In a late-breaking clinical trial presentation of neurocognitive outcomes from the OctoStent trial, part of the Octopus Study, researchers reported 7.5 year cognitive results for 201 of an initial 280 low-risk patients with blocked coronary arteries.

Researchers randomly assigned patients to either OPCAB or the less-invasive percutaneous coronary intervention (PCI) with implantation of bare metal stents (mesh tubes).

“We found that although the patients had similar cardiac outcomes, without significant between-group difference in the composite of death, stroke, heart attack and re-interventions, the OPCAB patients had better long-term cognitive performance than the PCI patients,” said Jakub J. Regieli, M.D., PhD executive investigator of the study and a cardiologist in training at the University Medical Center in Utrecht, The Netherlands.

“Although the cognitive differences were subtle, they occurred in all seven cognitive domains we tested, which is remarkable,” said Regieli.”

Conventional coronary artery bypass graft surgery (CABG) may be associated with cognitive declines postoperatively, and past studies of OPCAB (CABG without the use of CPB (cardiopulmonary bypass-heart/lung machine) do not show a reduction in these declines, said Regieli. On the other hand, PCI may also be associated with neurological complications, and there is accumulating evidence that procedural micro-embolization occurs more frequently than previously assumed. Comparisons of CABG, OPCAB and PCI have in general been short-term, and have produced inconsistent results. In this first long-term clinical outcome comparison of OPCAB to PCI-stenting regarding cognition, researchers found no difference in mortality or heart attack rates, but significantly better cognitive performance, particularly in the areas of learning and verbal memory (the ability to remember words), in OPCAB patients compared to PCI patients.

“In addition, we observed a much higher absolute risk of re-intervention in the PCI versus CABG patients (30 percent versus 17 percent),” Regieli said.

In CABG, a patient’s heart is temporarily stopped and a heart-lung machine supports the patient’s circulation while the surgeon uses a graft vessel to create a detour around the area of blockage in an artery.

In OPCAB, the surgery is done on a beating heart so the heart-lung machine is unnecessary. In PCI, a balloon-tipped catheter is threaded into the area of blockage and the balloon is inflated to reopen the artery; a stent is usually placed to hold open the vessel.

“There is no clear-cut explanation for the beneficial cognitive outcome after OPCAB and the mechanisms cannot be deduced from the current study per se,” Regieli said. “The avoidance of any aortic manipulation during OPCAB, as pertains to the 85 percent undergoing only arterial revascularization in that patient group, may have resulted in less cerebral micro-embolization (solid atherothrombotic particles or air bubbles that can travel to and damage the brain). At the same time, in patients treated with stents, and bare metal stents in particular, repeated catheterization and PCI may induce more cerebral micro-emboli than currently assumed.”

More research is needed to confirm the findings from this small study, especially whether the findings can be extrapolated to the current era of drug-eluting stents. Also, additional analyses to better define determinants of neurocognitive outcome in these patients are underway, he said.

Study sponsors: UMC Utrecht, The Netherlands.