Advanced Myocardial Tissue Characterization of Patients with Non-Ischemic Dilated Cardiomyopathy and Ring-like Hyperenhancement

Background: Recently, a “ring-like” pattern of hyperenhancement (HE) has emerged as an CMR phenotype in nonischemic dilated cardiomyopathy (DCM) which is associated with poor prognosis.1 The definition of “ring-like” HE requires ≥3 contiguous segments with subepicardial or midmyocardial HE in the same short-axis (SAX) slice. However, ≥3 contiguous segments of HE is not the same as a continuous ring of HE (i.e. without breaks) that spans ≥3 segments. Moreover, the ring phenotype could be quite distinct, ranging from sharp border striae to a diffuse border (Fig.1). The aim of this study was to evaluate different phenotypes of ring-like HE and to identify any relationships between these phenotypes and specific myocardial tissue characteristics such as fatty metaplasia (linked with pathogenic genetic variants leading to arrhythmogenic LV cardiomyopathy)2and papillary muscle scarring (linked with microvascular dysfunction in DCM and adverse outcome)3.

Methods: We identified 100 consecutive patients scanned at Duke Hospital from the SCMR registry database who fulfilled the definition of ring-like HE (≥3 contiguous segments of subepicardial or midmyocardial HE in the same SAX slice). Patients with known CAD or other non-DCM cardiomyopathy were excluded. Advanced tissue characterization included a validated out-of-phase (OOP) cine sequence for myocardial fat detection4 and flow-independent dark-blood delayed enhancement (FIDDLE) for the detection of papillary muscle3 and subendocardial HE5.

Results: Mean age was 58 (74% male), and mean LV ejection fraction (LVEF) was 41%. Of all 100 patients with ≥3 contiguous segments, the ring was continuous across ≥3 segments in 76 (76%) and non-continuous in 24 (24%) (Fig.1). Among those with continuous rings, patients could be further subdivided into those with sharp border striae (84%) and diffuse borders (16%). Advanced tissue characterization demonstrated that only patients with sharp border striae had associated fatty metaplasia (23% vs. 0%, p=0.09), while those with diffuse border rings were more likely to have subendocardial extension of the ring and papillary muscle scarring (75% vs. 48%, p = 0.09 and 83% vs. 47%, p=0.02) (Fig.2).

Conclusion: Ringlike HE can encompass several different HE phenotypes. The current definition does not account for HE continuity across segments. A continuous sharp-border striae ring may be characterized by fatty metaplasia. A continuous ring with diffuse borders has predilection for continuation of the midwall/epicardial ring to the subendocardial layer and papillary muscle scarring, which could reflect microvascular dysfunction in nonischemic DCM.

Figure 1. Definition and different phenotypes of “ring-like” hyperenhancement (HE). All patients had ≥3 contiguous segments of HE (blue arrows) but rings could be categorized as continuous or non-continuous. Further, continuous rings could be subdivided into rings with sharp borders or diffuse borders. In the patient example with a non-continuous ring, there is midwall HE in ≥3 contiguous segments (anteroseptal, anterior, anterolateral and inferolateral segments).
Figure 2. Advanced CMR tissue characterization in patients with continuous ring-like hyperenhancement (HE). Yellow box: Delayed-enhancement (DE) images show a sharp border striae of HE in the septum and anterolateral wall (blue arrows). The patient‘s corresponding out-of-phase (OOP) cine images, which are sensitive to detecting fatty metaplasia, demonstrate that the HE is predominantly secondary to intramyocardial fat (India ink appearance, yellow arrows). Overall, only patients with sharp border striae had associated fatty metaplasia. Pink box: Flow-independent dark-blood delayed enhancement (FIDDLE) imaging (right) demonstrates papillary muscle scarring (pink arrow) as well as an epicardial ring of HE which also involves the RV side of the septum (blue arrows). Green box: FIDDLE image shows a midwall ring of HE in the septum (blue arrows) with continuation of the ring to the subendocardial layer of the anterolateral wall (green arrows). Those with diffuse border rings were moderately more likely to have subendocardial extension of the ring and papillary muscle scarring.