Progression Of Cardiac Allograft Vasculopathy Research Articles

Cardiac allograft vasculopathy in pediatric heart transplant recipients does early-onset portend a worse prognosis?

We sought to evaluate the association between timing of cardiac allograft vasculopathy (CAV) occurrence post-heart transplant (HT) with graft survival and progression of CAV severity in pediatric HT recipients. Data from the Pediatric Heart Transplant Society for pediatric (<18 years old) HT recipients between 1993-2019 with available angiographic data were obtained (N=5,075). The timing of CAV diagnosis (<3; 3-<5; 5-<10; and ≥10 years post-HT) and severity of disease at each assessment (CAV 1-3) was determined. Associations between CAV timing, graft survival, and CAV progression were evaluated using Kaplan-Meier survival curves, multivariable COX proportional hazard regression analyses, and competing risk analyses. Over a median follow-up period of 4.1 (IQR 1.3-8.3) years, CAV was identified in 17% (885/5,075), 28% (252/885) of which were early-onset CAV. Compared with late onset CAV ≥10 years post-HT, patients with early CAV were older at the time of transplant (8.3 ± 6.2 vs. 3.8 ± 4.8 years, p < .0001). While the five-year graft-survival in the ≥10-year group (79.2%, p=0.03) was significantly higher than the <3, 3-<5, and 5-<10 years post-HT groups (65.0%-67%) (p=0.03), overall post-CAV graft survival was not significantly different across the CAV time-points. CAV disease progression did not vary with CAV timing post-HT, with an overall five-year freedom from CAV ≥2 of 75.4% (73.1%-77.6%). Later onset CAV (≥10-years post-HT) was associated with improved five-year graft survival compared with CAV onset at earlier time-points, but similar and poor long-term outcomes. CAV timing post-HT was not associated with progression of CAV disease severity.

Utility of High Sensitivity Troponin I to Monitor Cardiac Allograft Vasculopathy Progression

<h3>Purpose</h3> To determine whether high sensitivity troponin I (hsTnI) levels are associated with progression of cardiac allograft vasculopathy (CAV). <h3>Methods</h3> Heart transplant recipients undergoing surveillance coronary angiograms for CAV had hsTnI levels measured (Abbott Laboratories). CAV was graded according to ISHLT classification. CAV progression was defined as an increase in CAV grade compared to the prior angiogram. The associations between baseline (BL) hsTnI, hsTnI at serial evaluation, and the change in hsTnI levels between angiograms versus CAV progression were compared using Kruskal-Wallis test. Age, age at transplant, sex, BMI, race, smoking, diabetes, hypertension, cholesterol, and creatinine were assessed as potential covariates. <h3>Results</h3> In 136 patients (mean age 54, 80% male), baseline angiograms and 173 serial angiograms were evaluated, and 68 (39%) identified CAV progression. Baseline testing occurred 11.2 years after transplant (interquartile range 5.9 - 15.9 years) and the median time between evaluations was 3.0 years. The BL hsTnI was similar (median 4.60 pg/mL in progressors, 4.35 in non-progressors). In patients with progression, the median hsTnI level was 5.55 pg/mL compared to 4.35 pg/mL in patients without progression (p=0.011). The change in hsTnI level was also greater in progressors compared to non-progressors (1.30 vs. 0.25 pg/mL, p=0.015). Creatinine did not differ significantly between groups (median 1.5 vs 1.4 mg/dL). In a multivariate analysis including smoking history, BMI, total cholesterol, BL hsTnI, hsTnI, and change in hsTnI, CAV progression was associated with smoking history, BMI, and hsTnI (p=0.042), but associations with BL hsTnI (p=0.053) and change in hsTnI (p=0.076) were not statistically significant. <h3>Conclusion</h3> Serial hsTnI measurements may be useful in transplant recipients to identify CAV progression. Further study is needed to determine if serial hsTnI measurements can be used to obviate the need for routine angiography to detect CAV progression.

Safety and Efficacy of SGLT2i Post Orthotopic Heart Transplantation

<h3>Purpose</h3> Diabetes mellitus is common after orthotopic heart transplantation (OHT) due to steroid-induced hyperglycemia. Traditionally, it has been treated using parenteral insulin therapy. The use of sodium-glucose co-transporter 2 inhibitors (SGLT2i) in OHT recipients is not well established. <h3>Methods</h3> A retrospective chart review was performed on all the patients who underwent OHT at our center to identify patients on SGT2i post OHT. Clinical outcomes pre and post SGLT2i therapy were compared using the student t-test. <h3>Results</h3> Out of the 455 patients who had OHT at our single institution, 26 patients were on SGLT2i post OHT (1 patient was dual organ recipient - heart and liver transplant). The baseline characteristics are reported in Table 1. The median days from OHT to initiation of SGLT2i was 780 days (range 40-4986 days), and the median duration of therapy post-OHT was 169 days (range 38-2474 days). There was a statistically significant improvement in the average hemoglobin A1c, weight, and body mass index after starting SGLT2i (Results table). There was a trend towards improving renal function. There was no incidence of systemic infection, hypoglycemia, amputation, or euglycemic diabetic ketoacidosis while on SGLT2i. Two patients were able to discontinue insulin therapy after starting SGLT2i. There was no incidence or progression of cardiac allograft vasculopathy during the therapy. Two patients experienced graft rejection (1Antibody Mediated Rejection and 1 Acute Cellular Rejection) with drop in left ventricular systolic function that recovered after appropriate treatment. <h3>Conclusion</h3> SGLT2i can be used safely in OHT recipients. The renal protective mechanism of SGLT2i could be helpful to combat the nephrotoxicity of calcineurin inhibitors (CNI) used for immunosuppression and help prolong the use of CNI. Further randomized studies are required to explore the complete benefits of SGLT2i in OHT recipients

Single-Nuclear RNA-Sequencing Identifies Cell-Specific Transcriptional Programs in Cardiac Allograft Vasculopathy

<h3>Purpose</h3> Cardiac allograft vasculopathy (CAV) is the leading cause of late graft failure and mortality after heart transplantation (HT). Current therapies have limited efficacy in preventing or stalling the progression of CAV. Improved understanding of CAV biology is needed to identify novel therapeutics. <h3>Methods</h3> We performed single-nuclear RNA sequencing (snRNA-seq) on human cardiac tissue obtained by endomyocardial biopsy from the right ventricle of 3 HT recipients without CAV and at the time of heart explant in 3 HT recipients with severe CAV. Differentially expressed genes (DEGs) between cohorts were identified with DESeq2 using a 5% false discovery rate threshold for significant genes. <h3>Results</h3> Unsupervised clustering of 38,211 nuclei identified 15 major cell types (Figure A). Relative to cells from non-CAV hearts, endothelial cells and fibroblasts from hearts with severe CAV showed enrichment for genes and pathways associated with inflammation, angiogenesis, and extracellular matrix organization (Figure B and C; endothelial cells). Intersecting these DEGs with the druggable genome identified novel cell-specific drug targets. <h3>Conclusion</h3> We show feasibility of performing snRNA-seq from human endomyocardial biopsy samples and identify cell-specific transcriptional programs that are unique to patients with severe CAV. These data lay the groundwork for larger-scale studies that can accelerate mechanistic understanding of CAV development.

Long-Term Changes in the Coronary Artery Structure After Heart Transplantation: A Prospective Optical Coherence Tomography Study

<h3>Purpose</h3> Optical coherence tomography (OCT) enables detailed characterization of plaque composition in cardiac allograft vasculopathy (CAV) after heart transplantation (HTx). Using serial OCT scans, our research group previously demonstrated that early CAV is characterized by intimal thickening strongly associated with layered fibrotic plaques (LFPs) progression. Early changes after HTx are well-described, whereas no serial OCT studies in long-term HTx patients have been performed. We aimed to describe and characterize late changes in the coronary artery microstructure after HTx. <h3>Methods</h3> In 134 vessels from 56 long-term HTx patients (median 8.3 years), we performed OCT scans of the major coronary arteries in relation to routine annual coronary angiography at baseline and after 12 months. We contoured the vessel layers for absolute and relative measurements. Lipid plaques, calcified plaques, bright spots, and LFPs were analyzed by delineating circumferential borders and measuring angulation of total circumference. <h3>Results</h3> A total of 15.634 frames were analyzed. Mean intima area increased significantly (2.8 [1.9 to 4.4] mm² vs. 3.0 [2.0 to 4.5] mm², <i>p</i> <0.01) and mean lumen area decreased significantly (8.7 [6.9 to 10.3] mm² vs. 8.4 [6.8 to 10.3] mm², <i>p</i><0.05) during follow-up. A high prevalence of LFPs was observed and the extent increased 14 % during follow-up (38.0 [22.7 to 65.9] % vs. 43.4 [25.1 to 67.7] %, <i>p</i><0.0001). A low prevalence of lipid plaques was observed (0.65% [0.34% to 1.48%] vs. 0.71% [0.16% to 2.27%], <i>p</i>=0.11). We found no difference in the extent of bright spots (<i>p</i>=0.99), calcified plaques (<i>p</i>=0.60) or mean media area (<i>p</i>=0.23) during follow-up. <h3>Conclusion</h3> LFPs are highly prevalent in long-term HTx patients. Late progression of CAV is similar to the findings early after HTx with intimal thickening primarily characterized by progression of LFPs. In contrast, the extent of bright spots and calcified plaques remained stable, and lipid plaques were rarely observed.

Analysis of Fibrotic Plaques in Angiographic Manifest Cardiac Allograft Vasculopathy in Long-term Heart Transplanted Patients Using Optical Coherence Tomography

The development and progression of cardiac allograft vasculopathy documented by coronary angiography (CAVangio) after heart transplantation (HTx) has prognostic relevance. Yet there are limited data regarding the role of concomitant intracoronary imaging in the presence CAVangio. In particular, atherosclerotic plaques might represent a potential target for prevention, but their impact on stenosis is understudied. We used high-resolution intracoronary optical coherence tomography (OCT) to quantify and compare findings of intimal hyperplasia (IH) and plaque morphologies in HTx patients (fibrotic plaque, lipid plaque, and calcified plaque). OCT findings were related to the presence of CAVangio as well as to the severity of stenosis. We included 65 consecutive patients into analysis (66% with CAVangio, posttransplant interval 9.9 ± 7.6 y). Fibrotic, lipid, and calcified plaques were present in 41 (63.1%), 39 (60%), and 18 (27.7%) patients, respectively. In addition to IH, the presence of fibrotic, lipid, and calcified plaques was found to be associated with CAVangio. The prevalence of lipid plaque and quantitative measurements of fibrotic plaque increased with stenosis severity (lipid plaque, P < 0.001, maximal and mean fibrotic arc, P = 0.05 and P = 0.001, respectively). Receiver operating characteristic analysis showed that area under the curve of the fibrotic plaque parameter mean fibrotic arc (0.87, 95% confidence interval [0.76-0.99]; P = 0.002) was superior to area under the curve of intima parameters regarding CAVangio. The effect of mean fibrotic arc (r = 0.52, P < 0.001) was relevant regarding stenosis severity. After a longer posttransplant interval, CAV findings in OCT included a combination of IH and atherosclerotic plaques. In addition to IH, the presence of fibrotic, lipid, and calcified plaques is associated with CAVangio. Further studies are warranted to evaluate if the in vivo screening for plaque progress, particularly of fibrotic plaque, could improve individual secondary prevention and outcome in HTx patients.

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<.05]. The change was twofold higher in the MICT group (.6±1.2mm2 ) than in the HIT group (.3±.6mm2 ). However, the treatment effect of HIT was not significant (treatment effect=-.3mm2 , 95% CI [-.825 to .2mm2 ] P=.29). These results suggest that early initiation of HIT compared with MICT does not attenuate CAV progression in de novo HTx recipients.

Effect of Statin Intensity on the Progression of Cardiac Allograft Vasculopathy.

Background: In the non-transplant population, hyperlipidaemia has shifted from targeting LDL goals to statin intensity-based treatment. It is unknown whether this strategy is also beneficial in cardiac transplantation. Methods: This single-centre retrospective study evaluated the effect of statin use and intensity on time to cardiac allograft vasculopathy (CAV) after cardiac transplantation. Kaplan–Meier and Cox proportional hazards regression survival methods were used to assess the association of statin intensity and median post-transplant LDL on CAV-free survival. Results: The study involved 143 adults (71% men, average follow-up of 25 ± 14 months) who underwent transplant between 2013 and 2017. Mean CAV-free survival was 47.5 months (95% CI [43.1–51.8]), with 29 patients having CAV grade 1 or greater. Median LDL was not associated with time to CAV (p=0.790). CAV-free survival did not differ between intensity groups (p=0.435). Conclusion: Given the non-statistically significant difference in time to CAV with higher intensity statins, the data suggest that advancing moderate- or high-intensity statin after cardiac transplantation may not provide additional long-term clinical benefit. Trial registration: Not applicable.

Peripheral microvascular dysfunction is associated with plaque progression and adverse long-term outcomes in heart transplant patients.

AimsCardiac allograft vasculopathy (CAV) is the major cause of increased morbidity and mortality after heart transplantation. Peripheral endothelial dysfunction (PED) is associated with early atherosclerosis and future risk of major adverse cardiovascular events (MACE) in non‐heart transplant population. We aimed to investigate the association of PED with future MACE, and plaque progression assessed by intravascular ultrasound (IVUS) after heart transplantation.Methods and resultsWe included 66 transplant patients who underwent serial IVUS surveillance for CAV and baseline assessment of peripheral endothelial function using reactive hyperaemia peripheral arterial tonometry. PED was defined as reactive hyperaemia index < 2. The primary endpoint of the study was to investigate the association of PED with CAV progression assessed by intravascular ultrasound (IVUS). CAV progression was assessed as the change (Δ) in plaque volume divided by segment length, and Δ plaque index (plaque volume/vessel volume), adjusted for the time between IVUS measurements (median 3.0 [2.2, 3.1] years). The secondary endpoint was to investigate the association between PED and future MACE, which was defined as any incident of revascularization, heart failure hospitalization, stroke, myocardial infarction, re‐transplantation, and death. Patients with PED (n = 27) had more yearly plaque progression (0.50 ± 0.66 vs. 0.15 ± 0.50 mm3/mm/year, P = 0.02) and a higher Δ plaque index (2.41 ± 2.53% vs. 0.69 ± 2.22%, P = 0.01). Patients with PED were more likely to experience MACE during a median follow‐up of 8.2 years (interquartile range [7.6, 8.4]), after adjustment for potential cofounders such as age, high‐density lipoprotein cholesterol levels, total rejection score, baseline International Society for Heart & Lung Transplantation CAV grade, and indication of transplantation. (hazard ratio 2.15, 95% confidence interval [1.09, 4.23], P = 0.03).ConclusionsPeripheral endothelial dysfunction is associated with increased plaque progression and adverse long‐term cardiovascular outcomes in transplant patients. PED assessment might be a useful clinical tool for risk stratification after heart transplantation.

Coronary Flow Velocity Reserve and Myocardial Deformation Predict Long-Term Outcomes in Heart Transplant Recipients

After heart transplantation (HTx), invasive coronary angiography is the gold standard for surveillance of cardiac allograft vasculopathy (CAV). Noninvasive CAV surveillance is desirable. The authors examined left ventricular global longitudinal strain (LVGLS) and noninvasive coronary flow velocity reserve (CFVR) related to CAV and prognosis after HTx. Doppler echocardiographic CFVR and LVGLS were evaluated in 98 HTx patients. All-cause mortality and major adverse cardiac events (MACE), including hospitalization for heart failure, cardiovascular death, and significant CAV progression, were recorded. Median follow-up duration was 3.3years (range: 1.7-5.4years). Patients with low CFVR (<2.0; n=20) showed reduced MACE-free survival (hazard ratio, 4.3; 95% CI, 2.2-8.4; P<.0001) and increased all-cause mortality (hazard ratio: 4.7; 95% CI: 2.0-11.3; P<.0001) compared with patients with high CFVR (≥2.0; n=78). Worsened LVGLS (≥-15.5%) was also a strong independent predictor of MACE and cardiovascular and all-cause mortality. Combined low CFVR and worsened LVGLS provided incremental prognostic value, even after adjustment for CAV and time since HTx. The prevalence of low CFVR increased significantly with CAV severity, and the prevalence of combined low CFVR and/or worsened LVGLS was high in patients with moderate CAV (86%) and those with severe CAV (83%). The negative predictive value of combined high CFVR and improved LVGLS to rule out significant CAV was 94.5% (95% CI, 86.2%-98.4%), whereas the positive predictive value was 39.0% (95% CI, 25.3%-54.3%). The model had sensitivity of 84.2% (95% CI, 63.6%-95.3%) and specificity of 67.5% (95% CI, 56.6%-77.2%) for one or more abnormal parameters. In HTx patients with severe CAV, a higher prevalence of low CFVR and worsened LVGLS was observed. Both measurements were strong independent predictors of MACE and all-cause mortality in HTx patients. Combined CFVR and LVGLS provided incremental prognostic value and showed an excellent ability to rule out significant CAV and may be considered as part of routine CAV surveillance of HTx patients.

Oxygen-sensitive Magnetic Resonance Imaging: A Noninvasive Step Forward for Diagnosing Vasculopathy in the Cardiac Allograft.

Oxygen-sensitive Magnetic Resonance Imaging: A Noninvasive Step Forward for Diagnosing Vasculopathy in the Cardiac Allograft.

Circulating progenitor cells are associated with plaque progression and long-term outcomes in heart transplant patients.

Circulating progenitor cells (CPCs) play a role in vascular repair and plaque stability, while osteocalcin (OC) expressing CPCs have been linked to unstable plaque and adverse cardiovascular outcomes. However, their role in cardiac allograft vasculopathy (CAV) has not been elucidated. This cohort study aimed to investigate the contribution of CPCs on CAV progression and cardiovascular events after heart transplantation. A total of 80 heart transplant patients (mean age 55 ± 14 years, 72% male) undergoing annual intravascular ultrasound (IVUS) had fresh CPCs marked by CD34, CD133, and OC counted in peripheral blood using flow cytometry, on the same day as baseline IVUS. CAV progression was assessed by IVUS as the change (Δ) in plaque volume divided by segment length (PV/SL), adjusted for the time between IVUS measurements [median 3.0, interquartile range (2.8-3.1) years] and was defined as ΔPV/SL that is above the median ΔPV/SL of study population. Major adverse cardiac events (MACEs) were defined as any incident of revascularization, myocardial infarction, heart failure admission, re-transplantation, stroke, and death. Patients with higher CD34+CD133+ CPCs had a decreased risk of CAV progression [odds ratio 0.58, 95% confidence interval (CI) (0.37-0.92), P = 0.01] and MACE [hazard ratio (HR) 0.79, 95% CI (0.66-0.99), P = 0.05] during a median (interquartile range) follow-up of 8.0 years (7.2-8.3). Contrarily, higher OC+ cell counts were associated with an increased risk of MACE [HR 1.26, 95% CI (1.03-1.57), P = 0.02]. Lower levels of CD34+CD133+ CPCs are associated with plaque progression and adverse long-term outcomes in patients who underwent allograft heart transplantation. In contrast, higher circulating OC+ levels are associated with adverse long-term outcomes. Thus, CPCs might play a role in amelioration of transplant vasculopathy, while OC expression by these cells might play a role in progression.

Association of Aspirin Treatment With Cardiac Allograft Vasculopathy Progression and Adverse Outcomes After Heart Transplantation

BackgroundEnhanced platelet reactivity may play a role in cardiac allograft vasculopathy (CAV) progression. The use of antiplatelet agents after heart transplantation (HT) has been inconsistent and although aspirin (ASA) is often a part of the medication regimen after HT, limited evidence is available on its benefit. Methods and ResultsCAV progression was assessed by measuring the difference in plaque volume and plaque index between the last follow-up and the baseline coronary intravascular ultrasound examination. Overall, 529 HT recipients were retrospectively analyzed (337 had ≥2 intravascular ultrasound studies). The progression in plaque volume (P = .007) and plaque index (P = .002) was significantly attenuated among patients treated with early ASA (within the first year after HT). Over a 6.7-year follow-up, all-cause mortality was lower with early ASA compared with late or no ASA use (P < .001). No cardiac deaths were observed in the early ASA group, and the risk of CAV-related graft dysfunction was significantly lower in this group (P = .03). However, the composite of all CAV-related events (cardiac death, CAV-related graft dysfunction, or coronary angioplasty) was not significantly different between the groups (P = .16). ConclusionsEarly ASA use after HT may delay CAV progression and decrease mortality and CAV-related graft dysfunction, but does not seem to affect overall CAV-associated events.

Cardiac Allograft Vasculopathy in Pediatric Heart Transplant Recipients: Does Early Onset Portend a Worse Prognosis?

<h3>Purpose</h3> We sought to evaluate the association between early-onset cardiac allograft vasculopathy (CAV) [<3 years post heart transplant (HT)] & graft survival (freedom from death & re-transplantation), compared with CAV development at later time-points in pediatric HT recipients. <h3>Methods</h3> Data from the Pediatric Heart Transplant Society (PHTS) for pediatric (<18 years old) HT recipients between 1993-2019 with available angiographic data were obtained (N = 5,075). Patients with a diagnosis of CAV were categorized according to the timing of disease post-HT; <3 years; 3-<5 years; 5-<10 years; & ≥10 years. CAV severity was graded at each assessment (CAV 1-3). Kaplan-Meier survival curves were generated to evaluate the association between CAV timing & graft survival (primary outcome). A competing risk analysis was used to evaluate the association between CAV timing & the progression of CAV severity (secondary outcome). <h3>Results</h3> Over a median follow-up period of 4.1 (IQR 1.3 - 8.3) years, angiographic evidence of CAV was identified in 17% (885/5,075) of patients, 28% (252/885) of which were early-onset CAV. Compared to those who developed CAV >10 years post HT, patients with early-onset CAV were older at transplant (8.3 +/- 6.2 vs. 3.8 +/- 4.8 years, p < .0001). Five-year graft survival following CAV diagnosis at any time point was 68.7% (66.8% - 70.4%). Graft survival post-CAV diagnosis was not significantly different for early-onset CAV compared with CAV at later time points (Figure). For patients with CAV-1, freedom from progression to CAV-2 did not vary according to the timing of CAV onset, with an overall five-year freedom from CAV-2 of 75.4% (73.1%-77.6%). <h3>Conclusion</h3> Following diagnosis, the progression of CAV & graft survival was similar for patients with early-onset CAV compared with CAV at other time points. These findings suggest that early-onset CAV does not necessarily represent a more aggressive phenotype of disease.

Low-Density Lipoprotein Cholesterol Trends and the Development of Cardiac Allograft Vasculopathy after Heart Transplantation

<h3>Purpose</h3> The relationship between low-density lipoprotein cholesterol (LDL-C) and cardiac allograft vasculopathy (CAV) is unclear. The objectives of this study were to characterize lipid profiles early after heart transplant (HT), and to evaluate the relationship between early serum LDL-C and the development of CAV. <h3>Methods</h3> We retrospectively reviewed consecutive adults who underwent HT at the University of Ottawa Heart Institute (Ottawa, Canada) and Toronto General Hospital (Toronto, Canada) from 2010-2018. The primary outcome was the incidence of CAV (ISHLT grade 1-3). The relationship between LDL-C and CAV was assessed using Cox proportional hazards and logistic regression models adjusted <i>a priori</i> for clinically important covariates including recipient and donor age, recipient sex, ischemic time and pre-HT diabetes. <h3>Results</h3> 386 patients followed for 4.4 (2.8-6.8) years were included. LDL-C at baseline (2.11±0.86 mmol/L) and at 1-year after HT (2.20±0.88 mmol/L) was similar (p=0.21) but was significantly lower at the end of study follow-up (1.89±0.74 mmol/L) (p<0.01). Of 309 patients who underwent angiography, 54% developed CAV. The risk of CAV did not vary according to baseline, 1-year or change from baseline to 1-year pre-specified LDL-C thresholds (Figure). The odds of CAV at 1-year was equally likely across LDL-C values (adjusted OR 1.00, 95% CI: 0.61-1.63 for baseline and adjusted OR 1.25, 95% CI: 0.74-2.10 for 1-year LDL-C). <h3>Conclusion</h3> There was no relationship between early LDL-C and the development of CAV after HT. Our findings do not support targeting a specific LDL-C for patients who do not otherwise meet criteria for non-HT guideline recommended LDL-C targets. Randomized studies are warranted to determine if lipid-lowering to a specific LDL-C target decreases the development and progression of CAV.

Is Donor-Derived Cell Free DNA a Useful Biomarker of Cardiac Allograft Vasculopathy? (FreeDNA-CAV Study)

<h3>Purpose</h3> To evaluate the performance of Donor-derived Cell Free DNA (ddcf-DNA) as a biomarker of cardiac allograft vasculopathy (CAV) in a cohort of heart transplant (HT) recipients undergoing routine coronary angiography. <h3>Methods</h3> We prospectively obtained ddcf-DNA levels in all patients who underwent routine coronary angiography > 1 year after HT in our center between Jan 2019 and Sept 2020. Patients with concomitant acute rejection (n=10), circulating HLA-antibodies (n=1) or multiorgan transplant (n=8) were excluded. Ddcf-DNA levels were correlated with CAV degree (ISHLT 2010 classification). <h3>Results</h3> We included 82 HT recipients, median age 56 years (IQR 49.3-66), 68% men, a median of 10 years (IQR 4.2-17.7) after transplant. Coronary angiogram revealed CAV0 in 68%, CAV1 in 13%, CAV2 in 5% and CAV3 in 13%. Median ddcf-DNA values in each group are shown in Figure 1A. Ddcf-DNA levels did not differ significantly between patients with and without CAV (Table 1 and Figure 1B). No significant differences were found between patients with "stable CAV" (no new significant coronary lesions since previous angiogram, n=67) and "progressive CAV" (those with new coronary stenosis, n=15), median values were 0.8% (IQR 0.26-2.0) and 0.87% (IQR 0.12-4.2) respectively, p=0.635 (Figure 1C). No correlation was found between ddcf-DNA and troponin I (ρ=0.086, p=0.568) or NTproBNP levels (ρ=-0.137, p=0.238). <h3>Conclusion</h3> In this preliminary experience, ddcf-DNA level did not seem to correlate with CAV presence, severity or progression. We hope that ongoing recruiting will help to establish a definitive conclusion in this topic.

Predicting Cardiac Allograft Vasculopathy Profiles Using Machine Learning Clustering

<h3>Purpose</h3> Cardiac Allograft Vasculopathy (CAV) is the leading cause of graft dysfunction in heart transplantation (HT). Identifying CAV profiles is critical in determining the intensity of surveillance required to appropriately prevent and treat this complication. We sought to identify CAV profiles using maximal intimal thickness (MIT) and a latent-class mixed-effect regression model. <h3>Methods</h3> This analysis includes an adult HT patients from a single centre from 2010 to 2018. Latent class mixed-effect regression models were used to simultaneously identify latent classes (or clusters) of MIT trajectories post-HT and to quantify risk factors associated with the cluster membership. The outcome of interest was MIT from baseline (0-6 months) to 5 years after HT. We considered recipient and donor age, sex, and ischemic time as risk factors. We subsequently characterized the association between the clusters and ISHLT CAV grade using a competing risk model. <h3>Results</h3> Overall 186 consecutive adult HT recipients, predominantly male (70%), Caucasian (58%), 54 (43-61) years of age were included. In a covariate-adjusted model, 4 CAV profiles were identified (Figure 1A). Class 1 and 2 consisted of patients with stable MIT over time; patients in Class 3 and 4 experienced elevated MIT. Patients in Class 3 had a lower MIT and slower progression than those in Class 4. There were significant between-class differences in recipient age (p=0.002), recipient sex (p=<0.001), ischemic time (p<0.001), and donor age (p<0.004). Moreover, Figure 1B shows that recipients in Class 3 and 4 had a significantly higher proportion of CAV at 5 years compared to Class 1 and 2 (p< 0.001). <h3>Conclusion</h3> This work builds on previous ML models to differentiate trajectories of CAV using MIT. In our model, MIT at baseline and year-1, in addition to baseline demographics, can be used to discriminate the progression of CAV at 5 years. Recipients in CAV Class 3 and 4 would benefit from more intensive surveillance and early CAV directed therapies.

Coronary Flow Reserve Predicts Major Adverse Cardiac Events and All-Cause Mortality in Heart Transplant Recipients

<h3>Purpose</h3> Cardiac allograft vasculopathy (CAV) after heart transplantation (HTx) affects the epicardial arteries and veins and also the coronary microcirculation. In the absence of proximal epicardial artery stenosis, coronary flow velocity reserve (CFVR) reflects the function of the myocardial microcirculation. We aimed to determine the prognostic value of 1) CFVR and 2) a combination of CFVR and left ventricular global longitudinal strain (LVGLS) in HTx patients. <h3>Methods</h3> CFVR was evaluated using pulsed wave Doppler echocardiography in 98 HTx patients (median 6.9 years from HTx) examined with coronary angiography. Patients were enrolled from 2013 to 2018 and prospectively followed until June 1^st 2020. All-cause mortality and major adverse cardiac events (MACE) including heart failure, significant CAV progression, coronary intervention or cardiovascular death, were recorded. <h3>Results</h3> Median follow-up was 3.2 [interquartile range 1.9-5.1] years. Patients with low CFVR (<2.0, n=20) had a significantly reduced event-free survival rate compared with patients with high CFVR (≥2.0, n=78) (35% vs. 82%, hazard ratio (HR) 4.6, 95% CI 2.3-9.1, <i>p</i><0.0001) and had a higher rate of mortality than patients with high CFVR with an absolute difference of 43.3% (65.3% vs. 22.0%; HR 5.0, 95% CI 2.1-11.9, <i>p</i><0.0001). By combining low CFVR and low LVGLS magnitude (>-15.5%), we obtained a strong predictive model for MACE (HR 10.5, 95% CI 4.5-24.5, <i>p</i><0.0001) and all-cause mortality (HR 10.3, 95% CI 3.5-30.6, <i>p</i><0.001), which remained strong after adjustment for angiographic CAV. <h3>Conclusion</h3> CFVR strongly predicts MACE and all-cause mortality in HTx-patients. A model combining low CFVR and low LVGLS magnitude was a strong model for MACE and all-cause mortality prediction and could be considered as a non-invasive method for routine CAV surveillance.

Bone marrow-derived AXL tyrosine kinase promotes mitogenic crosstalk and cardiac allograft vasculopathy

Cardiac Allograft Vasculopathy (CAV) is a leading contributor to late transplant rejection. Although implicated, the mechanisms by which bone marrow-derived cells promote CAV remain unclear. Emerging evidence implicates the cell surface receptor tyrosine kinase AXL to be elevated in rejecting human allografts. AXL protein is found on multiple cell types, including bone marrow-derived myeloid cells. The causal role of AXL from this compartment and during transplant is largely unknown. This is important because AXL is a key regulator of myeloid inflammation. Utilizing experimental chimeras deficient in the bone marrow-derived Axl gene, we report that Axl antagonizes cardiac allograft survival and promotes CAV. Flow cytometric and histologic analyses of Axl-deficient transplant recipients revealed reductions in both allograft immune cell accumulation and vascular intimal thickness. Co-culture experiments designed to identify cell-intrinsic functions of Axl uncovered complementary cell-proliferative pathways by which Axl promotes CAV-associated inflammation. Specifically, Axl-deficient myeloid cells were less efficient at increasing the replication of both antigen-specific T cells and vascular smooth muscle cells (VSMCs), the latter a key hallmark of CAV. For the latter, we discovered that Axl-was required to amass the VSMC mitogen Platelet-Derived Growth Factor. Taken together, our studies reveal a new role for myeloid Axl in the progression of CAV and mitogenic crosstalk. Inhibition of AXL-protein, in combination with current standards of care, is a candidate strategy to prolong cardiac allograft survival.

Extracellular HMGB1 Contributes to the Chronic Cardiac Allograft Vasculopathy/Fibrosis by Modulating TGF-β1 Signaling.

Cardiac allograft vasculopathy (CAV) charactered with aberrant remodeling and fibrosis usually leads to the loss of graft after heart transplantation. Our previous work has reported that extracellular high-mobility group box 1 (HMGB1) participated in the CAV progression via promoting inflammatory cells infiltration and immune damage. The aim of this study was to investigate the involvement of HMGB1 in the pathogenesis of CAV/fibrosis and potential mechanisms using a chronic cardiac rejection model in mice. We found high levels of transforming growth factor (TGF)-β1 in cardiac allografts after transplantation. Treatment with HMGB1 neutralizing antibody markedly prolonged the allograft survival accompanied by attenuated fibrosis of cardiac allograft, decreased fibroblasts-to-myofibroblasts conversion, and reduced synthesis and release of TGF-β1. In addition, recombinant HMGB1 stimulation promoted release of active TGF-β1 from cardiac fibroblasts and macrophages in vitro, and subsequent phosphorylation of Smad2 and Smad3 which were downstream of TGF-β1 signaling. These data indicate that HMGB1 contributes to the CAV/fibrosis via promoting the activation of TGF-β1/Smad signaling. Targeting HMGB1 might become a new therapeutic strategy for inhibiting cardiac allograft fibrosis and dysfunction.