בדיקות דימות למערכת הלב וכלי הדם IV: דימות תהודה מגנטית לבבית (CMRI)

Cardiovascular magnetic resonance imaging (CMRI) is a noninvasive diagnostic test using radiofrequency waves and a magnetic field to create precise images of the heart and blood vessels. It provides comprehensive information about cardiac anatomy, function, perfusion, and tissue characterization without ionizing radiation, allowing physicians to diagnose conditions like tissue damage from heart attacks, valve disorders, and congenital heart defects.

CMRI is contraindicated for patients with non-MRI-safe pacemakers, implantable cardioverter defibrillators, cochlear implants, neuromuscular stimulators, implanted drug infusion pumps, non-MRI-approved brain aneurysm clips, and certain dental implants. Metal fragments in the body, especially near the eyes, pose risks due to potential movement by the magnetic field. A detailed questionnaire identifies contraindications before the procedure.

CMRI diagnoses various heart conditions including tissue damage from heart attacks, ischemic heart disease, myocarditis, aortic issues such as tears and aneurysms, constrictive pericarditis, cardiomyopathies, heart muscle diseases including heart failure and tumors, valve disorders like regurgitation and stenosis, and congenital heart defects. It provides detailed tissue characterization and functional assessment of cardiac structures.

Patients should eat normally and take usual medications as prescribed. All metal objects including jewelry, hairpins, dentures, watches, and hearing aids must be removed before entering the MRI room. Credit and debit cards should be kept out to prevent magnetic strip damage. Healthcare professionals can provide documentation verifying the MRI safety of any implants or clips the patient may have.

The patient lies supine on a table that slides into the MRI machine, resembling a long metal tube. ECG leads are placed on the chest to monitor heart activity and enhance image quality. The patient must remain still to prevent blurry images. Earplugs or headphones block the machine's loud tapping noises. For magnetic resonance angiography, a gadolinium-based contrast agent may be injected intravenously. The scan typically lasts 30 to 90 minutes.

Advanced kidney failure patients usually avoid gadolinium-based contrast agents used in some CMRIs due to the risk of nephrogenic systemic fibrosis. Patients with kidney problems should consult their healthcare team regarding CMRI safety before the procedure. Those who receive contrast agents are monitored for allergic reactions and encouraged to drink fluids to help flush out the agent.

After the procedure, patients can resume routine activities immediately. Those who received sedatives must stay at the MRI center until effects wear off and require a driver to return home. Patients receiving contrast agents are monitored for allergic reactions or side effects. Follow-up consultations discuss findings and plan further management if necessary, potentially including blood studies for cardiovascular system assessment.