If a "standard approach" to identifying and diagnosing heart disease exists, it goes something like this: You notice pain or tightness in your chest. Your doctor sends you for an exercise stress test. As you walk on the treadmill, the electrocardiogram shows that part of your heart isn't getting enough oxygenated blood. Next stop: angiography. This special x-ray shows that cholesterol-filled plaque has narrowed one of your coronary arteries by 75% or more. Treatment follows.
This sequence, it turns out, doesn't work nearly as well in women as it does in men. Many women don't have the strength or endurance to complete an exercise stress test. And a whopping half or more of women who have alarming stress tests have what look to be clear coronary arteries on an angiogram.
In the past, such women were told not to worry; this wasn't really dangerous heart disease. Ongoing work from a study of women with chest pain is replacing this with a more urgent message: There's a stealth form of heart disease that doesn't show up on angiograms, and it might be just as bad for you as the traditional type.
Doctors have traditionally used a one-size-fits-all approach to identifying and diagnosing heart disease. In this view, women often lack the "classic" signs of reduced blood flow to part of the heart, a condition known as ischemia. They have "false-positive" stress tests nearly five times as often as men.
This is gradually giving way to the realization that ischemia can have different causes and different effects in women and men.
Inside arteries, LDL (bad) cholesterol particles work their way into the inner lining of an artery. White blood cells migrate to these deposits and gorge on LDL particles. Over time, as the cycle is repeated, the mixture of LDL and dead white blood cells expands and bulges into the artery. Cardiologists call this bulge a plaque. The more a plaque pushes into the blood vessel, the less room there is for blood flow.
But chest pain or pressure can't always be traced to a bulging plaque. Between 50% and 60% of women, and about 20% of men, have chest pain or other symptoms when they are active or stressed even though an angiogram shows no plaques big enough to limit blood flow through the coronary arteries.
This condition has been attributed to spasms of the coronary arteries, heightened sensitivity to pain in and around the heart, or problems with small arteries that can't be seen on an angiogram.
To get a better handle on the origins and effects of chest pain, researchers started the WISE study back in 1996. They are tracking nearly 1,000 women who had chest pain or other symptoms of a blocked coronary artery but whose angiograms showed no plaques large enough to limit blood flow. Here are some eye-opening results:
Greater hazard. Data from studies show that women with coronary microvascular syndrome continue to have symptoms that disrupt their lives and are at greater risk for a subsequent heart attack or stroke, and have a poorer quality of life.
Outward expansion. In many women and some men, plaque expands outward, away from blood flow. Seen from the inside, the artery looks bulge-free and fine.
Size matters. Plaque can build up in coronary arteries that are too small to be seen on an angiogram. Problems in these smaller arteries could limit blood flow to the heart.
Endothelial function. In some women with coronary microvascular syndrome, a malfunction in the endothelium prevents coronary arteries from opening up and delivering more blood to the heart when needed, which can cause ischemia.
Beyond the stress test. Some women don't have the strength to do a full exercise stress test. An incomplete one doesn't yield useful results. The researchers show that answering simple questions about the ability to climb stairs, do housework, have sex, can help determine who is a good candidate for an exercise stress test and who might be better off with other tests.
Early warning. In the WISE study, the early onset of high systolic or pulse pressure was linked with higher chances of having significant coronary artery disease.
Anemia. Women with anemia were more likely to have had a heart attack or stroke or to develop heart failure.
This research has raised many questions, but one message is crystal clear: If you have chest pain or other worrisome symptoms when you exercise or are under stress, clean arteries don't necessarily mean your heart and arteries are fine. If your doctor dismisses you or your symptoms, it may be time to dismiss your doctor.
July 2006 update