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Harvard Heart Letter | April 2008
Big trouble from small arteries
Problems in the heart’s tiniest arteries can pose challenges for diagnosing and treating chest pain.
The
old adage “Out of sight, out of mind” captures a common response to a
seemingly mysterious condition — frequent chest pain or other telltale
signs of poor blood flow to the heart muscle with “clean” coronary
arteries. People with this puzzling combination are often told they are
“fine” in spite of symptoms every bit as real, and as debilitating, as
those caused by a cholesterol-clogged coronary artery. Some struggle
with the problem for years, doubted by their doctors, their symptoms
chalked up to depression, anxiety, or even hypochondria.
The
large coronary arteries don’t have a monopoly on heart disease.
Research is revealing that trouble in the heart’s smallest arteries can
cause classic symptoms of heart disease, like chest pain and shortness
of breath, along with less well-recognized ones such as diffuse
discomfort in the chest or unusual exhaustion.
This
condition, called coronary microvascular disease, affects as many as
three million American women and an unknown, but probably smaller,
number of men.
Peeking into microvessels
Chest
pain and other symptoms that the heart muscle isn’t getting enough
blood have traditionally signaled a narrowing or blockage in one or
more of the heart’s large arteries. Advances in technology that let
doctors “see” into the heart’s smallest arteries, called coronary
microvessels, are broadening the concept of coronary heart disease.
In
some people — women more than men — coronary microvessels stiffen and
become unable to relax and dilate. “When microvessels lose their
ability to respond to the heart’s changing demands for oxygenated
blood, chest pain and other symptoms can follow no matter how clean the
larger coronary arteries are,” says Dr. Jane A. Leopold, a cardiologist
who directs the Women’s Interventional Cardiology Health Initiative at
Harvard-affiliated Brigham and Women’s Hospital.
Microvessel disease
The arteries that actually deliver blood to the heart muscle are too small to be seen on an angiogra
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Detecting microvascular disease
There
isn’t yet an easy way to identify coronary microvascular disease. The
best test so far, called coronary artery flow reserve or coronary
vascular reactivity, requires maneuvering an ultrathin wire with
sensors at the tip into a coronary artery. It measures blood flow and
pressure before and after infusing into the heart medications that
should cause microvessels to dilate. The smaller the change in pressure
and flow, the stiffer the microvessels. This test is done only at a
small number of cardiac centers in the country.
Researchers
are exploring noninvasive ways to detect coronary microvascular
disease. One possibility is cardiac magnetic resonance imaging (MRI).
It entails making MRI scans before and after infusing the heart with a
drug that dilates the tiniest coronary arteries. Another test, called
reactive hyperemia peripheral arterial tonometry, uses a sensor placed
on a fingertip to gauge blood vessel flexibility.
“You’re fine” isn’t an answer
The
concept of coronary microvascular disease hasn’t yet percolated into
mainstream medicine. One reason for the slow spread is that “we don’t
yet have good tools for diagnosing coronary microvascular disease or
know how best to treat it,” says Dr. C. Noel Bairey-Merz, director of
the Women’s Heart Center at Cedars-Sinai Medical Center in Los Angeles
and a leading researcher in this field. But take heart, she counsels
women. The rise of centers devoted to women’s cardiovascular care
coupled with intense research into coronary microvascular disease
should mean that even community cardiologists will recognize it in a
few years.
How best to treat coronary microvascular disease
is another gray area. Relieving symptoms is essential. It helps an
individual feel better, be more active, and get on with her or his
life. It also indicates that the small arteries are open, which is good
for the heart’s long-term health. Standard anti-angina drugs that work
by relaxing blood vessels, such as nitroglycerin, can help ease
symptoms. Beta blockers and calcium-channel blockers work, too, though
whether one is better than the other must be hashed out in future
studies.
Preventing a heart attack is the other goal of
treatment. Key strategies for this include taking low-dose aspirin,
aggressively managing blood pressure, cholesterol, and blood sugar
levels, and addressing smoking, excess weight, inactivity, and other
risk factors.
Although much remains to be learned about
coronary microvascular disease, it’s time for doctors to wake up to the
fact that heart disease doesn’t always look the same in women and men.
Diagnosing it requires careful listening as much as judicious testing.
If you have recurrent chest pain and your doctor says you’re fine just
because you have clean coronary arteries, seek a second opinion. A
doctor affiliated with a women’s cardiovascular care center may be your
best bet.
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