Detection of myocardial ischaemia

In the situation of a patient who can present a coronary disease, the first step consists in evaluating the probability of a myocardial ischemia. The European Society of Cardiology recommends to take into consideration age and sex of the patient, clinical characteristics of thoracic pain or its equivalent such as dyspnea on exertion and circumstances of occurrence such as on exertion.

Coronary disease probability is classified in three categories: very weak <15% without systematic need for any test, possible with an intermediary risk of 15 to 85%, and very likely with a risk >85%. The need for non invasive imaging applies mainly to intermediate risk.

Electrocardiography (ECG) stress test has weak diagnostic sensitivity and specificity mainly in women and is not interpretable in case of left bundle-branch block.

Magnetic resonance imaging (MRI) is a reliable imaging method but its availability prevents its use to a large number of patients. It is mainly used for diagnosis of cardiomyopathy.

Cardiac scan has a high negative predictive value and consequently allows, when it is normal, to rule out a myocardial perfusion abnormality, it is mainly used in young patients at the early stage of atherosclerosis.

Single photon emission tomography (SPECT) commonly called scintigraphy and carried out with thechnetium 99-m labelled agents is widely used in the world. Low uptake in the area of one coronary artery is visualized with much more precision than in the case of pluri-troncular abnormalities mainly when they are balanced.

Positron Emission Tomography (PET) imaging with rubidium-82 is routinely used in the USA. The mainly used positron-emitting radionuclide is rubidium-82 with a very short half-life of 1.27 min and which is produced and injected to a patient after elution of a generator loaded with strontium-82 which has a 25.4 days half-life. Its diagnostic specificity is higher than that of SPECT (Single Photon Emission Computed Tomography) in obese persons and women. Image interpretation is easier often allowing to assure decision certainty. Especially PET imaging allows an absolute quantification of myocardial blood flow and coronary reserve measurement which is particularly useful for diagnosis of tri-troncular abnormalities especially when they are balanced. Finally patient exposure to radiation is significantly smaller than with SPECT.