Heart MRI – obtaining images of slices of the heart in different planes when scanning with radio waves in conditions of a powerful magnetic field. The high resolution characteristics of MRI allow to obtain detailed information about the structure of the cavities and valves of the heart, to conduct a study of the functional parameters of cardiac activity, intracardiac hemodynamics. The role of MRI is invaluable in detecting heart defects and tumors, aneurysms and aortic coarctation, cardiomyopathies, pulmonary hypertension, and monitoring the results of cardiac surgery.
Modern cardiology uses the MRI procedure to identify a wide range of cardiopathology. Thanks to the detailed visualization of the aortic bed with the help of MRI, any practical changes in the aorta are determined, its condition is dynamically monitored against the background of pharmacotherapy or after cardiac surgery. The ability to assess the structure and contractility of the myocardium makes it possible to distinguish areas of infarct, ischemic and viable tissues, to carry out differential diagnosis of cardiomyopathies, myocarditis. Cardiac tomography is one of the few techniques that make it possible to examine the structure of the pericardium, to identify hemodynamic disorders associated with pericarditis.
Under the assumption of congenital heart defects, MRI helps to analyze intracardiac hemodynamics (regurgitation, aortic or mitral stenosis), identify combined defects, recreate the three-dimensional structure of valves, measure the volume of cardiac chambers. MRI allows you to diagnose defects that are not determined by other methods. Magnetic resonance imaging of the heart reveals volumetric formations located in the chambers of the heart, pericardium, myocardium, lungs or mediastinum. In the study of the pulmonary arteries, MRI can compete with invasive angiopulmonography, allowing to judge secondary disorders of the hemodynamics of the heart. Before performing the study, an echocardiogram, a rengenography of the heart, an ECG is performed.
The effect of a magnetic field and non-ionizing radiofrequency radiation imposes a number of contraindications to MRI. The procedure is not performed in patients with implanted magnetic and electronic devices. The alternating magnetic field used in MRI can provoke asynchronous operation of artificial pacemakers (EX) or cardioverter defibrillators. Ferromagnetic hemostatic clips located in the cranial cavity can shift, damaging blood vessels and causing bleeding. Metallic foreign bodies of the eyes when displaced can also damage the eyeball. MRI can cause malfunction of cochlear implants containing parts made of ferromagnetic materials.
The presence of metal occluders used in the closure of defects of the MPP, defects of the MLP or OAP, stents, embolization spirals, cava filters in the first 6-8 weeks after implantation also serves as a contraindication. In the future, after fixing these devices in the tissues, cardiac tomography seems safe. Valvular prostheses can initiate artifacts on cardiac tomograms. When planning an MRI, they always specify the presence and type of the available implant, the manufacturer’s information about the characteristics of the metal and the possibility of carrying out the study.
Claustrophobia, especially accompanied by hysteroid reactions, can serve as a serious obstacle to MRI. They also refrain from carrying out epilepsy, congestive heart failure, in the I and III trimesters of pregnancy. Factors that reduce the image quality during MRI are external radio frequency radiation, patient mobility (heartbeat, breathing, vascular pulsation, involuntary movements), metal objects. To exclude external sources of artifacts, additional fixation of the body is used, synchronization of tomograms with ECG, pulse, breathing.
Methodology of conducting
During the heart MRI, the patient is placed on a special moving tomograph table, which is wound up in the scanner to the required level. During the study, ECG, hemodynamics, respiration and mental status of the patient are monitored. If it is necessary to introduce contrast enhancement, intravenous infusion is adjusted. The study requires the patient to remain motionless and follow the operator’s commands (periodic short-term breath retention). An MRI scan of the heart lasts from 30 to 60 minutes.
During the MRI process, the patient is in the zone of action of a high-intensity magnetic field and is scanned by radio waves. The signals captured by the sensors are converted into a series of static and dynamic tomographic images in various projections. Images of virtual slices are projected onto a monitor, recorded on video and magnetic film, and transmitted to the patient after the end of the study.