Hopkins study finds no "cognitive decline" after use of heart-lung machine during bypass surgery

Nov 10 2005

The use of a cardiopulmonary heart pump during coronary artery bypass grafting (CABG) surgery does not significantly damage such high-level mental tasks as thinking, reasoning and remembering, according to a study by Johns Hopkins researchers recently published in Neurology.

CABG surgery is effective for the relief of angina and reducing the risk of a heart attack but has been widely feared to cause "pump-related" damage to the cerebral cortex, according to Guy M. McKhann, M.D., a professor in the Department of Neurology at The Johns Hopkins University School of Medicine.

To gauge whether there was a clinical basis for this concern, McKhann led a non-randomized study comparing the cognitive abilities of on-pump CABG patients, off-pump CABG patients, nonsurgical patients with coronary artery disease and heart- healthy individuals.

The results of the study showed that on-pump CABG patients had no significant differences in their higher-level mental functions than the other groups tested, according to McKhann.

"This outcome should be reassuring to both patients and surgeons engaged in on-pump CABG surgeries," McKhann said.

The study, conducted between September 1997 and September 2003, involved 380 individuals -- 140 on-pump CABG patients, 72 off-pump CABG patients, 99 nonsurgical patients with coronary artery disease and 69 heart-healthy patients.

Both the on-pump CABG patients and the nonsurgical patients with coronary artery disease were exclusively Hopkins-based, whereas the off-pump CABG patients came from Hopkins; Sinai Hospital, Baltimore, Md.; Washington Adventist Hospital, Takoma Park, Md.; University of Maryland Medical Center, Baltimore, Md., and Pinnacle Health System, Harrisburg, Pa.

Study participants were given a battery of standardized neuropsychological tests that were repeated three months and 12 months later.

Test scores were sorted and combined into eight areas: verbal memory, visual memory, language, attention span, visuoconstruction (the ability to copy a complex figure), motor speed (the time to perform motor activity, such as writing the alphabet), psychomotor speed (the time to complete an action that requires some planning) and executive function (the ability to plan ahead and make judgments).

The Center for Epidemiologic Studies Depression scale (CESD) and Functional Status Questionnaire (FSQ) were also administered at baseline and follow-up and all subjects were tested by the same team of study investigators who traveled to all the sites in the study to examine patients. Previous test results were not reviewed before subsequent testing so that testers were unlikely to be able to bias results based on such knowledge.

Self-reporting of well-being was included in the study in the areas of memory, mental arithmetic, personality, and reading newspapers and books. For example, subjects were asked whether they thought their personality had improved, changed for the worse, or stayed the same over time and since the previous interview. Reading, defined as whether or not a patient typically read either newspapers or books, was assessed at each visit.

At the start of the study, subjects with coronary artery disease (CABG on-pump, CABG off-pump, and nonsurgical) had overall lower performance than the heart-healthy group in several cognitive domains. But by three months, all groups had improved, which McKhann says was most likely due to familiarization with the testing procedures. Between three and 12 months, there were minimal changes in individual subjects for all groups, and no consistent differences between the CABG and off-pump patients were observed.

"These results offer no evidence that the cognitive test performance of on-pump CABG patients differed from that of off-pump control groups with coronary artery disease over a one-year period," McKhann said.

Other researchers who participated in the study include O.A. Selnes, Ph.D., Department of Neurology, School of Medicine; W.A. Baumgartner, M.D., and M.A. Grega, R.N., M.S.N., Department of Surgery, School of Medicine; L.M. Borowicz Jr., M.S., and M.M. Bailey, B.A., the Zanvyl Krieger Mind/Brain Institute; S.J.E. Barry, M.S., and S.L. Zeger, Ph.D., Department of Biostatistics, Bloomberg School of Public Health.

The study was supported by a grant from the National Institute of Neurological Diseases and Stroke of the National Institutes of Health, a Johns Hopkins Medical Institutions GCRC grant, and the Dana Foundation.