A caliper is a measurement tool used to measure thickness, distance and diameter. EKG calipers are most commonly of a type called divider calipers, consisting of two pivoting, adjustable legs with a point or tip at the end of each leg. They are used in medicine, mainly in cardiology, and are specifically calibrated to measure the distance, or interval, between the lines on a graph called an electrocardiogram (abbreviated as ECG or EKG). Many EKG calipers include a separate ruler to measure the distance between the tips of the caliper after they have been positioned on the lines, or waves, of the EKG graph. The ruler then gives a measurement that often translates distance into seconds, for example 25 mm can equal 1 second, allowing the user to examine the EKG and make a diagnosis.
Electrocardiography is a way of examining heart activity, and is used to diagnose various kinds of heart problems, such as myocardial infarction. This diagnostic procedure is considered especially effective when diagnosing heart problems related to abnormal heart rhythm. To do the exam, skin electrodes are fastened to the legs, arms and chest. These electrodes are connected to an ECG device which is then able to provide a detailed, noninvasive recording of the electrical impulses of the heart as a series of waves. The graph produced is then examined and interpreted by a specialist, and EKG calipers are commonly used to help interpret the readings.
EKG calipers are often made from steel or other metal, and a common size is approximately 4-5 inches (10-15 cm) long, though they come in different sizes. The tips of the EKG calipers are very fine and sharp in order to be securely and accurately positioned on the EKG graph paper. These tips are often covered with a removable, protective cap. Some EKG calipers are vernier calipers, meaning they have tips that slide along the tool rather than pivoting legs for measuring. Vernier calipers usually have a built-in ruler or scale on the instrument itself.
There are computer versions of EKG calipers available as software programs. This type of software allows for the measuring and interpreting of EKG results directly on a computer screen in cases where the EKG is available as a computer file rather than printed on graph paper. The interface for this type of EKG calipers is commonly designed to look like the hand-held measurement tool, and is manipulated with the computer mouse on the screen.