Noninvasive Diagnosis of Cardiac Allograft Rejection Using Echocardiography Indices of Systolic and Diastolic Function

A Comprehensive Excursus of the Roles of Echocardiography in Heart Transplantation Follow-Up

Current guidelines for the care of heart transplantation recipients recommend routine endomyocardial biopsy and invasive coronary angiography as the cornerstones in the surveillance for acute rejection (AR) and coronary allograft vasculopathy (CAV). Non-invasive tools, including coronary computed tomography angiography and cardiac magnetic resonance, have been introduced into guidelines without roles of their own as gold standards. These techniques also carry the risk of contrast-related kidney injury. There is a need to explore non-invasive approaches providing valuable information while minimizing risks and allowing their application independently of patient comorbidities. Echocardiographic examination can be performed at bedside, serially repeated, and does not carry the burden of contrast-related kidney injury and procedure-related risk. It provides comprehensive assessment of cardiac morphology and function. Advanced echocardiography techniques, including Doppler tissue imaging and strain imaging, may be sensitive tools for the detection of minor myocardial dysfunction, thus providing insight into early detection of AR and CAV. Stress echocardiography may offer a valuable tool in the detection of CAV, while the assessment of coronary flow reserve can unravel coronary microvascular impairment and add prognostic value to conventional stress echocardiography. The review highlights the role of Doppler echocardiography in heart transplantation follow-up, weighting advantages and limitations of the different techniques.

Cardiac Allograft Injuries: A Review of Approaches to a Common Dilemma, With Emphasis on Emerging Techniques

Clinical features of allograft injury are often unreliable, and context within the transplant journey is key. In the setting of post-transplant allograft dysfunction, the choice of initial investigation depends on clinical assessment and history. One of the major considerations is the time post transplantation in helping to decide a likely cause for allograft injury. Immediately post transplantation, it is important to consider donor factors (including donor demographics as well as immunological match), ischaemic times, surgical issues as well as early rejection. Clinical suspicion needs to remain high with variable presentations, including haemodynamic instability, arrhythmia, as well as left ventricular dysfunction. Symptoms of allograft dysfunction may include dyspnoea, exertional intolerance, dizziness / lightheadedness, palpitations, as well as right or left heart failure. In the coming weeks and months, endomyocardial biopsy and blood-based biomarkers may be helpful including high sensitivity troponin and donor-derived cell-free DNA. Molecular markers for rejection are hopeful, and may also be useful in non-ischaemic causes of allograft dysfunction. Screening remains important late post heart transplant due to variety of signs associated with rejection (early) and lack of typical anginal symptoms (later). New imaging modalities - especially cardiac magnetic resonance imaging, have been shown to be useful for assessing cause of allograft dysfunction including ischemia, infarction and rejection.

Novel left and right ventricular strain analysis to detect subclinical myocardial dysfunction in cardiac allograft rejection

Early detection of acute cellular rejection (ACR) by echocardiography shows potential clinical benefit as ACR remains a significant contributor to morbidity and mortality. This retrospective, longitudinal study sought to investigate the use of novel left (LV) and right ventricular (RV) strain analysis to detect biopsy proven ACR. 46 heart transplant patients (Mean age 46 ± 16 years) with biopsy proven ACR were grouped according to biopsy results: 1R-ACR (n = 36) and 2R-ACR (n = 10). Serial two-dimensional transthoracic echocardiography with strain analysis was performed. Echocardiographic parameters were serially measured: (1) rejection free period (0R-ACR); (2) pre-ACR period (pre-ACR); (3) during ACR (1R-ACR or 2R-ACR) and (4) post-ACR (Post-ACR). Significant reductions for LV Global Longitudinal Strain (LV GLS) and LV Early diastolic Strain rate (LV ESr) were observed between 0R-ACR and pre-ACR (LV GLS 0R-ACR: 17.3% vs Pre-2R ACR: 15.4%, p = 0.016; LV ESr 0R-ACR: 1.00/s vs Pre-2R ACR: 0.74/s, p = 0.007) with LV ESr demonstrating the highest sensitivity (92%) and specificity (81%) to predict ACR. LV ESr and the E/LV ESr ratio were significantly different (p = 0.0001; p = 0.016) during pre-1R ACR period vs 0R whereas LV GLS showed no significant differences for grade 1R-ACR. Diastolic mechanical dispersion showed significant increases in dispersion during ACR for the 1R-ACR group and early significant increases pre-2R ACR. Systolic and diastolic RV strain parameters showed a similar trend for both ACR groups. Systolic and diastolic strain parameters can detect myocardial dysfunction before biopsy confirmed 2R-ACR. Early diastolic strain rate parameters are most sensitive detecting subclinical myocardial dysfunction pre-ACR. Novel strain parameters are potentially useful clinical tool for prediction of early ACR in heart transplant.

Assessment of Acute Rejection by Global Longitudinal Strain and Cardiac Biomarkers in Heart-Transplanted Patients

Aims

The aim of this study was to evaluate left ventricular global longitudinal strain (LVGLS), N-terminal pro brain natriuretic peptide (Nt-ProBNP), and Troponin T as non-invasive markers for acute cellular rejection (ACR) diagnosis and severity assessment after heart transplantation (HTx).

Methods

We retrospectively included all HTx patients transplanted from 2013 to 2019. At each visit, the patients were subjected to endomyocardial biopsy (EMB), measurement of Nt-ProBNP and Troponin T, and protocoled echocardiography with assessment of LVGLS. Sudden drop in graft function (SDGF) was defined as a drop in LVGLS ≥-2% in combination with either an increase in Troponin T ≥20% or Nt-ProBNP ≥30% compared with levels at the latest visit.

Results

We included 1,436 EMBs from 83 HTx patients. The biopsies were grouped as 0R (n = 857), 1R (n = 538), and ≥2R (n = 41). LVGLS was lower and Troponin T and Nt-ProBNP higher in the 2R group than in the 0R and 1R groups (LVGLS: -12.9 ± 3.8% versus -16.9 ± 3.1% and -16.1 ± 3.3%; Troponin T: 79 [33;230] ng/l versus 27 [13;77] ng/l and 27 [14;68] ng/l; Nt-ProBNP: 4,174 [1,095;9,510] ng/l versus 734 [309;2,210] ng/l and 725 [305;2,082], all p < 0.01). A SDGF was seen at 45 visits of which 19 had ≥2R ACR. EMBs showed ACR in 20 cases without SDGF. Finally, neither was SDGF seen nor did the EMB show rejection in 1,136 cases. Thus, the sensitivity of SDGF for ≥2R ACR detection was 49% (32–65) and specificity 98% (97–99). The positive predictive value (PPV) was 42% (31–55) and the negative predictive value (NPV) 98% (98–99). The diagnostic value improved in a sub-analysis excluding EMBs within 3 months after HTx, clinically interpreted false positive ≥2R ACR cases, and cases with ≥2R ACR who recently (<2 weeks) were treated with intravenous methylprednisolone due to ≥2R ACR (sensitivity 75% (48–93), specificity 97% (96–98), NPV 99% (99–100), and PPV 39% (27–52).

Conclusions

Patients with ≥2R ACR have lower LVGLS and higher Troponin T and Nt-ProBNP than patients without 2R rejection. A non-invasive model combining changes in LVGLS and Troponin T or Nt-ProBNP showed excellent negative predictive value and moderate sensitivity and may be used as a gatekeeper to invasive biopsies after HTx.

Prognostic Value of Left and right ventricular deformation strain analysis on Acute Cellular rejection in Heart Transplant recipients: A 6-year outcome study

PURPOSE

Two-dimensional (2D) strain analysis is a sensitive method for detecting myocardial dysfunction in acute cellular rejection (ACR) from post-transplant complications. This study aims to evaluate the utility of novel left (LV) and right ventricular (RV) strain parameters for prognostic risk stratification associated with ACR burden at 1-year post transplantation.

METHODS

128 Heart transplant patients, assessed between 2012 and 2018, underwent transthoracic echocardiography and endomyocardial biopsy. 2D strain analysis was performed and history of rejection burden was assessed and grouped according to ACR burden at 1-year post transplantation. The primary endpoint was all-cause mortality at 6-years follow up.

RESULTS

21 patients met primary the endpoint. Multivariate analysis of 6-year all-cause mortality showed LV global longitudinal strain (LV GLS) (Hazard Ratio [HR] = 1.21, CI = 1.06-1.49), LV early diastolic strain rate (LV ESr) (HR = 1.31, CI = 1.12-1.54), RV GLS (HR = 1.12, CI = 1.02-1.25) and RV ESr (HR = 1.26, CI = 1.12-1.47) were significant predictors of outcome. Univariate analysis also showed LV GLS, LV ESr, RV GLS and RV ESr were significant predictors of outcome. Optimal cut-off for predicting 6-year mortality for LV GLS by receive operator characteristic was 15.5% (sensitivity: 92%, specificity: 79%). Significant reductions (p < 0.05) in LV GLS, RV GLS and LV and RV ESr between rejection groups were seen.

CONCLUSIONS

Non-invasive LV and RV strain parameters are predictors of mortality in post-transplant patient with ACR. LV GLS and LV ESr are superior to other strain and conventional echo parameters.

Assessment of left-ventricular diastolic function in pediatric intensive-care patients: a review of parameters and indications compared with those for adults

BACKGROUND

The incidence of diastolic heart failure has increased over time. The evaluation of left-ventricular diastolic function is complex, ongoing, and remains poorly performed in pediatric intensive-care patients. This study aimed to review the literature and to provide an update on the evaluation of left-ventricular diastolic function in adults and children in intensive care.

DATA SOURCES

We searched data from PubMed/Medline. Thirty-two studies were included. Four pragmatic questions were identified: (1) What is the physiopathology of diastolic dysfunction? (2) Which tools are required to evaluate diastolic function? (3) What are the echocardiographic criteria needed to evaluate diastolic function? (4) When should diastolic function be evaluated in pediatric intensive care?

RESULTS

Early diastole allows characterization of relaxation, whereas compliance assessments and filling pressures are evaluated during late diastole. The evolution of diastolic function differs between adults and children. Unlike in adults, decreased compliance occurs at the same time as delayed relaxation in children. Diastolic function can be evaluated by Doppler echocardiography. The echocardiographic criteria for ventricular relaxation include the E wave, E/A wave ratio, and isovolumic relaxation time. Ventricular compliance can be assessed by the E/e' wave ratio, atrial volume, and Ap wave duration during pulmonary vein flow. In adult intensive-care patients, the E/e' ratio can be used as an index of tolerance for volume expansion in septic patients and to adjust the inotropic support.

CONCLUSION

Clinical studies would allow some of these parameters to be validated for use in children in intensive care.

Non-invasive cardiac allograft rejection surveillance: reliability and clinical value for prevention of heart failure

Allograft rejection-related acute and chronic heart failure (HF) is a major cause of death in heart transplant recipients. Given the deleterious impact of late recognized acute rejection (AR) or non-recognized asymptomatic antibody-mediated rejection on short- and long-term allograft function improvement of AR surveillance and optimization of action strategies for confirmed AR can prevent AR-related allograft failure and delay the development of cardiac allograft vasculopathy, which is the major cause for HF after the first posttransplant year. Routine non-invasive monitoring of cardiac function can improve both detection and functional severity grading of AR. It can also be helpful in guiding the anti-AR therapy and timing of routine surveillance endomyocardial biopsies (EMBs). The combined use of EMBs with non-invasive technologies and methods, which allow detection of subclinical alterations in myocardial function (e.g., tissue Doppler imaging and speckle-tracking echocardiography), reveal alloimmune activation (e.g., screening of complement-activating donor-specific antibodies and circulating donor-derived cell-free DNA) and help in predicting the imminent risk of immune-mediated injury (e.g., gene expression profiling, screening of non-HLA antibodies, and circulating donor-derived cell-free DNA), can ensure the best possible surveillance and management of AR. This article gives an overview of the current knowledge about the reliability and clinical value of non-invasive cardiac allograft AR surveillance. Particular attention is focused on the potential usefulness of non-invasive tools and techniques for detection and functional grading of early and late ARs in asymptomatic patients. Overall, the review aimed to provide a theoretical and practical basis for those engaged in this particularly demanding up-to-date topic.

Diastolic strain imaging: a new non-invasive tool to detect subclinical myocardial dysfunction in early cardiac allograft rejection

Acute cellular rejection (ACR) remains a significant contributor to increased morbidity and mortality in heart transplant recipients. Early detection of ACR by non-invasive imaging is of potential clinical benefit. This study sought to investigate the use of non-invasive early global diastolic strain rate (GDSRe) and global longitudinal strain (GLS) in the detection of biopsy proven ACR. We retrospectively analysed 31 heart transplant patients (Mean age 52 ± 14 years) with biopsy proven ACR who underwent serial transthoracic echocardiographic examination and 2D strain analysis. Traditional echocardiographic systolic and diastolic parameters and novel systolic and diastolic strain imaging were measured during (1) early rejection free period (0R); (2) pre-rejection period (pre-1R); and (3) grade 1R acute cellular rejection (1R-ACR). GDSRe was significantly reduced (p = 0.0001) during the pre-rejection period (pre-1R) (0.74/s) when compared with 0R (0.97/s). GLS was only significantly reduced during 1R-ACR (17.7%), p = 0.001 but could not detect pre-1R (19.9%). Global diastolic strain rate at isovolumic relaxation showed no significant differences between any of the rejection periods. Traditional systolic and diastolic indices showed no significant differences. In conclusion, early global diastolic strain rate is the most sensitive parameter to detect subclinical myocardial dysfunction during early periods of pre-1R prior to biopsy confirmed 1R-ACR. GDSRe is a potential new tool for non-invasive screening of early post-transplant cardiac allograft rejection.

Right ventricle dimensions and function in response to acute hypoxia in healthy human subjects

AIM

Acute hypoxia produces acute vasoconstriction in the pulmonary circulation with consequences on right ventricular (RV) structure and function. Previous investigations in healthy humans have been restricted to measurements after altitude acclimatization or were interrupted by normoxia. We hypothesized that immediate changes in RV dimensions in healthy subjects in response to normobaric hypoxia differ without the aforementioned constraints.

METHODS

Transthoracic echocardiography was performed in 35 young, healthy subjects exposed to 11% oxygen, as well as six controls under sham hypoxia (20.6% oxygen, single blind) first at normoxia and after 30, 60, 100, 150 min of hypoxia or normoxia respectively. A subgroup of 15 subjects continued with 3-min cycling exercise in hypoxia with subsequent evaluation followed by an assessment 1 min at rest while breathing 4 L min^-1 oxygen.

RESULTS

During hypoxia, there was a significant linear increase of all RV dimensions (RVD1 + 29 mm, RVD2 + 42 mm, RVD3 + 41 mm, RVOT + 13 mm, RVEDA + 18 mm, P < 0.01) in the exposure group vs. the control group. In response to hypoxia, right ventricular systolic pressure (RVSP) showed a modest increase in hypoxia at rest (+7.3 mmHg, P < 0.01) and increased further with physical effort (+11.8 mmHg, P < 0.01). After 1 min of oxygen at rest, it fell by 50% of the maximum increase.

CONCLUSION

Acute changes in RV morphology occur quickly after exposure to normobaric hypoxia. The changes were out of proportion to a relatively low-estimated increase in pulmonary pressure, indicating direct effects on RV structure. The results in healthy subjects are basis for future clinically oriented interventional studies in normobaric hypoxia.

Diagnostic performance of echocardiography for the detection of acute cardiac allograft rejection: a systematic review and meta-analysis

Objective

Many studies have addressed the diagnostic performance of echocardiography to evaluate acute cardiac allograft rejection compared with endomyocardial biopsy. But the existence of heterogeneity limited its clinical application. Thus, we conducted a comprehensive, systematic literature review and meta-analysis for the purpose.

Methods

Studies prior to September 1, 2014 identified by Medline/PubMed, EMBASE and Cochrance were examined by two independent reviews. We conducted meta-analysis by using Meta-DiSc 1.4 software. An assessment tool of QUADAS-2 was applied to evaluate the risk of bias and applicability of the studies.

Results

Thirty studies met the inclusion criteria of meta-analysis. The four parameters of pressure half time, isovolumic relaxation time, index of myocardial performance and late diastolic mitral annular motion velocity were included in the meta-analysis, with a pooled diagnostic odds ratio of 10.43, 6.89, 15.95 and 5.68 respectively, and the area under the summary receiver operating characteristic curves value of 0.829, 0.599, 0.871 and 0.685 respectively.

Conclusion

The meta-analysis and systematic review demonstrate that no single parameter of echocardiography showed a reliable diagnostic performance for acute cardiac allograft rejection. A result of echocardiography for ACAR should be comprehensively considered by physicians in the context of clinical presentations and imaging feature.

Nrf2 deficiency prevents reductive stress-induced hypertrophic cardiomyopathy

AIMS

Mutant protein aggregation (PA) cardiomyopathy (MPAC) is characterized by reductive stress (RS), PA (of chaperones and cytoskeletal components), and ventricular dysfunction in transgenic mice expressing human mutant CryAB (hmCryAB). Sustained activation of nuclear erythroid-2 like factor-2 (Nrf2) causes RS, which contributes to proteotoxic cardiac disease. The goals of this pre-clinical study were to (i) investigate whether disrupting Nrf2-antioxidant signalling prevents RS and rescues redox homeostasis in hearts expressing the mutant chaperone and (ii) elucidate mechanisms that could delay proteotoxic cardiac disease.

METHODS AND RESULTS

Non-transgenic (NTG), transgenic (TG) with MPAC and MPAC-TG:Nrf2-deficient (Nrf2-def) mice were used in this study. The effects of Nrf2 diminution (Nrf2±) on RS mediated MPAC in TG mice were assessed at 6-7 and 10 months of age. The diminution of Nrf2 prevented RS and prolonged the survival of TG mice (∼50 weeks) by an additional 20-25 weeks. The TG:Nrf2-def mice did not exhibit cardiac hypertrophy at even 60 weeks, while the MPAC-TG mice developed pathological hypertrophy and heart failure starting at 24-28 weeks of age. Aggregation of cardiac proteins was significantly reduced in TG:Nrf2-def when compared with TG mice at 7 months. Preventing RS and maintaining redox homeostasis in the TG:Nrf2-def mice ameliorated PA, leading to decreased ubiquitination of proteins.

CONCLUSION

Nrf2 deficiency rescues redox homeostasis, which reduces aggregation of mutant proteins, thereby delaying the proteotoxic pathological cardiac remodelling caused by RS and toxic protein aggregates.

Pulsatility and the risk of nonsurgical bleeding in patients supported with the continuous-flow left ventricular assist device HeartMate II

BACKGROUND

Bleeding is an important cause of morbidity and mortality in patients with continuous-flow left ventricular assist devices (LVADs). Reduced pulsatility has been implicated as a contributing cause. The aim of this study was to assess the effects of different degrees of pulsatility on the incidence of nonsurgical bleeding.

METHODS AND RESULTS

The Utah Transplantation Affiliated Hospitals (U.T.A.H.) heart failure and transplant program databases were queried for patients with end-stage heart failure who required support with the continuous-flow LVAD HeartMate II (Thoratec Corp, Pleasanton, CA) between 2004 and 2012. Pulsatility was evaluated by means of the LVAD parameter pulsatility index (PI) and by the echocardiographic assessment of aortic valve opening during the first 3 months of LVAD support. PI was analyzed as a continuous variable and also stratified according to tertiles of all the PI measurements during the study period (low PI: <4.6, intermediate PI: 4.6-5.2, and high PI: >5.2). Major nonsurgical bleeding associated with a decrease in hemoglobin ≥2 g/dL (in the absence of hemolysis) was the primary end point. A total of 134 patients (median age of 60 [interquartile range: 49-68] years, 78% men) were included. Major bleeding occurred in 33 (25%) patients (70% gastrointestinal, 21% epistaxis, 3% genitourinary, and 6% intracranial). In multivariable analysis, PI examined either as a categorical variable, low versus high PI (hazard ratio, 4.06; 95% confidence interval, 1.35-12.21; P=0.04), or as a continuous variable (hazard ratio, 0.60; 95% confidence interval, 0.40-0.92; P=0.02) was associated with an increased risk of bleeding.

CONCLUSIONS

Reduced pulsatility in patients supported with the continuous-flow LVAD HeartMate II is associated with an increased risk of nonsurgical bleeding, as evaluated by PI.