Heterogeneity of cardiac allograft vasculopathy: clinical insights from coronary angioscopy

Interplay of coronary angiography and intravascular ultrasound in predicting long-term outcomes after heart transplantation

BACKGROUND

Cardiac allograft vasculopathy (CAV) remains the major cause of late graft-related death after heart transplantation (HT). Identification of patients at risk of cardiovascular events has relevant implications in appropriately guiding resources and intensity of follow-up. In this context, the prognostic relevance of serial coronary imaging long-term after HT is unexplored.

METHODS

Recipients with intravascular ultrasound (IVUS) and coronary angiography performed 1 and 5 years after HT were monitored for subsequent 1 to 10 years to analyze the association of serial coronary imaging with cardiovascular death and major cardiovascular events (MACEs).

RESULTS

Included were 131 patients. The MACE incidence was 31.8 per 1,000 patient-years, and cardiovascular mortality was 17.4 per 1,000 patient-years. Progression of coronary lesions detected by angiography and changes in IVUS-defined parameters, including an increase in maximal intimal thickness (MIT) ≥0.35 mm and vascular remodeling, predicted MACE occurrence. However, only MIT change ≥0.35 mm also predicted cardiovascular mortality. Among patients with normal or stable angiography, an MIT change ≥0.35 mm identified those with a significantly higher MACE rate (80 vs 13 events/1,000 patient-years). Worsening metabolic parameters appeared associated with the increasing severity of CAV development.

CONCLUSIONS

Combined imaging analysis of progression of angiographic lesions and IVUS-detected MIT between 1 and 5 years post-HT allows discriminating patients at high, intermediate, and low risk for adverse long-term cardiovascular outcomes. The metabolic syndrome milieu is confirmed as a key risk factor for long-term CAV progression and adverse prognosis.

Attenuation of cardiac allograft vasculopathy by sirolimus: Relationship to time interval after heart transplantation. J Heart Lung Transplant. 2013;32:784-791. [PMID: 23856215 DOI: 10.1016/j.healun.2013.05.015]

BACKGROUND

The aim of the study was to assess temporal changes in plaque size and components after heart transplantation (HTx), and to evaluate the differences in treatment effects on plaque progression between sirolimus and calcineurin inhibitors (CNIs).

METHODS

The study comprised 146 HTx recipients who were converted from CNIs to sirolimus as primary immunosuppressant (sirolimus group, n = 61) and those who were maintained on CNIs (CNI group, n = 85). A retrospective compositional analysis of serial virtual histology-intravascular ultrasound was performed.

RESULTS

During a median follow-up of 2.8 years, there was a significant difference in plaque volume in favor of sirolimus between groups (p = 0.004). When subjects were sub-classified according to the time interval between HTx and study inclusion, those in the early group (≤2 years after HTx) had a greater increase in plaque volume (p = 0.006), characterized by a higher progression rate of fibrous plaque volume (p = 0.01). The treatment difference between groups in plaque volume was identified in the early group in favor of sirolimus with attenuating effects on the progression of fibrous plaque component (both p = 0.03 for interaction). By contrast, there were significant differences in necrotic core and dense calcium volume (both p < 0.05 for interaction) in favor of CNIs in the late group (≥6 years after HTx).

CONCLUSIONS

Compared with continued CNI therapy, sirolimus attenuated plaque progression in recipients with early conversion, but contributed to increases in necrotic core and dense calcium volume in those with late conversion. Our study supports the hypothesis that early initiation of sirolimus offers greater benefits in the treatment of CAV.

Qualitative Perfusion Cardiac Magnetic Resonance Imaging Lacks Sensitivity in Detecting Cardiac Allograft Vasculopathy

BACKGROUND

Cardiac allograft vasculopathy (CAV) is a major complication after heart transplantation, requiring frequent surveillance angiography. Though cardiac angiography is the gold standard, it is insensitive in detecting transplant vasculopathy and invasive. Perfusion MRI provides a noninvasive alternative and possibly a useful modality for studying CAV. We sought to compare the accuracy of qualitative perfusion MRI to coronary angiography in detecting CAV.

METHODS

A retrospective analysis was performed in 68 heart transplant recipients who had simultaneous surveillance cardiac MRI and coronary angiogram and who underwent transplantation between 2000 and 2007. We compared results of qualitative MRI to those of the cardiac angiogram. Sensitivity and specificity of MR were calculated.

RESULTS

Sixty-eight patients underwent both cardiac MRI and coronary angiogram. 73.5% were male; mean age was 45.37 ± 14 years. Mean duration of heart transplantation was 7.9 ± 5.2 years. The mean ejection fraction was 55% in the patients without CAV and 57.4% in those with CAV. There were 48 normal and 24 abnormal MRI studies. The overall sensitivity was 41% and specificity was 74%.

CONCLUSIONS

Qualitative assessment of perfusion cardiac MR has low sensitivity and moderate specificity for detecting CAV. The sensitivity of MRI was slightly improved with severity of disease.

The effect of HMG-CoA reductase inhibitors on chronic allograft rejection

Hydroxy-methyl-glutaryl coenzyme A (HMG-CoA) reductase inhibitors have pleiotropic actions that affect many systems other than lowering blood cholesterol concentrations. Hypercholesterolaemia is an adverse effect of immunosuppressive drug therapy and hence it is a common finding after organ transplantation. HMG-CoA reductase inhibitors lower cholesterol concentrations in transplant recipients but they also offer additional benefits. Since they impair the production of mevalonate, they reduce the concentrations of downstream products including farnesyl and geranyl phosphate. These isoprenoid moieties are required for protein prenylation and HMG-CoA reductase inhibitors impair this function in some cells. This action affects the immune system, especially in patients taking cyclosporin, and has been proposed as the mechanism whereby these drugs increase the half-life of transplanted organs. Other mechanisms have also been proposed including an increase in the free fraction of cyclosporin and a reduction in the time that low density lipoprotein (LDL) spends in blood. The latter effect reduces the extent of oxidation of LDL and hence reduces the damage caused by oxidised LDL. Chronic rejection is poorly understood but appears to involve both immune and non-immune processes. HMG-CoA reductase inhibitors affect both processes. At present, the evidence of benefit from statin prescription is confined to heart and kidney transplant recipients but it is likely that recipients of other organ transplants would also benefit. Drug interactions between cyclosporin and HMG-CoA reductase inhibitors are a limiting factor to their use. Pravastatin appears to be the best HMG-CoA reductase inhibitor for organ transplant recipients because of its lesser potential to interact with cyclosporin and hence cause myositis, which may thus allow higher doses to be used. Other, non-immunosuppressive drugs (including diltiazem and ketoconazole) have been shown to reduce transplant organ damage by unknown mechanisms and are widely prescribed in some transplant centres. More specific inhibitors of protein prenylation may afford useful immunosuppression, thereby prolonging transplant organ half-lives and also reducing the risk of cancer.

Surrogate markers for late cardiac allograft survival

While no definite well-validated surrogate marker for late cardiac allograft outcome is available, the early detection of cardiac allograft vasculopathy represents the 'key' candidate as an effective surrogate. Intravascular ultrasound detected intimal thickening has been noted to possess prognostic capability despite the presence of a normal coronary angiogram. Several prospective investigations have pointed to accurate thresholds of intimal thickening that are prognostically relevant and predict not only future angiographic disease but also hard allograft related endpoints including ischemic cardiac events, allograft failure, and death. Because of the resolution of intravascular ultrasound, this technique accords reproducibility and the ability to standardize the degree of intimal thickening over time. Other candidates that may serve as surrogates once appropriately evaluated include measures of allograft pump function, intragraft histology, and peripheral markers including but not limited to structural proteins (cardiac specific troponins), inflammatory markers (CRP), fibrogenic markers (TGF-beta, fibroblast growth factor), and immune markers (anti-HLA Ab and indirect alloantibodies).

Does acute cellular rejection correlate with cardiac allograft vasculopathy?

BACKGROUND

Previous studies of the association between acute cellular rejection and cardiac allograft vasculopathy (CAV) have yielded conflicting conclusions. We explored a possible association between acute cellular rejection and the extent of CAV, and we found a potential confounding variable that may obscure such an association.

METHODS

We investigated 140 patients (mean age, 51 +/- 11 years) who underwent serial intravascular ultrasound examinations at baseline and at 1 year after heart transplantation to assess CAV as change in maximal intimal thickness (CMIT). Patients were classified according to the presence or absence of biopsy-proven myocardial fibrosis. We used a standard biopsy-scoring system and a novel biopsy-scoring system, developed in our institution, to assess acute cellular rejection. Using univariate analysis, we found that CMIT was not associated with acute cellular rejection in the overall patient population (n = 140). However, we observed a correlation between CMIT and acute cellular rejection (standard method, r = 0.30, p = 0.01; novel method, r = 0.51, p < 0.0001) in patients who had no evidence of ischemic injury or fibrosis in their biopsy specimens (n = 57). Step-wise multiple regression showed that the rejection score derived from our novel method was associated more closely with the CMIT than was that derived from the traditional method.

CONCLUSIONS

This data indicate that the presence of myocardial fibrosis masks an actuarial association between acute cellular rejection and the development of de novo allograft vasculopathy. As previously suspected, myocardial fibrosis is a marker for non-immune-mediated graft injury independently associated with an increased incidence of CAV.

Non-invasive detection of coronary artery disease by dobutamine-stress echocardiography in children after heart transplantation

BACKGROUND

Coronary vasculopathy is the main cause of cardiac graft failure. Because yearly coronary angiography is invasive in children, a non-invasive method for detecting graft vasculopathy is needed. The aim of this study was to test dobutamine-stress echocardiography in a pediatric population to determine its feasibility, safety and reliability in the detection of graft coronary artery disease.

METHODS

Eighteen patients, aged 2 days to 16.8 years at transplantation (mean 8.4 years), underwent 44 dobutamine-stress echocardiography (DSE) exams, at a follow-up of 1.1 to 11.8 years (mean 5.1 years). Selective coronary angiography was performed for comparison. Echocardiographic recordings were obtained in 4 standard views of the left ventricle and measurements carried out within the frames of a 16-segment model. Segmental scores of contractility were obtained for each segment and a total segmental contractility index was calculated at each stage.

RESULTS

All patients reached the maximum dose stage. Maximum heart rate was 57% to 90% of predicted maximum. Maximum systolic blood pressure reached 190 mmHg. Segmental scores were normal in 37 and abnormal in 7 cases. Echographic results were concordant with angiography in 82% and discordant in 18% of the cases (4 negative DSEs with minor angiographic lesions, 2 positive DSEs with normal angiography), but there was no significant angiographic lesion with normal DSE.

CONCLUSIONS

DSE is a safe and highly feasible non-invasive technique in transplanted children. A normal DSE study successfully predicts the absence of significant coronary artery disease in the post-transplant population.

Drug treatment of clinical problems related to cardiac transplantation

In recent years, several new immunosuppressive agents have become available for the treatment of cardiac transplant recipients. Use of these agents and their potential side effects are reviewed.

Late rejection is a predictor of transplant coronary artery disease in children

OBJECTIVE

The study objectives were to determine posttransplant coronary artery disease (TxCAD) incidence, predisposing factors and optimal timing for retransplantation (re-Tx) in pediatric heart transplantation (Tx) recipients.

BACKGROUND

The TxCAD limits long-term survival following heart Tx, with re-Tx being the primary therapy. Information on risk factors and timing of listing for re-Tx is limited in children.

METHODS

The records of children who survived >1 year post-Tx at Loma Linda University were reviewed. Nonimmune and immune risk factors were analyzed.

RESULTS

TxCAD was documented in 24 of 210 children. Freedom from TxCAD was 92 +/- 2% and 75 +/- 5% at 5 and 10 years' post-Tx, respectively. The TxCAD diagnosis was established at autopsy in 10 asymptomatic patients who died suddenly within nine months following the most recent negative angiograms. The remaining 14 children had angiographic diagnoses of TxCAD and had symptoms and/or graft dysfunction (n = 10) or positive stress studies (n = 4). Three of 14 died within three months after the diagnosis was made. Eleven patients underwent re-Tx within seven months of diagnosis; nine survived. Univariate and multivariate analyses showed that only late rejection (>1 year posttransplant) frequency (p = 0.025) and severity (hemodynamically compromising) (p < 0.01) were independent predictors of TxCAD development. Freedom from TxCAD after severe late rejection was 78 +/- 8% one year postevent and 55 +/- 10% by two years.

CONCLUSIONS

Late rejection is an independent predictor of TxCAD. Patients suffering severe late rejection develop angiographically apparent TxCAD rapidly and must be monitored aggressively. Both TxCAD mortality and morbidity occur early; therefore, we recommend immediate listing for re-Tx upon diagnosis.

Coronary vasomotor dysfunction in the cardiac allograft: impact of different immunosuppressive regimens

Immunosuppression may have an important impact on early graft coronary endothelial injury. We investigated functional and morphologic coronary alterations, myocardial expression, and cardiac release of possible mediators of allograft vasculopathy within 6 months after cardiac transplantation with respect to different immunosuppressive regimens. Epicardial and microvascular endothelium-dependent and endothelium-independent vasomotor function and epicardial intimal thickening were measured in 8 transplant recipients treated with cyclosporin A (CyA), azathioprine, and prednisone (group 1), 9 transplant recipients treated with tacrolimus (TKL), azathioprine, and prednisone (group 2), and 14 patients treated with TKL, mycophenolate mofetil (MMF), and prednisone (group 3). The gene expressions of inducible and endothelial nitric oxide synthase (iNOS and eNOS), endothelin-1, prostacyclinsynthase, and thromboxansynthase were analyzed in endomyocardial biopsy specimens using semiquantitative reverse transcription polymerase chain reaction. Transcardiac cytokine release, endothelin-1, and nitrate-release were determined from plasma samples. Epicardial endothelial dysfunction (vasoconstriction to acetylcholine > 10%) and microvascular smooth muscle cell dysfunction (flow velocity increase to adenosine and nifedipine < 2.0) were enhanced in heart transplant recipients immunosuppressed with TKL, azathioprine, and prednisone. The prevalence of epicardial dysfunction was 78% in group 2 versus 44% and 46% in group 1 and 3 (p < 0.05), respectively. The prevalence of microvascular dysfunction was 56% in group 2 versus 13% and 7% in group 1 and 3 (p < 0.02), respectively. Coronary vasomotor dysfunction was associated with increased myocardial iNOS expression (p < 0.05), decreased eNOS expression (p < 0.05), and enhanced cardiac immunoreactive interleukin-6 (p < 0.01). Coronary intimal thickening was not different between the groups. The combination of TKL and MMF appears to be superior to TKL and azathioprine (and comparable to CyA and azathioprine) concerning preservation of early coronary vasomotor function, eNOS expression, iNOS suppression as well as cardiac interleukin-6 release. This may have an important impact on subsequent development of transplant coronary atherosclerosis.

Coronary stenting in cardiac allograft vasculopathy

OBJECTIVE

The purpose of this study was to evaluate acute angiographic success, in-hospital complications and long-term outcome after intracoronary stenting in patients with cardiac allograft vasculopathy.

BACKGROUND

The application of conventional interventional modalities to treat discrete lesions in patients with cardiac allograft vasculopathy is associated with higher procedural morbidity, mortality and higher restenosis compared to atherosclerotic coronary artery disease. Elective coronary stenting has been shown to lower restenosis rates and improve long-term outcome in selected patients with native coronary artery disease; however, its safety and efficacy in reducing restenosis in patients with cardiac allograft vasculopathy is unknown.

METHODS

Ten patients with 19 discrete lesions in a major coronary artery without diffuse distal disease underwent intracoronary stenting using Palmaz-Schatz stents. The average stent size was 3.4 mm, and the stent/artery ratio was 0.99+/-0.07. Eight of ten (80%) patients received antiplatelet therapy (aspirin plus ticlopidine) only.

RESULTS

Procedural success was 100% with no in-hospital stent thrombosis, Q-wave myocardial infarction or death. Minimal luminal diameter increased from 0.83+/-0.38 mm to 3.23+/-0.49 mm after stenting. Diameter stenosis decreased from 74.91+/-11.52% to 5.90+/-4.09% after stenting. Follow-up angiography was performed in 8 of 10 (80%) patients and 16 of 19 (84%) lesions. Target lesion revascularization was required in 2 of 10 (20%) patients and 3 of 16 (19%) lesions. Allograft survival was 7 of 10 (70%) at the end of 22+/-11 months follow-up.

CONCLUSIONS

Intracoronary stenting can be performed safely with excellent angiographic success in selected patients with cardiac allograft vasculopathy. The restenosis rate appears to be low despite the aggressive nature of the disease. A multicenter study with a larger number of patients is required to assess its efficacy in reducing restenosis and improving allograft survival.

Obesity and hypercholesterolemia following heart transplantation

Successful strategies for avoiding obesity and hypercholesterolemia are difficult to validate because of imprecise problem identification. The purpose of this study was to describe the incidence, severity, and onset of obesity and hypercholesterolemia among heart transplant recipients and identify relationships between demographic variables and weight or cholesterol levels during the first year following transplantation. Data were collected from retrospective chart review. Forty-two patients were randomly selected from 224 patients who were undergoing heart transplantation at the Johns Hopkins Hospital between July 1983 and December 1995. Significant differences were found in weight and cholesterol level during the first 12 months. Patients with ideal body weight less than 110%, compared with greater than 110%, survived longer. Relationships were identified between prednisone dose and weight, cumulative prednisone dose and weight, and weight change and change in total cholesterol level 1 year following transplantation. Multivariate analysis showed cumulative prednisone as an independent predictor of weight. Obesity and hypercholesterolemia were significant problems within 3 months of transplantation. Although prednisone dosage should be adjusted to the lowest possible dose, dietary and lifestyle changes remain the foundation of effective management of these posttransplant complications.

Derivatives of the triazoloquinazoline adenosine antagonist (CGS 15943) having high potency at the human A2B and A3 receptor subtypes

The adenosine antagonist 9-chloro-2-(2-furanyl)[1,2,4]triazolo[1, 5-c]quinazolin-5-amine (CGS 15943) binds nonselectively to human A1, A2A, and A3 receptors with high affinity. Acylated derivatives and one alkyl derivative of the 5-amino group and other modifications were prepared in an effort to enhance A2B or A3 subtype potency. In general, distal modifications of the N5-substituent were highly modulatory to potency and selectivity at adenosine receptors, as determined in radioligand binding assays at rat brain A1 and A2A receptors and at recombinant human A3 receptors. In Chinese hamster ovary cells stably transfected with human A2B receptor cDNA, inhibition of agonist-induced cyclic AMP production was measured. An N5-(2-iodophenyl)acetyl derivative was highly selective for A2A receptors. An (R)-N5-alpha-methyl(phenylacetyl) derivative was the most potent derivative at A3 receptors, with a Ki value of 0.36 nM. A bulky N5-diphenylacetyl derivative, 13, displayed a Ki value of 0. 59 nM at human A3 receptors and was moderately selective for that subtype. Thus, a large, nondiscriminating hydrophobic region occurs in the A3 receptor in proximity to the N5-substituent. A series of straight-chain N5-aminoalkylacyl derivatives demonstrated that for A2B receptors the optimal chain length occurs with three methylene groups, i.e., the N5-gamma-aminobutyryl derivative 27 which had a pA2 value of 8.0 but was not selective for A2B receptors. At A1, A2A, and A3 receptors however the optimum occurs with four methylene groups. An N5-pivaloyl derivative, which was less potent than 27 at A1, A2A, and A3 receptors, retained moderate potency at A2B receptors. A molecular model of the 27-A2B receptor complex based on the structure of rhodopsin utilizing a "cross-docking" procedure was developed in order to visualize the environment of the ligand binding site.