There's something wrong with Denise Weiss.
''It's like somebody is squeezing my heart," she said, ''and their hand is like a red hot poker."
Once every couple of months, her heart convulses, always triggered by a different event: The first time, a year and a half ago, she was hiking in the mountains. Another time she was on her way out of a doctor's office. Then there was last Thanksgiving, when she was bathing her beloved German shepherd.
But when doctors peered into the major arteries of Weiss's heart using an angiogram, the gold-standard X-ray technique, they could find no blockages -- none of the evidence traditionally used to prove the existence of a serious cardiac condition.
The case of Weiss, 43, is the case of millions of women whose heart disease is missed by doctors and tests more accustomed to detecting problems in men.
When it comes to affairs of the heart, women really are different from men: They're much more likely to have trouble with the avenues and alleys that branch off from the major highways of the heart. And problems in those smaller vessels can't be detected by conventional methods.
Medical research published this month shows that as many as 3 million women in the United States suffer from a form of heart disease that hides from angiograms, which examine only the heart's three big arteries. That discovery is the product of a major study that aims to better understand the distinctive heart disease suffered by many women.
It promises to alter the way both doctors and patients respond to the signs of heart disease in women -- which may be more subtle than the clutched chest. And it offers hope that lives can be saved and improved.
Every year since 1984, heart disease, America's number-one killer, has claimed more women than men.
''In the past, those patients whose angiograms showed no big blockages would have been sent home and told you have no problem or it's in your head," said Dr. George Sopko, a cardiologist at the National Heart, Lung, and Blood Institute. ''Now, instead of saying, 'Go home, don't worry about it,' the patient needs to be carefully looked at and provided a plan."
The human heart is a marvel of engineering, with a network of pumping chambers and intricate plumbing that keeps oxygen-laden blood coursing through the body.
Everything keeps working as long as the heart itself gets enough blood.
When it doesn't, patients can be left with acute pain, shortness of breath, nausea. The heart begins to starve from lack of oxygen.
''In fact," said Dr. Alice Jacobs, a Boston University professor and past president of the American Heart Association, ''women have a greater degree of symptoms than men, but they have less evidence of blockage in the big arteries."
The landmark study that appeared this month in the Journal of the American College of Cardiology tracked 936 women with symptoms so concerning that doctors ordered an angiogram, an X-ray that's taken after dye is injected into the heart.
Only one-third of the women had significant blockages, while the rest appeared to have free-flowing arteries. But further tests showed that half of the women whose angiograms were clear actually had problems in other, smaller vessels that carry oxygen to the far reaches of the heart.
''What we've forgotten is these small vessels play a critical role," said Dr. C. Noel Bairey Merz, chairwoman of the study and medical director of the Women's Health Program at Cedars-Sinai Medical Center in Los Angeles. ''Their inability to dilate can result in the same consequences as if there were blockages in the big arteries."
So why do women have problems with that network of tiny vessels?
Scientists are still trying to figure out what's to blame -- and what's not.
They know, for example, that women's blood vessels tend to be smaller than men's, and that could predispose them to a condition known as coronary microvascular syndrome.
In women with that condition, a fatty substance called plaque tends to spread out along the inside of the vessels rather than clumping, as it does in the arteries of many men.
''There's not plaque in the traditional way that we think of it in the three major coronary arteries," said Dr. Francine Welty, a cardiologist at Beth Israel Deaconess Medical Center. In those big arteries, plaque is like a bad car wreck that gums up traffic.
In the small arteries, the effect is less dramatic. But plaque could be quietly causing structural defects, compromising their ability to narrow and widen so that blood can pass through.
One thing is certain: Researchers say it's no longer acceptable for a woman who shows signs of heart disease to be given an automatic clean bill of health if an angiogram fails to turn up problems.
''If the cardiologist a woman is seeing is brushing her off, doesn't want to do further testing, she should see another cardiologist," Bairey Merz said.
Further testing could mean something simple, like asking 12 questions to gauge her ability to perform routine physical tasks. The answers to those questions, researchers found, can provide valuable clues about how well a woman's heart is working.
In other cases, doctors use chemicals to stimulate a woman's heart to pump faster and harder; if her vessels don't respond by pumping more blood, physicians know there's a problem. In still other cases, high-tech snapshots, such as magnetic resonance imaging, are used to see how well vessels are functioning.
But those technologies aren't perfect, and neither are the treatment options.
So women are told to look at conditions and behaviors that might be contributing to their heart disease, such as diabetes and high blood pressure. They're told to stop smoking and start exercising. They're prescribed pills called statins to boost their good cholesterol and other drugs to quiet the roar of high blood pressure.
Denise Weiss of Beverly Hills, Calif., takes those kinds of medications now. And today, she is scheduled to have a picture of her heart taken by one of those sophisticated imaging machines.
Maybe, she said, it will help answer why, every other month, her heart betrays her.
Stephen Smith can be reached at email@example.com.