Related terms: myocardium, coronary arteries, myocardial ischemia
Your heart is made of muscle, called the myocardium. The heart muscle, like every other organ or tissue in your body, needs oxygen-rich blood to survive. Blood is supplied to the heart muscle by the coronary arteries, which sit on the surface of the heart. The coronary arteries branch off into smaller vessels that "dive" into the muscle and provide blood and nutrients to every part of the heart.
What is a myocardial bridge?
A myocardial bridge is a band of heart muscle that lies on top of a coronary artery, instead of underneath it. With a myocardial bridge, part of a coronary artery dips into and underneath the heart muscle and then comes back out again. The band of muscle that lies on top of the coronary artery is called a "bridge," and this is how the condition gets its name.
What are the risks of a myocardial bridge?
For the most part, a myocardial bridge is harmless. Patients with a myocardial bridge will have had it since birth, and most patients live their whole lives without ever knowing they have the condition.
However, some patients can develop myocardial ischemia because of a myocardial bridge. Myocardial ischemia means that the heart muscle is not getting enough oxygen-rich blood. When the heart "squeezes" (contracts) during the heartbeat, the bridge of heart muscle can "tighten down" on the artery, pinching it and decreasing the blood flow. Luckily, most of the blood flow through the heart happens during the "rest" phase of the heartbeat, not during the "squeezing" phase. Even so, the tightening of the bridge on the artery can decrease blood flow enough that myocardial ischemia develops, especially during exercise or when the heart is beating quickly.
What are the symptoms?
Up to one-third of patients with a myocardial bridge do not have any symptoms, even if their hearts are not getting enough blood supply. If patients do have symptoms, they are most likely caused by the myocardial ischemia. Symptoms may include
- Chest pain
- Tightness in the chest or a feeling of pressure or heaviness on the chest
- Pain in the left arm or jaw
- Shortness of breath
- Fatigue (feeling very tired)
How is it diagnosed?
If your doctor thinks your symptoms might be caused by ischemia, he or she will want to use tests that show how blood is delivered to parts of your heart. A diagnosis is usually made using one or more of these tests:
- Cardiac catheterization, which is a method that involves threading a long, thin tube (called a catheter) through an artery or vein in the leg or arm and into the heart. Doctors usually combine cardiac catheterization with a test called angiography, which is an x-ray technique where dye is injected into the heart's chambers and the coronary arteries. The test lets doctors measure the blood flow and blood pressure in the heart chambers and see if the coronary arteries are blocked.
- An exercise stress test, which helps doctors see how the heart performs during exercise. You may also hear exercise stress tests called exercise tolerance tests, stress tests, exercise EKGs, or treadmill tests. Exercise stress tests can give doctors a lot of information about the structure of and the blood flow through your heart.
- A nuclear (thallium) stress test, which lets doctors see pictures of your heart while you are resting and shortly after you have exercised. The test can give information about the size of the heart's chambers, how well the heart is pumping blood, and whether the heart has any damaged or dead muscle.
How is it treated?
In most patients, a myocardial bridge is not treated if it is not causing any symptoms. In patients with symptoms, medicines such as beta-blockers and calcium channel blockers are usually the first line of treatment.
In rare cases, patients need surgery to relieve their symptoms. Surgery involves removing the bridge that is pressing on the coronary artery.
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Updated October 2012