Mechanisms of Cerebral Injury from Cardiac Surgery

Abstract

Cerebral injury is a frequent complication of cardiac surgery and has been associated with high mortality, morbidity, hospital costs, and an increased likelihood of admission to a secondary care facility after hospital discharge, and impaired quality of life. 47,71,78,86 There are a variety of manifestations of perioperative cerebral injury including ischemic (or, less commonly, hemorrhagic) stroke that occurs in 1.5% to 5.2% of patients, encephalopathy affecting 8.4% to 32% of patients, and neurocognitive dysfunction affecting 20% to 30% of patients one month after surgery. 47,71,78,86 The range in reported incidences between studies is likely due to different patient populations (e.g., patient age and risk status, types of procedures), diagnostic definitions, and the intensity of clinical surveillance. Contemporary studies using sensitive brain MRI with diffusion weighted imaging report that as many as 45% of patients who have undergone cardiac surgery have new ischemic brain lesions that are often clinically undetected. 47,63The prevailing hypothesis, though not definitively proven, is that all forms of injury associated with cardiac surgery (i.e., stroke, encephalopathy, and neurocognitive dysfunction) have a similar etiology and that the manifestations depend on the extent and location of brain injury (e.g., motor cortex vs. areas subserving cognition). Many earlier studies that have described long-term neurocognitive changes after cardiac surgery have failed to include a non-surgical control group. 47,79 In a longitudinal study of patients with coronary artery disease undergoing either percutaneous coronary interventions or coronary artery bypass grafting (CABG), there were no differences in cognitive measures 36 months after either procedure. 88 These data imply that the effects of cardiac surgery on cognition may be short-lived (i.e., ~ 3 mo) and that progression of inherent cerebral vascular disease is a more important determinant of long-term cognitive decrements. These results further underscore the low sensitivity and specificity of psychometric testing for detecting cerebral injury in elderly populations with a high prevalence of preexisting cognitive impairment. 47In this paper, we will examine postulated mechanisms for cerebral injury from cardiac surgery. Most emphasis has been placed in the past on the intraoperative interval as being the period of highest cerebral vulnerability. Many clinical cerebral events, however, occur in the postoperative period. We have reported, in fact, that > 20% of clinical strokes occur after recovery from surgery and anesthesia. 45,71 Thus, patients must be considered vulnerable to cerebral injury any time during the perioperative period.

Statin use and neurologic morbidity after coronary artery bypass grafting

“…Cardiopulmonary bypass may result in stroke by systemic hypotension and diffuse embolization of fibrin or gaseous material as demonstrated by transcranial Doppler ultrasonography. 29,30 The majority of strokes are recognized within 48 hours of surgery.…”

“…30 While some reports have indicated that statins are associated with a reduced incidence of atrial fibrillation after CABG, 31 it has not been clearly Values are mean Ϯ SD or %. ACE ϭ angiotensin converting enzyme; CABG ϭ coronary artery bypass grafting.…”

Impact of Intracranial Artery Disease and Prior Cerebral Infarction on Central Nervous System Complications After Off-Pump Coronary Artery Bypass Grafting

“…In previous studies [6,8,9,21], the causative mechanisms and risk factors for perioperative strokes in patients undergoing CABG were determined. The incidence of postoperative stroke correlates mainly with the adverse effect of cardiopulmonary bypass due to large numbers of microemboli built by fragments of atheromatous plaques from the ascending aorta, thrombi, platelets, destroyed red blood cells, white blood cells, lipids, and gas [11,13,22].…”

Embolic Protection Devices in Transcatheter Aortic Valve Replacement

“…As opposed to TAVR, cardiac surgery involves a wide spectrum of neurological injuries, including ischemic stroke, encephalopathy, and neurocognitive decline. 38 Embolism is considered the main mechanism of neurological injury, 39 and embolic material released into the cerebral circulation has been detected during various aortic manipulations performed in cardiac surgery. 40 Similar to TAVR patients, an increased risk of silent CNS infarction related to cognitive decline has been reported for cardiac surgery patients.…”