Nuclear Medicine is an imaging technique used for several decades in brain diseases (e.g. cognitive impairment), bone, thyroid gland and, of course, heart. It is also widely used in oncology (sentinel node in breast cancer) and, combined with CT (PET-CT), in the study of multiple tumors.
The technique consists of the use of radioactive isotopes that are totally harmless (since they have a minimum dose of radioactivity) which are injected into the blood and fixed in a specific organ. Thanks to the use of an apparatus called Gammacamera, we obtain images (Gammagraphies) of these organs that will allow us to study if they have any alteration in their anatomy or function.
Applications of Nuclear Medicine in Cardiology
Within Cardiology, the main application of Nuclear Medicine is the evaluation of the heart’s blood flow in order to detect lesions in the coronary arteries that may be the cause of heart attacks or angina pectoris. To do this, a normal stress test is performed, the isotope is injected before finishing it and then the scintigraphy is performed, allowing us to see how the blood is distributed through the heart (MIBI-SPECT ERGOMETRY).
Usually, a conventional stress test is performed to detect ischemic heart disease. The one performed with isotopes has some advantages over it:
- It has greater sensitivity and specificity (it is more accurate), detecting or ruling out the disease in 90% of cases.
- It allows us to see the heart irrigation in the event that the patient’s ECG prevents the interpretation of the normal stress test due to some anomaly.
- It clarifies those situations in which the normal stress test is doubtful.
- In the event that the patient has several coronary arteries affected, it allows to see which of them is the one that produces more alteration of the blood flow, that is, which is the most dangerous.
- Through the GATED-SPECT technique, used in our service, it is also possible to see the functioning of the heart before and after exercise.
- It provides fairly accurate information on the prognosis -good or bad- of patients with known coronary lesions, facilitating the indication and choice of treatment.
- It detects the existence of cardiac cells still alive after an infarction (Myocardial Viability Study) when indicating coronary artery dilatation (Angioplasty) or surgery (Coronary artery bypass grafting).
On the other hand, it has no disadvantage over the conventional stress test, since the dangers and complications are the same.
Another very important application is the fact of being able to perform the study in people who for some reason or other cannot walk on the treadmill and, therefore, cannot perform a normal stress test (mobility problems in the legs, advanced age, etc.). In these cases a drug (Dipyridamole or Adenosine) is injected to replace the stress and, subsequently, the scintigraphy (MIBI-DIPIRIDAMOL OR MIBI-ADENOSINE) is performed, obtaining the same information.
Nuclear Medicine techniques are also used in Cardiology to see the functioning of the heart (Isotopic Ventriculography) in patients with Myocardiopathies, valvular lesions or under treatment with chemotherapy that can be cardiotoxic, as well as in some Congenital Heart Diseases, in which the amount of blood that passes through a short circuit (shunt) can be calculated and surgical intervention can be indicated.
The reason why these imaging techniques are not as well known as others (CT, ultrasound, MRI) is the lack of Nuclear Medicine Services in many hospitals, so that, obviously, the cardiologist cannot indicate them and has to use other techniques that are available (stress echocardiography), which are equally effective.
In summary, the techniques used by the so-called Nuclear Cardiology offer a high diagnostic and prognostic accuracy, allow the evaluation of both the functioning and the blood supply of the heart and are totally harmless.