Diagnosis of graft coronary artery disease

Imaging of Cardiac Transplantation: An Overview

Heart transplantation (HTx) remains the optimal treatment for selected patients with end-stage advanced heart failure. However, survival is limited early by acute rejection and long term by cardiac allograft vasculopathy (CAV). Even though the diagnosis of rejection is based on histology, cardiac imaging provides a pivotal role for early detection and severity assessment of these hazards. The present review focuses on the use and reliability of different invasive and non-invasive imaging modalities to detect and monitor CAV and rejection after HTx. Coronary angiography remains the corner stone in routine CAV surveillance. However, angiograms are invasive and underestimates the CAV severity especially in the early phase. Intravascular ultrasound and optical coherence tomography are invasive methods for intracoronary imaging that detects early CAV lesions not evident by angiograms. Non-invasive imaging can be divided into myocardial perfusion imaging, anatomical/structural imaging and myocardial functional imaging. The different non-invasive imaging modalities all provide clinical and prognostic information and may have a gatekeeper role for invasive monitoring. Acute rejection and CAV are still significant clinical problems after HTx. No imaging modality provides complete information on graft function, coronary anatomy and myocardial perfusion. However, a combination of invasive and non-invasive modalities at different stages following HTx should be considered for optimal personalized surveillance and risk stratification.

Novel Cytokine Score and Cardiac Allograft Vasculopathy

To date, there are no established noninvasive biomarkers available for prediction of cardiac allograft vasculopathy (CAV) after orthotopic heart transplantation (OHT). Inflammatory processes are supposed to play a central role in the pathogenesis of CAV. Recent studies have suggested that immune mediators could serve as biomarkers for cardiovascular diseases. We hypothesized particular cytokines or a combination thereof may serve as noninvasive biomarkers for CAV. Plasma cytokines were screened from 27 patients with CAV and 27 patients without CAV after OHT. The concentrations of interleukins-4, -6, -10, -21, -23, -31, -33, interferon gamma, tumor necrosis factor alpha, and the soluble activation marker CD40 ligand were determined using Luminex-based multiplex analyses. Although concentrations of all cytokines except interferon gamma were on average higher in the CAV group, there were no significant differences between the groups for any 1 cytokine. Using a binary logistic regression model, we were able to develop a probability score for detecting patients at elevated risk for advanced CAV with a sensitivity of 92.31% and a specificity of 60.71% (receiver-operating characteristic area under the curve 0.799 ± 0.06; p<0.0001). In conclusion, analyzing the concentration of specific inflammatory cytokines could be meaningfully included in evaluation of CAV after OHT.

Applicability of cardiogoniometry as a non-invasive screening tool for the detection of graft vasculopathy in heart transplant recipients

Currently available diagnostic modalities for the detection of graft vasculopathy following orthotopic heart transplantation are subject to various restrictions. We hypothesized that cardiogoniometry, a novel non-invasive diagnostic tool for the detection of atherosclerotic coronary vessel disease, is applicable in the graft vasculopathy setting. Cardiogoniometric results were obtained during routine follow-up in 49 consecutive, unselected heart transplant recipients and then retrospectively correlated blindly by an independent reader to recent angiographic findings. Sensitivity of cardiogoniometry was 100%, specificity 62.3%, positive predictive value 68.75%, negative predictive value 100%, negative likelihood ratio 0 and positive likelihood ratio 2.888. Cardiogoniometry is potentially applicable as an easy-to-perform, non-invasive screening tool predominantly for the exclusion but also for the detection of graft vasculopathy in heart transplant recipients.

Longitudinal Strain and Strain Rate Abnormalities Precede Invasive Diagnosis of Transplant Coronary Artery Vasculopathy in Pediatric Cardiac Transplant Patients

Transplant coronary artery vasculopathy (TCAV) is the primary cause of late graft loss in pediatric heart transplant recipients. TCAV is diagnosed using angiography or intravascular ultrasound; however, noninvasive methods remain elusive. We sought to define patterns of myocardial mechanics in patients with TCAV and to determine whether this can detect TCAV before invasive methods. In this retrospective study, we queried our heart transplant database to identify all recipients with TCAV since 2006 (n = 41). Echoes were reviewed from the last normal catheterization and at TCAV diagnosis, and from time-matched transplant controls (n = 33) without TCAV. Peak global circumferential and longitudinal strain and systolic and diastolic strain rate (SSR and DSR) of the left ventricle were derived using velocity vector imaging. T tests were used to compare both groups longitudinally and between groups at both time points. Longitudinal strain, SSR, and DSR were diminished in the TCAV group compared to the transplant control group at both time points. No differences were found across time points in either group. Retrospective modeling using a longitudinal strain cutoff of 15 % on echoes 2 years prior to TCAV diagnosis predicted development or exclusion of TCAV with sensitivity of 53 %, specificity of 89 % with an area under the curve of 0.8. Decreases in longitudinal strain measurements demonstrate that alterations in myocardial mechanics occur in patients with TCAV at least 2 years prior to invasive diagnosis. These early changes may be due to microvascular disease. This modality could aid in earlier treatment and intervention for this challenging problem .

Relationship between ventricular pressure and coronary artery disease in asymptomatic adult heart transplant recipients

INTRODUCTION

The association between data of right heart catheterization and cardiac allograft vasculopathy (CAV) in adult heart transplant (HTx) recipients remains to be determined.

METHODS AND RESULTS

This is an observational, retrospective study, including all consecutive asymptomatic HTx patients undergoing routine right and left catheterization. The independent predictive power of pulmonary capillary wedge pressure (PCWP) to predict CAV (classified according to working formulation of a standardized nomenclature for CAV-2010) was the primary end point. Seventy-one patients were included, with a mean time from HTx to procedure of 19 ± 25 months. At coronary angiography first degree of CAV was found in eight patients (11.2%), second degree of CAV in two patients (2.8%), and third in two (2.8%). PCWP values were significantly higher in patients with CAV compared with patients without CAV (17.5 ± 7.5 vs. 10.4 ± 5.6, P < 0.001) and values of 15 mmHg or greater had an AUC of 0.71 (0.48-0.92), with a sensitivity of 71% and a specificity of 73% in predicting CAV, with an independent relationship confirmed at logistic regression analysis (odds ratio 1.28, IC 1.06-1.53; P = 0.008).

CONCLUSION

A significantly elevated PCWP at the time of the diagnosis of transplant coronary artery disease may be considered as an early marker of CAV, especially in asymptomatic HTx recipients.

Clinical and angiographic outcomes with everolimus eluting stents for the treatment of cardiac allograft vasculopathy

OBJECTIVES

This study aimed to examine clinical efficacy, safety, and intermediate clinical outcomes with everolimus-eluting stents (EESs) in patients with transplant coronary artery disease (TCAD).

BACKGROUND

TCAD is a major cause of mortality in patients following orthotopic heart transplantation (OHT). Systemic everolimus in OHT patients has been shown to reduce TCAD. The safety and efficacy of an EES, the Xience V, have not been evaluated in this population.

METHODS

Patients post-OHT with hemodynamically significant CAD who underwent percutaneous coronary intervention (PCI) with EES were included. Participants were maintained on dual antiplatelet therapy for 1-year post-PCI. We examined procedural success, in-hospital and 1-year mortality, stent thrombosis, angiographic restenosis, and myocardial infarction rates. All patients had follow-up angiography 1-year after PCI. Target vessel revascularization (TVR), target lesion revascularization (TLR), in-segment restenosis, target vessel failure (TVF), and lumen late loss were noted.

RESULTS

PCI was performed in 34 de novo lesions in 21 patients, and 40 EES were placed. Procedural success rate was 100%. Average stent was 16.5 ± 5.1 mm long and 3.0 ± 0.6 mm in diameter. All patients had angiographic follow-up (409 ± 201 days). There was no stent thrombosis, deaths, or myocardial infarctions during follow-up. Two patients had focal in-stent restenosis. TLR rate was 5.9% (2/34), and TVR rate was 11.1% (3/27). Quantitative coronary angiography (QCA) showed stenosis diameter to be 19.98 ± 17.57%.

CONCLUSIONS

Use of an EES is associated with a low incidence of TVR and TLR in patients with TCAD. Further studies are needed to determine whether PCI with EES changes long-term outcomes.

Heart rate variability arterial hypertension in young heart-transplanted recipients: association progression of cardiac allograft vasculopathy?

Hypertension and reduced HRV are frequent in heart-transplanted recipients. We studied 26 young recipients to investigate the relationship between BP and HRV during simultaneous 24-h monitoring. Presence of CAV was considered. All HRV measures were significantly lower than normal values. Significant correlations were found between mean daytime systolic BP and the rMSSD (p = 0.04), and mean daytime DBP and SDANN for all 5-min segments (p = 0.03) and between rMSSD and mean nighttime DBP (p = 0.03). Four patients were hypertensive during daytime, seven had a reduced nocturnal fall and two had a nocturnal rise in BP. Eight patients showed severe CAV grade (grade IV) on the Stanford scale, 13 moderate (grade III) and five mild (grade I-II). After a follow-up time of 30 months, four of the 13 patients (30%) with CAV grade III showed an increase to grade IV and all showed abnormalities of both HRV and ABPM patterns. The relationship between HRV abnormalities and arterial hypertension and CAV should be further explored.

PET assessment of myocardial perfusion reserve inversely correlates with intravascular ultrasound findings in angiographically normal cardiac transplant recipients

Cardiac allograft vasculopathy (CAV) is the major determinant of long-term survival after heart transplantation. We aimed to evaluate the efficacy of PET as a noninvasive way to assess the early stages of CAV.

METHODS

Twenty-seven consecutive patients (20 men and 7 women; mean age +/- SD, 46 +/- 12 y) who had normal results on coronary angiography and normal left ventricular systolic function (ejection fraction >or= 60%) were enrolled at 2.5 +/- 2.1 y after transplantation. Myocardial blood flow (MBF) was assessed using dynamic (13)N-ammonia PET at rest and during adenosine-induced hyperemia, and myocardial perfusion reserve (MPR) was calculated as the ratio of hyperemic MBF to resting MBF. Regional (13)N-ammonia PET was assessed using a 5-point scoring system. The intravascular ultrasound (IVUS) measurements for the extent of intimal hyperplasia, including plaque volume index (calculated as [total plaque volume/total vessel volume] x 100%) and maximum area of stenosis, were compared with MPR by linear regression analysis.

RESULTS

In 27 angiographically normal cardiac transplant recipients, MBF at rest and during adenosine stress and MPR of the left anterior descending artery distribution correlated strongly with the other 2 coronary artery distribution territories (r >or= 0.97, P < 0.0001). Summed stress score and summed difference score showed a moderate inverse correlation with MPR (r = -0.41 and -0.49, respectively; P < 0.05) but not with IVUS measurements. MPR correlated inversely with plaque volume index (r = -0.40, P < 0.05) but not with maximal luminal stenosis as assessed by IVUS. In addition, MPR and IVUS measurements gradually inversely changed after heart transplantation (all P < 0.05).

CONCLUSION

This study confirms that CAV is a progressive process, diffusely involving the epicardial and microvascular coronary system. Plaque burden as determined by IVUS agrees well with MPR as assessed by PET in recipients with normal coronary angiography results. This finding suggests that dynamic (13)N-ammonia PET is clinically feasible for the early detection of CAV and can be used as a reliable marker of disease progression.

Cardiac allograft vasculopathy: recent developments

Cardiac allograft vasculopathy (CAV) continues to limit the long-term success of cardiac transplantation. Recent insights have underscored the fact that innate and adaptive immune responses are involved in the pathogenesis of CAV. Vascular lesions are the result of cumulative endothelial injuries induced both by alloimmune responses and by nonspecific insults (including ischemia-reperfusion injury, viral infections, and metabolic disorders) in the context of impaired repair mechanisms. Intravascular ultrasound is the most sensitive method for detection of CAV, and progressive intimal thickening in the first posttransplant year identifies patients at high risk for future cardiovascular events. Encouraging results with regard to the detection of CAV by noninvasive methods should be an incentive to apply routine noninvasive imaging during mid- to long-term follow-up. Improved immunosuppressive drugs, including mycophenolate mofetil and proliferation signal inhibitors, as well as statins (in part via immunomodulation), have beneficial effects on CAV progression, although there is still a need to confirm the impact of vasodilators in improving outcome after heart transplantation. Coronary revascularization for CAV is only palliative, with no long-term survival benefit. Three main strategies for CAV prevention are currently under investigation: inhibition of growth factors and cytokines, cell therapy, and tolerance induction. However, because individual responses to an allograft change over time, assays to monitor the recipient's immune response and individualized methods for therapeutic immune modulation are clearly needed.