A new analysis of half a million heart attack patients found that people with the warning signs of heart disease -- such as high blood pressure and cholesterol -- are more likely to survive their hospital stay than those with a cleaner bill of health.
Even when taking into account influences such as age and weight, the more heart-related risk factors patients had, the lower their chances of dying.
While it may seem counterintuitive, researchers said one possible explanation for the finding is that people who already had known health problems might have been on medications, including statins and beta blockers, that helped protect them after a heart attack.
"It certainly shows clinicians that if you don't have risk factors but you've had a heart attack, don't assume that they're going to do well," Dr. Carl Lavie, from the John Ochsner Heart and Vascular Institute in New Orleans, told Reuters Health.
"On the other hand, it's not doomsday for the person that has all the bad risk factors -- they can actually end up doing well," added Lavie, who wasn't involved in the study.
Data for the analysis came from a national registry of close to 550,000 first-time heart attacks in the U.S. between 1994 and 2006. During their hospital stays, doctors noted whether patients had some of the standard risk factors for heart disease, including high blood pressure or cholesterol, diabetes, a family history of heart disease and if they were smokers.
Among all patients, more than 85 percent had at least one of those risk factors -- and people with more of them had their heart attacks younger, on average.
Just over 50,000 of the patients in the study died in the hospital, according to findings published in the Journal of the American Medical Association and presented this week at the American Heart Association Scientific Sessions in Orlando, Fla.
After taking into account the fact that people with no risk factors were more often older, and adjusting for weight, race and gender, the study found that non-smokers with no high blood pressure, high cholesterol, diabetes or family history of heart disease were still 50 percent more likely to die in the hospital than people with all of those risk factors.
One in seven of those with none of the heart warning signs died after suffering a heart attack, compared to one in 28 patients with all five risk factors who didn't survive.
Dr. John Canto from the Watson Clinic in Lakeland, Fla. and his colleagues noted that patients with more risk factors were also more likely to get medications within the first 24 hours of their stay or to have heart surgery.
Those with pre-existing warning signs may also have been on heart-protecting medications before the heart attack, or had more regular contact with their doctors, Canto said -- but there's no way to know that for sure based on the data.
It's also possible that people without the traditional risk factors may have had other, unmeasured health risks that caused their heart attacks in the first place and upped their chance of death -- or that something about their blood flow after an attack was different than in people with more health problems, researchers speculated.
The findings mean that doctors shouldn't view patients who otherwise seem healthy as a group that's bound to do well after a first heart attack, Canto's team wrote -- in fact, they could do worse than other patients.
Still, the study doesn't suggest that smoking or having high blood pressure is in any way good for your heart, researchers emphasized.
"One of the important messages is that patients who have been diagnosed with a heart attack should not take this as evidence that those factors don't matter, or that having high cholesterol or high blood pressure protects them after the heart attack," said Dr. Francisco Lopez-Jimenez, a cardiologist at the Mayo Clinic in Rochester, Minn., who didn't participate in the new research.
"What's not apparent here is that people with more risk factors have a much higher risk of having a heart attack to begin with," Lavie agreed.
Canto told Reuters Health that what's most important is that people with high blood pressure or cholesterol, for instance, are treated with medication or make diet and lifestyle changes.
"The general population really needs to identify these risk factors so they can potentially be treated, and these treatments will improve your outcome" after a heart attack, he said.
In addition, he added, "As one ages, just because you have no risk factors, doesn't mean you shouldn't be seeing a doctor on a regular basis."