Cardiology Services - Electrocardiology

CARDIAC STRESS TESTING

What is a cardiac stress test? 
Cardiac stress testing is used to asses your heart for coronary artery disease. It is an indirect way of assessing the coronary arteries.  The test is performed by attaching the patient to a special EKG machine and then speeding your heart up by either walking on a treadmill or by giving you a special drug if you cannot walk on a treadmill.  The special drug causes your heart to mimic exercise.  Usually images of the heart are taken with a nuclear camera or with an ultrasound machine before and after the stress test is performed. These images are compared later to see if there has been a change in cardiac perfusion or heart muscle contractility.  The EKG tracings are also examined for evidence of cardiac ischemia during the exam. Cardiac ischemia is essentially heart muscle that is starved of oxygen from a decrease in arterial blood flow. An electrocardiogram (EKG) is a tracing of the hearts electrical activity. This tracing or wave form is drawn on graph paper. Your physician analyzes the tracing to determine if your heart is functioning normally.

Types of cardiac stress testing:

Regular treadmill stress test:
The patient will be hooked up to a special EKG machine.  The patient is then placed on a treadmill. The treadmill will start off very slow and every three minutes it will increase its speed and elevation. The patient will stay on the treadmill until their heart rate reaches a predetermined limit which is calculated based on age. The patients EKG is monitored while they are on the treadmill. Blood pressure is also monitored while on the treadmill.  Once the predetermined heart rate is reached the patient is taken off the treadmill and recovered for a few minutes. The EKG tracing that were acquired while the patient was on the treadmill are then read by a physician and a report is sent to the ordering physician.

Nuclear stress test:
A nuclear stress test uses a radioactive tracer that is injected into a vein to image the heart.  Pictures of the heart are taken before you exercise and again after you are done exercising with a nuclear camera. These images are then compared to determine if there was a change in cardiac muscle perfusion.  The patient’s EKG and blood pressure are monitored during the exam and a physician will look at the EKG and the nuclear images to determine if there is evidence of coronary artery disease.

Stress echocardiogram
A stress echocardiogram uses ultrasound images of the heart to look for evidence of cardiac ischemia. Ultrasound images of the heart are taken before and after exercise and then compared to determine if there was a change in the way the heart muscle thickens. The patient’s EKG and blood pressure are monitored during the exam and a physician will look at the EKG and the ultrasound images to determine if there is evidence of coronary artery disease.

Chemical stress tests:
Chemical stress tests are used for patients that cannot walk on a treadmill. Lexiscan and Dobutamine are most commonly used in our institution. Lexiscan and Dobutamine are used in place of the treadmill.  Dobutamine speeds the heart up and mimics exercise while Lexiscan dilates the coronary arteries and increases perfusion of the cardiac muscle. 

What kind of preparation is required? 
You cannot eat or drink anything after midnight on the day of the test. If you are taking certain breathing medications such as theophylline or aminophylline you may be asked to stop taking them for 48 hours before your exam.  If you are taking a Beta blocker you may be asked to stop taking it 24-48 hours prior to having the stress test. If you are asthmatic you need to let the stress technician or nurse know this prior to your test. You will need to wear comfortable walking shoes and clothes if you will be walking on the treadmill. If you work on a military base and are having a nuclear stress test you will need paper work filled out at the time of your test due to being injected with a radioactive tracer.

Are cardiac stress tests dangerous? 
Cardiac stress tests are very safe. Heart attack and death are very rare occurrences during stress tests. You will be monitored by trained personnel that will stop your test at the first signs of cardiac ischemia.