Multiparametric MRI Assessment of Atrial Heart Disease as a Predictor of Atrial Fibrillation After Myocardial Revascularization Surgery

• 4D cardiac MRI with gadoteric acid (Device), also known as 4D flow Magnetic Resonance Imaging with Late Gadolinium Enhancement: 4D cardiac MRI with gadoteric acid injection will be performed prior the surgery, according to a standardized technical protocol.
• Blood sample (Biological): Peripheral venous blood sample (1 x 6 ml EDTA tube): taken during preoperative assessment to measure inflammatory biomarkers (CRP, IL-1, TNF-α).
• Implantable Loop Recorder (ILR) (Device): Implantation of a Holter monitor (Implantable Loop Recorder) prior to surgery, performed preoperatively under local anesthesia. The ILR will enable continuous recording of the heart rhythm for 12 months with automatic data transmission via remote monitoring. The minimally invasive procedure will be performed by an experienced cardiologist under the usual safety conditions.
• Right atrial biopsy (Procedure): During the surgical procedure (coronary artery bypass grafting), a right atrial biopsy will be performed using a brief, low-risk procedure on a small tissue sample. The sample will be analyzed using Masson's trichrome staining to assess atrial fibrosis.

Primary outcomes

• Evaluate the predictive value of atrial heart disease characterized by multiparametric MRI (late enhancement fibrosis, atrial strain, and exploratory 4D flow parameters) for the recurrence of atrial fibrillation documented by Implantable Loop Recorder. [through study completion, an average of 12 months]: Recurrence of atrial fibrillation, defined as an episode lasting ≥ 30 seconds documented by the Implantable Loop Recorder (ILR) implanted preoperatively and recorded during the 12-month follow-up period.

Secondary outcomes

• Evaluate the link between atrial heart disease characterized by MRI (fibrosis, strain, 4D flow) and the occurrence of postoperative atrial fibrillation (POAF) during the first week following coronary artery bypass grafting. [through the first postoperative week]: POAF will be defined as an episode of AF ≥ 30 seconds, detected by the preoperatively implanted ILR and recorded during the first postoperative week.
• Correlate MRI parameters of atrial remodeling with histological assessment of fibrosis on intraoperative atrial biopsy [through the first postoperative week]: Percentage of histological fibrosis. Analysis of atrial fibrosis using Masson's trichrome staining on intraoperative atrial biopsy (normal threshold ≤ 10%). The objective is to establish a correlation between histological data and MRI parameters.
• Exploring the value of atrial hemodynamic parameters obtained by 4D flow MRI (vorticity, intra-atrial velocities) as predictive markers of atrial fibrillation [Before the surgery]: measurement of intra-auricular blood flow using 4D-flow MRI, including velocities (cm/s), flow volumes (mL/s or mL), and vorticity indices (s-¹)
• To study the association between serum inflammatory biomarkers (CRP, IL-1, TNF-α) and Atrial Fibrillation recurrence. [before the surgery]: Preoperative measurement of pro-inflammatory cytokines (IL-1, TNF-α, CRP).
• Determine the impact of atrial fibrillation recurrence documented by ILR on the occurrence of major cardiovascular events [through study completion, an average of 12 months]: Number of ischemic strokes, hospitalizations for heart failure, cardiovascular deaths occurring within one year of surgery, and all-cause deaths.

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Age ≥ 18 years
* Indication for surgical myocardial revascularization by isolated coronary artery bypass grafting, to be performed in the cardiac surgery department of Saint-Étienne University Hospital.
* Patient affiliated with or entitled to social security coverage
* Patient who has received informed information about the study and has co-signed, with the investigator, a consent form to participate in the study

Exclusion Criteria:

* Contraindication related to cardiac MRI
* Contraindication related to ILR implantation
* Documented history of atrial fibrillation
* Concomitant indication for valve surgery or other associated cardiac intervention
* Inability to understand French
* Patient refusal to participate in the study and/or inability to express consent or sign the informed consent form
* Patient subject to legal protection measures

• Jean-Baptiste GUICHARD, MD, Study director, Hospital Clinic of Barcelona