Angina and its silent cousin

When your heart muscle doesn't get enough blood, chest pain is possible. But you might not feel anything at all.

The word ischemia comes from a Latin term that means "stopping blood." But if you have cardiac ischemia, blood flow to your heart doesn't actually stop. Instead, the supply of blood is temporarily less than the heart muscle needs. The most likely culprit is a coronary artery narrowed by cholesterol-laden plaque. A bout of ischemia can happen when your heart works harder, such as during exercise or emotional stress.

The resulting shortfall in oxygen-rich blood to your heart muscle can cause the chest discomfort known as angina. This pain may spread to your shoulders, arms, neck, or jaw. But here's a little-known fact: some of the time, ischemia causes no symptoms. And this so-called silent ischemia is surprisingly common.

"People with heart disease may have five to 10 times as many episodes of silent ischemia as symptomatic ischemia," says Dr. Peter Stone, a professor of medicine at Harvard Medical School and director of the vascular profiling research group at Brigham and Women's Hospital. Silent ischemia is exactly like angina, except that you don't feel it. While some people have only angina and others have only silent episodes, most people with narrowed arteries have both types. In both conditions, the heart's nerves seem to react in the same way. But when silent ischemia occurs, the pain signal may be processed differently in the brain, says Dr. Stone.

Detecting ischemia

Diagnosing angina is sometimes straightforward. Shortness of breath and sweating often accompany the chest discomfort. The more common form, called stable angina, lasts just a few minutes and goes away quickly when you rest or take medication such as nitroglycerin. Unstable angina, which builds in intensity and lasts minutes to hours, requires a trip to the emergency department. It often occurs with only slight physical exertion and can even happen when you're resting or sleeping.

Detecting silent ischemia is much more challenging. Most of the time, it's discovered during a stress test to check for possible heart disease. The electrocardiogram (ECG) tracing, which records the heart's electrical activity, shows a distinct pattern that suggests the heart is not getting enough blood. When the pattern (called ST segment depression) occurs without symptoms, it may indicate silent ischemia. ECG monitoring with a portable device that you wear for a day or two may also reveal silent ischemia.

Restoring the heart's blood flow

Having ischemia—whether it's painful or not—does make you more prone to a heart attack. That's particularly true if you have other factors that raise your risk of heart disease, such as smoking or having high cholesterol or high blood pressure.

Treatment may include drugs such as

•  beta blockers, which lower the heart's workload

•  calcium-channel blockers and nitrates, which widen blood vessels

•  ranolazine (Ranexa), a drug that appears to increase the blood flow to areas of the heart muscle with ischemia.

People with severe ischemia may need additional testing and, in some cases, an artery-opening angioplasty plus a stent.

But the nature or magnitude of the pain doesn't always affect a person's prognosis. The main problem with angina is that it's very distressing. "The pain creates anxiety and is a constant reminder that you have a disease," says Dr. Stone. For people with chronic angina, anti-angina medications can be increased to reduce both angina and silent ischemia. Still, the most important steps are to follow the standard heart-protecting habits: eating right, getting regular exercise, maintaining a healthy weight, and keeping blood pressure and cholesterol down—with medications if necessary.