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Introduction ⬇

Myocardial Infarct Imaging (99mTc Stannous Pyrophosphate [PYP] Scanning)

Myocardial infarct imaging, also known as 99mTc stannous pyrophosphate (PYP) scanning, is an imaging test that utilizes the radioactive imaging agent 99mTc-PYP to evaluate the general location, size, and extent of myocardial infarction (MI) 24–96 hours after a suspected MI occurs and as an indication of myocardial necrosis to differentiate between old and new infarcts. In some instances, the test is sensitive enough to detect an MI 12 hours to 7 days after its occurrence. An acute MI is associated with an area of increased radioactivity (hot spot) on the myocardial image. This test is useful when ECG and enzyme studies are not definitive.

Procedure ⬆ ⬇

  1. Myocardial infarct imaging involves a 4-hour delay after the IV injection of the radionuclide before performing the imaging test. During this waiting period, the radioactive material accumulates in the damaged heart muscle.

  2. Alert the patient that imaging takes 30–45 minutes, during which time the patient must lie still on an imaging table.

  3. See Chapter 1 guidelines for safe, effective, informed intratest care.

Clinical Implications ⬆ ⬇

  1. Imaging that is entirely normal indicates that an acute MI is not present and the myocardium is viable.

  2. Myocardial uptake of the PYP is compared with the ribs (2+) and sternum (4+). Higher uptake levels (4+) reflect greater myocardial damage.

  3. Larger defects have a poorer prognosis than small defects.

Interventions ⬆ ⬇

Pretest Patient Care

  1. Imaging can be performed at the bedside in the acute phase of infarction if the nuclear medicine department has a mobile gamma camera.

  2. Explain the purpose, procedure, benefits, and risks of the nuclear medicine study. See standard pretest precautions.

  3. Remember that imaging must occur within a period of 12 hours to 7 days after the onset of symptoms of MI. Otherwise, false-negative results may be reported.

  4. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Review test results; report and record findings. Modify the nursing care plan as needed. If heart surgery is needed, counsel the patient concerning follow-up testing after surgery.

  2. Refer to standard precautions and posttest care.

  3. Follow additional guidelines in Chapter 1 for safe, effective, informed posttest care.

Interfering Factors ⬆ ⬇

False-positive infarct-avid PYP can occur in cases of chest wall trauma, recent cardioversion, and unstable angina.

Reference Values ⬆

Normal

Normal distribution of the radiopharmaceutical in sternum, ribs, and other bone structures

No myocardial uptake