Role of vascular remodeling in the pathogenesis of early transplant coronary artery disease: a multicenter prospective intravascular ultrasound study

A randomized clinical study using optical coherence tomography to evaluate the short-term effects of high-intensity interval training on cardiac allograft vasculopathy: a HITTS substudy

Cardiac allograft vasculopathy (CAV) remains a leading cause of long-term mortality after heart transplantation. Both preventive measures and treatment options are limited. This study aimed to evaluate the short-term effects of high-intensity interval training (HIT) on CAV in de novo heart transplant (HTx) recipients as assessed by optical coherence tomography (OCT). The study population was a subgroup of the 81-patient HITTS study in which HTx recipients were randomized to HIT or moderate intensity continuous training (MICT) for nine consecutive months. OCT images from baseline and 12 months were compared to assess CAV progression. The primary endpoint was defined as the change in the mean intima area. Paired OCT data were available for 56 patients (n = 23 in the HIT group and n = 33 in the MICT group). The intima area in the entire study population increased by 25% [from 1.8±1.4mm² to 2.3±2.0mm² , p<0.05]. The change was twofold higher in the MICT group (0.6±1.2 mm² ) than in the HIT group (0.3±0.6 mm² ). However, the treatment effect of HIT was not significant (treatment effect = -0.3 mm² , 95% CI [-0.825 to 0.2 mm² ] p = 0.29). These results suggest that early initiation of HIT compared with MICT does not attenuate CAV progression in de novo HTx recipients. This article is protected by copyright. All rights reserved.

Vascular Signaling in Allogenic Solid Organ Transplantation - The Role of Endothelial Cells

Graft rejection remains the major obstacle after vascularized solid organ transplantation. Endothelial cells, which form the interface between the transplanted graft and the host’s immunity, are the first target for host immune cells. During acute cellular rejection endothelial cells are directly attacked by HLA I and II-recognizing NK cells, macrophages, and T cells, and activation of the complement system leads to endothelial cell lysis. The established forms of immunosuppressive therapy provide effective treatment options, but the treatment of chronic rejection of solid organs remains challenging. Chronic rejection is mainly based on production of donor-specific antibodies that induce endothelial cell activation—a condition which phenotypically resembles chronic inflammation. Activated endothelial cells produce chemokines, and expression of adhesion molecules increases. Due to this pro-inflammatory microenvironment, leukocytes are recruited and transmigrate from the bloodstream across the endothelial monolayer into the vessel wall. This mononuclear infiltrate is a hallmark of transplant vasculopathy. Furthermore, expression profiles of different cytokines serve as clinical markers for the patient’s outcome. Besides their effects on immune cells, activated endothelial cells support the migration and proliferation of vascular smooth muscle cells. In turn, muscle cell recruitment leads to neointima formation followed by reduction in organ perfusion and eventually results in tissue injury. Activation of endothelial cells involves antibody ligation to the surface of endothelial cells. Subsequently, intracellular signaling pathways are initiated. These signaling cascades may serve as targets to prevent or treat adverse effects in antibody-activated endothelial cells. Preventive or therapeutic strategies for chronic rejection can be investigated in sophisticated mouse models of transplant vasculopathy, mimicking interactions between immune cells and endothelium.

Progression of cardiac allograft vasculopathy assessed by serial three-vessel quantitative coronary angiography

Background

The purpose of the present study was to assess the short- and long-term progression of cardiac allograft vasculopathy (CAV) using serial 3-vessel quantitative coronary angiography (QCA).

Methods

CAV progression was assessed using serial 3-vessel QCA analysis at baseline, 1-year and long-term angiographic follow-up (8.5±3.7 years) after heart transplantation. The change in minimal lumen diameter (MLD) and percent diameter stenosis (%DS) was serially assessed within matched segments. Patients were graded according to the ISHLT-CAV classification and grouped as ISHLT-CAV₀ and ISHLT-CAV_1-3. The primary endpoint was mean change in MLD and %DS.

Results

A total of 41 patients and 520 matched segments were available for serial 3-vessel QCA. Overall, MLD decreased non-significantly from baseline to 1-year follow-up and significantly from 1-year to the long-term angiographic follow-up (Δ-0.08mm/year [95%CI -0.11 to -0.05], P<0.001). %DS increased significantly from baseline to 1-year (Δ+0.96%/year [95%CI 0.04 to 1.88], P = 0.041) and from 1-year to long-term angiographic follow-up (Δ+0.61%/year [95%CI 0.33 to 0.88], P<0.001). ISHLT-CAV_1-3 at 1 year and at long-term angiographic follow-up was observed in 22% and 61%, respectively. Between baseline and long-term angiographic follow-up, a significant reduction in MLD was observed within both groups without a significant difference in the reduction between the two groups (ISHLT-CAV₀: median -0.49mm [IQR -0.54 to -0.43] vs. ISHLT-CAV_1-3: median -0.40mm [IQR -0.44 to -0.35], P = 0.4).

Conclusion

The current data suggest that QCA can’t predict CAV beyond 1 year, but, QCA affirmed that CAV progresses to a similar extent in patients who do not develop visual CAV during long-term follow-up.

The effect of negative remodeling on fractional flow reserve after cardiac transplantation

BACKGROUND

Negative remodeling is a common occurrence early after cardiac transplantation. Its impact on the development of myocardial ischemia is not well documented. The aim of this study is to investigate the impact of negative remodeling on fractional flow reserve after cardiac transplantation.

METHODS

Thirty-four cardiac transplant recipients underwent intravascular ultrasound (IVUS) and fractional flow reserve (FFR) assessment soon after transplantation and one year later. Patients were divided into those with and without negative remodeling based on IVUS, and the impact on FFR was assessed. In the 19 patients with negative remodeling, there was no significant change in plaque volume (119.3±82.0 to 131.3±91.2mm³, p=0.21), but vessel volume (775.6±212.0 to 621.9±144.1mm³, p<0.0001) and lumen volume (656.3±169.1 to 490.7±132.0mm³, p<0.0001) decreased significantly and FFR likewise decreased significantly (0.88±0.06 to 0.84±0.07, p=0.04). In the 15 patients without negative remodeling, vessel volume did not change (711.7±217.6 to 745.7±198.5, p=0.28), but there was a significant increase in plaque volume (126.8±88.3 to 194.4±92.7, p<0.001) and a resultant significant decrease in FFR (0.89±0.05 to 0.85±0.05, p=0.01).

CONCLUSION

Negative remodeling itself, without any change in plaque volume can cause a significant decrease in fractional flow reserve after cardiac transplantation and appears to be another possible mechanism for myocardial ischemia.

Donor-Transmitted Atherosclerosis Associated With Worsening Cardiac Allograft Vasculopathy After Heart Transplantation: Serial Volumetric Intravascular Ultrasound Analysis

BACKGROUND

The influence of preexisting donor-transmitted atherosclerosis (DA) on cardiac allograft vasculopathy (CAV) development remains unclear.

METHODS

We performed 3-dimensional intravascular ultrasound (3D-IVUS) analysis in 42 heart transplantation (HTx) recipients at 2.1 ± 0.9 months (baseline) and 12.2 ± 0.4 months post-HTx, as well as consecutive 3D-IVUS analyses up to 3 years post-HTx in 35 of the 42 recipients. Donor-transmitted atherosclerosis was defined as a maximal intimal thickness of 0.5 mm or greater at baseline. Changes in volumetric IVUS parameters were compared in recipients with (DA group) and without DA (DA-free group) at baseline, 1 year, and 3 years post-HTx.

RESULTS

Donor-transmitted atherosclerosis was observed in 57.1% of 42 recipients. The DA group exhibited a significantly greater increase in plaque volume at 1 year post-HTx (P < 0.001), leading to increased percent plaque volume (plaque volume/vessel volume, [%]) (P < 0.001) and decreased luminal volume (P = 0.021). Donor-transmitted atherosclerosis was independently associated with a greater increase in percent plaque volume during the first post-HTx year (P = 0.011). From 1 to 3 years post-HTx, the DA group underwent continuous reduction in luminal volume (P = 0.022). These changes resulted in a higher incidence of angiographic CAV at 3 years post-HTx in the DA group (58.8% vs 5.6%, P = 0.002).

CONCLUSIONS

This volumetric IVUS study suggests that DA correlates with the worsening change in CAV several years post-HTx. Donor-transmitted atherosclerosis recipients may require more aggressive treatment to prevent subsequent CAV progression.

Noninvasive Monitoring of Immune Rejection in Face Transplant Recipients

BACKGROUND

Chronic rejection leading to allograft loss remains a significant concern after facial allotransplantation. Chronic rejection may occur without clinical signs or symptoms. The current means of monitoring is histologic analyses of allograft biopsy specimens, which is both invasive and impractical. Prior data suggest that chronic rejection is associated with changes in intima and media thickness of vessels in arms and solid organ allografts; such data have not been published for face transplant recipients.

METHODS

The authors used a 48-MHz transducer to acquire images of the bilateral facial, radial, dorsalis pedis and, if applicable, sentinel flap arteries in five face transplant recipients (8 months to 4.5 years after transplantation) and five control subjects. The authors assessed the intima, media, and adventitia thickness plus lumen and the total vessel diameter and area.

RESULTS

Face transplant recipients had thicker intima in all sites compared with controls, but the ratio of the intimal thickness of facial and radial arteries was similar in face transplant recipients compared with controls (1.00 versus 0.95; p = 0.742). Intraobserver correlation showed reliable reproducibility of the measurements (r = 0.935, p ≤ 0.001). Interobserver correlation demonstrated reproducibility of intima measurements (r = 0.422, p ≤ 0.001).

CONCLUSION

The authors demonstrate that ultrasound biomicroscopy is feasible for postsurgical monitoring, and have developed a new benchmark parameter, the facial artery-to-radial artery intimal thickness ratio, to be used in future testing in the setting of chronic rejection.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Diagnostic, IV.

Immunobiology in VCA

Transplantation of vascularized composite tissue is a relatively new field that is an amalgamation of experience in solid organ transplantation and reconstructive plastic and orthopedic surgery. What is novel about the immunobiology of VCA is the addition of tissues with unique immunologic characteristics such as skin and vascularized bone, and the nature of VCA grafts, with direct exposure to the environment, and external forces of trauma. VCAs are distinguished from solid organ transplants by the requirement of rigorous physical therapy for optimal outcomes and the fact that these procedures are not lifesaving in most cases. In this review, we will discuss the immunobiology of these systems and how the interplay can result in pathology unique to VCA as well as provide potential targets for therapy.

Myofibroblast-mediated adventitial remodeling: an underestimated player in arterial pathology

The arterial adventitia has been long considered an essentially supportive tissue; however, more and more data suggest that it plays a major role in the modulation of the vascular tone by complex interactions with structures located within intima and media. The purpose of this review is to summarize these data and to describe the mechanisms involved in adventitia/media and adventitia/intima cross-talk. In response to a plethora of stimuli, the adventitia undergoes remodeling processes, resulting in positive (adaptive) remodeling, negative (constrictive) remodeling, or both. The differentiation of the adventitial fibroblast into myofibroblast (MF), a key player of wound healing and fibrosis development, is a hallmark of negative remodeling; this can lead to vessel stenosis and thus contribute to major cardiovascular diseases. The mechanisms of fibroblast-to-MF differentiation and the role of the MF in adventitial remodeling are highlighted herein.

Cardiac allograft vasculopathy: advances in diagnosis

Cardiac allograft vasculopathy (CAV), characterized by diffuse intimal thickening and luminal narrowing in the arteries of the allograft, is the leading cause of morbidity and mortality in cardiac transplant recipients. Many transplant centers perform routine annual surveillance coronary angiography. However, angiography can underdiagnose or miss CAV due to its diffuse nature. Intravascular ultrasound (IVUS) is more sensitive than angiography. IVUS provides not only accurate information on lumen size, but also quantification of intimal thickening, vessel wall morphology, and composition. IVUS has evolved as a valuable adjunct to angiography and the optimal diagnostic tool for early detection. Noninvasive testing such as dobutamine stress echocardiography and nuclear stress test have shown considerable accuracy in diagnosing significant CAV. Computed tomographic imaging and cardiac magnetic resonance imaging are promising new modalities but require further study. This article reviews the diagnostic methods that are currently available.

The use of proliferation signal inhibitors in the prevention and treatment of allograft vasculopathy in heart transplantation

Cardiac allograft vasculopathy (CAV) currently represents one of the most important causes of long-term morbidity and mortality in the heart transplant population. In well-designed studies with de novo patients, the use of proliferation signal inhibitors (PSIs; everolimus and sirolimus) has been shown to significantly prevent the intimal growth of graft coronary arteries in comparison to other immunosuppressive regimens, reducing the incidence of vasculopathy at 12 and 24 months. In addition, conversion to PSIs in maintenance patients with established CAV has also shown promising results in the reduction of the progression of the disease and its clinical consequences. For these reasons the interest shown by various transplantation units in the potential role of PSIs in this field is growing. The aim of the present article is to review the information obtained to date on the use of PSIs in heart transplant recipients, both in the prevention and the treatment of CAV. The principal published recommendations on the introduction and appropriate management of these drugs in clinical practice are also collected, as well as certain recommendations given by the authors based on their experience.

Subclinical atherosclerosis after heart and heart-lung transplantation in childhood

Children after heart transplantation are considered as at-risk patients for extracardiac atherosclerotic complications. Noninvasive ultrasound measurement of the common carotid artery (IMT) provides valid information about the endothelial structure of the vascular system. Twenty-two patients (17 male, mean age 12.4 +/- 4.5 yr) after heart and (5.7 +/- 4.5 yr) heart-lung transplantation were enrolled. The mean IMT was measured and compared with a control group (18 children, 10 male, mean age 11.8 +/- 1.8 yr) and to normative data. Transplanted children had a higher IMT than controls (0.453 +/- 0.003 vs. 0.424 +/- 0.002 mm, p < 0.001). IMT-SDS was increased as well (1.6 +/- 0.1 vs. 0.8 +/- 0, p < 0.001). Transplanted children had a higher LDL/HDL-ratio (2.2 +/- 0.2 vs. 1.2 +/- 0.1, p < 0.001). Time after transplantation, age at the time of transplantation, or medical therapy did not influence the findings. We found evidence for subclinical atherosclerosis in children after heart and heart-lung transplantation. Even if single atherosclerotic risk factors could not be identified, transplanted children seem to be at risk for atherosclerosis. Our findings support the recently published statement of the AHA-Expert panel: after heart transplantation atherosclerotic complications may occur with increased incidence. We propose the IMT-measurement in these patients as an easy method to assess the vascular status and to guide preventive measures.

Alloimmune-mediated vascular remodeling of human coronary artery grafts in immunodeficient mouse recipients is independent of preexisting atherosclerosis

Vascular remodeling rather than intimal thickening is the most important determinant of luminal loss in cardiac graft arteriosclerosis. The impact of donor-transmitted atherosclerotic lesions on alloimmune-mediated arterial injury in an experimental setting is not known. We investigated this issue in a chimeric model of human coronary artery grafts to immunodeficient mouse recipients reconstituted with allogeneic human peripheral blood mononuclear cells. Rejecting grafts demonstrated robust intimal expansion, outward vascular remodeling, and variable lumen loss. There was no significant relationship between preexistent atherosclerosis, gender, and age of the artery donors vs. the degree of alloimmune-induced changes in vessel morphology. Our experimental findings, in a system without the potentially confounding variable of immunosuppressive drugs, are in agreement with the majority of clinical studies that alloimmune-mediated intimal injury and vascular remodeling is independent of preexisting coronary atherosclerosis. Our results support the concept of extending the criteria for organ donors to include modest coronary atherosclerosis.

Cardiovascular risk reduction in high-risk pediatric patients: a scientific statement from the American Heart Association Expert Panel on Population and Prevention Science; the Councils on Cardiovascular Disease in the Young, Epidemiology and Prevention, Nutrition, Physical Activity and Metabolism, High Blood Pressure Research, Cardiovascular Nursing, and the Kidney in Heart Disease; and the Interdisciplinary Working Group on Quality of Care and Outcomes Research

Although for most children the process of atherosclerosis is subclinical, dramatically accelerated atherosclerosis occurs in some pediatric disease states, with clinical coronary events occurring in childhood and very early adult life. As with most scientific statements about children and the future risk for cardiovascular disease, there are no randomized trials documenting the effects of risk reduction on hard clinical outcomes. A growing body of literature, however, identifies the importance of premature cardiovascular disease in the course of certain pediatric diagnoses and addresses the response to risk factor reduction. For this scientific statement, a panel of experts reviewed what is known about very premature cardiovascular disease in 8 high-risk pediatric diagnoses and, from the science base, developed practical recommendations for management of cardiovascular risk.

Changes in coronary arterial dimensions early after cardiac transplantation

BACKGROUND

Significant changes in coronary artery structure, including intimal thickening and vessel remodeling, occur early after cardiac transplantation. The degree to which these changes compromise coronary lumen dimensions, and the clinical factors that affect these changes, remain controversial.

METHODS

Thirty-eight adult cardiac transplant recipients underwent coronary angiography and volumetric intravascular ultrasound (IVUS) evaluation of the left anterior descending artery within 8 weeks of transplantation and at 1 year. Clinical parameters including donor and recipient characteristics, rejection episodes, and serology were prospectively recorded. Two-dimensional IVUS measurements and vessel, lumen and plaque volume were calculated at both time points and compared. Multivariate regression analysis was performed to reveal clinical predictors of change in coronary dimensions.

RESULTS

During the first year after transplantation, significant decreases in vessel size (negative remodeling) and lumen size were observed with significant increases in plaque burden based on IVUS analyses. Loss of lumen volume correlated significantly with the degree of negative remodeling (R=0.82, P<0.0001), but not with changes in plaque burden (R=0.08, P=0.64). Patients with the greatest increase in plaque volume had significantly less negative remodeling (R=0.53, P=0.0006). Transplant recipient cytomegalovirus (CMV) antibody seropositivity and lack of aggressive prophylaxis against CMV infection/reactivation were significant independent predictors of greater negative remodeling (P<0.01 and P=0.03, respectively) and greater lumen loss (P=0.02 and P=0.03, respectively).

CONCLUSION

Negative remodeling is primarily responsible for coronary artery lumen loss during the first year after cardiac transplantation. CMV seropositivity and lack of aggressive CMV prophylaxis correlate with increased negative remodeling, resulting in greater lumen loss.

Vascular Remodeling in Transplant Vasculopathy

As therapeutic strategies to prevent acute rejection progressively improve, transplant vasculopathy (TV) constitutes the single most important limitation for long-term functioning of solid organ allografts. In TV, allograft arteries characteristically develop severe, diffuse intimal hyperplastic lesions that eventually compromise luminal flow and cause ischemic graft failure. Traditional immunosuppressive strategies that check acute allograft rejection do not prevent TV; indeed 50% of transplant recipients will have significant disease within five years of organ transplantation, and 90% will have significant TV a decade after their surgery. TV can involve the entire length of the transplanted arterial bed, including penetrating intraorgan arterioles. Indeed, the luminal narrowing of such penetrating vessels may be the most functionally significant because arterioles represent the major contributors to tissue vascular resistance. Because of the diffuseness of TV involvement in the allograft vascular bed, the only currently definitive therapy requires re-transplantation. Nevertheless, as we better understand the pathogenesis and critical mediators of these lesions, pharmacological advances can be anticipated. Other articles in this thematic review series focus on the specifics of the inciting injury, the cytokines and chemokines that drive TV development, and the nature of the recruited cells in TV lesions, as well as the pathogenic similarities between TV and other vascular lesions such as atherosclerosis. This review focuses on the mechanisms of vascular wall remodeling in TV, including the intimal accumulation of smooth muscle-like cells and associated extracellular matrix, medial smooth muscle cell degeneration, and adventitial fibrosis. A brief overview highlights the aneurysmal changes that can accrue when vessel wall inflammation has a cytokine profile distinct from the typical proinflammatory interferon-gamma-dominated milieu.

Vascular Remodeling 1 Year After Cardiac Transplantation

BACKGROUND

The belief that vascular remodeling and intimal hyperplasia are causes of luminal narrowing in cardiac allograft vasculopathy (CAV) is controversial. This study evaluated the relationship of vascular remodeling and intimal hyperplasia to luminal narrowing 1 year after orthotopic heart transplantation.

METHODS

Intravascular ultrasound imaging was performed on 190 cardiac transplant recipients at baseline and again 1 year after transplantation as part of a randomized trial of mycophenolate mofetil (MMF) and azathioprine (Aza). Studies 1 year apart were matched at 625 sites. All sites were classified into positive, non-significant and negative remodeling patterns, depending on a change of +/-10% in external elastic membrane area. Of the 190 patients, 99 were randomized to receive MMF, and 91 to receive Aza.

RESULTS

A total of 625 sites were observed. Of these, 52% had no remodeling, 25% exhibited vessel dilation, and 23% had vessel shrinkage in the presence of variable intimal growth (Delta intimal area: 0.73 +/- 1.70 mm2, p < 0.0001; 1.23 +/- 2.02 mm2, p < 0.0001; and 0.20 +/- 1.40 mm2, p = 0.09, respectively). Sixty percent of the lumen loss was due to a decrease in external elastic membrane area and 40% to an increase in intimal area (p = 0.005). Compared with Aza-treated patients, the MMF-treated patients had a lower incidence of vessel shrinkage (17% vs 28%, p = 0.001), and a trend for smaller maximum intimal thickness (0.21 +/- 0.25 mm vs 0.29 +/- 0.31 mm, p = 0.052).

CONCLUSIONS

Positive remodeling is associated with intimal growth, but negative remodeling does not correlate with any specific change in intimal hyperplasia. Constrictive remodeling is more responsible than intimal hyperplasia for the luminal narrowing that occurs. MMF is more efficacious than azathioprine in preventing the development of CAV at 1 year, by reducing the degree and incidence of vessel shrinkage and the progression of intimal hyperplasia.

Cardiovascular Risk Reduction in High-Risk Pediatric Patients

Although for most children the process of atherosclerosis is subclinical, dramatically accelerated atherosclerosis occurs in some pediatric disease states, with clinical coronary events occurring in childhood and very early adult life. As with most scientific statements about children and the future risk for cardiovascular disease, there are no randomized trials documenting the effects of risk reduction on hard clinical outcomes. A growing body of literature, however, identifies the importance of premature cardiovascular disease in the course of certain pediatric diagnoses and addresses the response to risk factor reduction. For this scientific statement, a panel of experts reviewed what is known about very premature cardiovascular disease in 8 high-risk pediatric diagnoses and, from the science base, developed practical recommendations for management of cardiovascular risk.

Treatment of allograft vasculopathy in heart transplantation

Cardiac allograft vasculopathy remains one of the main causes of morbidity and mortality after heart transplantation, although its impact is becoming somewhat smaller as prophylactic measures are implemented. Advances in the understanding of the molecular and cellular mechanisms involved in the genesis and development of cardiac allograft vasculopathy are opening ways for new diagnostic and therapeutic strategies. Successful prophylaxis of the early stages of the disease has been demonstrated with the use of newer immunosuppressive agents, such as sirolimus and everolimus, that will probably be included in future protocols. For most patients with established cardiac allograft vasculopathy, currently available revascularisation methods and retransplantation are not appropriate options. Antiproliferative agents could provide significant improvement in terms of symptom relief and prognosis, but their definite value must be proven in well-designed trials.

Contemporary concepts in prevention and treatment of cardiac allograft vasculopathy

Cardiac allograft vasculopathy (CAV), is characterized by heterogeneous proliferative thickening of the vascular intima of the cardiac allograft vasculature. Since its presentation is commonly clinically silent, early diagnosis and preventative therapy are critical. Preventative therapy including optimization of immunosuppressive therapy and treatment of comorbidities associated with CAV progression must be initiated early since most of the intimal thickening occurs during the first year posttransplant. Long-term use of calcineurin inhibitors is associated with a high incidence of chronic renal disease and also contributes to hyperlipidemia and hypertension, all of which may exacerbate CAV. In addition, statins, antihypertensive agents and anti-CMV agents all have demonstrated benefits in reducing CAV. Once established, the limited treatment options include nonpharmacologic interventions such as retransplantation, percutaneous coronary interventions, coronary artery bypass grafting, transmyocardial laser revascularization and heparin-induced/mediated extracorporeal LDL plasmapheresis (HELP). As the use of new assessment tools increases our understanding of this disease, better preventative and treatment strategies are evolving.

Influence of Pre-Existing Donor Atherosclerosis on the Development of Cardiac Allograft Vasculopathy and Outcomes in Heart Transplant Recipients

OBJECTIVES

This study sought to evaluate the influence of donor lesions on the development of cardiac allograft vasculopathy and outcomes in heart transplant recipients.

BACKGROUND

After orthotopic heart transplantation (OHT), coronary artery narrowing occurs as a combination of pre-existing donor lesions and new lesions that develop as a result of cardiac allograft vasculopathy.

METHODS

Intravascular ultrasound (IVUS) studies were performed in 301 recipients at 1.3 +/- 0.6 months and again at 12.2 +/- 0.8 months after OHT. Additional IVUS studies were performed in 90 patients at two and three years of follow-up. Sites at baseline with maximum intimal thickness > or =0.5 mm were defined as pre-existing donor lesions. The angiographic diagnosis of transplant coronary artery disease (TCAD) was defined as a new > or =50% diameter narrowing of a major epicardial vessel.

RESULTS

Donor lesions were present in 30% of the hearts. By IVUS, sites with donor lesions did not have a greater increase in intimal area compared with sites without donor lesions. Angiographically, the incidence of TCAD up to three years after transplantation was higher in recipients with donor lesions than in recipients without donor lesions (25% vs. 4%, p < 0.001). However, the three-year mortality rate was similar between recipients with or without donor lesions (4.5% vs. 5.2%, p = 1.0).

CONCLUSIONS

Pre-existing donor lesions do not act as a nidus for accelerating the progression of intimal hyperplasia. However, patients with donor lesions have a higher incidence of angiographic TCAD. Donor lesions do not affect the long-term survival of patients with OHT up to three years.

Cardiac allograft vasculopathy: The achilles’ heel of long-term survival after cardiac transplantation

Over the past 40 years, cardiac transplantation has evolved as the single best long-term option for eligible candidates with end-stage heart failure. Approximately 2000 transplants are performed annually in the United States, and with the institution of calcineurin-based immunotherapy, surveillance biopsies, and programmatic-based patient care, life expectancy at 1 and 12 years is 85% and 50%, respectively. Cardiac allograft vasculopathy (CAV) is the number one cause of death after the first year of transplantation. The incidence of CAV remains as high as 50% at 5 years, with life expectancy significantly abbreviated once it is recognized. Although current immunotherapy has reduced the likelihood of cellular rejection, it has not impacted CAV substantially. Better treatment of established risk factors and the advent of newer antiproliferative immunotherapy may hold promise in treating CAV. However, future therapies must address the multitude of mechanisms underlying CAV. This manuscript reviews the pathophysiology, clinical manifestations, screening, and diagnostic strategies for cardiac allograft vasculopathy while emphasizing current treatment paradigms designed to stave off or retard the progression of CAV.

Angiogenesis occurs within the intimal proliferation that characterizes transplant coronary artery vasculopathy

BACKGROUND

Vascular remodeling is central to the development of transplant coronary artery vasculopathy (CAV). For remodeling to occur, a sustained blood and nutrient supply is essential. Here we report on the presence of angiogenesis within the neointima of coronary arteries from cardiac transplant recipients.

METHODS

Coronary arteries from 57 cardiac transplant recipients with CAV were analyzed. Immunocytochemistry with antibodies raised against endothelial cells (CD31, CD34, and vWF), vascular smooth muscle cells (SmA), and activated endothelial cells (MHC 2, P-SEL, E-SEL, and VCAM-1) was performed.

RESULTS

A total of 89% of patients had significant angiogenesis. These vessels appeared as endothelial lined channels and were present in a concentric circumferential pattern within the mid portion of the neointima. These new vessels were present at an interface between an area of intimal hyperplasia and below an area of fibrous regeneration. These 2 distinct zones were present in 64% of the cases, and were clearly demonstrated with an elastic van Gieson (EVG) stain and are distinctly different from that seen in native atherosclerosis. Endothelial activation markers were strongly expressed by the endothelial cells lining new vessels, suggesting that they are functional and may aid in the recruitment of inflammatory cells.

CONCLUSIONS

These data suggest that angiogenesis is present within the intima of CAV lesions and may contribute to the continued obliteration of the vessel lumen. The vessels appear to originate in the intima and may represent the location of the donor endothelium before transplantation. Inhibition of endothelial damage may provide therapeutic options to prevent the progression of CAV.

Angiographic, Pathologic, and Clinical Relationships in Coronary Artery Disease in Cardiac Allografts

BACKGROUND

To date, the etiologic factors involved in the development of allograft coronary disease remain speculative and the treatment uncertain. The purpose of this study was to review the relationship of clinical, angiographic, and pathologic features of cardiac allograft vascular disease in a large population of heart transplant recipients followed for up to 15 years.

METHODS

From 1981 to 1996, 789 angiograms from 255 cardiac allografts were reviewed to determine the prevalence and severity of coronary artery disease. Demographic, clinical, and laboratory variables were analyzed to identify factors associated with the presence of angiographic coronary artery disease. In addition, pathologic examination was performed on many of the lost grafts.

RESULTS

Unsuspected severe donor coronary artery disease may be responsible for up to 10% of early graft failures. Angiographic coronary artery disease prevalence increased by approximately 10% with every 2-year interval after transplantation. Angiographic coronary artery disease consisted most often of minor luminal irregularities. Severe disease occurred in 12% of patients. At 1 year, the most significant factors associated with the presence of coronary artery disease were older donor age and the number of rejection episodes. Immunologic factors as well as traditional coronary risk factors such as hypercholesterolemia and hyperglycemia may play an important role in the genesis and progression of later-developing abnormalities.

CONCLUSIONS

Cardiac allograft coronary artery disease is a major limiting factor to the long-term success of cardiac transplantation. Immune processes, as well as traditional coronary artery disease risk factors, appear to play a role in the development of this disease.

Usefulness of Stanford Scale of Intimal Hyperplasia Assessed by Intravascular Ultrasound to Predict Time of Onset and Severity of Cardiac Allograft Vasculopathy

BACKGROUND

The purpose of this study was to assess the prognostic value of a single IVUS result described by the Stanford scale to predict CAV development.

METHODS

Inclusion criteria were heart transplantation (OHT) before 1997 and at least one IVUS performed before 1998. IVUS studies were performed in 37 patients at 37 +/- 26 months after OHT. Based on the Stanford scale, were divided patients into Four groups: group I (grade 0 or 1): n = 4, 42 +/- 19 years, 2 men/2 women; group II (grade 2): n = 10, 44 +/- 15 years, 9 men/1 woman; group III (grade 3): n = 11, 48 +/- 11 years, 11 men; and group IV (grade 4): n = 12, 46 +/- 8 years, 12 men. We compared the incidence and time of onset of clinically significant CAV, namely significant coronary lesions, myocardial infarction and death caused by CAV.

RESULTS

There was no CAV diagnosed in group I. The rates of CAV in coronary angiograms in groups II, III and IV were: 80%, 36%, and 75%, respectively. Significant CAV was found in 30%, 9%, and 50% of patients, respectively. Average times of onset of any CAV in groups II, III and IV were 4.9, 5.6, and 3.3 years, and for significant CAV were 4.1, 3.6, and 5.5 years, respectively. Deaths in groups I to IV were 1, 4, 2, and 5, respectively. CAV was the reason for death in 1 patient from group III, and 3 patients from group IV.

CONCLUSIONS

Extreme grades on the Stanford scale (0, 1, and 4) describing a single IVUS study in OHT recipients appear useful to stratify patients with the lowest versus the highest risk of CAV development.

Remodeling of coronary arteries in diabetic patients-an intravascular ultrasound study

BACKGROUND

Coronary artery remodeling is a structural change in the vessel wall and typically in response to atherosclerotic plaque. The nature of coronary remodeling has been described in different clinical situations. However, remodeling characteristics of coronary arteries of diabetic patients have never been studied.

HYPOTHESIS

We tested the hypothesis that positive remodeling of coronary artery in response to atherosclerotic plaque in diabetic patients would be less compared to nondiabetic patients.

METHODS

Coronary intravascular ultrasound analysis of data in 26 consecutive patients (12 diabetic and 14 nondiabetic) was performed. Linear regression analyses of vessel area versus plaque area were carried out to establish a relation between the degree of plaque and the extent of remodeling in diabetic and nondiabetic groups.

RESULTS

The positive remodeling quantified as the slope of the regression line was similar in both the groups (diabetic group 1.32 and nondiabetic group 0.80) when all segments with different plaque areas were considered (P > 0.05). However, the diabetic group had greater positive remodeling in segments with plaque area less than 55%, as the slope for diabetic group was 2.01 and nondiabetic group was 1.40 (P < 0.05).

CONCLUSIONS

Both the diabetic and nondiabetic patients had positive remodeling in response to atherosclerotic plaque formation. Diabetics had greater positive remodeling in the early stages of atherosclerosis compared to nondiabetics, thus providing evidence against our hypothesis. The adverse clinical outcomes in diabetics may not be due to inadequate positive remodeling of coronary arteries as previously thought.

Cardiac allograft vasculopathy: advances in understanding its pathophysiology, prevention, and treatment

PURPOSE OF REVIEW

To discuss the current understanding of the pathogenesis, natural history, and diagnosis of cardiac allograft vasculopathy, and to outline new preventive and treatment strategies.

RECENT FINDINGS

The central event in the development of allograft vasculopathy is the inflammatory response to immune or nonimmune-mediated endothelial damage. This response is characterized by the release of inflammatory cytokines, upregulation of cell-surface adhesion molecules, and the subsequent binding of leukocytes. Once induced, vascular smooth muscle cells proliferate and migrate from the media to form a neointima. Circulating progenitor cells are recruited to sites of arterial injury where they may then differentiate into smooth muscle cells. Because of its diffuse nature, allograft vasculopathy is best detected by intravascular ultrasound. Noninvasive tests, such as dobutamine echocardiography, are gaining in favor. Although the only definitive treatment is retransplantation, the immunosuppressant rapamycin can limit disease progression. Its synthetic derivative, everolimus, effectively prevented intimal hyperplasia in de novo transplant recipients.

SUMMARY

These advances have provided hope that allograft vasculopathy may finally be manageable.

Cardiac Allograft Vasculopathy

The purpose of this article is to discuss the pathogenesis, characteristics, and treatment modalities for heart transplant recipients with cardiac allograft vasculopathy (CAV). Cardiac transplantation has become an acceptable mainstream treatment for end-stage cardiac disease. Unfortunately, CAV is the leading cause of death after the first year of transplant. CAV is an accelerated form of obliterative coronary artery disease that occurs in the heart transplant recipient. Currently, retransplantation is the only definitive treatment. Ethical concerns and the shortage of donor organs present a huge obstacle to retransplantation and the long-term outcome of heart transplant recipients.

Results after transplantation using donor hearts with preexisting coronary artery disease

OBJECTIVE

Cardiac allografts with coronary artery disease may permit a selective expansion of the donor pool. Twenty-two recipients who received donor hearts with mild to moderate coronary artery disease on angiography were reviewed. All donor organs had preserved left ventricle function on echocardiogram.

METHODS

The procedure was explained to the patients in detail. All survivors have at least 1 year of follow-up. If the coronary arteries of the donor heart were significantly occluded, then the implanting surgeon performed coronary revascularization. Donors were allocated to patients facing imminent death (group I, n = 4) or to those who would otherwise not have been transplanted (group II, n = 18). Median recipient age was 57 years old for group I and 68 years old for group II. Median follow-up was 25 months for group I and 44 for group II.

RESULTS

Outcome was evaluated using survival and freedom from graft coronary disease as end points. In group I, 3 of the 4 hearts required revascularization. In group II, 10 of the 18 required revascularization. The majority of the revascularizations were recipient saphenous vein grafts (84.6%) to the donor left anterior descending artery (50%). The 1-month and 2-year actual survivals for group I are 75% and 50% and 87.5% and 81.3 for group II. One patient in group I who was in extremis and 3 in group II died at less than 90 days. Group II early deaths had donor risk factor combinations of coronary artery disease, left ventricular hypertrophy, and long distance. Freedom from new graft coronary artery disease was 100% at 2 years in group I and 87.5% in group II.

CONCLUSIONS

Selective use of donor hearts with coronary artery disease is acceptable. Early deaths are related to recipient factors as well as associated donor risk factors. Donor hearts with mild or moderate coronary artery disease and preserved function on echocardiogram can be used but may require revascularization with recipient conduit and/or percutaneous transluminal coronary artery angioplasty. Coronary disease in donor hearts requires grading and does not categorically preclude use, particularly in risk-matched recipients.

Early constriction or expansion of the external elastic membrane area determines the late remodeling response and cumulative lumen loss in transplant vasculopathy: an intravascular ultrasound study with 4-year follow-up

BACKGROUND

Early constriction of the external elastic membrane (EEM) area has been observed after cardiac transplantation. The aim of this study was to compare the late disease process of transplant vasculopathy between coronary segments with early constrictive and expansive remodeling.

METHODS

Serial intravascular ultrasound data obtained annually for 4 years after transplantation in 38 transplant recipients was available. In 135 matched segments from 59 coronary arteries ultrasound images were digitized at 1-mm intervals. Mean values of the external elastic membrane (EEM), lumen and intimal areas were calculated. On the basis of a decrease or increase in EEM area within the first year after transplantation, we defined segments with early constrictive remodeling (CR, n = 71) or early expansive remodeling (ER, n = 64).

RESULTS

Annual changes in intimal area were similar between segments with early CR and ER throughout the follow-up period. However, during the second and third year, annual increases in EEM area were greater in segments with early CR than in segments with early ER (second year: 1.5 +/- 2.7 vs 0.6 +/- 2.8 mm(2), p = 0.052; third year: 1.3 +/- 2.5 vs -0.03 +/- 2.6 mm(2), p = 0.003). Despite this late expansion, segments with early CR showed a cumulative decrease in the EEM area and a greater lumen loss than segments with early ER (-2.5 +/- 3.4 vs -0.6 +/- 2.6 mm(2), p < 0.001).

CONCLUSIONS

In transplant vasculopathy, the late remodeling response was different between segments with early constrictive and expansive remodeling, despite similar intimal thickening. Early constriction caused an overall decrease in EEM area and greater loss of lumen during follow-up.

Relevance of cytomegalovirus infection and coronary-artery remodeling in the first year after heart transplantation: a prospective three-dimensional intravascular ultrasound study

BACKGROUND

Transplant coronary artery disease (TxCAD) is a major cause of long-term mortality after heart transplantation. Although vascular remodeling has been implicated in the pathophysiology of TxCAD, its determinants remain unknown.

METHODS

Twenty-nine consecutive heart-transplant recipients prospectively received intravascular ultrasound (IVUS) of the left-anterior descending artery 1 and 12 months after transplant, with volumetric reconstruction of the proximal 30 mm.

RESULTS

Overall, patients exhibited intimal volume increase (+83%, P<0.001), wheras vessel volume remained largely unchanged (+4%, P=0.270); consequently, overall lumen volume decreased (-6%, P=0.058). Among the clinical and laboratory variables, cytomegalovirus (CMV) infection requiring treatment (occurring in 12 patients), as assessed by pp65 antigenemia, was independently associated with the impaired ability of the vessel wall to enlarge in response to intimal volume increase, ultimately resulting in lumen loss (OR [95% CI]=0.098 [0.010-0.920]; P=0.042). However, adequate vessel response to intimal hyperplasia with consequent lumen preservation was observed in the remaining 17 patients who did not present CMV infection requiring treatment.

CONCLUSIONS

The present study demonstrates that either adequate or inadequate coronary remodeling may occur during the first year after transplantation. Moreover, for the first time, it strongly suggests that remodeling modalities may be negatively influenced by the occurrence of clinically relevant CMV infection. Randomized prospective trials are warranted to investigate whether aggressive treatment of CMV infection may help prevent TxCAD.

Relative contributions of intimal hyperplasia and vascular remodeling in early cardiac transplant-mediated coronary artery disease

The relative contribution of intimal hyperplasia and vascular remodeling in early transplant coronary artery disease (TxCAD) is unknown. This study was designed to determine the contributions of vascular remodeling and intimal hyperplasia in the initial year after transplantation by intravascular ultrasound (IVUS). Twenty-five patients underwent baseline (<6 weeks after transplant) and 1-year angiography and IVUS to evaluate total vessel, luminal, and intimal + medial areas in >or=3 segments of the coronary artery. Nine patients had donor atherosclerotic disease on baseline study (23% of segments), and at 1-year, 21 patients (84%) had intimal hyperplasia (70% of segments). Fourteen patients had positive remodeling in all arterial segments, whereas the remaining 11 had positive and negative remodeling in the same vessel. Mean plaque area and total vessel area increased significantly (p = 0.0001) in proximal, mid, and distal segments, whereas total vessel area was most pronounced in distal segments. Luminal area did not change over time. Of the 87 segments evaluated, 68 (78%) had an increase in total vessel area, 57 (66%) had intimal growth, and 54 (62%) had an increase in luminal area. Although changes in total vessel and luminal area were closely correlated, a decrease in luminal area was associated with positive and negative remodeling. In conclusion, luminal area is generally maintained during the initial transplant year despite significant intimal hyperplasia due to positive remodeling. Reduction in the luminal area results from either inadequate positive remodeling or negative remodeling without intimal growth and often occurs in the same artery.

A comparison of intravascular ultrasound with coronary angiography for evaluation of transplant coronary disease in pediatric heart transplant recipients

BACKGROUND

The purpose of this study was to assess the sensitivity of coronary angiography versus intravascular ultrasound for detecting significant transplant coronary artery disease in children. We also examined associations between potential risk factors for transplant coronary artery disease and intravascular ultrasound findings, and evaluated the safety of intravascular ultrasound.

METHODS

All pediatric heart transplant patients who had intravascular ultrasound following routine coronary angiography were included. Transplant coronary artery disease was quantified by assigning Stanford classes and calculating intimal indices for intravascular ultrasound images. These findings were compared with qualitative coronary angiography findings. Risk factors for transplant coronary artery disease, cardiac events and complications were recorded.

RESULTS

Sixteen patients had 27 intravascular ultrasound procedures during the study period. All patients had evidence of transplant coronary artery disease at their latest intravascular ultrasound study. Of the patients whose most severely afflicted coronary artery underwent both imaging modalities at the latest study, 50% had significant transplant coronary artery disease (Stanford Class >/=II) by intravascular ultrasound and normal coronary angiography. A higher mean first-year biopsy score may be associated with significant transplant coronary artery disease by intravascular ultrasound, but a large number of patients will be required to determine this with statistical certainty. One major complication occurred early in the experience.

CONCLUSIONS

In children, intravascular ultrasound is more sensitive for detecting significant transplant coronary artery disease than coronary angiography, but may add cost, time and potential morbidity to screening protocols. Prospective, multicenter studies are needed to best utilize intravascular ultrasound in this patient population.

The topography of intimal thickening and associated remodeling pattern of early transplant coronary disease: influence of pre-existent donor atherosclerosis

BACKGROUND

With native coronary disease, intimal plaque initially accumulates at focal areas in the artery, often accompanied by compensatory vessel enlargement. With transplant coronary disease, the topography of intimal thickening and associated remodeling pattern are less studied.

METHODS

We studied 72 prospectively recruited transplant patients with serial intravascular ultrasound using 4.3F catheters at baseline and at 1-year follow up. We considered 175 ultrasound-recorded segments (mean, 2.4 +/- 1.1 segments per patient) exactly matched on the serial studies by both angiographic criteria and ultrasound criteria, using arterial and venous branch points, pericardium, and sinuses as anatomic landmarks.

RESULTS

Eighty-eight segments had no donor disease, and 87 had donor disease (80 eccentric and 7 concentric intimal thickening). Progressive intimal thickening occurred in 48 segments without (55%) and 43 segments with donor disease (48%, p = NS). Thickening from segments without donor disease was mainly eccentric (81%). Thickening from segments with donor eccentric plaque was also mainly eccentric (67%, p = NS compared with segments without donor disease), with further thickening superimposed on the original plaque. Concentric intimal thickening was uncommon. Of the 58 patients who had >1 segment matched, intimal changes were discordant in 34 (59%), with progression in some and lack of progression in other segments. Total vessel area change correlated with intimal area change (r = 0.37 with a slope of 0.79, p < 0.001), including segments with (r = 0.39; slope, 0.69) and segments without (r = 0.37; slope, 1.16) donor disease.

CONCLUSION

The intimal thickening of early transplant coronary disease is mainly eccentric and often discordant within each individual patient. Donor eccentric plaque often serves as a nidus for further intimal growth. The topography of intimal thickening in transplant coronary disease resembles that of native coronary disease, but the presence of a pre-existent donor plaque may impede compensatory remodeling as further intimal thickening occurs after transplantation.