Cognitive Decline Does Not Last Long After CABG

Download this article's Factoid (PDF & PPT for Gold Subscribers)

Recovery from cognitive decline after coronary artery bypass graft (CABG) surgery occurs within 8 weeks after the procedure, and sometimes function reaches even higher levels than before the operation, according to a small study published in the April 2013 issue of Annals of Thoracic Surgery.

Researchers led by Stephen Robinson, PhD, of Royal Melbourne Institute of Technology (Bundoora, Australia), compared the cognitive status of 3 patient groups:

• On-pump CABG (n = 16)
• Thoracic surgical controls (n = 15)
• Nonsurgical controls (n = 15)

All surgical procedures were elective. Prior to the procedure, CABG patients showed higher levels of stress (18.9%) and anxiety (12.3%) compared with nonsurgical controls (5.1% and 2.7%, respectively; P < 0.05 for each comparison) as did surgical controls (14.5%, 10.0%; P < 0.05 for each comparison vs. nonsurgical controls). CABG patients were also more likely to be depressed than surgical controls (12.4% vs. 8.1%; P < 0.05).

One week after surgery, the CABG and surgical control group both performed worse than before the procedure on multiple cognitive tests including Grooved Pegboard on Dominant Hand (P < 0.01), Grooved Pegboard on Non-Dominant Hand (P < 0.01), and several subtests of the Rey Auditory Verbal Learning Task. Overall, 44% of CABG patients and 33% of surgical controls were significantly impaired.

Preprocedural anxiety, depression, and stress were associated with impaired cognitive performance at 1 week in the surgical groups.

Most Patients As Good or Better Than Before

At 8 weeks, however, nearly all patients had recovered to preoperative levels, with 25% of CABG patients and 13% of surgical controls improved above baseline. Eleven CABG patients (68.8%) and 12 surgical controls (80.0%) were at preoperative levels at 8 weeks.

“The results of the present study demonstrated that most of the cognitive decline observed a week after the operation is attributable to the confounding effects of stress, anxiety, and depression,” the researchers observe. They note that after controlling for mood state, “motor and information-processing domains showed the greatest likelihood of decline, whereas verbal memory and fluency and visuospatial functions were unaffected.”

Overall, the CABG group performed worse than surgical controls on all cognitive tests at every time point, although the difference was not always significant. Nevertheless, “the consistency of the difference indicates that CABG patients have impaired cognition before the operation and this disadvantage remains afterwards,” Dr. Robinson and colleagues note, adding that eventually patients “return to preoperative levels or better.”

Procedural Factors to Blame, Not Bypass

An important take-home message from the study, notes Ola A. Selnes, PhD, of the Johns Hopkins Hospital (Baltimore, MD), in an accompanying commentary, is that “both surgical groups had a similar degree of postoperative decline 1 week after operation, suggesting that factors relating to the operation itself and to anesthesia, rather than the use of cardiopulmonary bypass, could account for the immediate postoperative decline.”

In fact, the overall risk estimates for postoperative neurologic complications after CABG “have improved substantially,” he writes.

These gains should serve as reassuring news to patients, he added in a press release. “Patients can be told that since there is no evidence that conventional . . . on-pump CABG surgery . . . is associated with worse neurological outcomes than other types of revascularization, such as [PCI] or off-pump CABG surgery, the choice of procedure should be guided by what is good for the individual patient as opposed to the risk of adverse neurological outcomes,” Dr. Selnes said.

In a telephone interview with TCTMD, Michael E. Halkos, MD, of Emory University School of Medicine (Atlanta, GA), noted that he was not surprised at the transient dip in neurocognitive function and a return back to baseline. He cited previous research by Dr. Selnes and others at Johns Hopkins appearing in the Annals of Neurology (2008;63:581-90) in which long-term cognitive results were compared between CABG and nonsurgical patients with CAD.

Stroke Still a Concern with CABG

The earlier research showed that nonsurgical patients “had a comparable level of neurocognitive decline over many years, suggesting it wasn’t really the surgery that was associated with the neurocognitive dysfunction over the long term but really just the nature of atherosclerotic and cerebrovascular disease,” Dr. Halkos said. “There may be some transient problems after surgery associated with the bypass machine or microemboli or whatnot, but there is a substantial recovery to baseline.”

He agreed that the current study, though small, does support other large trials such as FREEDOM that support CABG vs. PCI over the long haul, but there are still issues to iron out with bypass surgery.

“This is further evidence that bypass surgery is probably associated with the most durable outcome,” he said. “The Achilles heel is the increased risk of stroke. Even though our stroke risks are low, they are still higher than PCI. Therefore it is imperative among surgeons to explore methods to minimize that risk; the ball’s in our court with regard to doing that.”

Study Details

Surgical controls received standard thoracotomies for lung biopsies or lobectomies.

 

---

Sources:
1. Bruce KM, Yelland GW, Smith JA, et al. Recovery of cognitive function after coronary artery bypass graft operations. Ann Thorac Surg. 2013;95:1306-1313.

2. Selnes OA. Invited Commentary: Recovery of cognitive function after coronary artery bypass graft operations. Ann Thorac Surg. 2013;95:1313-1314.

 

 

Related Stories:

• Studies Fail to Tame Controversy Over Off- vs. On-Pump CABG
• Japanese Registry Assesses Stroke Rates for Off- vs. On-pump CABG, PCI
• Off-Pump CABG Reduces Postoperative Stroke vs. Standard Surgery