Non-invasive assessment of early and acute myocarditis in a rat model using cardiac magnetic resonance tissue tracking analysis of myocardial strain

Cardiac magnetic resonance feature tracking myocardial strain analysis in suspected acute myocarditis: diagnostic value and association with severity of myocardial injury

BACKGROUND

Albeit that cardiac magnetic resonance feature tracking (CMR-FT) has enabled quantitative assessment of global myocardial strain in the diagnosis of suspected acute myocarditis, the cardiac segmental dysfunction remains understudied. The aim of the present study was using CMR-FT to assess the global and segmental dysfunction of the myocardium for diagnosis of suspected acute myocarditis.

METHODS

Forty-seven patients with suspected acute myocarditis (divided into impaired and preserved left ventricular ejection fraction [LVEF] groups) and 39 healthy controls (HCs) were studied. A total of 752 segments were divided into three subgroups, including segments with non-involvement (S_Ni), segments with edema (S_E), and segments with both edema and late gadolinium enhancement (S_E+LGE). 272 healthy segments served as the control group (S_HCs).

RESULTS

Compared with HCs, patients with preserved LVEF showed impaired global circumferential strain (GCS) and global longitudinal strain (GLS). Segmental strain analysis showed that the peak radial strain (PRS), peak circumferential strain (PCS), and peak longitudinal strain (PLS) values significantly reduced in S_E+LGE compared with S_HCs, S_Ni, S_E. PCS significantly reduced in S_Ni (-15.3 ± 5.8% vs. -20.3 ± 6.4%, p < 0.001) and S_E (-15.2 ± 5.6% vs. -20.3 ± 6.4%, p < 0.001), compared with S_HCs. The area under the curve (AUC) values of GLS (0.723) and GCS (0.710) were higher than that of global peak radial strain (0.657) in the diagnosis of acute myocarditis, but the difference was not statistically significant. Adding the Lake Louise Criteria to the model resulted in a further increase in diagnostic performance.

CONCLUSIONS

Global and segmental myocardial strain were impaired in patients with suspected acute myocarditis, even in the edema or relatively non-involved regions. CMR-FT may serve as an incremental tool for assessment of cardiac dysfunction and provide important additional imaging-evidence for distinguishing the different severity of myocardial injury in myocarditis.

Rodent Models of Dilated Cardiomyopathy and Heart Failure for Translational Investigations and Therapeutic Discovery

Even with modern therapy, patients with heart failure only have a 50% five-year survival rate. To improve the development of new therapeutic strategies, preclinical models of disease are needed to properly emulate the human condition. Determining the most appropriate model represents the first key step for reliable and translatable experimental research. Rodent models of heart failure provide a strategic compromise between human in vivo similarity and the ability to perform a larger number of experiments and explore many therapeutic candidates. We herein review the currently available rodent models of heart failure, summarizing their physiopathological basis, the timeline of the development of ventricular failure, and their specific clinical features. In order to facilitate the future planning of investigations in the field of heart failure, a detailed overview of the advantages and possible drawbacks of each model is provided.

Nicorandil Ameliorates Doxorubicin-Induced Cardiotoxicity in Rats, as Evaluated by 7 T Cardiovascular Magnetic Resonance Imaging

PURPOSE

Doxorubicin-induced cardiotoxicity (DIC) is a common side effect of doxorubicin chemotherapy, and a major mechanism of DIC is inflammation. However, no effective method exists to prevent DIC. In the present study, we investigated the cardioprotective effects of nicorandil against DIC using multiparametric cardiac magnetic resonance (CMR) imaging and elucidated the anti-inflammatory properties of nicorandil in rat models.

METHODS

Male Sprague-Dawley rats received four weekly intraperitoneal doxorubicin doses (4 mg/kg/injection) to establish the DIC model. After treatment with or without nicorandil (3 mg/kg/day) or diazoxide (10 mg/kg/day) orally, all the groups underwent weekly CMR examinations, including cardiac function and strain assessment and T2 mapping, for 6 weeks. Additionally, blood samples and hearts were collected to examine inflammation and histopathology.

RESULTS

According to our results, the earliest DIC CMR parameter in the doxorubicin group was T2 mapping time prolongation compared with the DIC rats treated with nicorandil (doxorubicin+nicorandil group) at week 2. Subsequently, the left ventricular ejection fraction (LVEF) and global peak systolic myocardial strain in the doxorubicin group were significantly reduced, and nicorandil effectively inhibited these effects at week 6. Our results were confirmed by histopathological evaluations. Furthermore, nicorandil treatment had a protective effect against the doxorubicin-induced inflammatory response. Interestingly, similar protective results were obtained using the KATP channel opener diazoxide.

CONCLUSION

Collectively, our findings indicate that nicorandil application ameliorates DIC in rats with significantly higher cardiac function and myocardial strain and less fibrosis, apoptosis and inflammatory cytokine production. Nicorandil prevents T2 abnormalities in the early stages of DIC, showing a high clinical value for early nicorandil treatment in chemotherapy patients.

Early and dynamic detection of doxorubicin induced cardiotoxicity by myocardial contrast echocardiography combined with two-dimensional speckle tracking echocardiography in rats

Background

Anthracycline-induced cardiotoxicity is well-known as a side effect of chemotherapy. Currently, clinical imaging techniques are not capable to detect doxorubicin (DOX)-induced cardiotoxicity before a functional decline. The purpose of this study was to evaluate whether myocardial contrast echocardiography (MCE) can dynamically monitor the cardiac changes in the early stage in the DOX-induced rat model of cardiotoxicity.

Methods

A weekly injection of 2.5 mg/kg of DOX was used to generate a rat model of cardiotoxicity. All groups underwent ultrasonic examinations including standard echocardiography, 2D speckle tracking echocardiography (2D-STE), and MCE. Then all rats were sacrificed immediately for histopathological evaluation.

Results

A total of eight control rats and 32 DOX-treated rats were included in the study and grouped according to their treatment period. Decreased quantitative parameters of myocardial blood flow (MBF) (control vs. group 1: 133.31 ± 20.23 dB/s vs. 103.35 ± 21.60 dB/s, P = 0.048) and β (control vs. group 2: 11.17 ± 1.48/s vs. 7.15 ± 1.23/s, P < 0.001) were observed after 2 and 4 weeks of treatment, respectively, while left ventricular global strain (control vs. group 3: -23.67 ± 3.92% vs. -16.01 ± 3.40%, P = 0.002) decreased after 6 weeks of treatment and left ventricular ejection fraction (LVEF) (control vs. group 4: 82.41 ± 3.20% vs. 70.89 ± 9.30%, P = 0.008) decreased after 8 weeks of treatment. The main histopathological features are increased myocardial vacuolization and interstitial fibrosis and decreased myocardial microvessel density.

Conclusion

Compared with standard echocardiography and 2D-STE, MCE can accurately and non-invasively detect changes in early myocardial perfusion, demonstrating the clinical potential of continuous and dynamic monitoring of DOX-induced cardiotoxicity.

Protective effect of a chronic hypobaric hypoxic environment at high altitude on cardiotoxicity induced by doxorubicin in rats: a 7 T magnetic resonance study

Background

Doxorubicin (DOX)-induced cardiotoxicity (DIC), a major clinical problem, has no effective preventive therapies. We hypothesized that left ventricular (LV) systolic function would be improved in a chronic hypobaric hypoxia environment at high altitude. The purpose of this study was to investigate whether cardiovascular magnetic resonance could reveal the cardioprotective effect of chronic hypobaric hypoxia on DIC.

Methods

In total, 60 rats were randomly assigned to 1 of 6 groups (n=10 per group): the P group (plain), PD group (plain + DOX), HH group (high altitude), HHD4 group (high altitude + DOX for 4 weeks), HHD8 group (high altitude + DOX for 8 weeks), and HHD12 group (high altitude + DOX for 12 weeks). The rats were transported to either Yushu (altitude: 4,250 m) or Chengdu (altitude: 500 m) where they underwent intraperitoneal injection of DOX (5 mg/kg/week for 3 weeks) or saline. Preclinical 7 T cardiovascular magnetic resonance was performed at weeks 4, 8, and 12. Tissue tracking was used to measure LV cardiac function and to analyze global and segmental strains. Subsequently, histological and oxidative stress tests were performed to evaluate the protective effect of a high-altitude environment on DIC.

Results

The left ventricular ejection fraction (LVEF) and global and regional strains in the middle, apical, anterior, septal, inferior, and lateral segments (all P<0.05) were improved in the HHD4 group compared with the PD group. The global strain was significantly greater in absolute value in the HHD8 and HHD12 groups than in the HHD4 group (all P<0.05). Additionally, histological and enzyme-linked immunosorbent assay evaluations supported the in vivo results.

Conclusions

A chronic hypobaric and hypoxic environment at high altitude partially prevented cardiac dysfunction and increased global and regional strain in DIC rat models, thereby minimizing myocardial injury and fibrosis. In addition, by increasing the total duration of chronic hypobaric hypoxia, the global strain was further increased, which was likely due to reduced oxidative stress.

Nicotinamide mononucleotide attenuates doxorubicin-induced cardiotoxicity by reducing oxidative stress, inflammation and apoptosis in rats

Doxorubicin (DOX) is an effective and widely used antineoplastic drug. However, its clinical application is limited due to its dose-dependent cardiotoxicity. Great efforts have been made to explore the pathological mechanism of DOX-induced cardiotoxicity (DIC), but new drugs and strategies to alleviate cardiac damage are still needed. Here, we aimed to investigate the effect of nicotinamide mononucleotide (NMN) on DIC in rats. The results of the present study showed that DOX treatment significantly induced cardiac dysfunction and cardiac injury, whereas NMN alleviated these changes. In addition, NMN inhibited Dox-induced activation of nucleotide-binding domain-like receptor protein 3 (NLRP3) inflammasome-mediated inflammation, as evidenced by decreased caspase 1 and IL-1β activity. Moreover, NMN treatment increased glutathione (GSH) levels and superoxide dismutase (SOD) activity and decreased the levels of malondialdehyde (MDA) and reactive oxygen species (ROS) in DOX-treated rats. Furthermore, NMN treatment mitigated DOX-induced cardiomyocyte apoptosis and cardiac fibrosis. In conclusion, the results indicated that NMN protects against DIC in rats by inhibiting NLRP3 inflammasome activation, oxidative stress, and apoptosis.