Lipp Vis Nursing ChaptLWBK1630_C02_p013-068

22  Chapter 2 • Cardiovascular Care

Individuals with any type of metal device inside the body should not have an MRI unless is certified as MRI safe. These devices include: • Pacemakers and ICDs • Inner ear (cochlear) implants • Neuromuscular stimulators such as those used for pain management or muscle rehabilitation • Implanted drug infusion pumps • Intrauterine devices (IUDs) • Brain aneurysm clips that are not approved for MRI • Some dental implants (check with your dentist to make sure they are not magnetic) • You should avoid MRI if you have metal fragments in your body. Metal fragments in the eyes can be especially dangerous because the magnet may move the metal, causing eye damage or blindness. Multiple-Gated Acquisition Scanning Radionuclide ventriculography (RVG, RNV) or radionuclide angiography (RNA) is often referred to as a multiple-gated acquisition (MUGA) scan. This test can view how well the heart’s ventricles are pumping. During a MUGA scan, a small amount of a radioactive substance or tracer (called a radionuclide) is put into the blood which attaches to red blood cells. A gamma camera takes pictures of the

heart. Pictures are taken at the same time during each heartbeat (ECG- gated) which is computer analyzed. POSITRON EMISSION TOMOGRAPHY A positron emission tomography (PET) scan of the heart is a noninvasive nuclear imaging test. It uses radioactive tracers (called radionuclides) to produce pictures of the heart and diagnose coronary artery disease (CAD). PET scans can show healthy and damaged heart muscle and if there will be benefit from a percutaneous coronary

intervention (PCI) such as angioplasty and stenting, coronary artery bypass surgery (CABG), or any other procedure. PET scans use radioactive material called tracers which mix with blood and are taken up by the heart muscle. A special “gamma” detector that circles the chest picks up signals from the tracer. A computer converts the signals into pictures of the heart at work. A PET scan determines if the heart is getting enough blood or if blood flow is reduced because of narrowed arteries. It also shows scaring from a prior heart attack. A radioactive tracer is injected into the bloodstream. The tracers used for PET are mostly natural body compounds such as glucose, water, or ammonia, which are labeled or “tagged” with a small amount of radioactive material. Inside the body the radioactive tracer produces a type of energy called a gamma ray. Gamma rays are detected by a gamma detector and are used to produce a series of clear images of your heart. Images of thin slices made all the way through the heart can be produced from all different directions and angles. Computer graphics can be used to create a 3-dimensional image of your heart from the thin-slice images. Viable heart tissue will take in more of the tracer than the tissue that is no longer viable. Different colors or degrees of brightness on the PET scan show different levels of tissue function.