Evaluation of myocardial viability by FDG PET/CT
1. Principle of operation of FDG PET/CT in cardiology
With the development of science and technology, the combination of PET and CT in the same PET/CT system allows optimal exploitation of the advantages of PET, which allows determining the metabolic activity of the resulting organization. CT image with information to determine the location, changes in morphology, structure of the lesion.
The principle of application of FDG-PET/CT in assessing the viability of the myocardium is as follows:
Blood glucose is mainly used by cardiomyocytes after a meal or in the state of myocardial ischemia. The level of glucose utilization reflects the metabolic capacity and viability of cardiomyocytes. FDG is injected into the body and is absorbed by cardiomyocytes into the cells. In cardiomyocytes, phosphorylated FDG becomes FDG-6 phosphate and is trapped there, radiating positrons. These positrons meet neighboring electrons, which will combine and annihilate, creating 2 photons, which are recorded and PET images are generated. CT and PET images are presented separately, and then combined to compare results. Evaluation of the results:
Areas of myocardium with concomitant hypoperfusion and FDG arrest i.e. perfusion-metabolism matching are considered to be areas of irreversible damage. Areas of FDG retention or increased FDG arrest but reduced perfusion i.e. a mismatch between perfusion and metabolism are considered to be areas of myocardial ischemia but the myocardium is still viable if reperfused. This area with perfusion intervention can be restored. Areas of FDG retention and normal perfusion are areas of undamaged myocardium.
2. Evaluation of myocardial viability by FDG PET/CT
However, now scientists have demonstrated that prolonged systolic dysfunction due to acute or chronic myocardial ischemia leads to changes in myocardial contractility but still recovery after reperfusion.
Decreased inotropic state in patients with coronary heart failure due to coronary artery disease, including post-MI, is often due to myocardial dizziness, myocardial stasis, and/or post-infarct scarring. myocardial blood.
Myocardial stupor is a potentially reversible myocardial contractility disorder that occurs after coronary blood flow recovers from an acute myocardial ischemic attack. The reduction in myocardial contractility in this state after ischemia can be fully reversed if there is no recurrent ischemia and sufficient time is given to allow the myocardium to recover. Myocardial stasis is a state of persistent left ventricular dysfunction caused by chronic but reversible decreased blood flow. Chronic inotropic state is due to a protective mechanism, myocardial cells reduce oxygen demand to maintain viability. However, this protective mechanism of the myocardium causes a decrease in contractile function leading to a total decrease in left ventricular function. Since the myocardium can completely recover with intervention, it is very important to assess the vital function of the myocardium, this assessment can be used by many different methods, but according to studies, FDG -PET/CT is the most sensitive method in diagnosing viable myocardium.
Assess myocardial viability in myocardial infarction patients with impaired systolic function with EF <40%; Identify patients suitable for coronary revascularization when partial myocardial contractility or stasis affects left ventricular systolic function; Differentiate between reduced functional myocardial tissue but still viable after reperfusion from myocardial infarction scar to decide on treatment in patients with ischemic heart disease or reduced left ventricular function. Contraindications:
Because it may affect the fetus, pregnant women need to notify if there is an indication to take a scan; Some patients are allergic to insulin or have severe hypokalemia that needs to be considered when proceeding. Some notes when taking FDG PET/CT scan:
Patients need to fast before 4-6 hours; Do not use injections or infusions of sugary drugs within 6 hours before the scan; Measure blood sugar before injecting FDG, if blood sugar is high, use insulin to stabilize before injection. Recognizing the viability of the myocardium helps patients receive early myocardial reperfusion intervention, thereby reducing left ventricular dysfunction due to myocardial ischemia, improving quality of life and prolonging life. life expectancy for patients.
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