PITTSBURGH, April 5 -- Diabetic patients on medication who have had coronary bypass surgery are more likely to survive a heart attack than are diabetics who have had angioplasty, announced researchers at the University of Pittsburgh's Graduate School of Public Health (GSPH) in the April 6, issue of The New England Journal of Medicine.
"Bypass surgery provides a protective effect that accounts for the dramatic difference we found in the overall death rates of diabetic patients who underwent one of these two revascularization procedures," said Katherine Detre, M.D., Dr. P.H., director of the Epidemiology Data Center at the University of Pittsburgh's GSPH and a principal investigator on the study.
This finding is a result of the Bypass Angioplasty Revascularization Investigation (BARI), an international, multi-center, randomized study coordinated by the University of Pittsburgh's GSPH and funded by the National Heart, Lung and Blood Institute (NHLBI), one of the National Institutes of Health. The study compared coronary artery bypass graft surgery with percutaneous transluminal coronary angioplasty in patients with multivessel coronary artery disease who had not previously received either procedure but who were medically qualified for both.
A total of 3,603 patients participated at 18 clinical centers, including two centers in Canada. Participants were classified as diabetic if they were receiving insulin or oral hypoglycemic medication. All participants underwent revascularization within three months of entry into the study.
BARI researchers found that mortality at five years was 8 percent for the 2,962 patients without diabetes and 20 percent for the 641 patients with diabetes. Mortality rates were 7 percent for non-diabetics and 18 percent for diabetics among those patients who underwent bypass surgery, and 8 percent and 25 percent respectively for those who had angioplasty. However, among diabetic patients who had heart attacks subsequent to the start of the study, mortality at five years after the heart attack was 17 percent for those who had undergone bypass surgery (similar to the rate for non-diabetics), as compared with 80 percent among those who had undergone angioplasty.
Both types of coronary revascularization resulted in an immediate increase in the amount of heart muscle receiving blood flow. But investigators noted that after one year, the vessels of those patients who had undergone bypass surgery remained open to a greater degree, thus protecting them from the potentially fatal damage brought on by a heart attack.
In a seven-year follow-up on study participants reported in the April issue of The Journal of the American College of Cardiology, Dr. Detre and other BARI researchers confirmed previous findings showing that diabetic patients with multivessel blockages who underwent coronary bypass surgery had at five years a markedly lower death than similar patients treated with angioplasty.
"Bypass surgery's protective effect for diabetic patients who have subsequent heart attacks helps to explain why bypass patients were experiencing dramatically lower seven-year death rates than those patients who had undergone angioplasty," said Dr. Detre.
The lower death rates were first announced in 1995 at a NHLBI press conference in Washington, D.C. While investigators were only five years into the BARI study at that time, those preliminary findings were announced to alert physicians treating diabetic patients.
"The announcement in 1995 had a profound effect on the way physicians care for diabetic patients who are on drug therapy and who have multiple coronary blockages," said Dr. Detre. "Through recommending bypass surgery as the first-time revascularization therapy for patients in this category, we are confident that many lives have been saved. Our latest findings confirm that bypass should be the standard of care in diabetic patients like those in BARI."
Approximately 14 million people in the United States have diabetes, either diagnosed or undiagnosed, making it one of the country's most common chronic health problems. These individuals are approximately two to four times more likely to have heart disease than are those without diabetes. Coronary revascularization is an important treatment for clinically severe coronary artery disease.
"Because of diabetics' increased incidence of coronary artery disease, we anticipated a higher mortality rate for them after seven years, regardless of the revascularization procedure. However, the excess mortality with angioplasty was unexpected," remarked Dr. Detre.
The goal of both bypass surgery and angioplasty is to relieve or bypass blockages in coronary arteries, thus improving blood flow to the heart. In angioplasty, a catheter with a tiny balloon at one end is used to flatten the build-up of plaque against the artery wall, thus opening up the passage and improving blood flow. In a coronary artery bypass operation, a blood vessel (usually taken from the leg or chest) is grafted onto a blocked artery, bypassing the obstruction. The blood is thus rerouted around the obstruction.
Before angioplasty was introduced in the United States in 1977, bypass surgery was the traditional revascularization strategy. But with improved technology and physician expertise, the use of angioplasty grew to include patients with more complex and numerous blockages. This growth in the use of angioplasty raised concerns over its long-term effectiveness and safety as compared with bypass surgery and prompted the NHLBI to fund BARI to evaluate the two methods.
Established in 1948, the GSPH at the University of Pittsburgh is world-renowned for contributions that have influenced public health practices and medical care for millions of people. It is the only fully accredited school of public health in the Commonwealth of Pennsylvania and is one of the top-ranked schools of public health in the United States.
For more information about the GSPH at the University of Pittsburgh, access the school's website at http://www.pitt.edu/~gsphhome .