Temporary blood ischemia that affects your heart is called myocardial ischemia, or cardiac ischemia, and results from a temporarily reduced flow of oxygen-rich blood to your heart. Cardiac ischemia can produce mild to severe effects on your heart. A stress-test exercise involving a treadmill and an electrocardiogram, or EKG, can help diagnose cardiac ischemia, notes the Texas Heart Institute.
Effects
Temporary cardiac ischemia is either a partial or complete blockage of an artery that carries blood and oxygen to your heart. This short loss of blood to your heart often results in chest pain, or angina pectoris, but can be asymptomatic, or silent, as well -- 3 to 4 million Americans have episodes of silent ischemia, according to a July 2010 report by the Texas Heart Institute. Any harmful effects of temporary cardiac ischemia can disappear spontaneously or with the use of medication -- as long as adequate blood supply is restored within the needed time frame. A heart attack can occur if an episode of cardiac ischemia lasts longer than 15 to 20 minutes, producing subsequent muscle and tissue damage, according to "Understanding Heart Disease" by Dr. Arthur Selzer.
Factors
The risks for myocardial ischemia include previous heart attack history, diabetes, high blood pressure, coronary artery anomalies, obesity, smoking and drug abuse. The most common cause of cardiac ischemia is coronary artery disease, or atherosclerosis -- the build up of plaque on your arterial walls. A brief coronary spasm, or contraction of arterial wall muscles, can also impede or prevent blood flow to parts of your heart muscles, notes MayoClinic.com. Additional contributing factors include blood clots resulting from atherosclerosis, severe illnesses, low blood pressure and infections.
Testing
Your doctor may advise you to take a treadmill stress test if you have symptoms of myocardial ischemia. Standard heart stress tests use an EKG machine in conjunction with a treadmill to determine the strength of your heart, your heart rate and whether your heart's rhythm is steady or abnormal. Other tests involve imaging machines that take pictures of your heart while you exercise to show how efficiently blood flows through your heart and how well your heart pumps blood as it beats. Little risk is involved in all types of stress testing: the risk of having a heart attack during a test is about 1 in 5,000, according to the National Heart, Lung and Blood Institute. More frequent, but less serious, side effects include arrhythmias, or abnormal heart beats, and low blood pressure.
Procedure
Make sure your doctor is aware of any medicines you are taking, and find out what, if any, dietary changes you need to make before the test. During the test, a nurse or technician places sticky patches or electrodes on your chest, arms and legs to prepare you for the EKG. Health factors such as chest pain and blood pressure are monitored as you gradually increase your walking or running speed on the treadmill to attain 90 percent of your predicted maximum heart rate, according to Dr. Selzer. After testing, depending on your test results and other factors, you can return to normal activities or your doctor may prescribe additional testing. Also, if your test involved imaging, which uses radioactive dye, you may need to drink plenty of liquids to wash the dye out of your system.
References
- Texas Heart Institute: Silent Ischemia
- Mayo Clinic: Myocardial Ischemia
- "Understanding Heart Disease"; Arthur Selzer; 1992
- National Heart, Lung and Blood Institute: Key Points
- National Heart, Lung and Blood Institute: What To Expect Before Stress Testing
- National Heart, Lung and Blood Institute: What To Expect During Stress Testing
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