Cardiac Magnetic Resonance Imaging and Arrhythmic Risk Stratification in Cardiomyopathies

Abstract

Cardiac magnetic resonance imaging (CMRI) has become an indispensable tool in evaluating arrhythmic risk and guiding therapeutic decisions in patients with non-ischemic cardiomyopathies (NICMs), including dilated (DCM), hypertrophic (HCM), and arrhythmogenic cardiomyopathies (ACM). Both European and American guidelines have given an additive and different value of late gadolinium enhancement (LGE) in specific morpho-functional (hypertrophic, dilated, and arrhythmogenic) phenotypes. In particular, LGE plays a different weight in relation to different cardiomyopathies. In dilated cardiomyopathy, LGE is able to predict arrhythmic risk in relationship to the presence and localization (septal and/or ring like LGE). On the contrary, in HCM, LGE is related to increased risk of cardiac death according to the extent (LGE >15%), while in ACM, it has a greater role in the presence of fat infiltration associated with LGE. In this review, we aim to identify predictors of sudden cardiac death related to myocardial structural features seen in CMRI in cardiomyopathies, going beyond the sole assessment of left ventricular function and ejection fraction.

Keywords: cardiac imaging; cardiac magnetic resonance imaging; cardiomyopathies; sudden cardiac death; ventricular arrhythmias.

Figure 1

A patient with DCM and severe LV impairment (EF 25%) with a dilated left ventricle, as shown in balanced steady-state free precession imaging (bSSFP) in 4-chamber view (A) and 2-chamber view (B). LGE imaging in the short axis (C) and vertical long axis (D) shows the presence of LGE in the interventricular septum and the inferior and lateral walls. The patient developed an episode of VT, which was effectively terminated by the ICD (implanted following MRI).

Figure 2

A 37-year-old patient with hypertrophic cardiomyopathy. (A) shows a short-axis bSSFP image in end diastole with focal thickening of the mid-anterior interventricular septum and mid-anterior wall. (B) shows a short-axis short tau inversion recovery (STIR) image demonstrating thickening of the same region without evidence of myocardial edema. In (C) is a short-axis LGE image showing mid-wall fibrosis in the mid-anterior wall and anterior septum (red arrows). (D) shows a three-chamber bSSFP image in end systole demonstrating LVOT obstruction with systolic anterior motion (SAM) of the anterior mitral leaflet and associated dynamic flow acceleration (purple arrow). (E) is a two-chamber bSSFP in end diastole showing focal basal anterior wall hypertrophy (red arrow). (F) reports a two-chamber LGE image depicting mid-wall late enhancement in the basal anterior wall (red arrow).

Figure 3

bSSFP imaging on four-chamber view shows India ink artifacts in left ventricular anterolateral wall (red arrows) and in inferior septum (white arrow), suggesting intramyocardial fat (A); T1 imaging (B) shows the presence of fibrofatty replacement (red arrows on inferolateral and white arrow on septal wall); LGE is observed in the same left ventricular areas (C), confirming the presence of fibrofatty LV damage and suggesting left-dominant ACM.