Attenuated-Signal Plaque Progression Predicts Long-Term Mortality After Heart Transplantation: IVUS Assessment of Cardiac Allograft Vasculopathy

The Biological Parallels Between Atherosclerosis and Cardiac Allograft Vasculopathy: Implications for Solid Organ Chronic Rejection

Atherosclerosis and solid organ chronic rejection are pervasive chronic disease states that account for significant morbidity and mortality in developed countries. Recently, a series of shared molecular pathways have emerged, revealing biological parallels from early stages of development up to the advanced forms of pathology. These shared mechanistic processes are inflammatory in nature, reflecting the importance of inflammation in both disorders. Vascular inflammation triggers endothelial dysfunction and disease initiation through aberrant vasomotor control and shared patterns of endothelial activation. Endothelial dysfunction leads to the recruitment of immune cells and the perpetuation of the inflammatory response. This drives lesion formation through the release of key cytokines such as IFN-y, TNF-alpha, and IL-2. Continued interplay between the adaptive and innate immune response (represented by T lymphocytes and macrophages, respectively) promotes lesion instability and thrombotic complications; hallmarks of advanced disease in both atherosclerosis and solid organ chronic rejection. The aim of this study is to identify areas of overlap between atherosclerosis and chronic rejection. We then discuss new approaches to improve current understanding of the pathophysiology of both disorders, and eventually design novel therapeutics.

Early optical coherence tomography evaluation of donor-transmitted atherosclerosis and cardiac allograft vasculopathy: insights from a prospective, single-center study

BACKGROUND

The impact of donor transmitted atherosclerosis as assessed by intravascular ultrasound on development and progression of cardiac allograft vasculopathy (CAV) after heart transplantation (HT) remains poorly defined in contemporary practice. In this exploratory analysis, we sought to assess the prognostic role of early qualitative assessment of donor artery morphology using optical coherence tomography (OCT) as a more sensitive imaging modality.

METHODS

HT recipients were prospectively enrolled for baseline OCT imaging of the left anterior descending coronary artery. OCT findings were classified as normal, homogeneous intimal thickening, and advanced plaque characteristics. The endpoint was a composite of cardiac death, myocardial infarction, or new angiographically detectable CAV stratified by the International Society of Heart and Lung Transplantation criteria up to 4 years of follow-up.

RESULTS

A total of 35 patients underwent baseline OCT of whom 51.4% had normal OCT, 14.3% had homogenous plaque, and 34.3% had advanced characteristics. There were no significant differences in baseline demographics between patients with and without normal morphology. During a mean follow-up of 3.3 ± 0.4 years, the endpoint occurred in 11 patients including 1 death, 7 CAV1, 3 CAV2, and 1 CAV3. Kaplan-Meier analysis revealed a significantly higher event rate in patients with advanced characteristics (log-rank p = 0.010). In multivariate analysis, OCT-based plaque morphology was an independent predictor of clinical events (adjusted hazard ratio 4.57, 95% confidence interval 1.50-13.92, p = 0.008) while maximal intimal thickness ≥0.5 mm was not.

CONCLUSIONS

Early qualitative OCT assessment of donor coronary artery morphology appears to be a reliable marker for predicting future cardiovascular events in HT recipients. Our findings warrant more careful study in a larger cohort.

Intravascular Ultrasound in Vulnerable Plaque and Acute Coronary Syndrome

Vulnerable plaque plays a pivotal role in the pathogenesis of acute coronary syndrome (ACS), being responsible for most ACS. The concept of vulnerable plaque has evolved with advancements in basic and clinical investigations along with developments and rapid expansion of coronary imaging modalities. Intravascular ultrasound (IVUS) is the first widely applied clinical technology with sufficient tissue penetration and enables us to identify vulnerable plaque and comprehensively understand the pathophysiology of ACS. In this review, we summarize current clinical evidence established by IVUS and the recent advancements in our understanding of vulnerable plaque and its role in ACS management.

Invasive Intracoronary Imaging of Cardiac Allograft Vasculopathy: Established Modalities and Emerging Technologies

Despite advances in the care of heart transplant recipients during the past 5 decades, cardiac allograft vasculopathy (CAV) continues to be a major barrier to long-term survival. The early diagnosis and treatment of CAV is crucial for improving long-term outcomes. Coronary angiography, the current gold standard for CAV screening, has low sensitivity for detecting early CAV. Increasingly, invasive intracoronary imaging modalities that provide a more detailed analysis of vessel anatomy and allow for plaque characterization are being used to detect CAV earlier after transplant and uncover mechanistic insights. Studies validating these emerging imaging platforms are needed before their widespread adoption.

Change in First-year Intravascular Ultrasound Results Predicts Adverse Events in Heart Transplant Recipients: Implications for Clinical Trial Endpoints

BACKGROUND

Heart transplantation (HTx) is an established therapeutic option for patients with advanced heart failure who are refractory to conventional guideline-directed treatments. This study aimed to reassess whether intravascular ultrasound variables could predict adverse events after HTx in the modern era.

METHODS

One hundred primary HTx recipients with available serial intravascular ultrasound examination results of the left anterior descending artery 4-8 wk and 1 y after HTx were enrolled, with an average follow-up duration of 5.7 y. The primary endpoint was a composite of all-cause death, nonfatal major adverse cardiac events, and angiographic cardiac allograft vasculopathy.

RESULTS

Forty-three patients developed primary endpoints. The baseline maximal intimal thickness was independently associated with the primary endpoint (hazard ratio, 8.24; 95% confidential interval [CI], 3.21-21.21; P  < 0.001), and the optimal cutoff value was 0.64 mm. A change in the plaque atheroma volume in a proximal 20-mm segment from the left anterior descending artery bifurcation >1.05 mm 3 /mm (hazard ratio, 2.75; 95% CI, 1.28-5.89; P  = 0.009) and a change in the first-year maximal intimal thickness >0.27 mm (hazard ratio, 2.63; 95% CI, 1.05-6.56; P  = 0.04) were independent predictors of the primary endpoint 1 y after intravascular ultrasonography.

CONCLUSIONS

The aforementioned important clinical implications of intravascular ultrasound parameters are useful predictors of outcomes, which may be considered endpoints in modern clinical HTx trials.

Invasive Coronary Imaging Assessment for Cardiac Allograft Vasculopathy: State-of-the-Art Review

Heart transplantation is the standard of care treatment for end-stage heart failure. Therapeutic advances including enhanced immunosuppression and aggressive infectious prophylaxis have led to increased life-expectancy following transplantation; however, cardiac allograft vasculopathy (CAV) remains a leading cause of morbidity and mortality. Although coronary angiography is the current guideline-recommended diagnostic modality for invasive CAV screening, it is limited in its ability to detect early and/or diffuse disease. Efforts to improve outcomes for heart transplant recipients with CAV have focused on developing diagnostic tools with greater sensitivity to capture early CAV in order to better understand the pathobiology and implement treatment to slow disease progression sooner after transplant. The contemporary invasive imaging armamentarium for CAV surveillance includes coronary angiography, intravascular ultrasound, and newer technologies including optical coherence tomography and near-infrared spectroscopy. The present review outlines the use of and data in support of these imaging platforms in the CAV arena and highlights the potential advantages and limitations of each of these modalities.

Clinical use of intracoronary imaging. Part 2: acute coronary syndromes, ambiguous coronary angiography findings, and guiding interventional decision-making: an expert consensus document of the European Association of Percutaneous Cardiovascular Interventions

This consensus document is the second of two reports summarizing the views of an expert panel organized by the European Association of Percutaneous Cardiovascular Interventions (EAPCI) on the clinical use of intracoronary imaging including intravascular ultrasound (IVUS), optical coherence tomography (OCT), and near infrared spectroscopy (NIRS)-IVUS. Beyond guidance of stent selection and optimization of deployment, invasive imaging facilitates angiographic interpretation and may guide treatment in acute coronary syndrome. Intravascular imaging can provide additional important diagnostic information when confronted with angiographically ambiguous lesions and allows assessment of plaque morphology enabling identification of vulnerability characteristics. This second document focuses on useful imaging features to identify culprit and vulnerable coronary plaque, which offers the interventional cardiologist guidance on when to adopt an intracoronary imaging-guided approach to the treatment of coronary artery disease and provides an appraisal of intravascular imaging-derived metrics to define the haemodynamic significance of coronary lesions.

Targeted galectin-7 inhibition with ultrasound microbubble targeted gene therapy as a sole therapy to prevent acute rejection following heart transplantation in a Rodent model

BACKGROUND

Despite significant advances in transplantation, acute cellular rejection (AR) remains a major obstacle that is most prevalent in the first months post heart transplantation (HT). Current treatments require high doses of immunosuppressive drugs followed by maintenance therapies that have systemic side effects including early infection. In this study, we attempted to prevent AR with a myocardial-targeted galectin-7-siRNA delivery method using cationic microbubbles (CMBs) combined with ultrasound targeted microbubble destruction (UTMD) to create local immunosuppression in a rat abdominal heterotopic heart transplantation acute rejection model.

METHODS AND RESULTS

Galectin-7-siRNA (siGal-7) bound to CMBs were synthesized and effective ultrasound-targeted delivery of siGal-7 into target cells confirmed in vitro. Based on these observations, three transplant rat models were tested：①isograft (ISO); ② Allograft (ALLO) +UTMD; and ③ALLO + PBS. UTMD treatments were administered at 1, 3, 5, 7 days after HT. Galectin 7 expression was reduced by 50% compared to ALLO + PBS (p < 0.005), and this was associated with significant reductions in both galectin 7 and Interleukin-2 protein levels (p < 0.001). The ALLO + UTMD group had Grade II or less inflammatory infiltration and myocyte damage in 11/12 rats using International Society For Heart and Lung Transplantation grading, compared to 0/12 rats with this grading in the ALLO + PBS group at 10 days post HT (p < 0.001).

CONCLUSIONS

Ultrasound-targeted galectin-7-siRNA knockdown with UTMD can prevent acute cellular rejection in the early period after allograft heart transplantation without the need for systemic immunosuppression.

KEY WORDS

Microbubble, Acute Rejection, Heart Transplantation, Galectin-7, RNA.

Low MicroRNA-126 Levels in Right Ventricular Endomyocardial Biopsies Coincide With Cardiac Allograft Vasculopathy in Heart Transplant Patients

Endothelium-enriched microRNAs (miRs) are involved in the development of cardiac allograft vasculopathy (CAV). Recently, serum-derived miR-126-3p and -5p, known endothelial microRNAs with a crucial function in angiogenesis and re-endothelialization, provided additional predictive power for cardiac allograft vasculopathy in addition to clinical predictors. However, their myocardial expression in and relationship with CAV are still unknown. Our study aim was to investigate the expression of endomyocardial microRNA-126-3p and microRNA-126-5p levels in heart transplant recipients and their relationship with allograft vasculopathy.

Methods

We studied 39 heart transplant recipients, 21 with proven allograft vasculopathy (CAV+) and 18 without allograft vasculopathy (CAV-) with serial coronary angiograms. Additionally, 8 patients with end-stage native coronary artery disease (CAD) were added to the study to investigate disease specificity of the microRNA signature. The mRNA levels of miR-126-3p and miR-126-5p were determined by qRT-PCR in the right ventricular endomyocardial biopsies obtained at baseline and during routine follow-up.

Results

MiR-126-3p levels were significantly lower in the CAV+ group compared to the CAV- group at follow-up, while miR-126-5p levels were unaltered. This was in stark contrast to native CAD patients in whom miR-126-3p and -5p levels were significantly higher. qPCR levels of miR-126 targets are differentially regulated in CAV versus ischemic cardiomyopathy and are influenced by the administration of immunosuppressive agents in endothelial cells.

Conclusions

Our data provide evidence for a distinct microRNA signature in heart transplantation patients with allograft vasculopathy. In contrast to CAD patients, lower miR-126-3p levels coincide with the development of cardiac allograft vasculopathy. Further studies in a larger patient population are warranted to determine if the serial measurement of myocardial microRNA-126 products could help in risk assessment and early detection of CAV.

Clinical use of intracoronary imaging. Part 2: acute coronary syndromes, ambiguous coronary angiography findings, and guiding interventional decision-making: an expert consensus document of the European Association of Percutaneous Cardiovascular Interventions

This consensus document is the second of two reports summarizing the views of an expert panel organized by the European Association of Percutaneous Cardiovascular Interventions (EAPCI) on the clinical use of intracoronary imaging including intravascular ultrasound (IVUS), optical coherence tomography (OCT), and near infrared spectroscopy (NIRS)-IVUS. Beyond guidance of stent selection and optimization of deployment, invasive imaging facilitates angiographic interpretation and may guide treatment in acute coronary syndrome. Intravascular imaging can provide additional important diagnostic information when confronted with angiographically ambiguous lesions and allows assessment of plaque morphology enabling identification of vulnerability characteristics. This second document focuses on useful imaging features to identify culprit and vulnerable coronary plaque, which offers the interventional cardiologist guidance on when to adopt an intracoronary imaging-guided approach to the treatment of coronary artery disease and provides an appraisal of intravascular imaging-derived metrics to define the haemodynamic significance of coronary lesions.

Testing the Efficacy of Contrast-Enhanced Ultrasound in Detecting Transplant Rejection Using a Murine Model of Heart Transplantation

One of the key unmet needs to improve long-term outcomes of heart transplantation is to develop accurate, noninvasive, and practical diagnostic tools to detect transplant rejection. Early intragraft inflammation and endothelial cell injuries occur prior to advanced transplant rejection. We developed a novel diagnostic imaging platform to detect early declines in microvascular perfusion (MP) of cardiac transplants using contrast-enhanced ultrasonography (CEUS). The efficacy of CEUS in detecting transplant rejection was tested in a murine model of heart transplants, a standard preclinical model of solid organ transplant. As compared to the syngeneic groups, a progressive decline in MP was demonstrated in the allografts undergoing acute transplant rejection (40%, 64%, and 92% on days 4, 6, and 8 posttransplantation, respectively) and chronic rejection (33%, 33%, and 92% on days 5, 14, and 30 posttransplantation, respectively). Our perfusion studies showed restoration of MP following antirejection therapy, highlighting its potential to help monitor efficacy of antirejection therapy. Our data suggest that early endothelial cell injury and platelet aggregation contributed to the early MP decline observed in the allografts. High-resolution MP mapping may allow for noninvasive detection of heart transplant rejection. The data presented have the potential to help in the development of next-generation imaging approaches to diagnose transplant rejection.