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The guidelines are developed jointly by the American Heart Association and the American College of Cardiology. They are recommendations that cover a number of clinical issues, from medication to surgery.
"It has not been shown before that guidelines covering a particular medical procedure might or might not affect outcomes," said Dr. H. Vernon Anderson, lead author of the study that appears in the Nov. 1 issue of Circulation. "What we learned, as everyone had hopefully anticipated, was that if you adhere to the guidelines, the outcome will be better."
The study analyzed the impact of the guidelines, issued in 2001, for the selection of patients for procedures that are formally called percutaneous coronary interventions -- angioplasty, in which a balloon-tipped catheter is used to keep cholesterol deposits from blocking an artery; and stenting, in which a flexible tube is implanted to keep the artery open.
The guidelines divide patients into four classes, ranging from those whose condition makes them most likely to receive the greatest benefit from a procedure to those judged least likely.
Led by Anderson, who is a professor of medicine at the University of Texas Health Science Center in Houston, the researchers looked at results of procedures performed on more than 400,000 patients in 393 hospitals.
They found that 64 percent of the procedures were done on patients most likely to benefit; 21 percent on those patients somewhat less likely to benefit; 7 percent on those even less likely to benefit; and 8 percent on those judged least likely to benefit.
The success rate was 92.8 percent in the first group, 91.7 percent in the second group, 89.0 percent in the third group, and 85.5 percent in the last group.
The rate of complications and deaths showed the same pattern, with only 1 percent of patients in the most-likely-to-benefit group suffering heart attacks before hospital discharge, compared to 1.5 percent in the least-likely-to-benefit group. The death rate was 0.5 percent for the first group, 1.7 percent in the last group.
"The differences are small but significant, and show for the first time that guidelines criteria are related to real-world outcome," Anderson said.
So why do some cardiologists go against the guidelines?
"Physicians may feel that their judgment in an individual case is better," said Dr. Gregg Fonarow, a professor of cardiovascular medicine at the University of California, Los Angeles, and a spokesman for the American Heart Association. "But we see in this large data set that these guidelines are quite applicable."
And guidelines can change "as new clinical trial evidence becomes available," Fonarow said. For example, the guidelines for treatment of heart failure were first released in 1995, but they were updated in 2001, and again earlier this year.
In the end, "guidelines are only a suggestion," Anderson said. "It is always up to the individual physician to factor these things into clinical decisions."
More information
For more on the guidelines program, visit the American Heart Association.
The Evanston Northwestern Health Care study analyzed data from more than 350 teaching and community hospitals in the United States, and found that while both tobacco and alcohol increase colorectal cancer risk, women who smoke are at an especially increased risk.
"We can see that while both men and women who use tobacco and alcohol are diagnosed with colorectal cancer at an earlier age, the effect of tobacco is significantly greater in women," researcher Dr. Anna L. Zisman said in a prepared statement.
The findings were presented Monday at the American College of Gastroenterology annual meeting, in Honolulu.
Another study presented at the meeting found that people aged 75 years and older still benefit from colorectal cancer screening and experience no more complications from colonoscopy than younger people.
Most current guidelines recommend that colorectal cancer screening begin at age 50 for people at average risk, but there is no consensus about what age to stop screening.
"Older patients often have other health problems that increase the risk of undergoing endoscopy, so we need more evidence regarding the usefulness of screening in this older population. Our data support continued screening of elderly patients," Dr. Aaron Walfish, of Beth Israel Medical Center in New York City, said in a prepared statement.
He and his colleagues did a retrospective study of 178 patients, aged 75 and older, and 318 patients, aged 65 to 69. Both age groups had similar rates of polyps or masses (43 percent in those aged 75 and older vs. 42 percent in those aged 65 to 69). No complications from the colonoscopy were reported in either group.
More information
The U.S. National Cancer Institute has more about colorectal cancer.
An enzyme called iNOS triggers the production of nitric oxide (NO) gas that accelerates the formation of brain lesions in mice prone to Alzheimer's disease, researchers report.
This finding suggests that iNOS inhibitors -- which have already been produced and tested in humans -- may help slow the progression of Alzheimer's disease.
The study, by researchers at Cornell University Weill Medical College, in New York City, appears in the Nov. 7 issue of the Journal of Experimental Medicine.
For nearly a decade, scientists have been aware that iNOS is present in the brain lesions of Alzheimer's patients, but so far researchers haven't examined whether the enzyme actually made the disease worse. This study found that Alzheimer's-prone mice bred to lack iNOS lived twice as long and developed fewer brain lesions than Alzheimer's-prone mice with iNOS.
While both groups of mice developed Alzheimer's disease, iNOS-deficient mice did not experience the rapid accumulation of brain lesions as they grew older.
According to the study authors, the results suggest that iNOS inhibitors may prove more effective than current treatments for Alzheimer's disease. These existing therapies temporarily improve patient performance on cognitive tests but do not increase survival.
More information
The U.S. National Institute on Aging has more about Alzheimer's disease.
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