May 20 (HealthDay News) -- Only one-third of the people who come to a hospital with the intense chest pain that doctors call acute coronary syndrome should be assessed for artery-opening procedures within a few hours, a new Canadian study finds.
The rest are at lower risk for a heart attack and won't be harmed by waiting a day or two, the researchers added.
There is often an issue about whether such assessment and treatment is needed quickly, said Dr. Shamir R. Mehta, director of interventional cardiology at McMaster University in Ontario and lead author of a report in the May 21 issue of the New England Journal of Medicine. "Settling this issue is very important, and that is why the study was done."
Acute coronary syndrome may mean "anything from a threatened heart attack all the way to a full-blown heart attack," Mehta said. "If it is not a full-blown heart attack, the patient may respond to medication, and we can wait a couple of days for it to stabilize."
The study included 3,031 people with acute coronary syndrome. Half were randomly assigned to get early assessment of coronary artery blockage followed by an artery-opening procedure if necessary -- on average, within 14 hours -- and the other half waited an average of 50 hours for such treatment. After six months, the incidence of death, heart attacks or stroke wasn't that different in the two groups -- 9.6 percent of those who had early intervention, 11.3 percent among those who waited.
But analysis of the results showed that the benefit was concentrated among those people who were graded as being at highest risk on a scale that included such factors as age, blood pressure and presence of biomarkers of heart injury. So the bottom line, Mehta said, is that "it is OK to wait unless you are at high risk."
The finding is useful in several practical ways, he said. For one, it helps settle a debate about whether early intervention might be harmful in some cases. "The study showed that early intervention does not increase the risk," Mehta said.
And then the findings can be applied to the not uncommon scenario when emergency department doctors have to deal with acute coronary syndrome at an awkward time or place -- late on Friday in a busy city hospital, for example.
"If you show up at 10 in the morning on Tuesday, you can have an angiography [which shows the extent of heart damage] by Tuesday afternoon," Mehta said. "If it is 10 p.m. on Friday, the vast majority of U.S. hospitals will not have an angiogram until Monday."
A judgment about whether quick treatment is needed can be made without much delay, said Dr. Richard A. Lange, vice chair of medicine at The University of Texas Health Science Center in San Antonio, and co-author of an editorial accompanying the study. "Most of the information can be gathered quickly, certainly by the time a patient is admitted to the intensive care unit," Lange said.
The issues with acute coronary syndrome start with "how intensive medical [drug] therapy should be," Lange said. "Then there is the question of whether the patient should go to the cath lab at all, or urgently. Those individuals who don't have many of the risk factors can receive less intensive treatment."
"Cath lab" is medical jargon for the hospital unit that does a coronary assessment by threading the thin tube called a catheter into a heart artery.
When the indicators show that someone is not at high risk, "you give intensive medical treatment and then go to the cath lab," Lange said. "For those at highest risk, you go right to the cath lab."
"The study showed that the majority of patients are not high risk," Mehta said. "They can go for angiography early or later."
SOURCES: Shamir R. Mehta, M.D., associate professor, medicine, and director, interventional cardiology, McMaster University, Hamilton, Canada; Richard A. Lange, M.D., vice chair, medicine, University of Texas Health Science Center, San Antonio; May 21, 2009, New England Journal of Medicine