Although the mortality rate associated with CABG has been declining, research suggests that patients who undergo these procedures are increasingly older and sicker. Risk factors for complications after CABG are high, and adverse neurologic outcomes (eg, stroke and cognitive decline) remain a major concern. Efforts to reduce post-CABG-related neurologic events have been hindered by an incomplete understanding of the pathophysiology of these events.
One of the justifications for developing off-pump CABG was the hope that rates of embolization, and therefore stroke, would be lower than those experienced with on-pump surgery. However, a number of large prospective randomized trials have failed to show a significant difference in rates of post-surgical stroke between on- and off-pump bypass. In light of these findings, strategies to reduce the incidence of adverse post-CABG neurologic and cognitive outcomes should focus more on patient-related risk factors rather than procedure-specific outcomes. (see also, Revised Guidelines for Evidence-Based PCI)
Changing Perceptions on CABG & Cognitive Decline
In the January 19, 2012 New England Journal of Medicine, my colleagues and I published a review article on neurocognitive outcomes following CABG. Studies in the past have suggested that CABG causes cognitive decline. For example, a Duke University study published about 10 years ago suggested a high rate of cognitive decline at 5 years after CABG. But this study was not randomized and had no control groups. In a more recent study (although not randomized), my colleagues at Johns Hopkins compared cognitive outcomes over 6 years in patients undergoing CABG, a group with the same vascular risk factors that did not undergo surgery, and a group of heart-healthy controls. Although those who underwent CABG experienced cognitive decline, so too did those with the same risk factors who did not undergo surgery. Cognitive decline was not observed in the healthy controls. This strongly suggests that pre-existing risk factors led to cognitive decline rather than CABG itself.
Those with hypertension, high cholesterol, carotid stenosis, previous stroke, advanced age, and/or diabetes are at higher risk for poor neurologic and cognitive outcomes. CABG may act as the surrogate for identifying these patients. These risk factors are the same for CABG patients as they are for non-surgical patients. Although research suggests that a longer bypass time may increase risk of stroke, outcomes are going to be much different for individuals with no vascular risk factors when compared with those who have many vascular risk factors. (click here to see a video of CABG)
Addressing Risk Factors for Poor CABG Outcomes
Preoperative assessment of known stroke risk factors will help minimize the incidence of postoperative stroke in CABG. Combined with intraoperative assessment of risk factors, this strategy allows for an individualized surgical approach that may reduce the incidence of perioperative and postoperative stroke in high-risk patients. Risk for late post-CABG cognitive decline—most likely related to progression or underlying cardiovascular and cerebrovascular disease—may be minimized with strict perioperative and postoperative control of modifiable risk factors (eg, diet, exercise, blood pressure, and cholesterol).
Optimizing Care for Patients Undergoing CABG
Becoming familiar with the literature and supporting research in CABG is important. Collaboration between neurologists, cardiac surgeons, and other disciplines will help optimize care for patients undergoing CABG. There is no clear data showing a causal relationship between CABG and dementia or cognitive problems. Many factors come into play when deciding if CABG is appropriate, but concern about dementia or cognitive outcomes should not be among these factors.
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