Back in 2001, a study from Duke University showed that many patients having coronary artery bypass grafting (CABG) experienced a measurable decrease in mental capacity after surgery, which persisted for up to five years. This cognitive decrease after CABG has been called "pump head," because doctors have speculated that perhaps the heart/lung machine (the "pump") that is used during CABG was the culprit.
In the last few years, however, a few studies compared outcomes in patients having typical "on-pump" CABG with those having minimally invasive bypass procedures (which do not require the heart/lung machine). These studies did not show any reduction in "pump head" with the minimally invasive surgeries.
And now a study from Utrecht suggests that pump head might not even exist. This study compared the outcomes in 152 patients having typical on-pump CABG surgery -- 75 patients had minimally invasive off-pump procedures, and 99 patients did not have any bypass surgery (their coronary artery disease, or CAD, was treated medically). All the patients had formal testing of their cognitive function prior to surgery (or, for those not having surgery, at the time of enrollment into the study) and then periodically for six years. The investigators also did the same cognitive testing in a group of healthy control patients for the same time period.
The results of this study found that all three groups of patients with CAD had (on average) some reduction in cognitive function at baseline, compared with the healthy control patients. Further, the cognitive performance of all three groups with CAD tended to deteriorate over the duration of the study, regardless of the type of therapy they received.
The authors of the Utrecht study concluded that the long-term cognitive decline often seen after bypass surgery is apparently not due to the surgery at all, but instead to the patient's underlying vascular disease. That is, they suggest that the atherosclerosis that causes CAD is also causing a certain degree of reduced blood flow to the brain, and a gradual reduction in mental capacity.
What Does This New Information Mean?The Utrecht study does not fully vindicate bypass surgery as a cause of mental status changes. In fact, a temporary reduction in mental capacity (lasting up to several months) is indeed seen in many people after traditional CABG, and even after minimally invasive bypass surgery. Furthermore, the people who experience these transient changes in mental function after surgery appear to be the very ones who, once they recover, are at particular risk for the kind of long-term deterioration in cognitive function that was measured in the Utrecht study.
Possibly the most important take-away here is that atherosclerosis is not "merely" a disease that can block the coronary arteries, or that can be "fixed" by surgery, stenting, or any other local procedure. Rather, atherosclerosis is a chronic, progressive vascular disease that can affect several important organs in the body, including the brain. Anyone who has atherosclerosis, or who is at increased risk for atherosclerosis, needs to do everything they can to reduce the risk factors that accelerate this chronic, progressive disease.
Newman MF, Kirchner JL, Phillips-Bute B, et al. Longitudinal assessment of neurocognitive function after coronary-artery bypass surgery. N Engl J Med 2001; 344:395-402.
Selnes OA, Grega MA, Bailey MM, et al. Do management strategies for coronary artery disease influence 6-year cognitive outcomes? Ann Thorac Surg 2009; 88:445-454.