Stress tests measure electrical (EKG/ECG) changes to your heart during stress and exercise. The results of the test help your doctor diagnose coronary artery disease (CAD). Stress tests include:
Nuclear Stress Test
A nuclear stress test measures blood flow to your heart muscle at rest and during stress/exercise. It is performed similar to a regular stress test but provides images in addition to electrocardiograms. During a nuclear stress test, a very low level of radioactive substance is injected into your bloodstream. This substance mixes with your blood and travels to your heart. A special scanner, which detects the radioactive material in your heart, creates images of your heart muscle. Inadequate blood flow to any part of your heart will show up as a light spot on the images, because not as much of the radioactive substance is getting there.
Nuclear stress testing combines a regular stress test with the powerful tool of nuclear imaging. The stress portion of the test may be similar to that done during regular stress testing (on a treadmill) or it may be a medication induced stress test with persantine or adenosine (a medication given intravenously). Nuclear pictures of the heart are taken before and after exercising. Abnormalities in these pictures tell us if there is a blockage in the arteries in your heart. It can even tell you if you had a heart attack in the past. The test will also calculate an "ejection fraction" which is a measure of how well the heart muscle is pumping.
Before Your Nuclear Stress Test
Do not smoke or drink caffeine for 24 hrs before the test. Do not eat for four hours before the test. Small sips of water are allowed. This type of test should not be performed during pregnancy.
During Your Nuclear Stress Test
Electrodes (small pads) are placed on your chest and stomach. These connect you to the EKG machine. The technician will show you how to walk on the treadmill. As the test goes on, the speed will increase and the angle will become steeper. Try to walk as long as possible. The further you go on the treadmill the more reliable the results will be. When you think you can only walk one more minute let the physician know so that the nuclear injection can be given. After the injection is in, you will need to walk an additional minute on the treadmill.
During the test, your EKG and your blood pressure will be monitored. Be sure to report any symptoms such as:
- Chest, arm or jaw discomfort
- Severe shortness of breath
- Fatigue or dizziness
- Leg cramps or soreness
Never stop walking suddenly or jump off the treadmill as serious injury can result. If you need to stop, notify the doctor and he/she will slow down or stop the treadmill.
Persantine or Adenosine Cardiolite
For patients that are unable to walk on the treadmill, an intravenous medication (persantine or adenosine) can be given. This replaces the need for walking on the treadmill and still allows the stress test to be performed.
Cardioversion is a brief procedure where an electrical shock is delivered to the heart to convert an abnormal heart rhythm back to a normal rhythm. Most elective or "non-emergency" cardioversions are performed to treat atrial fibrillation, also known as atrial flutter, a benign heart rhythm disturbance originating in the upper chambers (atria) of the heart.
External cardioversion is performed with a defibrillator, either in an emergency situation or as a scheduled treatment for arrhythmia. Internal cardioversion is delivered by a device similar to a pacemaker, called an implantable cardioverter defibrillator (ICD). ICDs are used to treat arrhythmias in the lower heart chamber (ventricle) such as ventricular tachyarrhythmia or fibrillation. These arrhythmias can cause sudden cardiac death (SCD) because of the dangerously fast heart rate.
Tilt Table Study
The tilt table study is used to evaluate patients who have had syncope (loss of consciousness). It is an extremely simple study, and in most cases is quite safe. In a tilt table study, the patient is strapped to a table, which is then mechanically tilted to an upright position. While monitoring the pulse, blood pressure, electrocardiogram, and sometimes blood oxygen saturation, the patient is left in a "motionless standing position" for 20 to 30 minutes. When the patient's syncope is reproduced during the test, a "positive" tilt table study is said to have occurred.