Heart disease does not always carry with it symptoms that announce its presence. This is especially true if you lead an inactive lifestyle that does not routinely put stress on your heart muscle. Because of this, your doctor may order a cardio treadmill test as a precautionary measure, whether or not you show symptoms of heart disease. Before starting an exercise program, or if your lifestyle or a medical condition such as diabetes places you at risk for developing heart disease, you can expect your doctor to use a cardio treadmill test to assess the effect exercise has on your heart.
Types
Most cardio treadmill tests --- about 70 percent according to the State of Nevada Risk Management --- follow an industry standard called the Bruce Protocol. This type uses a motorized treadmill, a machine called an electrocardiograph and a multistage test that places progressively higher demands on your heart to determine whether there is any level of impairment. Other types include stress echocardiography and the thallium stress test. Both of these use additional diagnostic tools, such as ultrasound or injection of a radioactive dye following the treadmill test, to help your doctor better assess the condition of your heart.
Process
A standard cardio treadmill test begins with a reading of your resting heart rate and blood pressure to establish a baseline for later comparison. Next, a technician hooks you up to a 12-line electrocardiograph machine by attaching electrode lines to points on your chest, shoulders and hips. Heartsite.com describes the test itself as occurring in three stages, each lasting for three minutes, with the treadmill running progressively faster and at a greater slope during each stage. The EKG machine constantly monitors your heart during the test and a technician checks your blood pressure at least once during each stage.
Results
As your doctor monitors your cardio treadmill test, he is looking for evidence that indicates the presence of coronary blockage. The EKG machine provides your doctor with information about your heart rate and rhythm. He looks for signs such as fluctuations in heart rate or an irregular heartbeat. Blood pressure readings also provide evidence. Normally, your systolic blood pressure, or the pressure on your heart as it contracts, will increase to about 200 at peak exercise. This occurs, says Heartsite.com, as your coronary artery begins to dilate to provide increased blood flow to your heart. Blood pressure increases as your heart pumps faster to supply additional blood to working muscles. Systolic blood pressure that does not rise above 120 signals coronary blockage preventing your artery from dilating and your muscles from getting the additional blood they need.
Safety
The MedlinePlus website says this is a generally safe procedure. Your doctor will most likely not order a cardio stress test if he suspects your heart cannot handle the procedure. In addition, your doctor or a technician will stop the test if insufficient blood flow produces symptoms such as shortness of breath, dizziness or chest pain.
Reliability
The greater the degree of blockage, the more accurate the results of a cardio treadmill test are. Reliability varies from about 50 percent in detecting early stages or coronary artery disease to about 80 percent in more severe cases. In addition, Heartsite.com estimates that about 10 percent of the time results will show a false positive.
