Remodeling of human transplanted myocardium in ten-year follow-up: a clinical pathology study

Speckle-Tracking Echocardiography in Right Ventricular Function of Clinically Well Patients with Heart Transplantation

Heart transplantation (HT) is the mainstream therapy for end-stage heart disease. However, the cardiac graft function can be affected by several factors. It is important to monitor HT patients for signs of graft dysfunction. Transthoracic echocardiography is a simple, first-line, and non-invasive method for the assessment of cardiac function. The emerging speckle-tracking echocardiography (STE) could quickly and easily provide additive information over traditional echocardiography. STE longitudinal deformation parameters are markers of early impairment of ventricular function. Although once called the "forgotten ventricle", right ventricular (RV) assessment has gained attention in recent years. This review highlights the potentially favorable role of STE in assessing RV systolic function in clinically well HT patients.

Approach to optimal assessment of right ventricular remodelling in heart transplant recipients: insights from myocardial work index, T1 mapping, and endomyocardial biopsy

AIMS

Right ventricular (RV) dysfunction is an important cause of graft failure after heart transplantation (HTx). We sought to investigate relative merits of echocardiographic tools and cardiac magnetic resonance (CMR) with T1 mapping for the assessment of functional adaptation and remodelling of the RV in HTx recipients.

METHODS AND RESULTS

Sixty-one complete data set of echocardiography, CMR, right heart catheterization, and biopsy were obtained. Myocardial work index (MWI) was quantified by integrating longitudinal strain (LS) with invasively measured pulmonary artery pressure. CMR derived RV volumes, T1 time, and extracellular volume (ECV) were quantified. Endomyocardial biopsy findings were used as the reference standard for myocardial microstructural changes. In HTx recipients who never had a previous allograft rejection, longitudinal function parameters were lower than healthy organ donors, while ejection fraction (EF) (52.0 ± 8.7%) and MWI (403.2 ± 77.2 mmHg%) were preserved. Rejection was characterized by significantly reduced LS, MWI, longer T1 time, and increased ECV that improved after recovery, whereas RV volumes and EF did not change MWI was the strongest determinant of rejection related myocardial damage (area under curve: 0.812, P < 0.0001, 95% CI: 0.69-0.94) with good specificity (77%), albeit modest sensitivity. In contrast, T1 time and ECV were sensitive (84%, both) but not specific to detect subclinical RV damage.

CONCLUSION

Subclinical adaptive RV remodelling is characterized by preserved RV EF despite longitudinal function abnormalities, except for MWI. While ultrastructural damage is reflected by MWI, ECV, and T1 time, only MWI has the capability to discriminate functional adaptation from transition to subclinical structural damage.

Longitudinal Strain and Strain Rate for Estimating Left Ventricular Filling Pressure in Heart Transplant Recipients

Traditional parameters have limited value to estimate left ventricular filling pressure (LVFP) in orthotropic heart transplant (OHT) recipients. We hypothesized that global longitudinal strain (GLS), diastolic, and systolic strain rate (SR) would be depressed in OHT recipients with elevated LVFP and could overcome the limitations of traditional parameters. We studied consecutively OHT patients at the time of endomyocardial biopsies and retrospectively pretransplantation studies conforming to the same protocol. Comprehensive echocardiography with strain measurements was performed. Results were compared with pulmonary capillary wedge pressure (PCWP) obtained from right heart catheterization that was performed just after the echocardiography study. In all, 74 studies were performed in 50 OHT recipients. Mean PWCP was 11.8 ± 4.3 mm Hg (range: 4 to 25 mm Hg). Several parameters, but not left atrial volume index, mitral inflow velocities, annular velocities, and their ratio (E/e'), were different between studies with normal (n = 47) and elevated PCWP (n = 27). Area Under Curve for GLS (0.932*), E/e'_SR (0.849*), and systolic SR (0.848*) (*p <0.0001) were more accurate than traditional parameters for predicting PCWP>12 mm Hg. GLS, systolic SR and E/e'_SR remained accurate regardless of LV ejection fraction and allograft vasculopathy. Meanwhile, E/e' was accurate to predict PWCP in native failing hearts before transplantation. Changes in GLS and E/e'_SR tracked accurately changes in PCWP. In conclusion, traditional indices of diastolic function perform poorly in OHT recipients, whereas GLS and E/e'_SR provide reliable means of LVFP, irrespective of ejection fraction and allograft vasculopathy. These parameters also track reasonably well the changes in LVFP.

Assessment of biventricular function by three-dimensional speckle-tracking echocardiography in clinically well pediatric heart transplantation patients

BACKGROUND

The biventricular function plays an important role in the prognosis of pediatric heart transplantation (HTx) patients. Therefore, in this study, we aimed to evaluate the biventricular function of pediatric HTx patients by three-dimensional (3D) speckle-tracking echocardiography (3D-STE).

METHODS

We enrolled 30 clinically well pediatric HTx patients and 30 healthy controls with a similar distribution of sex and age to the HTx. All participants underwent comprehensive two-dimensional (2D) and 3D echocardiography. Left ventricular (LV) global longitudinal strain (GLS), global circumferential strain (GCS), left and right ventricular ejection fraction (LVEF and RVEF, respectively), and right ventricular free wall longitudinal strain (RV FWLS) were acquired by 3D-STE. Moreover, the correlations between strains and clinical data were explored.

RESULTS

Compared with controls, LV GLS was decreased in pediatric HTx patients (P < .05), while LV GCS and LVEF showed no difference. LV GLS showed a weak correlation with cold ischemic time in HTx group (r = 0.396, P < .05). Meanwhile, RVEF and RV FWLS were significantly lower in the HTx group (P < .05). In the HTx group, RV FWLS showed a weak correlation with the preoperative mean pulmonary artery pressure (r = 0.420, P < .05) and postoperative pulmonary artery systolic pressure (r = 0.465, P < .05).

CONCLUSION

The 3D-biventricular mechanical functions were decreased in clinically well pediatric HTx patients. The provided characteristics and appropriate normal values of biventricular mechanical functions can be the basis in subsequent studies in the pediatric HTx patients.

Evaluation of Biventricular Functions in Transplanted Hearts Using 3-Dimensional Speckle-Tracking Echocardiography

Background The current study aims to validate the accuracy of 3-dimensional speckle-tracking echocardiography (3D-STE) in evaluating biventricular functions against the accuracy of cardiac magnetic resonance (CMR) and to explore the comprehensive characteristics and normal values for 3D-biventricular functions in transplanted hearts. Methods and Results A cohort of 35 heart transplant (HT) patients underwent both 3D echocardiography and CMR examination to validate the accuracy of 3D-STE in evaluating biventricular functions (Protocol 1). Then, 3D-STE derived biventricular functions were compared between 46 HT patients and 46 non-HT controls (Protocol 2). Protocol 1, validated that 3D-STE showed excellent accuracy in evaluating biventricular functions of transplanted hearts against CMR. Protocol 2, revealed lower (normal range) 3D-biventricular ejection fractions in HT patients than in controls (P<0.001). 3D-left ventricular global longitudinal strain, left ventricular-global circumferential strain, left ventricular-global radial strain, left ventricular-global performance index and right ventricular free-wall longitudinal strain were all lower in the HT patients than in healthy controls (P<0.001). Further, these strain values were all good for differentiating between groups (areas under the curve: 0.80-0.94, P<0.001). Moreover, left ventricular-lateral-wall radial displacement was higher and septal-wall radial displacement was lower in the HT group than in control group (P<0.001). Conclusions Compared with cardiac magnetic resonance, 3D-STE can evaluate biventricular functions of transplanted hearts accurately; 3D-biventricular mechanical functions are reduced even in clinically well HT patients. The provided characteristics and appropriate normal values of biventricular functions can be the basis for detection of ventricular dysfunction during follow-ups and further studies on transplanted hearts.

Normal Reference Ranges for Transthoracic Echocardiography Following Heart Transplantation

BACKGROUND

Heart function following heart transplantation (HTx) is influenced by numerous factors. It is typically evaluated using transthoracic echocardiography, but reference values are currently unavailable for this context. The primary aim of the present study was to derive echocardiographic reference values for chamber size and function, including cardiac mechanics, in clinically stable HTx patients.

METHODS

The study enrolled 124 healthy HTx patients examined prospectively. Patients underwent comprehensive two-dimensional echocardiographic examinations according to contemporary guidelines. Results were compared with recognized reference values for healthy subjects.

RESULTS

Compared with guidelines, larger atrial dimensions were seen in HTx patients. Left ventricular (LV) diastolic volume was smaller, and LV wall thickness was increased. With respect to LV function, both ejection fraction (62 ± 7%, P < .01) and global longitudinal strain (-16.5 ± 3.3%, P < .0001) were lower. All measures of right ventricular (RV) size were greater than reference values (P < .0001), and all measures of RV function were reduced (tricuspid annular plane systolic excursion 15 ± 4 mm [P < .0001], RV systolic tissue Doppler velocity 10 ± 6 cm/sec [P < .0001], fractional area change 40 ± 8% [P < .0001], and RV free wall strain -16.9 ± 4.2% [P < .0001]). Ejection fraction and LV global longitudinal strain were significantly lower in patients with previous rejection.

CONCLUSION

The findings of this study indicate that the distribution of routinely used echocardiographic measures differs between stable HTx patients and healthy subjects. In particular, markedly larger RV and atrial volumes and mild reductions in both LV and RV longitudinal strain were evident. The observed differences could be clinically relevant in the assessment of HTx patients, and specific reference values should be applied in this context.

Emerging imaging techniques after cardiac transplantation

Improvements in survival after cardiac transplantation have in part been driven by improved graft surveillance. Graft surveillance relies mainly on 3 techniques: coronary angiography, endomyocardial biopsy and echocardiography. Developments in invasive and non-invasive imaging technology have revolutionized assessment of the heart in both health and disease, offering new insights into tissue composition and myocardial metabolism. Herein we aim to review the strengths and weaknesses of these techniques, and summarize the evidence in the following 5 fields of cardiac imaging after transplantation: cardiovascular magnetic resonance; computed tomography; positron emission tomography; single-photon emission computed tomography; and optical coherence tomography and molecular imaging techniques.

Cold ischaemic time and time after transplantation alter segmental myocardial velocities after heart transplantation

OBJECTIVES

The aim of this study was to investigate changes in segmental, three-directional left ventricular (LV) velocities in patients after heart transplantation (Tx).

METHODS

Magnetic resonance tissue phase mapping was used to assess myocardial velocities in patients after Tx (n = 27) with normal LV ejection fraction (63 ± 5%) and those without signs of rejection. Regional wall motion and dyssynchrony were analysed in relation to cold ischaemic time (150 ± 57 min, median = 154 min), age of the donor heart (35 ± 13 years, median = 29 years), time after transplantation (32 ± 26 months, median = 31 months) and global LV morphology and function.

RESULTS

Segmental myocardial velocities were significantly altered in patients with cold ischaemic times >155 min resulting in an increase in peak systolic radial velocities (2 of 16 segments, P = 0.03-0.04) and reduced segmental diastolic long-axis velocities (5 of 16 segments, P = 0.01-0.04). Time after transplantation (n = 8 patients <12 months after Tx vs n = 19 >12 months) had a significant influence on systolic radial velocities (increased in 2 of 16 segments, P = 0.01-0.04) and diastolic long-axis velocities (reduced in 5 of 16 segments, P = 0.02-0.04). Correlation analysis and multiple regression revealed significant relationships of cold ischaemic time (R = -0.384, P = 0.048), the donor heart's age (β= 0.9, P = 0.01) and time from transplantation (β= -0.36, P = 0.03) with long-axis diastolic dyssynchrony.

CONCLUSIONS

Time after transplantation and cold ischaemic time strongly affect segmental systolic and diastolic motion in patients after Tx. The understanding of alterations in regional LV motion in the transplanted heart under stable conditions is essential in order to utilize this methodology in the future as a potentially non-invasive means of diagnosing transplant rejection.

Chronic cardiac allograft rejection: critical role of ED-A(+) fibronectin and implications for targeted therapy strategies

Chronic cardiac allograft rejection is characterized by cardiac allograft vasculopathy (CAV) and cardiac interstitial fibrosis (CIF) causing severe long-term complications after heart transplantation and determining allograft function and patients' prognosis. Until now, there have been no sufficient preventive or therapeutic strategies. CAV and CIF are accompanied by changes in the extracellular matrix, including re-expression of the fetal fibronectin splice variant known as ED-A(+) fibronectin. This molecule has been shown to be crucial for the development of myofibroblasts (MyoFbs) as the main cell type in CIF and for the activation of vascular smooth muscle cells (VSMCs) as the main cell type in CAV. Relevant re-expression and protein deposition of ED-A(+) fibronectin has been demonstrated in animal models of chronic rejection, with spatial association to CAV and CIF, and a quantitative correlation to the rejection grade. The paper by Booth et al published in this issue of The Journal of Pathology could prove for the first time the functional importance of ED-A(+) fibronectin for the development of CIF as a main component of chronic cardiac rejection. Thus, promising conclusions for the development of new diagnostic, preventive, and therapeutic strategies for chronic cardiac rejection focusing on ED-A(+) fibronectin can be suggested.

Extra cellular matrix remodelling after heterotopic rat heart transplantation: gene expression profiling and involvement of ED-A+ fibronectin, alpha-smooth muscle actin and B+ tenascin-C in chronic cardiac allograft rejection

Chronic cardiac rejection is represented by cardiac allograft vasculopathy (CAV) and cardiac interstitial fibrosis (CIF) known to cause severe complications. These processes are accompanied by remarkable changes in the cardiac extra cellular matrix (cECM). The aim of our study was to analyse the cECM remodelling in chronic rejection and to elucidate a potential role of ED-A domain containing fibronectin (ED-A(+) Fn), alpha smooth muscle actin (ASMA) and B domain containing tenascin-C (B(+) Tn-C). A model of chronic rejection after heterotopic rat heart transplantation was used. Allografts, recipient and control hearts were subjected to histological assessment of rejection grade, to real-time PCR based analysis of 84 genes of ECM and adhesion molecules and to immunofluorescence labelling procedures, including ED-A(+) Fn, ASMA and B(+) Tn-C antibodies. Histological analysis revealed different grades of chronic rejection. By gene expression analysis, a relevant up-regulation of the majority of ECM genes in association with chronic rejection could be shown. For 8 genes, there was a relevant up-regulation in allografts as well as in the corresponding recipient hearts. Association of ASMA positive cells with the grade of chronic rejection could be proven. In CAV and also in CIF there were extensive co-depositions of ED-A(+) Fn, ASMA and B(+) Tn-C. In conclusion, chronic cardiac allograft rejection is associated with a cECM remodelling. ASMA protein deposition in CAV, and CIF is a valuable marker to detect chronic rejection. Interactions of VSMCs and Fibro-/Myofibroblasts with ED-A(+) Fn and B(+) Tn-C might functionally contribute to the development of chronic cardiac rejection.

Pivotal karyometric measurements in different types of cardiomyopathic morphology: study of hearts explanted from transplant recipients

BACKGROUND

Morphometric studies based on the measurement of cardiocyte nuclei have focused on progressive hypertrophy rather than shape, which is a deciding factor for the diagnosis of hypertrophy in myocardial diseases. The aim of this research was to demonstrate how the digital morphology of cardiocyte nuclei change correlated with the type of myocardial pathology.

MATERIALS AND METHODS

The study groups encompassed 7 hearts with dilated cardiomyopathy (DCM) and 8 hearts with ischemic heart disease (IHD) which were explanted. A comparative group consisting of myocardial hypertrophy was contrasted with a control group of donor heart fragments. Cardiocyte nuclei were evaluated morphometrically on histologic slides. We calculated the nuclear area, length, breadth, perimeter, roundness, elongation, fullness factors, and nuclear chromatin mean gray level. The results were subjected to discriminant analysis.

RESULTS

All karyometric measurements analyzed by backward discriminant analysis showed only 2 powerful factors: nuclear breadth and chromatin mean gray level. The Mahalanobis distance showed the proximity of control and hypertrophy groups, whereas differences between IHD and DCM were nonsignificant.

CONCLUSION

The lack of karyometric differences between IHD and DCM suggested a common morphologic response for long-lasting progressive injury. The main morphologic differences were dependent on nuclear chromatin activity/stainability and nuclear breadth, suggesting darker and thinned nuclei in normal and adaptative stages and irregular brighter nuclei in cardiomyopathies.

Differences in antiapoptotic, proliferative activities and morphometry in dilated and ischemic cardiomyopathy: study of hearts explanted from transplant recipients

BACKGROUND

Antiapoptotic as well as replacement and proliferative mechanisms take place in the myocardium in dilated cardiomyopathy (DCM) and ischemic heart disease (IHD). We sought to estimate antiapoptotic, proliferative and replacement activities in cardiomyopathies.

MATERIALS

The study groups included seven hearts with DCM and eight with IHD, which had been explanted at the time of transplantation. The comparator group consisted of cases of myocardial hypertrophy and the control group, donor fragments.

METHODS

Antiapoptotic and proliferative responses were determined immunohistochemically as Bcl-2 and Ki67 expression by semiquantitative assessment of the intensity of staining. We also measured and statistically analyzed the integrative morphometric measurements of the fraction of fibrosis area, the nucleosarcoplasmic ratio, and cardiocyte diameter.

RESULTS

No Bcl-2 expression was observed in the controls. The strongest reaction was seen in the DCM group, then in the IHD, and in the comparator group of myocardial hypertrophy. Proliferative activity was seen only in endocardial and interstitial fibroblasts in DCM and IHD cases. The cardiocyte diameter showed no statistical association between myocardial hypertrophy and IHD, or IHD and DCM, whereas the nucleosarcoplasmic ratios were significantly different from control groups for all comparisons. Myocardial fibrosis showed the highest values in DCM and IHD. Discriminant analysis showed the value of interstitial fibrosis and cardiocyte diameter to categorize the analyzed groups.

CONCLUSIONS

Antiapoptotic Bcl-2 activity seemed to play an important role in cardiocyte preservation, while proliferative activity was resticted to interstitial connective tissue cells as a replacement process. Myocardial Bcl-2 expression, the extent of myocardial fibrosis, and cardiocyte diameter may serve as additional diagnostic tools to differentiate cardiomyopathies.

Cardiovascular magnetic resonance in the diagnosis of acute heart transplant rejection: a review

BACKGROUND

Screening for organ rejection is a critical component of care for patients who have undergone heart transplantation. Endomyocardial biopsy is the gold standard screening tool, but non-invasive alternatives are needed. Cardiovascular magnetic resonance (CMR) is well suited to provide an alternative to biopsy because of its ability to quantify ventricular function, morphology, and characterize myocardial tissue. CMR is not widely used to screen for heart transplant rejection, despite many trials supporting its use for this indication. This review summarizes the different CMR sequences that can detect heart transplant rejection as well as the strengths and weaknesses of their application.

RESULTS

T2 quantification by spin echo techniques has been criticized for poor reproducibility, but multiple studies show its utility in screening for rejection. Human and animal data estimate that T2 quantification can diagnose rejection with sensitivities and specificities near 90%. There is also a suggestion that T2 quantification can predict rejection episodes in patients with normal endomyocardial biopsies.T1 quantification has also shown association with biopsy proven rejection in a small number of trials. T1 weighted gadolinium early enhancement appeared promising in animal data, but has had conflicting results in human trials. Late gadolinium enhancement in the diagnosis of rejection has not been evaluated.CMR derived measures of ventricular morphology and systolic function have insufficient sensitivity to diagnose mild to moderate rejection. CMR derived diastolic function can demonstrate abnormalities in allografts compared to native human hearts, but its ability to diagnose rejection has not yet been tested.There is promising animal data on the ability of iron oxide contrast agents to illustrate the changes in vascular permeability and macrophage accumulation seen in rejection. Despite good safety data, these contrast agents have not been tested in the human heart transplant population.

CONCLUSION

T2 quantification has demonstrated the best correlation to biopsy proven heart transplant rejection. Further studies evaluating diastolic function, late gadolinium enhancement, and iron oxide contrast agents to diagnose rejection are needed. Future studies should focus on combining multiple CMR measures into a transplant rejection scoring system which would improve sensitivity and possibly reduce, if not eliminate, the need for endomyocardial biopsy.