Stress Test

On , in Diagnosis, by pacemakerwriter

Arrhythmia patient having stress testA common test for many cardiac conditions is the so-called stress test. There are two main types: in one, you are asked to perform some sort of exercise to “stress” your heart, that is, make it beat faster. This may involve walking or jogging on a treadmill or riding a stationary bicycle. There is also a chemical stress test, in which the doctor administers drugs that “stress” the heart in order to evaluate the heart’s response. If you are healthy enough for a physical stress test, that is usually the one you will get, in that it allows the clinical team to see how your heart responds to exertion under the most normal, natural conditions.

Of course, it does not feel very natural. The nurse will apply electrodes to your body, often a dozen or more, to capture all of the electrical activity from the heart. If you’ve ever wondered how this works, the heart generates electricity; in fact, by detecting this electricity, we can interpret what the heart is doing. The electrical energy produced by your body is strong enough to be picked up on the surface of the skin–that’s why the doctor wants the electrodes on the skin. The electrodes are placed in certain “vectors” or angles to capture the electrical signals which are then “translated” into a surface electrocardiogram or EKG. Surface refers to surface of the skin. Electrocardiogram means a picture (gram) of the heart’s (cardio) electrical activity (electro). This is abbreviated ECG or EKG in the hospital. I don’t know why they call it EKG, but I heard that it was to make sure nobody confused an ECG with an EEG, a brain-wave machine.

As the heart is stressed, it should start to beat more rapidly. Certain changes in the rhythm should occur, for instance, the time between the atrial contraction (beating of the upper chambers) and the ventricular contraction (beating of the lower chambers) should shorten. This is called the AV delay. In a normal healthy heart, the upper chambers beat slightly ahead of the lower chambers, but that time lapse (measured in fractions of a second) shortens with exercise … at least it should.

A stress test can evaluate what doctors call chronotropic competence or, the more common term, chronotropic incompetence. A person with chronotropic incompetence has a heart that does not beat sufficiently fast to keep up with activities. Chronotropic incompetence is not specifically a rhythm disorder, but it can be corrected by a rate-responsive pacemaker which helps the heart beat sufficiently rapidly during times of exercise.

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