Impact of Donor-Transmitted Atherosclerosis on Early Cardiac Allograft Vasculopathy: New Findings by Three-Dimensional Intravascular Ultrasound Analysis

Donor Selection for Heart Transplantation in 2025

The number of candidates on the waiting list for heart transplantation (HT) continues to far outweigh the number of available organs, and the donor heart nonuse rate in the United States remains significantly higher than that of other regions such as Europe. Although predicting outcomes in HT remains challenging, our overall understanding of the factors that play a role in post-HT outcomes continues to grow. We observe that many donor risk factors that are deemed "high-risk" do not necessarily always adversely affect post-HT outcomes, but are in fact nuanced and interact with other donor and recipient risk factors. The field of HT continues to evolve, with ongoing development of technologies for organ preservation during transport, expansion of the practice of donation after circulatory death, and proposed changes to organ allocation policy. As such, the field must continue to refine its processes for donor selection and risk prediction in HT.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Donor heart selection: Evidence-based guidelines for providers

The proposed donor heart selection guidelines provide evidence-based and expert-consensus recommendations for the selection of donor hearts following brain death. These recommendations were compiled by an international panel of experts based on an extensive literature review.

Paediatric heart transplantation recipients ≥7 years of age receiving donors with pre-existing coronary atherosclerosis showed progressive coronary artery disease

BACKGROUND

This study aimed to determine the effect of donor-transmitted atherosclerosis on the late aggravation of cardiac allograft vasculopathy in paediatric heart recipients aged ≥7 years.

METHODS

In total, 48 patients were included and 23 had donor-transmitted atherosclerosis (baseline maximal intimal thickness of >0.5 mm on intravascular ultrasonography). Logistic regression analyses were performed to identify risk factors for donor-transmitted atherosclerosis. Rates of survival free from the late aggravation of cardiac allograft vasculopathy (new or worsening cardiac allograft vasculopathy on following angiograms, starting 1 year after transplantation) in each patient group were estimated using the Kaplan-Meier method and compared using the log-rank test. The effect of the results of intravascular ultrasonography at 1 year after transplantation on the late aggravation of cardiac allograft vasculopathy, correcting for possible covariates including donor-transmitted atherosclerosis, was examined using the Cox proportional hazards model.

RESULTS

The mean follow-up duration after transplantation was 5.97 ± 3.58 years. The log-rank test showed that patients with donor-transmitted atherosclerosis had worse survival outcomes than those without (p = 0.008). Per the multivariate model considering the difference of maximal intimal thickness between baseline and 1 year following transplantation (hazard ratio, 22.985; 95% confidence interval, 1.948-271.250; p = 0.013), donor-transmitted atherosclerosis was a significant covariate (hazard ratio, 4.013; 95% confidence interval, 1.047-15.376; p = 0.043).

CONCLUSION

Paediatric heart transplantation recipients with donor-transmitted atherosclerosis aged ≥7 years had worse late cardiac allograft vasculopathy aggravation-free survival outcomes.

Prognostic value of comprehensive intracoronary physiology assessment early after heart transplantation

AIMS

We evaluated the long-term prognostic value of invasively assessing coronary physiology after heart transplantation in a large multicentre registry.

METHODS AND RESULTS

Comprehensive intracoronary physiology assessment measuring fractional flow reserve (FFR), the index of microcirculatory resistance (IMR), and coronary flow reserve (CFR) was performed in 254 patients at baseline (a median of 7.2 weeks) and in 240 patients at 1 year after transplantation (199 patients had both baseline and 1-year measurement). Patients were classified into those with normal physiology, reduced FFR (FFR ≤ 0.80), and microvascular dysfunction (either IMR ≥ 25 or CFR ≤ 2.0 with FFR > 0.80). The primary outcome was the composite of death or re-transplantation at 10 years. At baseline, 5.5% had reduced FFR; 36.6% had microvascular dysfunction. Baseline reduced FFR [adjusted hazard ratio (aHR) 2.33, 95% confidence interval (CI) 0.88-6.15; P = 0.088] and microvascular dysfunction (aHR 0.88, 95% CI 0.44-1.79; P = 0.73) were not predictors of death and re-transplantation at 10 years. At 1 year, 5.0% had reduced FFR; 23.8% had microvascular dysfunction. One-year reduced FFR (aHR 2.98, 95% CI 1.13-7.87; P = 0.028) and microvascular dysfunction (aHR 2.33, 95% CI 1.19-4.59; P = 0.015) were associated with significantly increased risk of death or re-transplantation at 10 years. Invasive measures of coronary physiology improved the prognostic performance of clinical variables (χ2 improvement: 7.41, P = 0.006). However, intravascular ultrasound-derived changes in maximal intimal thickness were not predictive of outcomes.

CONCLUSION

Abnormal coronary physiology 1 year after heart transplantation was common and was a significant predictor of death or re-transplantation at 10 years.

Validation of multiparametric rubidium-82 PET myocardial blood flow quantification for cardiac allograft vasculopathy surveillance

BACKGROUND

We previously demonstrated high diagnostic accuracy of Rubidium-82 positron emission tomography (PET) myocardial blood flow (MBF) quantification for CAV. The purpose of this study was to validate multiparametric PET detection of CAV by combined rate-pressure-product-corrected myocardial flow reserve (cMFR), stress MBF, and coronary vascular resistance (CVR) assessment.

METHODS AND RESULTS

Diagnostic CAV cut-offs of cMFR < 2.9, stress MBF < 2.3, CVR > 55 determined in a previous study (derivation) were assessed in heart transplant recipients referred for coronary angiography and intravascular ultrasound (IVUS) (validation). CAV was defined as International Society of Heart and Lung Transplantation CAV1-3 on angiography; and maximal intimal thickness ≥ 0.5 mm on IVUS. Eighty patients (derivation n = 40, validation n = 40) were included: 80% male, mean age 54±14 years, 4.5±5.6 years post transplant. The prevalence of CAV was 44% on angiography and 78% on IVUS. Combined PET cMFR < 2.9, stress MBF < 2.3, CVR > 55 CAV assessment yielded high 88% (specificity 75%) and 83% (specificity 40%) sensitivity for ≥ 1 abnormal parameter and high 88% (sensitivity 59%) and 90% (sensitivity 43%) specificity for 3 abnormal parameters, in the derivation and validation cohorts, respectively.

CONCLUSION

We validate the diagnostic accuracy of multiparametric PET flow quantification by cMFR, stress MBF, and CVR for CAV.

Initial Intravascular Ultrasound Without a Routine Early Baseline Study in the Evaluation of Cardiac Transplant Vasculopathy has Prognostic Valve

BACKGROUND

Abnormal minimal intimal thickening (MIT) on intravascular ultrasound (IVUS) defined as difference of ≥0.5 mm between baseline and one-year post-transplantation has been shown to have prognostic value. The goal of this retrospective cohort study was to evaluate whether abnormal MIT found on routine IVUS studies in cardiac transplant patients after 6 months without an early baseline study (modified MIT or MMIT), has any prognostic value. Furthermore, we evaluated the prognostic effect of serial IVUS performed beyond one year.

METHODS

A cohort of 149 cardiac transplant patients who underwent IVUS examination > 6 months post-transplant were evaluated retrospectively. Of these 149 patients, 109 patients underwent a subsequent IVUS study approximately 1 year following the initial study. MMIT values of ≥0.5 mm without an early baseline study were correlated with major adverse cardiac event (MACE).

RESULTS

The all-cause mortality was 4.7% (5/107) in patients with MMIT of <0.5 mm vs. 14.6% (6/41) in patients with MMIT of ≥0.5 mm [hazards ratio (HR): 3.2; 95% confidence interval (CI): 1.002-12.17; p = 0.039]. The overall MACE rate was 8.4% (9/107) in patients with MMIT of <0.5 mm vs. 24.4% (10/41) in patients with MMIT of ≥0.5 mm [HR: 6.7; 95% CI: 1.30-9.42; p = 0.009]. After adjusting for age, abnormal MMIT remained a significant independent predictor of MACE (HR: 3.93; CI 1.21-12.81; p = 0.023).

CONCLUSIONS

The presence of abnormal MMIT noted on IVUS performed after 6 months post-transplantation without a routine baseline IVUS carries important prognostic value.

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.

Percutaneous Coronary Intervention and Coronary Artery Bypass Grafting in Heart Transplant Recipients With Transplant Coronary Arterial Vasculopathy

BACKGROUND

Transplant coronary arterial vasculopathy (TCAV) is a major cause of death after heart transplantation (HTx). Palliative coronary revascularization has been attempted in patients with severe TCAV; however, the outcome has not been fully elucidated.

METHODS

Ninety-six patients who were treated after HTx at our institute between 1999 and 2015 were screened for TCAV. TCAV was defined as >70% stenosis on coronary angiography (CAG) or a maximal intimal thickness of >0.5 mm in the right or left coronary arteries on intracoronary ultrasonography (IVUS). In the present study, the outcomes of patients with severe TCAV who underwent percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) were investigated.

RESULTS

TCAV containing donor-transmitted atherosclerosis was cumulatively found in 69 patients (71.9% of the total; mean age, 34.6 ± 13.1 years; 52 men; mean follow-up duration, 83.0 ± 60.4 months). Five (7.2%) and 64 (92.8%) of the 69 patients were diagnosed as having TCAV by use of CAG and IVUS, respectively. All 5 patients diagnosed by with the use of CAG underwent coronary revascularization between 1 and 236 months after HTx. Three patients underwent PCI with drug-eluting stents, with a primary success rate of 100%. No angiographic restenosis occurred in 2 patients at 31 and 36 months after PCI, respectively. Meanwhile, 2 patients underwent CABG. No peri-operative complications occurred, and all grafts were patent as assessed by use of CAG at 34 and 5 months after CABG.

CONCLUSIONS

Coronary revascularization was feasible and effective for severe TCAV with middle-term follow-up.

Intravascular Ultrasonic Imaging of Coronary Arterial Remodeling in Heart Transplant Recipients

The purpose of this study was to evaluate long-term changes of transplant coronary arteries, including vessel, plaque, and lumen areas. There are limited long-term data on vessel remodeling after heart transplantation. We analyzed serial intravascular ultrasound images of the left anterior descending coronary artery (LAD) in 54 heart transplantation recipients. Nine patients (16.7%) had a history of rejection. Proximal left anterior descending artery segments were matched among time points, a ≥20-mm long segment was analyzed every 1 mm, and results were normalized for analysis length and reported as mm(3)/mm. During follow-up, vessel area decreased (-0.48 ± 1.3 mm(3)/mm/year), and plaque area did not change (-0.01 ± 0.47 mm(3)/mm/year). As a result, lumen area decreased (-0.52 ± 1.34 mm(3)/mm/year). The change in mean lumen area was well correlated to the change in mean vessel area (r = 0.94, p <0.01) but not to the change in mean plaque area (r = -0.27, p = 0.05). In conclusion, lumen loss occurred during long-term follow-up of patients who underwent heart transplantation, primarily secondary to negative remodeling (decrease in vessel dimensions).

Reduced progression of cardiac allograft vasculopathy with routine use of induction therapy with basiliximab

Background

Cardiac allograft vasculopathy (CAV) is a major limitation for long-term survival of patients undergoing heart transplantation (HT). Some immunosuppressants can reduce the risk of CAV.

Objectives

The primary objective was to evaluate the variation in the volumetric growth of the intimal layer measured by intracoronary ultrasound (IVUS) after 1 year in patients who received basiliximab compared with that in a control group.

Methods

Thirteen patients treated at a single center between 2007 and 2009 were analyzed retrospectively. Evaluations were performed with IVUS, measuring the volume of a coronary segment within the first 30 days and 1 year after HT. Vasculopathy was characterized by the volume of the intima of the vessel.

Results

Thirteen patients included (7 in the basiliximab group and 6 in the control group). On IVUS assessment, the control group was found to have greater vessel volume (120–185.43 mm³ vs. 127.77–131.32 mm3; p = 0.051). Intimal layer growth (i.e., CAV) was also higher in the control group (27.30–49.15 mm³ [∆80%] vs. 20.23–26.69 mm³ [∆33%]; p = 0.015). Univariate regression analysis revealed that plaque volume and prior atherosclerosis of the donor were not related to intima growth (r = 0.15, p = 0.96), whereas positive remodeling was directly proportional to the volumetric growth of the intima (r = 0.85, p < 0.001).

Conclusion

Routine induction therapy with basiliximab was associated with reduced growth of the intima of the vessel during the first year after HT.

Everolimus initiation and early calcineurin inhibitor withdrawal in heart transplant recipients: a randomized trial

In a randomized, open-label trial, everolimus was compared to cyclosporine in 115 de novo heart transplant recipients. Patients were assigned within 5 days posttransplant to low-exposure everolimus (3–6 ng/mL) with reduced-exposure cyclosporine (n = 56), or standard-exposure cyclosporine (n = 59), with both mycophenolate mofetil and corticosteroids. In the everolimus group, cyclosporine was withdrawn after 7–11 weeks and everolimus exposure increased (6–10 ng/mL). The primary efficacy end point, measured GFR at 12 months posttransplant, was significantly higher with everolimus versus cyclosporine (mean ± SD: 79.8 ± 17.7 mL/min/1.73 m2 vs. 61.5 ± 19.6 mL/min/1.73 m2; p < 0.001). Coronary intravascular ultrasound showed that the mean increase in maximal intimal thickness was smaller (0.03 mm [95% CI 0.01, 0.05 mm] vs. 0.08 mm [95% CI 0.05, 0.12 mm], p = 0.03), and the incidence of cardiac allograft vasculopathy (CAV) was lower (50.0% vs. 64.6%, p = 0.003), with everolimus versus cyclosporine at month 12. Biopsy-proven acute rejection after weeks 7–11 was more frequent with everolimus (p = 0.03). Left ventricular function was not inferior with everolimus versus cyclosporine. Cytomegalovirus infection was less common with everolimus (5.4% vs. 30.5%, p < 0.001); the incidence of bacterial infection was similar. In conclusion, everolimus-based immunosuppression with early elimination of cyclosporine markedly improved renal function after heart transplantation. Since postoperative safety was not jeopardized and development of CAV was attenuated, this strategy may benefit long-term outcome.