CMR in cardiac amyloidosis

Associate Editor-In-Chief: Caitlin J. Harrigan [mailto:charrigan@perfuse.org]]

Cardiac MR (CMR) and Cardiac Amyloidosis: An Overview

 * The primary method of diagnosing cardiac amyloidosis is myocardial biopsy, which is both invasive and cumbersome
 * CMR is a noninvasive imaging modality, offering considerable information which may support or question the diagnosis of cardiac amyloidosis before the necessary (or unnecessary) biopsy

Left and Right Atrial Size

 * The 4-chamber cine sequence allows for proper visualization of the atria
 * A maximum length is usually taken in an end-systolic frame
 * The right atrium can be measured from the annulus of the tricuspid valve back to the right atrial wall, and similarly, the left atrium can be measured from the annulus of the mitral valve back to the left atrial wall
 * This is particularly useful in cardiac amyloidosis, as the atria are typically enlarged

Left and Right Ventricular Mass and Volumes

 * Using the functional cine sequence known as the Short-Axis (SHAX) Stack, both left and right ventricular volumes and mass can be quantified
 * Using Simpson's Rule, and by planimetering the endocardial and epicardial borders of the left and right ventricles (LV and RV, respectively) in both end-diastole (ED) and end-systole (ES), we can easily assess volumes and mass
 * This method is extremely beneficial for a differential diagnosis, as patients with cardiac amyloidosis tend to have increased mass and volumes (particularly systolic volumes)
 * CMR also allows for sharpened visualization of the RV (as opposed to 2D-echocardiography)
 * Cardiac amyloidosis affects both the LV and RV, in that fibrillary protein deposition does not discriminate between ventricles

Myocardial Delayed Enhancement

 * Delayed enhancement (DE) imaging provides relevant information on both the pathology and morphology of patients with cardiac amyloidosis
 * Gadolinium is an inert extracellular contrast agent that cannot penetrate intact sarcomere
 * Normal, healthy myocardium is primarily intracellular
 * This is why hyperenhancement is absent in normal myocardium
 * Amyloid infiltration in cardiac amyloidosis causes gross expansion of the interstitial space
 * DE imaging using Gd allows for the Gd to pool or accumulate in these expanded areas of amyloid infiltration, usually causing large, diffuse areas of hyperenhancement (see image)