22 May No Difference in Dementia or Memory Decline After CABG or PCI
MedicalResearch.com Interview with:
Elizabeth L. Whitlock, MD, MSc
John W. Severinghaus Assistant Professor In Residence
Anesthesia & Perioperative Care
UCSF Medical Center
MedicalResearch.com: What is the background for this study?
Response: We have known for a while that, rarely, some older adults suffer substantial, durable cognitive decline after surgery, particularly after coronary artery bypass grafting (CABG) surgery; a larger proportion experience a decline in cognitive test performance which doesn’t necessarily affect function, but which has caused concern among researchers. This cognitive decline was attributed, in part, to the cardiac bypass pump. Many of the studies had methodological limitations which made it difficult to be sure that the cognitive change was due to surgery and not due more generally to heart problems or atherosclerotic disease, which may also imply cerebrovascular atherosclerosis.
Using a large database of older adults who undergo regular cognitive testing, we identified individuals who underwent CABG and compared them to those who underwent percutaneous coronary intervention (PCI), a minimally invasive, non-surgical method of opening blocked coronary arteries. This allowed us to model the rate of memory decline before surgery – which hadn’t been done in previous studies – and compare it to the rate of memory decline after surgery in older adults who had serious heart disease (some of whom were treated with CABG, and some treated with PCI).
MedicalResearch.com: What are the main findings?
Response: We expected to find that memory decline accelerated after CABG surgery. But instead, we found no difference between the pre-procedure and post-procedure rate of memory decline among CABG or PCI patients, and no difference in the post-procedure rate of decline between the CABG and PCI groups. We also saw no difference in the incidence of dementia 5 years after PCI vs CABG, or any evidence that dementia rates would be different even up to 10 years after the procedure.
This was unanticipated, because CABG exposes older adults to a huge range of things which are hypothesized to cause cognitive decline: surgery, anesthetic medications, the heart-lung bypass pump, intubation and mechanical ventilation, an ICU stay, postoperative delirium, opioids to treat pain, etc. — and yet there was no evidence of an effect, particularly after on-pump (traditional) CABG.
We also analyzed the older adults who had off-pump (or “beating-heart”) CABG surgery separately, because off-pump CABG was developed to try to avoid exposure to the cardiac bypass pump, theoretically improving cognitive outcomes. Surprisingly, older adults who underwent off-pump CABG had acceleration – worsening — of their rate of memory decline after the procedure.
While these results describe averages across a population, we also found that individuals may experience an adverse cognitive outcome after either CABG or PCI. That heterogeneity in cognitive outcome balances out at an average level, but it is important not to discount the experience of older adults who feel their cognition has changed after surgery or a minimally invasive procedure, or indeed after an acute health event like a heart attack.
MedicalResearch.com: What should readers take away from your report?
Response: There are some important implications of this work. First, with no evidence for a population-level acute change in memory or an increased rate of dementia associated with CABG compared to PCI, there is no cognition-related reason to avoid one procedure in favor of the other. Second, cognitive outcomes are worse after off-pump CABG compared to traditional CABG with the heart-lung bypass pump, which may be because cardiac outcomes are generally not as good after off-pump CABG. Since there is no cognitive or heart-related benefit of off-pump CABG, the justification for continuing to treat heart disease with off-pump CABG is growing increasingly weak.
MedicalResearch.com: What recommendations do you have for future research as a result of this work?
Response: We still need to understand more about which older adults experience exacerbated cognitive decline after surgery, non-invasive procedures and/or acute health events, so we can identify and support people who may need further follow-up to diagnose and treat cognitive problems. Adverse cognitive outcomes are not limited to surgical procedures, and we need to be vigilant for them, given the tremendous importance for older adults of maintaining their cognitive health.
Whitlock EL, Diaz-Ramirez LG, Smith AK, et al. Association of Coronary Artery Bypass Grafting vs Percutaneous Coronary Intervention With Memory Decline in Older Adults Undergoing Coronary Revascularization. JAMA. 2021;325(19):1955–1964. doi:10.1001/jama.2021.5150
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