stress_test : Treadmill Stress Test
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How does a Regular Stress Test Work?
Patients with coronary artery blockages may have minimal symptoms and an unremarkable or unchanged EKG while at rest. However, symptoms and signs of heart disease may become unmasked by exposing the heart to the stress of exercise. During exercise, healthy coronary arteries dilate (develop a more open channel) than an artery that maybe has a blockage. This unequal dilation causes more blood to be delivered to heart muscle supplied by the normal artery. In contrast, narrowed arteries end up supplying reduced flow to it's area of distribution. This reduced flow causes the involved muscle to "starve" during exercise. The "starvation" may produce symptoms (like chest discomfort or inappropriate shortness of breath), and the EKG may produce characteristic abnormalities. Most commonly, a motorized treadmill is used for exercise, while a stationary bicycle is used in some exercise laboratories. When is a Regular Stress Test ordered? A regular stress test is considered in the following circumstances:
Patients with symptoms or signs that are suggestive of coronary artery diseases (CAD). Patients with significant risk factors for CAD.
To evaluate exercise tolerance when patients have unexplained fatigue and shortness of breath.
To evaluate blood pressure response to exercise in patients with borderline hypertension.
To look for exercise-induced serious irregular heart beats. Please remember that the regular stress test is heavily dependent upon interpretation of EKG changes produced by exercise.
Therefore, the reliability drops drastically if there are significant EKG changes at rest (for example in patients with long standing high blood pressure, an artificial cardiac pacemaker, use of medications like digitalis, or presence of a bundle branch block pattern, etc.). In all such cases, the physician will usually order an Echo Stress Test or a Nuclear Stress Test, particularly if he or she is suspecting coronary artery disease. However, a regular stress may be sufficient in stable patients or those with a low suspicion of coronary artery disease who are being assessed for exercise, can be strenous or light, tolerance (for example, prior to undergoing a structured exercise or rehab program).
Preparing for the Regular Stress Test:
The following recommendations are "generic" for all types of cardiac stress tests: Do not eat or drink for three hours prior to the procedure. This reduces the likelihood of nausea that may accompany strenuous exercise after a heavy meal. Diabetics, particularly those who use insulin, will need special instructions from the physician's office. Specific heart medicines may need to be stopped one or two days prior to the test. Such instructions are generally provided when the test is scheduled. Wear comfortable clothing and shoes that are suitable for exercise. An explanation of the test is provided and the patient is asked to sign a consent form. How long does the entire test take? A patient should allow approximately one hour for the entire test, including the preparation.
How is a Regular Treadmill Stress Test Performed?
The patient is brought to the exercise laboratory where the heart rate and blood pressure are recorded at rest. Sticky electrodes are attached to the chest, shoulders and hips and connected to the EKG portion of the Stress test machine. A 12-lead EKG is recorded on paper. Each lead of the EKG represents a different portion of the heart, with adjacent leads representing a single wall. For example:
Leads 2, 3, and aVF = bottom or inferior portion of the heart.
Leads V1 and V2 = septum or partition of the heart.
Leads V3, V4, V5 and V6 = anterior or front portion of the heart. Leads 1 and aVL = superior or top and outer left portion of the heart.
Lead aVR looks at the cavity of the heart and has almost no clinical value in identifying coronary disease.
Three of the EKG leads are also constantly displayed on the treadmill monitor. Each lead representing a different wall. The physician has the option of selecting different combinations of three.
The treadmill is then started at a relatively slow "warm-up" speed. The treadmill speed and it's slope or inclination are increased every three minutes according to a preprogrammed protocol (Bruce is the commonest protocol in the USA, but several other protocols are perfectly acceptable). The protocol dictates the precise speed and slope. Each three minute interval is known as a Stage (Stage 1, Stage 2, Stage 3, etc. Thus a patient completing Stage 3 has exercised for 3 x 3 = 9 minutes). The patient's blood pressure is usually recorded during the second minute of each Stage. However, it may be recorded more frequently if the readings are too high or too low. As noted earlier, the EKG is constantly displayed on the monitor. It is also recorded on paper at one minute intervals. The physician pays particular attention to the heart rate, blood pressure, changes in the EKG pattern, irregular heart rhythm, and the patient's appearance and symptoms. The treadmill is stopped when the patient achieves a target heart rate (this is 85% of the maximal heart rate predicted for the patient's age).
However, if the patient is doing extremely well at peak exercise, the treadmill test may be continued further. The test may be stopped prior to achievement of the target heart rate if the patient develops significant chest discomfort, shortness of breath, dizziness, unsteady gait, etc., or if the EKG shows alarming changes or serious irregular heart beats. It may also be stopped if the blood pressure (BP) rises or falls beyond acceptable limits. Please note that the systolic BP (upper number) may normally rise to 200 at peak exercise. At the same time, the diastolic BP (lower number) remains unchanged or falls to a slight degree. In contrast, the BP of patients with hypertension or high BP will show a rise of both systolic and diastolic readings. The latter may rise above 90 - 100.
How safe is a Regular Treadmill Stress Test? The risk of the stress portion of the test is very small and similar to what you would expect from any strenuous form of exercise (jogging in your neighborhood, running up a flight of stairs, etc.). As noted earlier, experienced medical staff is in attendance to manage the rare complications like sustained irregular heart beats, unrelieved chest pain or even a heart attack. What is the reliability of a Regular Stress Test? If a patient is able to achieve the target heart rate, a regular treadmill stress test is capable of diagnosing important disease in approximately 67% or 2/3 rd of patients with coronary artery disease. The accuracy is lower (about 50%) when patients have narrowing in a single coronary artery or higher (greater than 80%) when all three major arteries are involved. Approximately 10% of patients may have a "false-positive" test (when the result is falsely abnormal in a patient without coronary artery disease). How quickly will I get the results and what will it mean? The physician conducting the test will be able to give you the preliminary results before you leave the exercise laboratory. However, the official result may take a few days to complete. The results of the test may help confirm or rule out a diagnosis of heart disease. In patients with known coronary artery disease (prior heart attack, known coronary blockages, previous treatment with angioplasty, stents or bypass surgery, etc.), the study will help confirm that the patient is in a stable state, or that a new blockage is developing. The results may influence your physician's decision to change your treatment or recommend additional testing such as cardiac catheterization, Echo Stress test, or a nuclear stress test.
Some people claim that whey protein (shakes) help reduce hair loss, as well as generally helping your health.
Whey protein is not something new and has been available for hundreds of years to individuals who valued the role of a nutritious diet in achieving optimal health. During the last 15-20 years the value of whey protein has become more widely known, especially in the area of sports nutrition. More recently, whey protein has been singled out as a super-star ingredient for other types of products including ones formulated for weight loss, infant nutrition and immune support.
Whey protein is a high quality protein powder from cow's milk. Milk has two proteins: Casein (approximately 80%) and Whey Protein (approximately 20%). Whey protein is more soluble than casein and also has a higher quality rating. It is often referred to as the "Gold Standard" of protein as it is the most nutritious protein available.
There may be a large difference between whey protein concentrate and isolate. Whey protein isolate is the most pure and concentrated form of whey protein available. It contains 90% or more protein and very little (if any) fat and lactose. Whey protein concentrate has anywhere between 29% and 89% protein depending upon the product. As the protein level in whey protein concentrate decreases the amounts of fat and/or lactose usually increase.
Protein is an important nutrient needed by everyone of a daily basis. It is made up of essential and non-essential amino acids, which are the "building blocks" for healthy bodies. Protein has a number of different roles in the body including the following:
- Repair body cells
- Build and repair muscles and bones
- Provide a source of energy
- Control many of the important processes in the body related to metabolism
The body is able to make non-essential amino acids from other amino acids in the body. However, the body is not able to make essential amino acids and the only way to get them is by eating high quality protein foods. Protein sources that contain all of the essential amino acids are called complete proteins. Whey protein is a naturally complete protein.
Protein needs vary by person depending upon age, weight, sex, activity level and overall health. Athletes and individuals with special medical needs often need more protein than the recommended dietary allowance, or RDA.
Whey protein is a high quality, complete protein, with all the essential amino acids. Whey protein is also the richest known source of naturally occurring branched chain amino acids (leucine, isoleucine and valine). These are important for active individuals, individuals who exercise and professional athletes. The body requires higher amounts of branched chain amino acids during and following exercise as they are taken up directly by the skeletal muscles versus first being metabolized through the liver, like other amino acids. Low BCAA levels contribute to fatigue and they should be replaced in one-hour or less following exercise or participation in a competitive event. Many athletes consume a BiPro beverage both before and immediately after exercise or an event to help repair and rebuild lean muscle tissue.
Adding whey protein to the diet is a great way to jump-start a weight loss program. Whey protein is a key ingredient in numerous weight loss and meal replacement products and whey protein isolate (with no fat or carbohydrates) is often the preferred choice. Studies have found that individuals who combine diets with leucine rich protein foods, like whey protein, and exercise have more lean muscle tissue and they lose more body fat. As they lose fat their metabolic rate increases and they naturally burn more calories each day. Another way that whey protein helps manage weight is by promoting satiety, or a feeling of fullness. One recent study showed that whey protein was superior to casein, the other protein in cow's milk, in promoting satiety.
Healthy diets should regularly include high quality, low fat sources of protein, like whey protein. Calories do count and you want to make sure that you are getting the most benefit from the calories you consume. Compared to other proteins, on a gram-to-gram basis whey protein isolate delivers more essential amino acids to the body but without the fat or cholesterol. Nutrition experts recommend a diet with a variety of protein foods but for optimal results make sure that one of them is whey protein.
Milk is a highly nutritious beverage however, it only contains about 1% of whey protein. In order to get all the benefits of whey protein, you need to take a concentrated whey protein powder like whey protein isolate.
Whey protein is a soluble, very easy to digest protein. It quickly enters the body to provide the important essential amino acids needed to nourish muscles and other body tissues. This is one of the reasons it is a common ingredient in infant formula and protein supplements for medical use.
What is a thallium stress test?
This is a type of nuclear scanning test or myocardial perfusion (mi"o-KAR'de-al per-FU'zhun) imaging test. It shows how well blood flows to the heart muscle. It's usually done along with an exercise stress test on a treadmill or bicycle.
The thallium stress test is useful to determine:
- Extent of a coronary artery blockage
- Prognosis of patients who've suffered a heart attack
- Effectiveness of cardiac procedures done to improve circulation in coronary arteries
- Cause(s) of chest pain
- Level of exercise that a patient can safely perform
When the patient reaches his or her maximum level of exercise, a small amount of a radioactive substance called thallium is injected into the bloodstream. Then the patient lies down on a special table under a camera ("gamma camera") that can see the thallium and make pictures. The thallium mixes with the blood in the bloodstream and heart's arteries and enters heart muscle cells. If a part of the heart muscle doesn't receive a normal blood supply, less than a normal amount of thallium will be in those heart muscle cells.
The first pictures are made shortly after the exercise test and show blood flow to the heart during exercise. The heart is "stressed" during the exercise test -- thus the name "stress test." The patient then lies quietly for 2-3 hours and another series of pictures is made. These show blood flow to the heart muscle during rest.
What does the thallium stress test show?
- If the test is normal during both exercise and rest, then blood flow through the coronary arteries is normal. The coronary arteries supply blood to the heart muscle.
- If the test shows that perfusion (blood flow) is normal during rest but not during exercise (a perfusion defect), then the heart isn't getting enough blood when it must work harder than normal. This may be due to a blockage in one or more coronary arteries.
- If the test is abnormal during both exercise and rest, there's limited blood flow to that part of the heart at all times.
- If no thallium is seen in some part of the heart muscle, the cells in this part of the heart are dead from a prior heart attack. (They have become scar tissue.)
What if I can't perform an exercise test?
Sometimes you can't do an exercise test because you're too sick or have physical problems. In this case, a drug such as dipyridamole (di-pi-RID'ah-mol) or adenosine is given. This drug increases blood flow to the heart and thus "mimics" an exercise test. Then the thallium test is given.
Most people can raise their HDL (good cholesterol) levels by exercising, not smoking and staying at a healthy weight.
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