Coronary plaque morphologic characteristics early and late after heart transplantation: in vivo analysis with intravascular ultrasonography

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.

Virtual histology assessment of cardiac allograft vasculopathy following introduction of everolimus--results of a multicenter trial

In this 12-month multicenter Scandinavian study, 78 maintenance heart transplant (HTx) recipients randomized to everolimus with reduced calcineurin inhibitor (CNI) exposure or continued standard CNI-therapy underwent matched virtual histology (VH) examination to evaluate morphological progression of cardiac allograft vasculopathy (CAV). Parallel measurement of a range of inflammatory markers was also performed. A similar rate of quantitative CAV progression was observed in the everolimus (n = 30) and standard CNI group (n = 48) (plaque index 1.9 ± 3.8% and 1.6 ± 3.9%, respectively; p = 0.65). However, VH analysis revealed a significant increase in calcified (2.4 ± 4.0 vs. 0.3 ± 3.1%; p = 0.02) and necrotic component (6.5 ± 8.5 vs. 1.1 ± 8.6%; p = 0.01) among everolimus patients compared to controls. The increase in necrotic and calcified components was most prominent in everolimus patients with time since HTx >5.1 years and was accompanied by a significant increase in levels of von Willebrand (vWF) factor (p = 0.04) and vascular cell adhesion molecule (VCAM) (p = 0.03). Conversion to everolimus and reduced CNI is associated with a significant increase in calcified and necrotic intimal components and is more prominent in patients with a longer time since HTx. A significant increase in vWF and VCAM accompanied these qualitative changes and the prognostic implication of these findings requires further investigation.

Virtual histology

As a luminogram, coronary angiography provides a good overview of the coronary artery tree. Using quantitative coronary measurements, the degree of coronary obstruction can be determined. The limitation of coronary angiography is that it does not provide information on the arterial wall structure and therefore cannot assess the extent of atherosclerosis. Knowledge about adaptive coronary remodelling processes as compensatory enlargement of the coronary artery has focused diagnostic interest on the non-stenotic lesions of the coronary tree. Intravascular ultrasound (IVUS) can reveal discrepancies between the extent of coronary atherosclerosis and angiography imaging by in vivo plaque imaging. Spectrum analysis of IVUS-derived radiofrequency (RF) data enables a more detailed analysis of plaque composition and morphology. Preliminary in vitro studies correlated four histological plaque components with a specific spectrum analysis of the RF data. The different components (fibrous, fibrofatty, necrotic core and dense calcium) are colour coded. Coronary tissue maps were reconstructed from RF data using IVUS-Virtual Histology (VH IVUS) software (Real-Time VH, Volcano Corporation, Rancho Cordova, California, USA). VH IVUS has the potential to detect high-risk lesions and can provide new insights into the pathophysiology of coronary artery disease. VH IVUS allows the differentiation of different lesion types based on information derived from histopathology. The in vivo specific histological analysis of coronary atherosclerosis may allow better stratification of treatment of patients with coronary artery disease.

Cardiac Allograft Vasculopathy

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

Intravascular ultrasound assessment of longitudinal plaque distribution patterns in patients with angiographically silent coronary artery disease after heart transplantation

AIMS

The purpose of this three-dimensional intracoronary ultrasound (ICUS) study was to assess longitudinal plaque distribution patterns in patients with angiographically silent coronary artery disease (CAD) after heart transplantation (HTX).

METHODS AND RESULTS

Out of 334 patients without diameter stenosis >/=25% determined by coronary angiography, 321 underwent successful three-dimensional ICUS (30 MHz) of the left main coronary artery (LMCA) and all segments of the left anterior descending coronary artery (LAD). Early plaque formation was found in 296 patients (92.2%). Single (focal CAD, n = 65) or multiple (polyfocal CAD, n = 77), discrete coronary lesions were found in 142 patients and continuous plaque formation of at least one entire coronary segment (diffuse CAD) in 154 patients. Using multivariate regression analysis, male sex (P = 0.01), increasing post-transplantation time (P = 0.003) and increasing donor age (P = 0.001) were independent clinical predictors for diffuse CAD. Both focal and diffuse CAD most frequently affected the proximal LAD (88% compared with 89.6%, NS). The mean intimal index of each LAD segment was significantly higher in patients with diffuse CAD (P < 0.001) and showed a proximal-to-distal decline in patients with focal/polyfocal (LMCA, 10.1 +/- 14.3, LAD-6, 30.1 +/- 17.4%, LAD-7, 16.3 +/- 14.1%, LAD-8, 4.6 +/- 11.1%; P < 0.001) and diffuse (LMCA, 27.0 +/- 16.0, LAD-6, 47.8 +/- 16.1%, LAD-7, 41.9 +/- 14.5%, LAD-8, 24.9 +/- 23.3%; P < 0.01) CAD.

CONCLUSION

Evaluation of longitudinal plaque distribution after HTX by three-dimensional ICUS revealed a time-dependent increase in the incidence of diffuse CAD and a proximal-to-distal decline in frequency and magnitude of early plaque formation.

Predictors of reduced coronary flow reserve in heart transplant recipients without angiographically significant coronary artery disease

BACKGROUND

Determination of coronary flow reserve (CFR) is increasingly used to assess the functional significance of cardiac allograft vasculopathy. Although the relation between CFR and angiographically defined vasculopathy has been studied extensively, little is known about other factors determining CFR in heart transplant recipients without significant lesions by coronary angiography.

METHODS

Sixty consecutive patients were studied 0.5 to 148 months after heart transplantation with intracoronary Doppler and intravascular ultrasound. An endothelium-independent CFR< or =2.5 was defined as abnormal. Stepwise logistic regression analysis was used to identify factors (demographic data of donor and recipient, lipid profile, epicardial vessel morphology by intravascular ultrasound, left ventricular hypertrophy, acute rejection episodes, and hemodynamics) potentially associated with a reduced CFR.

RESULTS

Only the presence of left ventricular hypertrophy (48% vs. 14%, P=0.007 and P=0.023, bivariate and multivariate analysis, respectively) and higher donor ages (41+/-12 vs. 29+/-11 years, P=0.002 and P=0.013, bivariate and multivariate analysis, respectively) showed an independent association with an abnormal flow reserve. CFR in patients with left ventricular hypertrophy was reduced due to higher baseline flow velocities (27+/-11 vs. 20+/-6 cm/sec, P=0.004). Furthermore, resting flow velocity increased as a function of donor age (r=0.264, P=0.047), while hyperemic flow velocity was not different. Other patient characteristics and hemodynamics did not affect CFR.

CONCLUSION

The presence of left ventricular hypertrophy and higher donor ages independently contribute to a reduced CFR in patients after heart transplantation. This reduction in CFR is due to elevated baseline flow velocities rather than to a change in hyperemic flow velocities. These findings should be taken into account for the interpretation of reduced CFR values obtained by intracoronary Doppler in heart transplant recipients without angiographically overt coronary lesions.