The emerging clinical role of cardiovascular magnetic resonance imaging

Abstract

Starting as a research method little more than a decade ago, cardiovascular magnetic resonance (CMR) imaging has rapidly evolved to become a powerful diagnostic tool used in routine clinical cardiology. The contrast in CMR images is generated from protons in different chemical environments and, therefore, enables high-resolution imaging and specific tissue characterization in vivo, without the use of potentially harmful ionizing radiation.CMR imaging is used for the assessment of regional and global ventricular function, and to answer questions regarding anatomy. State-of-the-art CMR sequences allow for a wide range of tissue characterization approaches, including the identification and quantification of nonviable, edematous, inflamed, infiltrated or hypoperfused myocardium. These tissue changes are not only used to help identify the etiology of cardiomyopathies, but also allow for a better understanding of tissue pathology in vivo. CMR tissue characterization may also be used to stage a disease process; for example, elevated T2 signal is consistent with edema and helps differentiate acute from chronic myocardial injury, and the extent of myocardial fibrosis as imaged by contrast-enhanced CMR correlates with adverse patient outcome in ischemic and nonischemic cardiomyopathies.The current role of CMR imaging in clinical cardiology is reviewed, including coronary artery disease, congenital heart disease, nonischemic cardiomyopathies and valvular disease.

Figure 1)

Examples of cardiovascular magnetic resonance imaging of congenital heart disease. A Sagittal black-blood image of a patient with repaired tetralogy of Fallot, showing right ventricular dilation and an aneurysm (A) of the right ventricular outflow tract patch. B Transverse static bright-blood image (steady-state free precession) of the pulmonary arteries (PAs) lying anterior to the aorta (Ao) following arterial switch repair with the Lecompte manoeuvre in transposition of the great arteries. C Diastolic frame of a steady-state free precession cine image series in a patient with repaired tetralogy of Fallot and pulmonary regurgitation showing severe right ventricular dilation. D Volume rendering of a gadolinium-enhanced magnetic resonance angiogram of the right ventricle (RV) and PAs in a patient with an RV-to-PA-valved conduit for repair of pulmonary atresia and ventricular septal defect. LA Left atrium; LV Left ventricle; RA Right atrium

Figure 2)

Adenosine stress perfusion imaging of a patient with coronary artery disease. A patient with a high-grade stenosis of a diagonal branch artery. The left image shows a short-axis view of an apical short-axis slice (still frame extracted from a movie). There is no significant perfusion deficit during contrast infusion at rest. When the examination is repeated 20 min later during the continuous infusion of adenosine, the second contrast infusion shows a stress-induced subendocardial perfusion deficit of the anterolateral wall (arrows). LV Left ventricle

Figure 3)

A patient with an acute posterolateral myocardial infarction. The image to the left displays a short-axis view using the ‘late enhancement’ sequence after application of gadolinium-diethylene triamine penta-acetic acid contrast. There is contrast enhancement indicating myocardial necrosis of the inferior lateral wall (bold arrows), but not in the anterior and septal wall. There is an area of microvascular obstruction, highlighted with the slim arrow. The image to the right is a T2-weighted spin-echo image, showing a regionally high signal in the inferior lateral wall (arrows), consistent with myocardial edema in the area of necrosis. The presence of edema indicates that the infarction is acute

Figure 4)

A patient with aortic valve stenosis. Both images are still frames extracted from steady-state free precession cine movies. The orifice of the aortic valve can be measured from the systolic image to the right. The contour of the orifice is marked in yellow. AoV Aortic valve; LA Left atrium; RA Right atrium; RV Right ventricle

Figure 5)

A patient with hypertrophic obstructive cardiomyopathy. Both images are extracted from functional steady-state free precession cine movies, at diastole (left) and mid-systole (right). The diastolic image displays marked thickening of the anterior septal wall. At mid-systole, there is an anterior movement of the anterior mitral valve leaflet, causing left ventricular outflow tract obstruction and a jet of high-velocity flow (arrow). Cardiovascular magnetic resonance imaging allows for quantification of the obstruction by planimetry of the left ventricular outflow tract and flow velocity quantification of the jet (not shown)

Figure 6)

A patient with myocarditis. The quantitative measurements of signal intensities in the myocardium normalized to skeletal muscle using a T1-weighted spin-echo sequence, before and after application of gadolinium contrast, allow for identification of patients with inflammatory myocardial disease (left image). In patients with acute severe myocarditis, patchy foci of delayed enhancement can be visualized, corresponding to foci of acute myocardial necrosis (right image, arrows)