Microstructural alterations of the myocardium in left ventricular non-compaction cardiomyopathy (RF_FR_340)

Left ventricular non-compaction cardiomyopathy (LVNC) is characterized by the presence of excessive trabeculation in the left ventricle. While early studies linked LVNC to high mortality and morbidity from heart failure, thrombo-embolic events, and arrhythmias, recent evidence suggests it doesn’t impair prognosis in otherwise healthy individuals. Hence, LVNC’s status as a distinct cardiomyopathy is debated (1).  However, the characteristic morphology of LVNC and consistent findings of reduced strain and apical rotation imply pathological myocardial alterations (2). This study aimed to investigate LVNC’s myocardial microstructure compared to healthy controls using cardiac diffusion tensor imaging (cDTI).



Methods:

Six patients with LVNC and six healthy controls were included in this on-going study. All participants provided written informed consent, and the protocol received local ethics committee approval. CMR was performed using a 1.5T system with a high-performance gradient system (80mT/m maximal gradient strength, 100mT/m/ms slew rate). Functional imaging was conducted with balance SSFP cine imaging, covering the heart in short-axis orientation. cDTI used a motion-compensated spin echo sequence (3) with water selective spectral spatial excitation, a reduced FOV (4), respiratory navigator based slice tracking and ECG triggering to 65% end systole. Cine data were analysed using clinical software, and LV volumes and function were reported. cDTI data were registered and complex averaged, and diffusion tensors were calculated using an in-house software tool. Measurements of MD, FA, helix angle maps, and right-handed helical alignment (HA > 30°) are reported. Additionally, one ex-vivo LVNC heart from a heart transplant patient was imaged using a spin echo sequence with 3D segmented echo planar imaging readout and conventional Stejskal-Tanner diffusion encoding.

Results:

In vivo:
Table 1 presents the baseline characteristics of LVNC patients and controls. LVNC patients had larger left ventricles, a higher non-compacted to compacted tissue (NC:C) ratio, and a trend towards lower LVEF, with two patients having LVEF < 50%. In the compacted myocardium, LVNC patients showed lower endocardial helix angles (p< 0.01) and a loss of right-handed endocardial helix (p=0.04) compared to controls. The absolute E2A sheet angle was lower (p=0.05), while MD, FA, and HA slope showed no significant differences between the groups (Figure 1). HA maps (Figure 2) highlight a loss of the right-handed helix, most pronounced in the lateral and inferior segments.
Ex vivo:
Figure 3 displays fiber tracking from a post-transplant ex-vivo LVNC heart, revealing extensive endocardial non-compaction in the lateral wall and loss of right-handed helical structure in the affected region.

Conclusion:

Our findings indicate that in LVNC patients, a portion of the endocardial helix is dissolved into the non-compacted myocardium, which may impair optimal myocardial contraction in the affected segments and might be the cause for the lack of apical rotation observed in LVNC patients. The finding of reduced absolute E2A has previously been described in patients with dilated cardiomyopathy (DCM), which appears coherent given the known overlap between DCM and LVNC cohorts. The small number of patients is the major limitation of this ongoing study.