If you want to put your heart through its paces and see how you measure up for cardiac fitness, treadmill cardiology is a good pace to start. Your doctor and stress lab tech might use special vocabulary throughout your run on the treadmill, but the terms are not hard to understand and the principles of the test are easy to comprehend.
The Bruce Protocol
If you jump on a moving treadmill, bump up its speed and elevate it so you can run uphill, you will get a workout for your heart, but you will gain little specific data unless you control the speed and elevation precisely. Most cardiologists use the Bruce Protocol, as developed by Dr. Robert. A. Bruce in 1963, which specifies speed, elevation and duration at each level or stage. The treadmill starts at 1.7 mph and a gradient, or incline, of 10%. At three-minute intervals the gradient increases by 2 percent, and the speed increases in small increments until at the end of stage 10, 30 minutes if you can last that long, you are running uphill at a 28 percent gradient at 7.5 mph. A Modified Bruce Test protocol stays at 1.7 mph and 0% grade and 1.7 mph and 5 percent grade for the first two stages for elderly or sedentary patients. The third stage corresponds to the first stage of the Standard Bruce Test protocol.
METS
When your doctor mentions METS, the term refers to metabolic equivalents. It helps your cardiologist calculate calories burned per hour and relate that to your exercise oxygen consumption. Your weight in kg multiplied by METS predicts your hourly calorie-burning rate. For instance a standard METS table says bicycling at about 10 mph uses 4 METS, so a 100kg man will burn 400 calories per hour of biking.
Nuclear Stress Cardiology
If your cardiologist calls your treadmill test "nuclear" the test will include an injection of a radioactive substance. This will measure blood flow within your heart muscle at rest and under exercise conditions. It provides images of the distribution of radioactivity showing areas of low coronary blood flow and areas of heart muscle damage. The first heart image is taken to see where radioactivity reaches inside your heart muscle at rest. The second is taken after you exercise on a treadmill to see how well your heart works and circulates its blood supply under stress.
Sestamibi And The Gamma Camera
The odd-sounding term sestamibi applied to treadmill cardiology refers to a specific radioactive tracer the cardiologist may use. It is a compound that contains the radioactive element technitium-99. The dose is small and carries no danger of radiation injury, and within hours to days its radioactivity decays to undetectable levels. However, the sestamibi emits gamma rays of an energy that can be detected, measured and localized within the anatomy of your heart muscle. The detector is called the gamma camera. Sestamibi's distribution in your heart produces the nuclear testing images
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