Neurologic complications after cardiac surgery are a major cause of morbidity, prolonged hospital stay and increased costings. In selected cases, postoperative neurologic damage leads to permanent disability or decease of the patient. The American College of Cardiology and the American Heart Association classified neurological sequelae after cardiac surgery into type 1 and type 2. Type 1 morbidities are cardiovascular accident (CVA) and transient ischemic attack (TIA) whereas delirium and postoperative cognitive dysfunction (POCD) are classified as type 2 neurologic injury. Reported incidence of TIA/CVA after coronary artery bypass grafting surgery (CABG) is about 1.6-2%. Incidence of delirium and POCD is more difficult to quantify but ranges from 10-20% for delirium and 30-80% for POCD. Exact pathophysiology remains unclear but seems to be a complex interplay between macro- and microembolization, hypoperfusion and systemic inflammation. Also, preoperative neurologic state might play a role in these frequently comorbid cardiac patients. Some recent papers tried to improve neurologic outcomes by surgical, perfusionist or anesthetic adjustments, with limited success.

Literature concerning neurological complications after minimally invasive cardiac surgery (MICS) is scarce. However, this might be of special concern since in MICS, perfusion to the brain is routinely provided via retrograde flow. By consequence, the brain is possibly exposed to aortic atheroma located distal to the cerebral vessels. This is of special interest since embolic phenomena are identified as a trigger for neurologic failure after cardiac surgery. As the practice of MICS is globally expanding, observations on neurologic outcome after MICS are desirable, with screening for short-term as well as long-term complications.

An important reference article concerning late cognitive outcome after CABG surgery prospectively followed a cohort of 102 CABG patients up until five years after surgery. Patients were tested on eight neurocognitive domains at four moments in time: preoperatively, 3 months after surgery, one year after surgery and ultimately five years after surgery. Somewhat surprisingly, at follow-up on one year after surgery, patients performed significantly better at 5/8 cognitive domains without significant worse scores in the remaining domains. The authors note this finding might be attributed to the learning effect. However, on follow-up after five years, a significant decline in several domains was noted, both compared to one year follow-up as to baseline test results. Unfortunately, due to the lack of a (non-surgical) control group, the authors were unable to attribute this finding to CABG surgery itself or to the normal cognitive evolution in this aging, co-morbid population. Therefore, the group performed a nonrandomized longitudinal prospective study between conventional CABG patients, off-pump CABG (OPCAB) patients, nonsurgical coronary artery patients and healthy controls over a six-year follow-up period. They found a larger decline in all three patient groups compared to the healthy control group although none of the groups was substantially worse compared to baseline. As a result, some authors deduct postoperative neurologic decline is more dependent on preoperative patient state rather influenced by procedure-related factors. However, the influence of MICS and retrograde cardiopulmonary bypass (CPB) flow on long-term neurologic decline remains a question.

Between December 2016 and May 2018 the NOMICS trial (Neurologic Outcome after Minimally Invasive Cardiac Surgery) was performed in Jessa Hospitals, Belgium. Three groups were prospectively followed for three months: an endoscopic-CABG group (endo-CABG), a PCI (Percutaneous Coronary Intervention) group and a healthy age and gender matched control group. A battery of neurocognitive tests was performed in all patients and control group to establish the incidence of POCD. By performing these tests again five years after baseline, the investigators will be able to screen for late cognitive decline in a MICS population undergone retrograde arterial CPB flow. Also, because of the presence of two control groups, it might be able to discriminate if the earlier established late decline is typical to the surgical population, to the coronary artery disease (CAD) population and/or normal aging effect.