Multiple coronary thrombosis and allograft vascular disease

Early optical coherence tomography evaluation of donor-transmitted atherosclerosis and cardiac allograft vasculopathy: insights from a prospective, single-center study

BACKGROUND

The impact of donor transmitted atherosclerosis as assessed by intravascular ultrasound on development and progression of cardiac allograft vasculopathy (CAV) after heart transplantation (HT) remains poorly defined in contemporary practice. In this exploratory analysis, we sought to assess the prognostic role of early qualitative assessment of donor artery morphology using optical coherence tomography (OCT) as a more sensitive imaging modality.

METHODS

HT recipients were prospectively enrolled for baseline OCT imaging of the left anterior descending coronary artery. OCT findings were classified as normal, homogeneous intimal thickening, and advanced plaque characteristics. The endpoint was a composite of cardiac death, myocardial infarction, or new angiographically detectable CAV stratified by the International Society of Heart and Lung Transplantation criteria up to 4 years of follow-up.

RESULTS

A total of 35 patients underwent baseline OCT of whom 51.4% had normal OCT, 14.3% had homogenous plaque, and 34.3% had advanced characteristics. There were no significant differences in baseline demographics between patients with and without normal morphology. During a mean follow-up of 3.3 ± 0.4 years, the endpoint occurred in 11 patients including 1 death, 7 CAV1, 3 CAV2, and 1 CAV3. Kaplan-Meier analysis revealed a significantly higher event rate in patients with advanced characteristics (log-rank p = 0.010). In multivariate analysis, OCT-based plaque morphology was an independent predictor of clinical events (adjusted hazard ratio 4.57, 95% confidence interval 1.50-13.92, p = 0.008) while maximal intimal thickness ≥0.5 mm was not.

CONCLUSIONS

Early qualitative OCT assessment of donor coronary artery morphology appears to be a reliable marker for predicting future cardiovascular events in HT recipients. Our findings warrant more careful study in a larger cohort.

Optical Coherence Tomography of Coronary Plaque Progression and Destabilization: JACC Focus Seminar Part 3/3

The development of optical coherence tomography (OCT) has revolutionized our understanding of coronary artery disease. In vivo OCT research has paralleled with advances in computational fluid dynamics, providing additional insights in the various hemodynamic factors influencing plaque growth and stability. Recent OCT studies introduced a new concept of plaque healing in relation to clinical presentation. In addition to known mechanisms of acute coronary syndromes such as plaque rupture and plaque erosion, a new classification of calcified plaque was recently reported. This review will focus on important new insights that OCT has provided in recent years into coronary plaque development, progression, and destabilization, with a focus on the role of local hemodynamics and endothelial shear stress, the layered plaque (signature of previous subclinical plaque destabilization and healing), and the calcified culprit plaque.

Platelet aggregation and response to aspirin therapy in cardiac allograft vasculopathy

BACKGROUND

Long-term survival after heart transplantation (HTx) is compromised by cardiac allograft vasculopathy (CAV) characterized by coronary macro- and microvascular disease. The pathogenesis of CAV is unclear and may involve coronary thrombosis. We investigated whether HTx patients with CAV had higher platelet aggregation and turnover than HTx patients without CAV and healthy controls. Furthermore, we investigated the anti-platelet effect of low-dose aspirin in HTx patients.

METHODS

We included 57 patients who had undergone HTx (median 8.3 years from HTx) and 57 healthy controls. Platelet aggregation was measured on-aspirin and off-aspirin using impedance aggregometry with adenosine diphosphate (ADP) and arachidonic acid (AA). We evaluated platelet turnover by flow cytometry, CAV burden by coronary angiography and echocardiography, and microvascular function by echocardiographic coronary flow velocity reserve (CFVR).

RESULTS

Off-aspirin, HTx patients with CAV (n = 21) had higher ADP-induced platelet aggregation than healthy controls (p < 0.01) and HTx patients without CAV (n = 36) (p < 0.05). Aspirin treatment reduced AA-induced platelet aggregation in both HTx groups, but HTx patients with CAV had higher platelet aggregation on-aspirin than HTx patients without CAV (p < 0.05). Platelet turnover did not differ between HTx patients with CAV and HTx patients without CAV (p > 0.34). HTx patients with lower CFVR values had higher platelet aggregation than HTx patients with higher CFVR values (p < 0.05).

CONCLUSIONS

Off-aspirin, platelet aggregation was higher in HTx patients with CAV than in HTx patients without CAV and healthy controls. On-aspirin, platelet aggregation was higher in HTx patients with CAV than in HTx patients without CAV. Aspirin monotherapy may not provide sufficient platelet inhibition in HTx patients with CAV.

Comparison Between Cardiac Allograft Vasculopathy and Native Coronary Atherosclerosis by Optical Coherence Tomography

We sought to explore differences in distribution and morphology of coronary lesions comparing cardiac allograft vasculopathy and native coronary atherosclerosis (NCA) using intravascular imaging with optical coherence tomography (OCT). At the time of routine surveillance angiography, 17 heart transplant (HT) recipients with a history of high-grade cellular rejection (HGR) and 43 HT recipients with none/mild (low)-grade rejection underwent OCT imaging of the left anterior descending and were compared to 60 patients with NCA without HT. Compared with patients with NCA, patients with HGR had similar intima areas but smaller external elastic lamina areas (7.9 mm(2) [6.3, 11.2] versus 6.6 mm(2) [4.8, 7.5], p = 0.02) resulting in smaller lumen areas (4.5 mm(2) [3.4, 6.6] versus 3.3 mm(2) [2.8, 4.7], p = 0.04) in distal segments and smaller lumen diameters in side branches (1.28 mm [1.19, 1.37] versus 1.09 mm [0.94, 1.24], p = 0.04). Compared with patients with NCA, lesions in patients with HT were more homogeneous, involving the entire coronary vascular tree. Patients with HGR had a higher prevalence of macrophages involving ≥1 quadrant in all 3 segments compared with patients with NCA. The number of microvessels was greater in patients with both HGR and LGR HT versus NCA. In conclusion, distinct findings in the distribution and morphology of coronary lesions between HT recipients and patients with NCA are evident by OCT imaging, suggesting that OCT might be useful to help differentiate cardiac allograft vasculopathy from NCA in vivo.

Coronary atherosclerosis with vulnerable plaque and complicated lesions in transplant recipients: new insight into cardiac allograft vasculopathy by optical coherence tomography

AIMS

Cardiac allograft vasculopathy (CAV) is a major limitation to long-term survival following cardiac transplantation. Conventional imaging modalities such as angiography and intravascular ultrasound fail to characterize CAV plaque morphology. Our aim was to characterize CAV in vivo using the high spatial resolution of intracoronary optical coherence tomography (OCT).

METHODS AND RESULTS

We prospectively enrolled 53 cardiac transplant patients to undergo OCT of the left anterior descending coronary artery (LAD) in addition to annual CAV screening by coronary angiography and intravascular ultrasound (IVUS). The proximal 30 mm of the LAD was divided into three segments of 10 mm each (n = 156). Segments with CAV plaque on IVUS were analysed by OCT for specific CAV morphological characteristics within the framework of three groups according to follow-up time after heart transplantation: (i) 0-3 months (n = 18), (ii) 12-36 months (n = 55), and (iii) ≥48 months (n = 83). The prevalence of atherosclerotic characteristics such as eccentric plaques, calcification, and lipid pools increased from 6, 0, and 6% in group 1 to 78, 42, and 61% in group 3, respectively (all P < 0.001). The prevalence of vulnerable plaque features such as thin-cap fibroatheroma, macrophages, and microchannels increased from 0% in group 1 to 12, 29, and 33% in group 3, respectively (P = 0.19, P = 0.006, and P = 0.003). Complicated coronary lesions such as intimal laceration, intraluminal thrombus, and layered complex plaque increased from 0% in group 1 to 18, 19, and 57% in group 3 (P = 0.009, P < 0.001, and P < 0.001). Plaque rupture was identified in 4% of group 3 segments.

CONCLUSION

The current study gives new insight into CAV that extends far beyond the current concept of concentric and fibrosing vasculopathy, that is, the development of atherosclerosis with vulnerable plaque and complicated coronary lesions.

Repeated episodes of thrombosis as a potential mechanism of plaque progression in cardiac allograft vasculopathy

AIMS

The pathogenesis of cardiac allograft vasculopathy (CAV) remains complex and may involve multiple mechanisms. We tested the hypothesis that the multilayer (ML) appearance, an intravascular ultrasound (IVUS) finding suggestive of repetitive thrombosis, is associated with plaque progression in heart transplant (HTx) recipients.

METHODS AND RESULTS

Our study population consisted of 132 HTx recipients undergoing at least two grayscale and virtual histology (VH)-IVUS examinations. A retrospective serial analysis was performed between the first (baseline) and the last (follow-up) IVUS data during a median follow-up of 3.0 years. The subjects were divided into two groups based on the presence of the ML appearance on the baseline IVUS. At baseline, subjects with ML appearance (n = 38) had a longer time elapsed since transplant, larger vessel volume, and larger plaque volume than those without (n = 94) (all P < 0.01). Intraluminal thrombi and plaque ruptures were identified only in subjects with ML appearance (P < 0.01 vs. those without). More subjects with ML appearance at baseline developed subsequent ML formation compared with those without [21 (55%) vs. 22 (23%), P < 0.01] during follow-up. There was an increase in plaque volume, necrotic core volume, and dense calcium volume in subjects with ML appearance (all P < 0.01 vs. those without). Multivariable linear regression analysis showed that ML appearance was a potential predictor of plaque progression (regression coefficient 0.28, 95% CI 0.10-0.45, P < 0.01).

CONCLUSIONS

The current study demonstrates that a finding of ML appearance, indicative of repeated episodes of mural thrombosis, is not infrequent in asymptomatic HTx recipients and possibly contributes to progression of CAV.

Immunohistochemical characterization of coronary thrombi in allograft vascular disease

BACKGROUND

Coronary thrombosis is a frequent complication of allograft vascular disease (AVD) in cardiac transplant recipients. No data are available on thrombus composition in these hearts.

METHODS

The present study aimed at characterizing thrombus components in coronary arteries from transplanted hearts with AVD, using single and double immunostain with anti-gpIIb-IIIa, anti-fibrin, and anti-endothelial antibodies. The pathologic series consists of 55 grafts survived longer than 2 months, and obtained from 55 patients deceased (n=44) or undergone repeat transplantation (n=11).

RESULTS

Mural thrombi were found in multiple segments of 75 of 440 total coronary vessels (17%) (recent in 33, organizing in 28, and organized in 14), whereas occlusive thrombi were found in 19 vessels (8 recent and 11 with multichannel pattern of organization). Recent and thin mural thrombi were mostly constituted of CD41a- and CD61-positive platelets; the amount of fibrin progressively increased with the increase of thrombus size. In organizing mural thrombi, gpIIb-IIIa immunostain was still present. Fibrin was the only identifiable thrombus component in old mural thrombi embedded within the intimal lesions. Recent occlusive thrombi immunoreacted both with anti-CD41a and anti-CD61 and with anti-fibrin antibodies, whereas organized occlusive thrombi with multichannel pattern exclusively immunoreacted with anti-fibrin antibodies. Double immunostain showed that mural thrombi were stratified on de-endothelized arterial segments.

CONCLUSIONS

Thrombus composition is related to both type and "age" of thrombus, with platelets as the early and major components of mural microthrombi at one end of the spectrum, and fibrin as the dominant component of occlusive thrombi at the other end.