From Textbook (Diagnostic Test Vocabulary) - Unit 6: The Circulatory System

cardiac enzymes

Test that measures enzymes released into the blood during a myocardial infarction; higher levels indicate a more severe infarction. Key enzymes include CK-MB (creatine kinase-MB), which rises in 2–6 hours, and lactate dehydrogenase (LDH), which rises in 12 hours. Often used alongside troponin tests.

C-reactive protein (CRP)

Test that measures inflammation in the body, which can cause blood vessel damage, clot formation, and myocardial infarction. The high-sensitivity CRP test is used to assess a healthy person's risk for cardiovascular disease.

homocysteine

Test for an amino acid that damages blood vessel walls, with elevated levels indicating an increased risk of arteriosclerosis, heart attack, or stroke.

lipid profile

Test that measures blood levels of cholesterol, triglycerides, and their associated lipoprotein carriers (HDL, LDL, VLDL).

troponin

Test for two proteins (Troponin I and T) released during myocardial cell death. Levels rise within 4–6 hours of a heart attack and stay elevated for up to 10 days, making it useful for diagnosing infarctions days later.

cardiac catheterization

A procedure, sometimes called a cardiac cath, used to study heart anatomy and pressures. A catheter is guided to the heart via veins (right heart) or arteries (left heart) to measure pressures and, with contrast dye, map out the chambers or coronary arteries to detect blockages and, if needed, perform angioplasty.

cardiac exercise stress test

Procedure performed to evaluate the heart's response to exercise in patients with chest pain, palpitations, or arrhythmias (see Figure 5-21). The patient walks on a motorized treadmill (treadmill exercise stress test) or rides a stationary bicycle while an ECG is performed. The speed of the treadmill and the steepness of its incline (or the resistance of the bicycle) are gradually increased while the patient's heart rate, blood pressure, and ECG are monitored. The procedure is stopped if the patient complains of angina, palpitations, shortness of breath, or tiredness, or if the ECG pattern becomes abnormal. The patient's resting heart rate and maximum heart rate are compared to standards for other people of the same age and sex. Any abnormality in the ECG pattern is analyzed.

electrocardiography (ECG, EKG)

Procedure that records the electrical activity of the heart (see Figure 5-22). Electrodes (metal pieces in adhesive patches) are placed on the limbs (both arms and one leg) to send the electrical impulses of the heart to the ECG machine. These are the three limb leads (leads I–III). Electrodes placed on the chest are known as the precordial leads (V₁–V₆). A 12-lead ECG records the electrical activity between different combinations of electrodes to give an electrical picture of the heart from 12 different angles. Samples of each of these 12 tracings are printed out and mounted on a backing for an electrocardiogram. A longer sample of just a single lead tracing (usually lead II) is known as a rhythm strip.

electrophysiologic study (EPS)

Procedure to map the heart's conduction system in a patient with an arrhythmia. While an ECG is performed, catheters are inserted into the femoral vein and subclavian vein. X-rays are used to guide the catheters to the heart. The catheters send out electrical impulses to stimulate the heart and try to cause an arrhythmia to pinpoint the ectopic site where the arrhythmia is coming from.

Holter monitor

Procedure during which the patient's heart rate and rhythm are continuously monitored as an outpatient for 24 hours. The patient wears electrodes attached to a small portable ECG monitor (carried in a vest or placed in a pocket). The patient also keeps a diary of activities, meals, and symptoms. A Holter monitor procedure is used to document infrequently occurring arrhythmias and to link them to activities or symptoms such as chest pain.

pharmacologic stress test

Procedure performed instead of a cardiac stress test for patients who cannot exercise vigorously. The vasodilator drug dipyridamole (Persantine) is given to cause normal coronary arteries to dilate. Occluded arteries cannot dilate, and this stresses the heart and causes angina in a way that is similar to an exercise stress test.

telemetry

Procedure to monitor a patient's heart rate and rhythm in the hospital. The patient wears electrodes connected to a device that continuously transmits an ECG tracing to a central monitoring station in the coronary care unit or intensive care unit. A nurse at the station constantly watches all of the patients' cardiac monitors.

angiography

Procedure in which radiopaque contrast dye is injected into a blood vessel to fill and outline it. In arteriography, it is injected into an artery to show blockage, narrowed areas, or aneurysms (see Figure 5-17). In venography, it is injected into a vein to show weakened valves and dilated walls. The x-ray image is an angiogram or, more specifically, an arteriogram or venogram. In coronary angiography, a catheter is inserted into the femoral artery and threaded to the aorta. The radiopaque contrast dye is injected to outline the coronary arteries and show narrowing or blockage. The x-ray is a coronary angiogram. In rotational angiography, multiple x-rays are taken as the x-ray machine goes around the patient. This technique is particularly helpful in documenting tortuous blood vessels in three dimensions. Digital subtraction angiography (DSA) combines two x-ray images, one taken without radiopaque contrast dye and a second image taken after radiopaque contrast dye has been injected to outline the blood vessel. A computer compares the two images and digitally "subtracts" or removes the soft tissues, bones, and muscles, leaving just the image of the arteries.

echocardiography

Procedure that uses a transducer to produce ultra high-frequency sound waves (ultrasound) that are bounced off the heart to create an image. Two-dimensional echocardiography (2-D echo) creates a real-time picture of the heart and its chambers and valves as it contracts and relaxes. The image is an echocardiogram (see Figure 5-24). Transesophageal echocardiography (TEE) may be ordered when a standard echocardiogram has a poor-quality image. For a TEE, the patient swallows an endoscopic tube that contains a tiny, sound-emitting transducer. This is positioned in the esophagus directly behind, and closer to, the heart. Doppler ultrasonography images the flow of blood in an artery or vein (see Figure 5-25). The two-dimensional ultrasound image shows blockages or clots in the blood vessel. Doppler technology shows how fast blood is traveling in that artery or vein. Doppler technology is also used in automatic blood pressure machines, in hand-held devices that give the heart rate if placed on the skin over an artery, and in fetal monitors that, when placed on the mother's abdomen, give the heart rate of the fetus. Color flow duplex ultrasonography combines the ultrasound image with a color-coded Doppler image. Variations in blood flow and turbulence are shown, with faster flow in red and slower flow in blue. Color flow duplex ultrasonography is the "gold standard" for evaluating tortuous varicose veins.

multiple-gated acquisition (MUGA) scan

Nuclear medicine procedure that uses the radioactive tracer technetium-99m. First, pyrophosphate is injected intravenously to allow red blood cells to bind with technetium-99m. Then technetium-99m is injected. A gamma camera records gamma rays emitted by the technetium-99m bound to red blood cells. The camera is coordinated (gated) with the patient's ECG so that images of the heart chambers (with blood—and red blood cells—in them) are taken at various times. A MUGA scan also calculates the ejection fraction (how much blood the ventricle can eject with one contraction). The ejection fraction is the most accurate indicator of overall heart function. This procedure is also known as a radionuclide ventriculography (RNV) or gated blood pool scan.

myocardial perfusion scan

Nuclear medicine procedure that combines a cardiac exercise stress test with intravenous injections of a radioactive tracer. The radioactive tracer collects in those parts of the myocardium that have the best perfusion (blood flow). A gamma camera records gamma rays emitted by the radioactive tracer and creates a two-dimensional image of the heart. Areas of decreased uptake ("cold spots") indicate poor perfusion from a blocked coronary artery. The artery must be about 70% blocked before any abnormality is evident on the image. Areas of no uptake indicate dead tissue from a previous myocardial infarction. Technetium-99m is joined to a synthetic molecule (sestamibi). The combination of technetium-99m with sestamibi is the drug Cardiolite, so this test is also known as a Cardiolite stress test. In a thallium stress test, thallium-201 is the radioactive tracer, or thallium-201 and technetium-99m can be used. Myocardial perfusion PET scans are used to image the metabolism of the heart.

single-photon emission computed tomography (SPECT) scan

Procedure that is a variation of a myocardial perfusion scan or a MUGA scan. Instead of being stationary above the patient's chest, the gamma camera is moved in a circle around the patient. The computer creates many individual images or "slices" (tomography) and compiles them into a three-dimensional image of the heart.