To the best of our knowledge, the present study is the first to assess the feasibility and performance in patients with NIDCM combined with VAs using CMR-FT methods. Firstly, we found that LV deformation analysis can differentiate patients NIDCM with VAs from controls using CMR-FT. Secondly, we proved that the LV global strain values had a linear correlation with LVEF. Moreover, we performed pair-wise comparison among the LV global strain values, which showed linear correlations among one another. These findings which to detect early deregulated LV function in patients with NIDCM with VAs have great implication on clinical decision, which might help improve clinical outcomes.
CMR-FT has been proposed as an alternative method to quantify the myocardial strain calculated by post processing the conventional cine magnetic resonance imaging [16, 22]. Yu et al  performed that LV myocardial strain in patients with dilated cardiomyopathy can be sensitively detected by CMR-FT. Similar to the study by Yu et al., we research showed that GPRS, GPCS, and GPLS were significantly reduced in patients with NIDCM combined with VAs, suggesting global LV myocardial deformation impairment in all directions. Additionally, in this study, our research also evaluated the LV strains rate of NIDCM patients with VAs using CMR-FT. Here, we revealed that NIDCM patients with VAs was associated with a significant impairment of myocardial deformation rate in all directions, indicating that LV function relies on coordinated wall motion from all directions.
Consistent with previous research by Yu, et al., in this study, we observed that the degree of damage was not same in each direction. However, surprisingly, in contrast to other work , our research found that GPCS, rather than GPRS changed more than GPRS and GPLS, indicating that patients with NIDCM combined with VAs had more serious damage in the circumferential direction of the LV. Some differences in patients’ characteristics could explain this discordance. For example, our research objects for patients with NIDCM combined with VAs while Yu’s subjects were only just DCM. Because in this study, we showed that late gadolinium enhancement (LGE) was present in 29 (85%) of largely patients with NIDCM combined with VAs. In addition, previous studies have shown that LGE is the substrate for the occurrence of VAs , and VAs mainly occur in the areas of myocardial fibrosis of the dilated myocardium of NIDCM. Furthermore, several other studies proved that classical NIDCM showed the LGE positivity in nonischemic patterns with involvement of areas subjected to increased tension, such as the interventricular septal mid-wall at the site of insertion of ventricular fibers [25, 26]; it is mostly influenced by circumferentially oriented muscle fibers in the mid-wall. Since NIDCM shows typical mid-wall fibrosis on CMR, it more affects the myocardial circumferential strain, which leads to a decrease in GPCS in patients with NIDCM combined with VAs. All of these changes can lower the middle-wall or epicardial oxygen demand and increase the middle-wall and epicardial blood flow, finally leading to reduced peak stains (GPCS, GPRS, and GPLS) in patients with NIDCM combined with VAs.
Additionally, for the segmental myocardial strains, our research demonstrated that the PCS, PRS, PLS, PCSR, PRSR, and PLSR were significantly decreased in most LV myocardial segments, but the intensities of different strains were widely different from one another. This is concomitant with the truth that NIDCM is characterized as diffuse progression over all the whole heart; however, the degree of impairment was heterogeneous.
The LVEF is used as an important marker with which to assess LV function. Regarding the correlation between the LV global strain values and LVEF for patients with NIDCM, only a few studies have been published [23, 27]. They found that the LV myocardial strains were significantly associated with the LVEF. Similar to previous studies [23, 27], in this study, we proved that the LV myocardial strains and myocardial strains rate were significantly associated with the LVEF. The reason may be as follows. Myocardial strain measures the degree of deformation of a myocardial segment from its initial length (usually in end-diastole) to its maximum length (usually in end-systole) and is expressed as a percentage. Thus, the strain determines the fractional change in the one-dimensional length from end-diastole to end-systole , and the LVEF reflects the fractional change in the three-dimensional volume; therefore, these two measures are in parallel, which may lead to the significant correlation between the myocardial strain and the LVEF. Moreover, in this study, we showed that GPCS was better negatively correlated with LVEF (r=-0.946, P < 0.001), and proved that the higher reproducibility intraobserver and interobserver ICC were respectively 0.96 and 0.96 for GPCS measurements, indicating GPCS was a feasible feature tracking parameter in detecting patients with NIDCM combined with VAs. Because the GPCS was not affected by poor tracking of the subannular region, unlike GPLS. For this reason, it was considered the most robust parameter in CMR-FT studies of myocardial strain.
Furthermore, regarding the correlations among the LV global strain values for patients with NIDCM, only a few studies have been published [23, 29]. Maciver. et al. investigated that the GPCS had a linear correlation with the GPLS by three-dimensional speckle tracking echocardiography . And, Yu, et al showed linear correlations among GPRS, GPCS, and GPLS one another . In this present research, we carried out pair-wise contrast among the GPRS, GPCS, and GPLS, which demonstrated linear correlations among one another. Moreover, we showed pair-wise comparison among the GPRSR, GPCSR, and GPLSR, which proved linear correlations among one another (Fig. 3). These consequences suggested that the generation of LV global myocardial strain and strain rate were based on integrated rather than isolated.
Firstly, this was a single-center observational study with a limited number of patients with NIDCM combined VAs. Records were retrospectively collected and diagnosed for NIDCM combined with VAs. Secondly, lots of different factors may influence the quantification of LV strain, including image acquisition, algorithms and even CVI software versions . The strains values supplied by our study are algorithms and software specific, they can’t be simply used under other circumstances.