It’s not easy to operate on a beating heart, but that’s exactly what the surgeons who performed the first coronary artery bypass surgeries in the 1960s did. As soon as there were machines up to the task, doctors began using heart-lung pumps to still patients’ hearts during the surgery. The pump – as the heart-lung machine is informally called – removes the patient’s blood, adds oxygen and pushes it back out into the patient’s body.
If this sounds Frankensteinian, well, let’s just say it is a heavy-hitting surgery. Patients are terrified of it. When anecdotes and research began to suggest that patients who undergo these “on-pump” bypass surgeries (which doctors call “CABG,” pronounced cabbage) experience cognitive decline afterwards, surgeons increasingly moved back to “off-pump” methods, using fancy – and expensive – new technologies to do a better job wrangling beating hearts to create life-saving detours for blood to move through the arteries.
Patients like the off-pump option. It sounds less scary. And there’s less risk of cognitive decline, right?
Wrong, according to a UCSF study published today in JAMA. The researchers, led by anesthesiologist Elizabeth Whitlock, MD, with Maria Glymour, SciD, as senior author, found that, in fact, patients who had off-pump CABG surgeries were more likely to experience accelerated cognitive decline afterwards.
The study compared older adults who had CABG surgery to their peers who underwent percutaneous coronary intervention (PCI), a method of opening blocked coronary arteries without surgery by feeding a stent in through an artery.
“We expected to find that memory decline accelerated after CABG surgery,” Whitlock explained. “CABG implies a lot of exposures that have been associated, or potentially associated, with memory problems: major surgery, the cardiopulmonary bypass pump, general anesthesia, opioids, recovery in the intensive care unit, intubation and mechanical ventilation, delirium – it's a huge list.”
Instead, they found no difference in the rate of cognitive decline for patients who had PCI versus those who had CABG surgery. They also found no difference in the rates of dementia 5 or 10 years after the procedures.
The team also separately analyzed the older adults who had off-pump CABG surgery, expecting to see that they fared better cognitively than the on-pump patients. But they discovered these patients fared worse. The researchers hypothesize that the difference results from the less-good cardiac outcomes after off-pump CABG. (It’s not easy to operate on a beating heart.)
“Since there is no cognitive or heart-related benefit, the justification for continuing to treat heart disease with off-pump CABG is growing increasingly weak,” Whitlock said.
The difficulty of measuring the impact of surgery on cognition among older adults – who are declining anyway – accounts for Glymour’s role as senior author. The researchers used a large database of older adults who undergo regular cognitive testing. By focusing on CABG and PCI patients, the team only considered those with major heart disease, which is itself a risk factor for cognitive decline and dementia. They calculated a rate of memory decline for patients before their procedures, which hadn't been done in previous studies, and then compared that to their rate of decline after surgery.
The mean rate of memory decline was slightly slower after the procedure for patients who underwent PCI and slightly faster after the procedure for patients who underwent either type of CABG surgery. But the difference in rates was only statistically significant when comparing off-pump CABG patients to PCI patients: The off-pump CABG patients lost 0.046 memory units more per year, almost double the post-procedure rate of cognitive decline of the PCI patients.
The good news is that on-pump CABG remains a viable option.
“There is no reason to avoid CABG in older adults just because of memory or dementia concerns,” Whitlock said. “If an older adult's heart disease is best treated with a CABG, they should get a CABG!”