Diastology with Cardiac MRI: A Practical Guide

Diastolic filling of the ventricle is a complex in-terplay of volume and pressure, contingent on active energy-dependent myocardial relaxation and myocardial stiffness. Abnormal diastolic function is the hallmark of the clinical entity of heart failure with preserved ejection fraction (HFpEF), which is now the dominant type of heart failure and is associated with significant morbidity and mortality. Although echocardi-ography is the current first-line imaging modal-ity used in evaluation of diastolic function, car-diac MRI (CMR) is emerging as an important technique. The principal role of CMR is to cat-egorize the cause of diastolic dysfunction (DD) and distinguish other entities that manifest similarly to HFpEF, particularly infiltrative and pericardial disorders. CMR also provides prog-nostic information and risk stratification based on late gadolinium enhancement and paramet-ric mapping techniques. Advances in hardware, sequences, and postprocessing software now enable CMR to diagnose and grade DD accu-rately, a role traditionally assigned to echocardi-ography. Two-dimensional or four-dimensional velocity-encoded phase-contrast sequences can measure flow and velocities at the mitral in-flow, mitral annulus, and pulmonary veins to provide diastolic functional metrics analogous to those at echocardiography. The commonly used cine steady-state free-precession sequence can provide clues to DD including left ventric-ular mass, left ventricular filling curves, and left atrial size and function. MR strain imaging provides information on myocardial mechanics that further aids in diagnosis and prognosis of diastolic function. Research sequences such as MR elastography and MR spectroscopy can help evaluate myocardial stiffness and metabo-lism, respectively, providing additional insights on diastolic function. The authors review the physiology of diastolic function, mechanics of diastolic heart failure, and CMR techniques in the evaluation of diastolic function.