Neurological complications of cardiac surgery: Stroke, encephalopathy, and cognitive decline

Cardiac surgical procedures continue to be associated with postoperative neurological complications in a subset of patients, despite technological advances in surgical technique. This is primarily because individuals who are referred for cardiac surgery often have pre-existing risk factors that increase their risk of these complications. These risk factors include vascular risk factors as well as sometimes subclinical cerebrovascular disease. An increasing number of individuals undergoing cardiac surgery have old strokes, both clinical and radiographic, intra- and extracranial atherosclerosis, and leukoaraiosis. Thus, their risks for a postoperative neurological complication are increased. Specifically, individuals continue to experience stroke, delirium, and cognitive decline postoperatively, and rates of some of these complications – particularly stroke – are even more frequent in individuals having combined cardiac surgical procedures. In addition, with the increasing use of MRI diffusion-weighted imaging (DWI), individuals are found to have subclinical infarcts, which may be associated with subtle changes in cognition, or even global encephalopathy or delirium. Potential mechanisms of neurological injury after cardiac surgery are discussed, including embolization (both macro- and micro-), hypoperfusion, and inflammation. Data on the role of off-pump (as compared to on-pump) coronary artery bypass grafting surgery is discussed, particularly with regards to postoperative stroke and cognitive impairment, with no clear benefit from the use of off-pump surgery. Finally, the data on the short- and long-term cognitive outcomes of individuals undergoing cardiac surgery are discussed, including the controversy over the development of Alzheimer’s disease in association with cardiopulmonary bypass. Individuals undergoing cardiac surgical procedures remain at risk for neurological injury, despite many improvements in surgical technique over the past decade. Neurological injury can take the form of stroke, encephalopathy or delirium, or postoperative cognitive decline. In addition, as MRI techniques have improved and allowed for detection of more subtle brain injury, subclinical brain infarction has been identified as another potential complication of cardiac surgery.