STRESS TEST

A stress test is the generic term for a test to determine if one has blocked coronary arteries. As the name implies, it is basically a treadmill walker, similar the ones at gyms, or perhaps even your home, that is gradually accelerated and elevated in 3 minute intervals for the effect of speeding up or ?stressing? your cardiovascular system, specifically the heart.
This test is done whenever your doctor thinks you may have coronary artery disease, but is unsure of the severity.
In order to determine if in fact someone has blocked arteries, different types of stress tests can be used. . For patients who are unable to walk due to arthritis or disability, a pharmacologic test is administered where a vasodilating medication (a medication given that causes the bloodvessles to dilate) is administered intravenously. This effect in essence is similar to the effect we would get by having a patient walk.
Regardless of whether a patient walks or is given a pharmacologic stress, it is most common to also administer a radioactive tracer substance along with the stress test as this has shown to increase the ability to detect coronary disease if present. These ?nuclear? stress tests, are by far typical and the most commonly used whenever a stress test is requested.

How It Works
You come to the office where the test is to be performed. It is preferable if you STOP certain medications 24-48 hours before the test. These medications are beta blockers, calcium blockers, and digoxin (these can affect the heart rate), as well as avoid smoking and caffeinated drinks (these may interfere with the medications given). Your doctor must be the one who stops them if he/she believes it is safe to do so in your particular case.
You show up, we place a little plastic catheter in your arm/hand vein and administer a radioactive tracer. The tracers we use are of very small quantities and last approximately 6 hours in your body. We inject this tracer on 2 different occasions. These tracers do not interfere with bodily functions or cause long lasting harm. Pregnant women should avoid this and any radiation dose and so at our office we routinely check pregnancy state with a pregnancy test as a routine practice on all women of child bearing age. Once administered, the radioactive tracer, (we use technecium 99m, while other labs may use thallium) follows the blood flow. As it does it gives off photons or the product of its radioactive decay or breakdown. It is this breakdown and the intensity and rate of decay that we measure by the ?pictures? we take, approximately half an hour after the first administration. This image is taken because it will give us a baseline of the blood flow in the coronary circulation under normal, basal condition.
We then walk the patient on the treadmill or perform the pharmacologic stress and administer the second dose of radioactive tracer. After approximately another hour we again take a second picture of the heart to measure the decay of substance from the blood flow in the coronary artery circulation. We then compare the intensity and quantity of blood flow in the basal and stress image to determine whether or not blockage exists.
That is essentially what the stress test consists of. The entire procedure takes approximately 4 hours if its done in one day. There are other variations which can extend the test into 2 days, but the process is similar and the end result is as well.

Addicted to Stress Tests

A stress test is just that, a test. Treatment should always be individualized and not based on any one test. If a stress test is read as normal, yet the patient continues to have symptoms suggestive of coronary artery disease (CAD), additional investigation should be done. Likewise, a stress test has its indications. It should only be done if and when the patients symptoms are equivocal, meaning not definite for CAD. If a patient has typical angina type pain, a stress is not indicated, and the person should be referred straight for cardiac cath. A patient who presents with chest pain, 6 month or less after having had a bypass surgery or angioplasty should also have a cath not a stress. This is because stress test has its own limitations.
We perform too many, too often and quality of care has not significantly improved because of this technology.
Reading the stress result is very critical as there are many who over read, resulting in needless referrals to catheterizations. 

Downside
It is possible to have normal stress test one day, and have a heart attack the next.
What did I say?
How can someone have a normal stress test suggestive of no significant blockage one day and then have a heart attack a day or a few days later? Is it possible?
The answer I?m afraid is absolutely yes its possible.

The majority of heart attacks occur not from blocked arteries, but rather from arteries that have plaque buildup inside their walls. Atheroma is also another term for plaque. These result form accumulation of fats, fatty acids and degraded blood components, which will be explained at a later time. A stress test can determine a reduced blood flow within the coronary artery but as plaque builds up inside the vessel wall it causes the artery to dilate away from the lumen. We do not ?see? any narrowing many times, yet the artery is and continues being clogged up. Instead of causing an occlusion and narrowing on the inside of the blood vessel, the occlusion and narrowing is going in the opposite direction outward and missed by stress test imaging. Cardiac catheterization or angiography is also not any better. In both these tests despite the presence of plaque and build up occurring, the inside of the artery looks clean and open.
So the majority of patients who die suddenly do so because of a rupture of one of these plaques. Consider if you will a volcano. Over time pressure builds up, until some triggering even occurs that causes its top to blow open, rupture, and spyouing its contents out into the atmosphere. Likewise a plaque is building up until its surface is damaged from anyone of many causes. When it ruptures, platelets and other components of the blood rush to the area to try to limit damage to the blood vessel wall and control bleeding from the site. What happens instead is that in so doing, a blockage is formed on the entire blood vessel causing a sudden and total occlusion or blockage of blood flow in the artery which results in major heart muscle damage and death of the heart tissue supplied by the particular artery.