Duke Study: Canadian Health System Misses More People With Severe Heart Disease Compared to U.S. System
ANAHEIM, CALIF. -- Canada's health care system, which uses significantly fewer invasive procedures than the United States' system, fails to identify a significant number of severely ill heart attack patients who could benefit from coronary artery surgery, according to a study by cardiologists at Duke University Medical Center.
The study, presented Monday at the 68th annual American Heart Association meeting, is the first report to suggest long-term survival of heart attack patients may be greater in the United States than in Canada. The finding is significant especially in light of the vast difference in the number of heart attack patients who receive catheterization in the United States versus Canada. In the United States, about 71 percent of heart attack patients receive catheterization, versus 27 percent in Canada, the study found.
Cardiac catheterization or angiography allows physicians to see how many heart vessels are narrowed and how severely blocked they are to determine if bypass surgery or angioplasty is necessary. Catheterization involves inserting a thin tube into the coronary arteries. But while the procedure is an effective diagnostic tool, it is expensive, invasive and presents some small risk to the patient.
To determine how the more conservative Canadian approach compares to the more aggressive American approach, Duke cardiologists, led by Dr. Eric Peterson, and Canadian cardiologist Dr. Paul Armstrong of the University of Alberta, Edmonton, used data collected during the GUSTO (global utilization of streptokinase and tPA for occluded arteries) I study. The researchers included outcomes data from almost 20,000 U.S. patients and 2,500 Canadian patients. Previous studies have shown that the one-year survival rates after heart attack are equal in the two countries, but no data are yet available on long-term survival.
"This study is one of the first to show that aggressive intervention may be worth the extra cost," said Dr. Eric Peterson, assistant professor of cardiology at Duke. "Clearly, the more aggressive approach identified more patients with severe coronary artery disease."
After a heart attack, doctors must determine how diseased the patient's heart is before deciding the most effective treatment. Studies show that patients with severe disease, defined as three diseased coronary arteries or a blocked left, main artery, benefit greatly from bypass surgery.
The investigators had predicted the more conservative Canadian strategy, in which doctors pre-select who should get angiography, would result in a greater number of patients diagnosed with severe disease relative to the total number who underwent the procedure.
"We were surprised to find the Canadian physicians didn't use the test more efficiently, since they appear to be more selective in its use," Peterson said. "On the contrary, even though U.S. doctors use the test more frequently, they identify more severely ill patients."
The result is 12 of every 100 heart attack patients are identified as having severe heart disease in the United States versus only 4.5 of 100 in Canada. Alternately, the Canadian physicians may be missing 7.5 heart attack patients who have severe disease, according to Peterson.
To further refine who is at risk for severe coronary artery disease, the Duke investigators created a predictive model based on known coronary risk factors to predict how many heart attack patients have severe heart disease. The Duke doctors say the model could help identify more of the patients who would benefit from bypass surgery or angioplasty.
"The study showed that Canada's selective catheterization strategy did not result in a more efficient use of catheterization, but rather missed a significant number of patients who could benefit from revascularization," Peterson said. "These results are significant because no data is available on long-term heart attack survival rates between the U.S. and Canadian systems of health care. We predict based on these results differences will be seen in long-term survival when such data becomes available."