Author + information
- Published online March 14, 2018.
- Zohya Khalique, MBBS,
- Pedro F. Ferreira, PhD,
- Andrew D. Scott, PhD,
- Sonia Nielles-Vallespin, PhD,
- Rick Wage, DCR(R),
- David N. Firmin, PhD and
- Dudley J. Pennell, FMedSci∗ ()
- ↵∗Cardiovascular Magnetic Resonance Unit, Royal Brompton Hospital, Sydney Street, London SW3 6NP, United Kingdom
Diffusion tensor cardiovascular magnetic resonance (DT-CMR) evaluates myocardial microstructure, using helix angle (HA) and absolute angulation of the second eigenvector (E2A) to assess cardiomyocyte and sheetlet orientation respectively. In health, sheetlets align more wall-parallel in diastole and more wall-perpendicular in systole. However, in dilated cardiomyopathy (DCM), with left ventricle (LV) dilatation and systolic dysfunction, sheetlet mobility is reduced (1). In one-third of idiopathic DCM patients, LV size and ejection fraction (EF) can improve with pharmacological and device therapy (2). We performed DT-CMR to assess microstructural recovery in recovered DCM (R-DCM).
Twelve DCM patients, 12 R-DCM patients, and 12 controls were studied using standard criteria (1). In R-DCM, LV size and EF were within normal indexed ranges, and evidence of prior LV dilation and reduced EF by CMR or echocardiogram was required. Patients with a clinical diagnosis of idiopathic, genetic, or familial R-DCM were included. DT-CMR was performed as previously described (1). The Mann-Whitney test compared groups with Bonferroni correction.
Groups were well-balanced for age and sex. Median (interquartile range) age was 61 (44 to 66) years in R-DCM, 54 (41 to 59) years in DCM, and 54 (43 to 60) years in controls. In DCM, LV size and mass were increased (end-diastolic volume 154 ml/m2 [123to 201 ml/m2] and 88 g/m2 [72 to 115 g/m2]), whereas EF was reduced (33% [29% to 45%]). LV volume and mass were not significantly different between R-DCM (82 ml/m2 [75 to 91 ml/m2]; 62 g/m2 [54 to 72 g/m2]) and controls (80 ml/m2 [70 to 87 ml/m2]; 66 g/m2 [59 to 74 g/m2]). Controls EF was 66% (62% to 66%). In R-DCM, baseline EF was 27% (25% to 38%) and current EF was 64% (60% to 66%). For the imaged slice midwall, late gadolinium enhancement was present in 9 of 12 DCM patients and 5 of 12 R-DCM patients. All patients were in New York Heart Association functional class 1.
Myocyte orientation HAs were negative epicardially, near circumferential mesocardially, and positive HAs endocardially and similar across groups. Median (interquartile range) diastolic E2A in R-DCM was 25° (22 to 30°), which was similar to DCM (19° [16 to 27°]; p = 0.11) and controls (20° [15 to 29°]; p = 0.24). However, systolic E2A in R-DCM was 59° (52 to 66°), significantly greater than DCM (35° [22 to 38°]; p < 0.0001), but lower than controls (65° [63 to 71°]; p = 0.01). E2A mobility was 35° [29 to 39°] in R-DCM, greater than DCM (9.6° [3.4 to 19°]; p < 0.0001), but less than controls (46° [41 to 51°]; p = 0.001) (Figure 1).
Myocardial contractile recovery is complex and multifactorial, with increasing focus on different patients groups with reverse remodeling, remission and full recovery (3). Clinically, R-DCM is based upon structural, biochemical, and symptomatic improvement with improved LV size and LVEF >40% to 50%. However, recovered patients can still demonstrate abnormal biomarker levels, subclinical dysfunction, and substantial cardiac hospitalizations and heart failure symptoms (4,5). In this study, all R-DCM patients described symptomatic and structural improvement with entirely recovered LV size and EF within reference ranges. However, systolic E2A and sheetlet mobility remained significantly reduced in R-DCM compared with controls indicating persistent microstructural abnormalities in R-DCM, despite normalization of LV size and EF. E2A mobility in R-DCM was greater than in DCM, however, implying a variable microstructural measure that alters along the disease trajectory. This suggests a potential role of DT-CMR in the assessment of DCM recovery/remission and predicting patients at risk of relapse, and reinforces the ability of DT-CMR to provide insight into LV dynamics beyond the limitations of EF.
Limitations of DT-CMR (1) include low spatial resolution, affecting measurements in thin walls. In this cross-sectional study with retrospective analysis of DCM diagnosis, patient heterogeneity remains. This includes disparity between echo and CMR derived EF. Further work in DCM of extrinsic origin such as myocarditis may yield different microstructural findings.
Please note: This work was supported by the National Institute for Health Research Funded Cardiovascular Biomedical Research Unit at The Royal Brompton Hospital and Imperial College London, London, UK. Prof. Firmin has received research support from Siemens. Prof. Pennell has received research support from Siemens; and is a stockholder in and director of Cardiovascular Imaging Solutions. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. Profs. Firmin and Pennell contributed equally to this work and are joint senior authors.
- 2018 American College of Cardiology Foundation
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