Heart Surgery and Quality of Life
After demonstrating earlier this year that more than 40 percent of coronary artery bypass patients have measurable cognitive declines five years after surgery, Duke University Medical Center researchers have now shown that these patients also have a worse quality of life.
The researchers say that their findings provide compelling evidence that more research is needed in developing strategies that can be employed either before or during surgery to protect the brain.
"Given the trends of operating on the hearts of older and older patients, the effects on cognitive functioning must be considered if we are to restore the quality as well as the quantity of life," said Duke anesthesiologist Dr. Mark Newman, who led a team of Duke investigators whose findings were published Dec.7 in the December issue of the journal Stroke.
The Duke study was supported by grants from the National Heart, Lung and Blood Institute, as well as the American Heart Association.
"We should spend as much attention on ways to improve the protection of the brain, and thus the quality of life, as has been spent in preserving the health of heart tissue," Newman said. "While it is generally appreciated that heart surgery improves the quality of life, it appears that these cognition issues can be a factor limiting quality of life improvements."
In February, the Duke team published in The New England Journal of Medicine the results of the largest study of its kind, which showed that five years after heart surgery, 42 percent of patients had measurable cognitive decline. In this study, 261 heart surgery patients took the same battery of standardized cognition and quality-of-life tests at different intervals during a five-year.
While the researchers reported the results of the cognition tests in February, the current paper is an analysis of seven standardized tests that measure different aspects of quality of life, ranging from employment status, depression, social support and physical limitations.
"In this additional analysis of quality-of-life data, we found a consistent and broad association between the decline in cognitive function and worse quality of life, independent of the recognized effects of age, gender, diabetes and education," Newman added. "With reduced cognition, patients are less likely to be working, are more likely to be depressed or anxious, and have a reduced ability to maintain normal functions of independent living."
Researchers used the following seven standardized tests, which, when taken together, provided a broad indication of how a patient perceives their quality of life:
* The Duke Activity Status Index, a 12-item scale that measures a patient's physical capacity for such everyday activities as walking, personal grooming, sexual relations and household tasks.
* The Medical Outcomes Study 36-Item Short Form Health Survey, which measures respondents perceptions of their overall health status.
* The Center for Epidemiological Studies Depression Scale, a 20-question test which measures symptoms of depression. Patients rate the degree to which they have experienced depression on such items as "I had crying spells" or "I feel lonely."
* The Spielberger State and Trait Anxiety Inventory, a 40-item test that measures current and chronic anxiety. Patients rate such items as "I feel nervous" or "I feel worried" on a four-point scale.
* The Mini-Mental State Examination is a general assessment of cognitive functioning which tests such areas memory, reading and writing capabilities, orientation, mathematical calculations and language.
* The Perceived Social Support Scale, a 12-item scale measuring how strongly patients agree that there "is a special person who is around when I am in need" and "my family really tries to help me."
* Working Status, a one-item scale ranging from full-time employment to disabled.
"By tapping into a broad range of measures, we tried to get an overall picture of quality of life, and across all the measurements we used, there was a consistent and significant association between impaired cognitive function and quality of life," Newman said. "While similar associations have been drawn in other diseases, no one before has looked at these issues in heart surgery patients.
Coronary artery bypass grafting (CABG) is a surgical procedure performed more than 600,000 times a year in the United States for the treatment of coronary artery disease. Typically, surgeons use pieces of blood vessels from other parts of the body to "bypass" clogs in coronary arteries, thereby restoring blood flow to the heart.
The researchers say it is likely that many factors contribute to the cognitive declines, although they believe that blood clots caused by the heart-lung bypass machine commonly used in CABG surgery is an important underlying cause. This machine essentially pumps and oxygenates the blood for the body while surgeons operate on the stopped heart. Researchers believe that tiny blood clots form and travel to the brain, causing cell death in effected areas.
The Duke team is investigating strategies to better understand cognitive decline with the hope of developing ways to protect the brain. These strategies include minimally invasive surgery, which does not require the heart-lung machine, as well as re-warming patients at a slower rate after surgery. The Duke team has even found a genetic component that may contribute to cognitive decline. Patients with the E-4 variant of the APOE gene (which has also been linked to early onset Alzheimer's disease) tend to do worse than patients with other variants of the gene.
Joining Newman in this study were Duke researchers Dr. Hilary Grocott, Dr. Joseph Mathew, William White, Dr. Kevin Landolfo, Dr. Jerry Reves, Dr. Daniel Laskowitz, Dr. Daniel Mark and James Blumenthal. All are members of the Duke Neurological Outcome Research Group and the Cardiothoracic Anesthesiology Research Endeavors group.
DURHAM, N.C. - DukeMed News