Evaluation of fractional flow reserve (FFR) is a key method for assessing ischemia with a view to guiding revascularization strategy following acute coronary syndrome. A stenosis that appears to be severe by angiography may cause limited ischemia (with an FFR value >0.80) due to the incapacity of the necrotic zone to achieve physiological hyperemia, i.e. maximal coronary flow. Recently, it has been demonstrated that absolute coronary flow, and micro- and macrovascular resistance, as measured by a thermodilution technique, using the Rayflow microcatheter (Hexacath) are strongly associated with myocardial mass. In extensive necrosis, there is a loss of myocardial mass, and these tools could be of potential interest in measuring myocardial viability, which reflects the extent of remaining viable myocardial mass.

Therefore, this study aims to investigate the relationship between both absolute coronary flow and microvascular resistance, and myocardial viability assessed by MRI.

In a prospective, single-centre, interventional study, we will compare absolute coronary flow and microvascular resistance in the left anterior descending artery, in patients with and without a history of ST segment elevation MI.

Inclusion Criteria:

• Inclusion criteria for the STEMI group:

  • ST segment elevation MI ≥7 days treated by angioplasty of the left anterior descending (LAD) artery
  • Scheduled to undergo angiography for fractional flow reserve (FFR) assessment of a lesion other than the infarct-related artery.

• Inclusion criteria for the control group:

  • patients undergoing non-urgent coronary angiography for stable angina or silent ischemia
  • with measure of the FFR on one or more vessels (intermediate lesion <90% without proven ischemia)

• absence of any significant lesion on the LAD (as assessed by angiography or FFR>0.8)

• Inclusion criteria for both groups:

  • Written informed consent
  • Affiliation to a social security regimen (or beneficiary thereof).

Exclusion Criteria:

• Target vessel (LAD) not permeable.
• FFR <0.8 in the LAD
• Coronary spasm
• Left ventricular ejection fraction <0.50 or a history of anterior MI in patients in the control group
• Hypertrophic cardiomyopathy
• Severe valvular heart disease
• History of coronary artery bypass graft
• Patients with limited legal capacity or patients under guardianship/tutorship
• Patients with anticipated poor compliance as assessed by the investigator
• Patients not affiliated to any social security regime.
• Pregnant women.
• Subjects within the exclusion period of another clinical trial as noted in the national registry of research volunteers

Patients with recent (>=7 days) ST segment elevation MI for the intervention group, and patients with stable angina or silent ischemia for the control group.