In what will come as a surprise to many doctors, researchers in the United States how found that contrary to current belief, heart attack survivors with mild or no symptoms who wait three days or more to seek medical help, will achieve little benefit from the procedures used to open clogged arteries.
Opening arteries that are 100 percent blocked in the first 12 hours after a heart attack with angioplasty can quickly restore vital blood flow to the heart, and is considered the best treatment for almost all patients.
However doctors in the U.S. often open blocked coronary arteries with angioplasty in stable patients who have passed beyond this treatment window.
The early treatment restores blood flow to the heart, preserving the heart muscle and reducing the risks of death and heart failure, a chronic condition in which the heart pumps blood less efficiently.
But it seems 30 percent of acute heart attack patients, around 100,000 patients per year, arrive at the hospital after the 12-hour treatment window has closed.
This latest study says though many doctors assume some benefit would still be achieved with angioplasty, in fact it is at this stage no better than standard drug therapy at reducing the risk of death, a second heart attack or heart failure.
Lead study author, Dr. Judith Hochman of New York University School of Medicine says the findings that there was absolutely no benefit in performing angioplasty after the 12 hour window had passed were not what was expected.
Hochman says the research underscores the need for patients to seek treatment early for a heart attack.
She says though in some ways the results are disappointing, they do demonstrate how good medical therapy such as beta-blockers, ACE inhibitors, statins, and aspirin, has become, as critical life-saving medicines.
The study covered a four-year period, involving 2,166 stable heart attack survivors at 217 sites on five continents and looked at patients who were treated with either drugs or angioplasty to see how long their arteries stayed open and whether angioplasty helped improve the heart's pumping efficiency.
The patients were randomly assigned by computer to receive medical therapy alone or medical therapy plus balloon angioplasty and stenting, a procedure where a catheter is passed through the artery, inflating a balloon in the blocked vessel and inserting a tiny, wire-mesh tube or stent to keep the artery open.
The study found there was no statistically significant difference between the two groups in the occurrence of death, heart attacks, or heart failure in up to five years of follow up.
The researchers say however that they saw a "worrisome" trend toward excess rates of repeat heart attack in the group receiving the angioplasty and stents.
The study called TOSCA-2 originally started as an independent trial funded by the National Institutes of Health and was later combined with a larger trial, Occluded Artery Trial known as OAT.
It found that 83 percent of arteries stayed open in patients treated with angioplasty, compared with only 25 percent in the medication group, but the treatment did not improve the heart's pumping ability.
The study is published in the New England Journal of Medicine.