Radionuclide Myocardial Perfusion Study

Radionuclide Myocardial Perfusion Study

Radionuclide Myocardial Perfusion Study is a non-invasive imaging technique typically employed in order to accurately diagnose and predict the evolution of coronary artery disease in patients affected by this disorder. This procedure relies on the administration of radiopharmaceutical agents through an intra-venous injection in order to obtain images of myocardial perfusion system both during stimulation and at rest. The images are obtained by using a gamma camera. Tomographic imaging, providing improved contrast resolution and three dimensional imaging, is preferred instead of planar imaging. Comparing the distribution of the radiopharmaceutical agents in both stages (at rest and after stress) allows the observer to draw conclusions regarding the regional and global myocardial function (when using ECG gate imaging), inducible perfusion abnormalities and myocardial viability.

Specialists employ Radionuclide Myocardial Perfusion Study in order to detect and assess a number of coronary disorders (such as coronary obstruction), to determine the risks of recurrence or the probability of occurrence of coronary events in the future (for instance after myocardial infarction), to assist in the management of coronary disease in patients diagnosed with this condition, to determine the viability of interventions such as surgical or percutaneous revascularization and to determine the significance and consequences of coronary lesions in order to assist with myocardial revascularization. Also, Radionuclide Myocardial Perfusion Study may be used to determine and analyze the haemodynamic significance of anomalous coronary arteries (whether known or suspected) and of coronary aneurysms in patients affected by Kawasaki’s disease, and may also provide valuable information regarding myocardial hibernation and viability prior to revascularization procedures.

Currently, Radionuclide Myocardial Perfusion Study is the only widely available procedure allowing direct assessment of the myocardial perfusion. Also, the exact method of performing this procedure may differ from one medical center to another, as currently there are no universal guidelines regarding this matter – however the differences are minor and do not have any impact on the final clinical outcome.

Radionuclide Myocardial Perfusion Study Description

Radionuclide Myocardial Perfusion Study implies observation of the myocardial perfusion both after stress and at rest. Stress can be induced in several ways; the most common method is the induction of stress through physical exercise – of course, in situations where the patient is capable of exercising to a sufficient workload; this method is ideal for patients who are affected by or suspected of muscle bridging, coronary artery anomalies or microvascular disease. If possible, the patient should discontinue treatment with any medication that may interfere with the response to the physical exercise, and should avoid consuming coffee or beverages, foods or medicines containing caffeine at least 12 hours before the test. A physical examination may be in order prior to the beginning of the procedure, especially in cases where the patient is suspected of dynamic exercise contraindications. The stress test will be supervised by a specialized health care professional and will typically take place on a bicycle ergometer or a treadmill. The exercise will start with warming up, then increasing the workload progressively towards an end point and an intravenous line is secured. The ECG and haemodynamic parameters should be monitored both at rest and during the exercise, at each stage, and monitoring must continue for at least 5 minutes after completing the exercise. The radiopharmaceutical agent is injected at around the peak of the exercise and, if possible, the patient should continue the exercise for 1 minute (in case Thallium-201 is used) or up to 2 minutes (after using Technetium-99m perfusion tracer).

An alternative to physical exercise is the pharmacological induction of stress, also commonly used in Radionuclide Myocardial Perfusion Study. The stress may be induced by use of vasodilators (Dipyridamole or Adenosine) or Dobutamine. This is an excellent alternative, as it does not require ECG and symptom changes during exercise or exercise tolerance. The Radionuclide Myocardial Perfusion Study methods have several contraindications; your personal health care professional will inform you if you are not able to undergo this procedure.

Radionuclide Myocardial Perfusion Study Related Medication

The Radionuclide Myocardial Perfusion Study relies on administration of radiopharmaceuticals in order to obtain an accurate assessment of the myocardial perfusion system. The most commonly employed agents are Thallium-201 and Technetium-99m.

Thallium-201 is administered through intravenous injection to the myocardium; the initial distribution depends on perfusion and myocardial viability, and it redistributes over several hours allowing the recording of perfusion-independent images which accurately reflect myocardial viability. The usual dose for the Radionuclide Myocardial Perfusion Study imaging of redistribution and stress is of 80 MBq, and another 40 MBq may be injected at rest in situations where redistribution is incomplete or slow. The radiopharmaceutical agent is administered through a secure IV line, either as a bolus injection or, in case the agent is administered concurrently with Adenosine or Dobutamine, over 20 seconds to avoid a bolusing of the stressor ahead of the radiopharmaceutical agent. Different imaging protocols may be employed. Stress imaging should start within 5 minutes and be concluded within at most 30 minutes from administration of the agent. Redistribution imaging can be performed after three to four hours of the injection.

The other radiopharmaceutical agent employed during Radionuclide Myocardial Perfusion Study, Technetium-99m, is distributed according to perfusion and myocardial viability, after intravenous administration. The redistribution is minimal, and as such rest and stress studies require separate injections. This agent yields better images due to the higher energy of the radiopharmaceutical, as it allows for less scatter and attenuation, and ECG gating may be employed offering additional information. The reference dosage totals to 1000 MBq in the case of one-day protocols (250 MBq and 750 MBq), while for two day protocols the dosage is of 400 MBq per day. The agent is administered intravenously; resting injections may be administered under nitrate cover – the lack of redistribution causes the viability to be underestimated, particularly in areas where the resting perfusion is reduced. The imaging protocols used may differ on account of local practices and / or clinical indications. The imaging typically begins within 30 to 60 minutes after the agent is injected.