IRM des cardiopathies ischémiques : indications et protocoles

Ischemic heart disease is the primary cause of mortality in industrialized countries. Cardiac MRI can analyze global and regional myocardial function, can demonstrate the presence of underlying myocardial infarction and can demonstrate the presence of myocardial ischemia via the infusion of vasodilatator drugs. Myocardial infarction MRI features associate wall-motion abnormalities and myocardial late enhancement whose extension is predictive of functional recovery after revascularization. Microcirculatory damage (no-reflow) may be also detected on first-pass images and 10 minutes after injection. Their presence is correlated with the appearance of negative events in the following months. MRI study of ventricular remodeling and its complications such as ventricular wall aneurysm is also reliable. Identification of and ischemic cardiac area requires a first-pass perfusion MR sequence and vasodilatator drugs infusion such as adenosine or dypiridamole. The principle of vasodilatator stress is based on a reduction of coronary blood flow in the ischemic area during maximal vasodilatation, and not at rest, because of a flow competition with non ischemic areas. Assessment of myocardial viability may be also performed using low-dose dobutamine infusion and cine MR sequences. Improvement of contraction of a dysfunctional segment on cine MR during low-dose infusion dobutamine is predictive of a functional recovery after revascularization. Lastly, MRI can evidence differential diagnosis such as myocarditis or systemic diseases.