-indication for DW MRI e.g. claustrophobia, unable to lie flat for the duration of the study, pacemaker or ICD in-situ, or other metal implants

Patients aged 21 years or more scheduled to undergo isolated coronary artery bypass grafting (CABG) surgery with a median sternotomy and at least one vascular risk factor.