Ressonância magnética é útil em valvopatia

Abstract

Reperfusion injury, hemodynamics, blood volume.conformation, it shows low intra- and interobserver variability and allows right ventricle quantification, a chamber usually difficult to access on echocardiograms. These qualities are the CMR’s calling card for inclusion in the follow-up of ventricular function and mass of patients with valvular heart disease (such as aortic stenosis), as well as for functional comparison after surgical intervention. Velocity-encoded cine-MRI allows the assessment of blood flow velocity across a cardiac vessel or valve. It is equivalent to Doppler echocardiography, but offers the advantage of accessing blood flows in any orientation without being limited by an acoustic window. Using the modified Bernoulli equation, it is possible also to derive transvalvular pressure gradient. One of the cardiologist’s biggest concerns is that of CMR safety in patients with a mechanical prosthetic valve. It is well established that it is safe to expose a patient with this type of prosthesis to the magnetic fields generally used on CMR (1.5 Tesla). The magnetic force acting on the material is too weak compared to that imposed by the surgical attachment of the prosthesis. On the other hand, these prostheses produce artifacts of signal void (dark area on the MRI image), because the magnetic field becomes distorted by the metallic content. These artifacts often extend to the surrounding structures, depending on the pulse sequence used (this is usually less marked in spin-echo sequences). Consequently, the evaluation of turbulent jets, especially those of lower magnitude, is compromised. With bioprostheses, this effect is usually restricted to the valve annulus and does not interfere significantly in the MRI interpretation.Described around six years ago, the delayed-enhanced technique consists in acquiring images approximately 10 to 20 minutes after the intravenous injection of a contrast medium (gadolinium) preceded by an inversion-recovery pulse6. In addition to allowing the visualization of minimal areas of myocardial necrosis/fibrosis, this technique shows excellent correlation with the pathological anatomy in several heart diseases