Time-dependent cardiac structural and functional changes after kidney transplantation: a multi-parametric cardiac magnetic resonance study

Elevated Septal Native T1 Time in CMR Imaging Suggesting Myocardial Fibrosis in Young Kidney Transplant Recipients

BACKGROUND

Patients after kidney transplantation (KTx) in childhood show a high prevalence of cardiac complications, but the underlying mechanism is still poorly understood. In adults, myocardial fibrosis detected in cardiac magnetic resonance (CMR) imaging is already an established risk factor. Data for children after KTx are not available. This study aimed to explore cardiac function and structure with focus on myocardial fibrosis and associated risk factors in KTx recipients.

METHODS

46 KTx recipients (mean age 16.0 ± 3.5 years) and 46 age- and sex-matched healthy controls were examined with non-contrast CMR imaging. Native T1 time (nT1), a marker for myocardial fibrosis, was measured at the interventricular septum. Other parameters comprised left ventricular mass index (LVMI), ejection fraction (LVEF), and global longitudinal strain (GLS). Multivariable linear regression analyses were used to explore associations with nT1.

RESULTS

Mean nT1 was significantly higher in KTx recipients than in controls (1198.1±48.8ms vs. 1154.4±23.4ms, p<0.0001). Twenty-one (46%) had a nT1 above above the upper limit of the normal range (mean + 2SD of controls). KTx recipients showed higher LVMI z-scores (0.1±1.1 vs. -0.3±0.7, p=0.026), higher LVEF (67.3±3.8% vs. 65.3±3.6%, p=0.012), and lower GLS (-19.0±2.1% vs. -20.3±2.7%, p=0.010). Higher systolic blood pressure (SBP; ß=1.284, p=0.001), LVMI (ß=1.542, p<0.001), and LVEF (ß=3.535, p=0.026) were associated with longer nT1 only in KTx recipients, but not in controls. Only two KTx recipients exhibited left ventricular hypertrophy, however, a total of 18 displayed elevated nT1 with LVMI z-score within the normal range.

CONCLUSION

Our data suggest the presence of cardiac remodeling with myocardial fibrosis in a significant proportion of young KTx recipients. Non-contrast CMR imaging has the potential to visualize early structural cardiac changes and could become an important diagnostic adjunct in the follow-up of KTx recipients. Longitudinal studies are needed to further evaluate the importance of nT1 in early identification of those at high risk for sudden cardiac death allowing to integrate preventive strategies.

Evaluation of the effect of kidney transplantation on left ventricular myocardial work by noninvasive pressure-strain loops

Purpose

Kidney transplantation (KT) has the potential to reverse the cardiac changes caused by end-stage renal disease, and it may be inaccurate to analysis the left ventricular function by conventional echocardiography due to afterload. This study aimed to investigate the utility of pressure strain loops (PSLs) in evaluating left ventricular performance in patients underwent KT.

Methods

We enrolled 60 patients with end-stage renal disease who underwent KT between January 2022 and July 2023, and 60 healthy controls with a similar distribution of gender and age to the patients. All participants underwent conventional echocardiography and three-dimensional speckle tracking echocardiography (3D-STE). Long axis, short axis, and four cavity images were collected and cardiac parameters were measured. The echocardiographic changes of cardiac structure and function of all patients before KT and about 12 months after KT were recorded. Left ventricular myocardial work parameters were acquired by PSLs, including the global work index (GWI), global constructive work (GCW), global wasted work (GWW), global work efficiency (GWE) and global longitudinal strain (GLS). In addition, the correlation between PSLs and clinical data were explored.

Results

Compared with controls, the conventional echocardiographic parameters, myocardial function indicators GWI and GCW appeared no difference in post-KT group, while the GWE and GLS decreased (p < 0.05), and the GWW increased (p < 0.05). Compared with pre-KT, the GLS, GWI, GCW and GWE increased in post-KT group, while the GWW decreased (all p < 0.05). The above indicators were correlated with left ventricular GLS and left ventricular ejection fraction.

Conclusion

PSLs were more sensitive than traditional echocardiographic indicators in detecting changes in myocardial work and predicting left ventricular myocardial damage. This indicator could quantitatively evaluate myocardial work and provide a new and reliable non-invasive reference for clinical diagnosis and treatment of patients underwent KT.

Left Ventricular Hypertrophy After Renal Transplantation: Systematic Review and Meta-analysis

Background

Left ventricular hypertrophy (LVH) in patients with end stage renal disease undergoing renal replacement is linked to an increased risk for cardiovascular diseases. Dialysis does not completely prevent or correct this abnormality, and the evidence for kidney transplantation (KT) varies. This analysis aims to explore the relationship between KT and LVH.

Methods

MEDLINE and Scopus were systematically searched in October 2023. All cross-sectional and longitudinal studies that fulfilled our inclusion criteria were included. Outcome was left ventricular mass index (LVMI) changes. We conducted a meta-analysis using a random effects model. Meta-regression was applied to examine the LVMI changes dependent on various covariates. Sensitivity analysis was used to handle outlying or influential studies and address publication bias.

Results

From 7416 records, 46 studies met the inclusion criteria with 4122 included participants in total. Longitudinal studies demonstrated an improvement of LVMI after KT -0.44 g/m2 (-0.60 to -0.28). Blood pressure was identified as a predictor of LVMI change. A younger age at the time of KT and well-controlled anemia were also associated with regression of LVH. In studies longitudinally comparing patients on dialysis and renal transplant recipients, no difference was detected -0.09 g/m2 (-0.33 to 0.16). Meta-regression using changes of systolic blood pressure as a covariate showed an association between higher blood pressure and an increase in LVMI, regardless of the modality of renal replacement treatment.

Conclusions

In conclusion, our results indicated a potential cardiovascular benefit, defined as the regression of LVH, after KT. This benefit was primarily attributed to improved blood pressure control rather than the transplantation itself.

Multiparametric Cardiovascular Magnetic Resonance in Nonhospitalized COVID-19 Infection Subjects: An Intraindividual Comparison Study

PURPOSE

To investigate intraindividual cardiac structural and functional changes before and after COVID-19 infection in a previously healthy population with a 3T cardiac magnetic resonance (CMR).

MATERIALS AND METHODS

A total of 39 unhospitalized patients with COVID-19 were recruited. They participated in our previous study as non-COVID-19 healthy volunteers undergoing baseline CMR examination and were recruited to perform a repeated CMR examination after confirmed COVID-19 infection in December 2022. The CMR parameters were measured and compared between before and after COVID-19 infection with paired t tests. The laboratory measures including myocardial enzymes and inflammatory indicators were also collected when performing repeated CMR.

RESULTS

The median duration was 393 days from the first to second CMR and 26 days from clinical symptoms onset to the second CMR. Four patients (10.3%, 4/39) had the same late gadolinium enhancement pattern at baseline and repeated CMR and 5 female patients (12.8%, 5/39) had myocardial T2 ratio >2 (2.07 to 2.27) but with normal T2 value in post-COVID-19 CMR. All other CMR parameters were in normal ranges before and after COVID-19 infection. Between before and after the COVID-19 infection, there were no significant differences in cardiac structure, function, and tissue characterization, no matter with or without symptoms (fatigue, chest discomfort, palpitations, shortness of breath, and insomnia/sleep disorders) (all P >0.05). The laboratory measures at repeated CMR were in normal ranges in all participants.

CONCLUSIONS

These intraindividual CMR studies showed unhospitalized patients with COVID-19 with normal myocardial enzymes had no measurable CMR abnormalities, which can help alleviate wide social concerns about COVID-19-related myocarditis.

Image Improved Intravoxel Incoherent Motion MRI With Optimized Trigger Delays Based on Strain Curve Analysis to Evaluate Myocardial Microvascular Dysfunction of Exertional Heat Illness

BACKGROUND

Intravoxel incoherent motion (IVIM) MRI has not been widely used and its role in evaluating exertional heat illness (EHI)-related myocardial involvement remains unknown.

PURPOSE

To investigate the feasibility of strain curve-derived trigger delay (TD) IVIM-MRI and its role in assessing myocardial diffusion and microvascular perfusion of EHI patients.

STUDY TYPE

Prospective.

SUBJECTS

A total of 42 male EHI patients (median age: 21 years) and 22 age- and sex-matched healthy controls (HC).

FIELD STRENGTH/SEQUENCE

A 3-T, diffusion-weighted spin-echo echo-planar-imaging sequence.

ASSESSMENT

IVIM-MRI was acquired by conventional TD method (group A) or strain curve-based TD method (group B) in random order. IVIM image quality was evaluated on a 3-point Likert scale (1, nondiagnostic; 2, moderate; 3, good). Technical success was defined as image quality score = 3. IVIM-MRI-derived parameters (pseudo diffusion in the capillaries [D*], perfusion fraction [f], and slow apparent diffusion coefficient [D]) were compared between EHI and HC.

STATISTICAL TESTS

Student's t-tests, chi-square tests, one-way analysis of variance, receiver operating characteristic (ROC) curve analysis, Pearson's correlation coefficient (r). The statistical significance level was set at P < 0.05.

RESULTS

IVIM-MRI image quality score (median [interquartile range]: 3 [2, 3] vs. 2 [1-3]) and technical success rate (61.9%[13/21] vs. 28.6%[6/21]) were significantly improved in group B. EHI patients showed significantly decreased D* (118.1 ± 23.3 × 10-3  mm2 /sec vs. 142.7 ± 42.6 × 10-3  mm2 /sec) and f values (0.42 ± 0.12 vs. 0.51 ± 0.11) and significantly higher D values (3.0 ± 0.9 × 10-3  mm2 /sec vs. 2.5 ± 0.6 × 10-3  mm2 /sec) compared to HC. Relative to D and D*, f showed the most robust efficacy for detecting EHI-related myocardial injury with the highest area under the ROC curve (0.906: 95% confidence interval, 0.799, 0.967) and sensitivity of 88.5% and specificity of 85.6%.

CONCLUSION

The strain curve-based TD method significantly improved image quality and technical success rate of IVIM-MRI, and f value may be an effective biomarker to assess myocardial microcirculation abnormalities of EHI patients.

EVIDENCE LEVEL

2.

TECHNICAL EFFICACY

Stage 3.