Community-based statins and advanced carotid plaque: Role of CD163 positive macrophages in lipoprotein-associated phospholipase A2 activity in atherosclerotic plaque.

BACKGROUND AND AIMS: Lipoprotein-associated phospholipase A2 (Lp-PLA2), an enzymatic inflammatory biomarker primarily bound to low-density lipoprotein cholesterol, is associated with an approximate twofold increased risk of cardiovascular disease and stroke. Despite indications that circulating Lp-PLA2 is sensitive to statins, it remains largely unknown whether statin usage exerts local effects on Lp-PLA2 expression at the site of atheromatous plaque. METHODS: Carotid plaques (n = 38) were prospectively collected from symptomatic (n = 18) and asymptomatic (n = 20) patients with (n = 20) or without (n = 18) documented statin history. In all cases, endarterectomy was performed where the primary stenosis was removed in an undisturbed manner. Serial cryosections of the presenting lesion were assessed histologically for macrophages, Lp-PLA2, and cell death (apoptotic index). RESULTS: Symptomatic lesions exhibited less calcification, with greater inflammation characterized by increased expression of CD68+ and CD163+ macrophage subsets, and Lp-PLA2. Symptomatic plaques also exhibited greater necrotic core area and increased apoptosis, as compared with asymptomatic lesions. In contrast, statin treatment did not appear to influence any of these parameters, except for the extent of apoptosis, which was less in statin treated as compared with statin naïve lesions. Overall, Lp-PLA2 expression correlated positively with necrotic core area, CD68+ and CD163+ macrophage area, and cell death. Finally, in vitro assays and dual immunofluorescence staining confirmed CD163-expressing monocytes/macrophages are also a major source of Lp-PLA2. CONCLUSIONS: Statin treatment has no effect on local atherosclerotic lesion Lp-PLA2 activity, therefore, the addition of anti-inflammatory treatments to further decrease macrophage Lp-PLA2 expression in atherosclerotic lesions may reduce lesional inflammation and cell death, and prevent necrotic core expansion and lesion progression.

Additive Value of Integrated Backscatter IVUS for Detection of Vulnerable Plaque by Optical Frequency Domain Imaging: An Ex Vivo Autopsy Study of Human Coronary Arteries.

OBJECTIVES: This study sought to evaluate the diagnostic performance of optical frequency domain imaging (OFDI) for recognition of coronary plaque morphologies and to assess additive values of integrated backscatter intravascular ultrasound (IB-IVUS) in detection of vulnerable plaque. BACKGROUND: Precise diagnosis of coronary lesions susceptible to plaque rupture and thrombosis may serve to stratify the risk of future coronary events and to make decisions for appropriate treatment of choice. METHODS: Twenty-seven coronary arteries from 14 human autopsy hearts were interrogated ex vivo by OFDI and IB-IVUS. Imaged segments were sectioned at 3 mm intervals where a total of 360 pairs of cross-sectional images coregistered to histology were investigated. RESULTS: Overall, OFDI could depict various plaque components and structures such as fibrous tissue, sheet and nodular calcification, lipid, cholesterol crystals, and healed plaque rupture. OFDI could detect 14 of 18 thin-cap fibroatheroma (TCFA), however, the diagnostic accuracy was not high (positive predictive value [PPV] = 60.9%, κ = 0.664; area under the curve [AUC]: 0.88) mainly because of signal interference from macrophages. Further, we defined IB-IVUS-derived TCFA by recursive partitioning analysis as: 1) cross-sectional % lipid area >65.1%; 2) % lipid area >32.3 but <65.1% with plaque area >10.5 mm(2), where TCFA detection by IB-IVUS alone was marginal (PPV = 50.0%, κ = 0.545; AUC: 0.82). However, when IB-IVUS was combined with OFDI, all pseudo OFDI-derived TCFA (non-TCFA on histology) were excluded. Accordingly, PPV of TCFAs diagnosed by both OFDI and IB-IVUS was improved to 100.0% (κ = 0.704; AUC: 0.93). CONCLUSIONS: OFDI could recognize detailed morphologies of human coronary plaque. However, diagnostic accuracy of both OFDI alone and IB-IVUS alone to identify TCFA is limited. Combination of IB-IVUS with OFDI improved the accuracy for TCFA detection, suggesting hybrid imaging or further development of novel devices will be required to identify coronary lesions responsible for future events.

Human autopsy study of drug-eluting stents restenosis: histomorphological predictors and neointimal characteristics.

AIMS: Restenosis in drug-eluting stents (DESs) occurs infrequently, however, it remains a pervasive clinical problem. We interrogated our autopsy registry to determine the underlying mechanisms of DES restenosis, and further we investigated the neointimal characteristics of DESs and compared with bare metal stents (BMSs). METHODS AND RESULTS: Coronary lesions from patients with DES implants (n = 82) were categorized into four groups based on cross-sectional area narrowing: patent (<50%), intermediate (50-74%), restenotic (≥ 75% with residual lumen), and total occlusion (organized thrombus within the stent). Restenosis and occlusion were significantly dependent on the total stented length: restenosis (26.7 mm) and occlusion (25.7 mm) compared with patent DESs (17.3 mm). Further, restenotic and occluded lesions were located more distally in the coronary arteries and had greater vessel injury and uneven strut distribution suggesting local drug gradient. Multivariate analysis revealed that normalized maximum inter-strut distance was associated with DES restenosis (OR: 17.4, P = 0.04) while medial tear length was a predictor of DES occlusion (OR: 5.1, P = 0.03). No differences were observed between different DESs (sirolimus-, paclitaxel-, and everolimus-eluting stents) for restenosis and occlusion. Further, neointimal compositions of restenotic DESs demonstrated greater proteoglycan deposition and less smooth muscle cellularity over time, when compared with BMS with greater cell density and collagen deposition. CONCLUSIONS: Our study indicates the impacts of inadequate drug concentration due to wider inter-strut distance and vessel injury as primary mechanisms of DES restenosis and occlusion, respectively. Moreover, the differences in neointimal compositions between DESs and BMSs might serve as a potential target for the suppression of late neointima growth via inhibition of proteoglycans in DESs.

Ex vivo assessment of vascular response to coronary stents by optical frequency domain imaging.

OBJECTIVES: This study sought to examine the capability of optical frequency domain imaging (OFDI) to characterize various morphological and histological responses to stents implanted in human coronary arteries. BACKGROUND: A precise assessment of vascular responses to stents may help stratify the risk of future adverse events in patients who have been treated with coronary stents. METHODS: Fourteen human stented coronary segments with implant duration ≥ 1 month from 10 hearts acquired at autopsy were interrogated ex vivo by OFDI and intravascular ultrasound (IVUS). Comparison with histology was assessed in 134 pairs of images where the endpoints were to investigate: 1) accuracy of morphological measurements; 2) detection of uncovered struts; and 3) characterization of neointima. RESULTS: Although both OFDI and IVUS provided a good correlation of neointimal area with histology, the correlation of minimum neointimal thickness was inferior in IVUS (R(2) = 0.39) as compared with OFDI (R(2) = 0.67). Similarly, IVUS showed a weak correlation of the ratio of uncovered to total stent struts per section (RUTSS) (R(2) = 0.24), whereas OFDI maintained superiority (R(2) = 0.66). In a more detailed analysis by OFDI, identification of individual uncovered struts demonstrated a sensitivity of 77.9% and specificity of 96.4%. Other important morphological features such as fibrin accumulation, excessive inflammation (hypersensitivity), and in-stent atherosclerosis were characterized by OFDI; however, the similarly dark appearance of these tissues did not allow for direct visual discrimination. The quantitative analysis of OFDI signal reflections from various in-stent tissues demonstrated distinct features of organized thrombus and accumulation of foamy macrophages. CONCLUSIONS: The results of the present study reinforce the potential of OFDI to detect vascular responses that may be important for the understanding of long-term stent performance, and indicate the capability of this technology to serve as a diagnostic indicator of clinical success.

Coronary responses and differential mechanisms of late stent thrombosis attributed to first-generation sirolimus- and paclitaxel-eluting stents.

OBJECTIVES: The purpose of this study was to assess the mechanism(s) of late stent thrombosis (LST) and vascular healing responses in first-generation polymeric drug-eluting stents (DES). BACKGROUND: Recent clinical trials have reported variations in late lumen loss between first-generation sirolimus-eluting stents (SES) and paclitaxel-eluting stents (PES). Little is known, however, about the vascular responses, time course of healing, and underlying mechanism(s) of complications of LST between platforms in human coronary implants. METHODS: The overall analysis included 174 cases (230 DES lesions) from the CVPath Institute's stent registry. Histomorphometry was performed on coronary stents from 127 patients (171 lesions) who died ≥ 30 days after receiving stent implants in which fibrin deposition, endothelial strut coverage, inflammatory response, and mechanism(s) of in-stent thrombosis were assessed. RESULTS: Both platforms demonstrated increased neointimal thickness over time where values were greater in PES (mean 0.13 mm; range 0.03 to 0.20 mm) than SES (mean 0.10 mm; range 0.04 to 0.15 mm; p = 0.04). The percentage of uncovered struts was similar between SES and PES including stents with LST (SES = 21% vs. PES = 27%; p = 0.47). The underlying mechanism(s) of LST, however, was strikingly different between platforms; localized strut hypersensitivity was exclusive to SES, whereas malapposition secondary to excessive fibrin deposition was the underlying cause in PES. Moreover, although both PES and SES showed nearly complete strut coverage after 12 months for on-label use, the majority of stents placed for off-label indications remained unhealed after 12 months in both types of DES. CONCLUSIONS: Differential mechanisms of LST involving either hypersensitivity or excessive fibrin were identified between first-generation DES in which overall stent healing was further delayed in DES placed for off-label indications.

Relationship of thrombus healing to underlying plaque morphology in sudden coronary death.

OBJECTIVES: The aim of this study was to assess differences in thrombus healing between ruptured and eroded plaques, given the natural difference in lesion substrate and that thrombi might exist days to weeks before the presentation of sudden coronary death. BACKGROUND: Although the ability to distinguish ruptures and erosions remains a major clinical challenge, in-hospital patients dying with acute myocardial infarction establish that erosions account for 25% of all deaths, where women experience a higher incidence compared with men. METHODS: Coronary lesions with thrombi (ruptures, n = 65; erosions, n = 50) received in consultation from the Medical Examiner's Office from 111 sudden death victims were studied. Thrombus healing was classified as early (<1 day) or late stage characterized in phases of lytic (1 to 3 days), infiltrating (4 to 7 days), or healing (>7 days). Morphometric analysis included vessel dimensions, necrotic core size, and macrophage density. RESULTS: Late-stage thrombi were identified in 79 of 115 (69%) culprit plaques. Women more frequently had erosion with a greater prevalence of late-stage thrombi (44 of 50, 88%) than ruptures (35 of 65, 54%, p < 0.0001). The internal elastic lamina area and percent stenosis were significantly smaller in erosions compared with ruptures (p < 0.0001 and p = 0.02), where plaque burden was greater (p = 0.008). Although macrophage infiltration in erosions was significantly less than ruptures (p = 0.03), there was no established relationship with thrombus organization. Other parameters of thrombus length and occlusive versus nonocclusive showed no association with healing. CONCLUSIONS: Approximately two-thirds of coronary thrombi in sudden coronary deaths are organizing, particularly in young individuals-especially women, who perhaps might require a different strategy of treatment.

Patent foramen ovale closure by radiofrequency thermal coaptation: first experience in the porcine model and healing mechanisms over time.

BACKGROUND: Percutaneous transcatheter patent foramen ovale (PFO) closure is now standard practice and may limit embolic complications for at least 10 years. Implantable PFO closure devices may be complicated by thrombosis, infection, device fracture, or embolization. A novel strategy uses radiofrequency-based thermal energy to seal PFO membranes, with no implanted device. We successfully used this method and examined histopathologic events in swine to characterize safety and efficacy. METHODS AND RESULTS: Thirteen domestic swine were examined over time after thermal PFO closure. Three animals were euthanized within 1 hour of treatment, 5 after 7 days, and 5 at 28 days. Gross and histopathologic findings were examined. Radiofrequency energy was delivered successfully in all cases, and PFOs were closed in 12 of 13 cases. One case was not suitable for histological examination because of laceration at euthanasia, and the other PFO was clinically closed, with no shunt at 7 days, but was histologically open. All of the other PFOs were confirmed closed histologically. Acute histological results showed edema, hemorrhage, and myocyte necrosis. Minimal thrombus formation occurred on the left atrial endocardial surface. At day 7, transmural thermal effects occurred through the atrial wall that extended to the epicardial surface. At day 28, thermal effects showed excellent scar formation. Collagen, matrix, and neovascularization were present in all cases. No animal experienced adverse events. CONCLUSIONS: Thermal PFO closure is feasible, safe, and effective in swine. Thermal healing is nearly complete by 4 weeks and consists of collagen formation and tunnel closure. This technique may allow substantial reduction in PFO closure risk over current device-based therapy.

Histopathology of carotid atherosclerotic disease.

Stroke is the third leading cause of death in the United States, constituting approximately 700,000 cases each year, of which about 500,000 are first attacks and 200,000 are recurrent attacks. Ischemic stroke accounts for the majority of all strokes (88%), followed by intracerebral hemorrhage (9%) and subarachnoid hemorrhage (3%). Patients with substantial carotid narrowing are at increased risk for major stroke; however, recent studies suggest that factors other than the degree of carotid stenosis are involved in ischemic stroke pathogenesis. Atherosclerotic plaque of the stenotic carotid artery is the underlying cause of the majority of ischemic strokes and specific plaque characteristics have been associated with ischemic brain injury. Several studies have demonstrated that the mechanisms of plaque instability in the carotid circulation are similar to those in the coronary circulation. The purpose of this review is to characterize atherosclerotic carotid disease in light of our knowledge of coronary atherosclerosis and relate carotid plaque morphology to cerebral ischemic syndromes. Histological examination of the carotid plaque specimen should provide insights into the underlying plaque morphology that is responsible for the disease and should help determine the potential treatments that are likely to be beneficial in the prevention of a subsequent event.

Pathology related to chronic arsenic exposure.

Millions now suffer the effects of chronic arseniasis related to environmental arsenic exposure. The biological mechanisms responsible for arsenic-induced toxicity and especially chronic effects, including cancer, are not well known. The U.S. Armed Forces Institute of Pathology (AFIP) is participating in an international research effort to improve this understanding by the development of the International Tissue and Tumor Repository for Chronic Arsenosis (ITTRCA). The ITTRCA obtains, archives, and makes available for research purposes, tissues from subjects exposed to arsenic. We provide here a short overview of arsenic-induced pathology, briefly describe arsenic-induced lesions in the skin and liver, and present five case reports from the ITTRCA. Arsenic-induced skin pathology includes hyperkeratosis, pigmentation changes, Bowen disease, squamous cell carcinoma, and basal cell carcinomas. A unique spectrum of skin lesions, known as arsenical keratosis, is rather characteristic of chronic arseniasis. Bowen disease, or squamous cell carcinoma in situ of the skin, has been well documented as a consequence of arsenical exposure. A spectrum of liver lesions has also been attributed to chronic arseniasis. Of these, hepatocellular carcinoma, angiosarcoma, cirrhosis, and hepatoportal sclerosis have been associated with arsenic exposure. We present case reports that relate to these health conditions, namely, squamous cell carcinoma, basal cell carcinoma, and Bowen disease of the skin and hepatocellular carcinoma and angiosarcoma of the liver. Four patients had been treated with arsenical medications for such conditions as asthma, psoriasis, and syphilis, and one case occurred in a boy chronically exposed to arsenic in drinking water.

A histopathological study of head and neck specimens from a cohort of Persian Gulf War military veterans.

Approximately 700,000 U.S. military personnel were deployed to the Persian Gulf region during the Gulf War. Since their return, many Persian Gulf War veterans (GWVs) have presented with various medical symptoms, including those related to the head and neck. A study devoted to the histopathology of head and neck specimens from GWVs has not been previously reported. Surgical, autopsy, and cytological specimens from GWVs were evaluated by light microscopy at the Armed Forces Institute of Pathology with additional studies as required and were entered into the Kuwait Registry. The Kuwait Registry contained 361 head and neck specimens from 264 GWVs. Neoplasms were relatively infrequent, including six malignant neoplasms and 14 benign neoplasms. The most frequent diagnoses were chronic sinusitis, allergic rhinitis, and lymphoid hyperplasia of the tonsils. These conditions are frequently encountered in routine anatomic pathology practice in the general U.S. population.