Radionuclide examinations of the heart

Radionuclide examinations are increasingly used in cardiology, as they can be diagnostic in themselves. We use them to monitor the basic functional and spatial parameters of the heart. The most basic ones include ventriculography, myocardial perfusion scintigraphy, monitoring of metabolic processes and the search for necrosis. Unique to nuclear cardiology is the innervation of the heart.

Examination of myocardial metabolism
During normal blood circulation, the myocardium consumes mainly fatty acids as an energy source. When the supply of oxygen is reduced (ischemia), there is first a transition to aerobic, later to anaerobic glycolysis. In the phase of anaerobic glycolysis, the myocardial cell no longer contracts, saving energy for its most essential processes. The myocardium is so-called hibernating. When blood flow is restored, the cell gradually returns to its original state and its contractility is restored. If reperfusion does not occur, the cell dies.

Monitoring myocardial viability is of great importance in decision-making in revascularization procedures. A dead myocardium is not worth saving, on the contrary, a hibernating one is.

Viability examination
Radiopharmaceutical 18F-FDG is taken up by the living myocardium as a glucose analogue. By performing PET, it is possible to monitor its distribution and thus very accurately determine the location of viable muscle tissue. Loss of activity means a non-viable myocardium that is unable to accumulate FDG.

Viability can be monitored indirectly by radiopharmaceuticals used in perfusion scintigraphy (thallium, Tc-MIBI) (see above).

Fatty acid metabolism
The uptake of 123 I-labeled fatty acids is not yet widely used in practice. Experimentally, however, they are important in monitoring changes in myocardial metabolic pathways in some diseases.

Search for necrosis
The radiopharmaceutical binds specifically to dead myocardial cells. These sites then show up in scintigraphy as increased accumulation (hot spot ).

Radiopharmaceuticals
99mTc-pyrophosphate binds to the calcium released from the damaged mitochondria of the necrotic muscle.

111In-antimyosin is a monoclonal labeled antibody that is taken up by myosin. It is normally inaccessible to antibodies, it is hidden in the cell. During necrosis and disintegration of the cell membrane, it comes into contact with plasma.

Myocardial innervation
With the help of various radiopharmaceuticals, it is possible to monitor the distribution and functionality of nerve tissue in the heart. We investigate the accumulation of radiopharmaceuticals in synapses and neurons.

We use innervation monitoring to examine transplanted hearts, suspected heart attacks and ischemic heart disease, arrhythmias, heart failure and some neurological diseases.

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