Detection of early stage of human coronary atherosclerosis by angioscopic imaging of collagen subtypes.

BACKGROUND: Detection of the early stage of atherosclerosis, which does not exhibit macroscopic morphological changes, is currently beyond the scope of any available imaging techniques. Collagens provide mechanical support of vascular wall and subtype I is the major component of the normal vascular wall. During the process of atherosclerosis, collagen III appears first, followed by subtypes IV and V during fibrosis of the intima. Therefore, the presence of collagen III indicates initiation of atherosclerosis. Here, we aimed to visualize collagen subtypes in human coronary wall. METHODS: Under microscopy, collagen III was stained emerald-green, collagen I was red, and IV and V were pink in the presence of a mixture of Silius red and Fast green dyes. Fifty-one coronary arteries excised from 20 human autopsy subjects were classified by angioscopy and histology as normal segments, white and yellow plaques, and examined after staining collagen subtypes in their superficial layer with the same dye mixtures. RESULTS: Normal coronary segments with intimal thickness ≦200 µm stained red, with thickness >200 µm stained red and emerald-green in a mosaic pattern or emerald-green alone, yellow plaques without a necrotic core were pink, and those with a necrotic core showed no staining. CONCLUSION: The results suggested that coronary segments stained red indicate no atherosclerosis, red and emerald-green in a mosaic pattern indicates initiation of atherosclerosis, emerald-green is early-stage atherosclerosis, pink is advanced stage of atherosclerosis, and no staining shows the end stage of atherosclerosis at least in superficial layer of coronary artery. Therefore, dye-staining angioscopy using Silius red and Fast green dyes in combination could be used to detect the early and advanced stage of atherosclerosis in superficial layer of human coronary artery.

Detection of Ceramide, a Risk Factor for Coronary Artery Disease, in Human Coronary Plaques by Fluorescent Angioscopy.

BACKGROUND: The presence of ceramide in human coronary plaques is a risk factor for ischemic heart disease, but its visualization in the human vessel wall is currently beyond the scope of any available imaging techniques.Methods and Results:Deposition of ceramide was examined by fluorescent angioscopy (FA) and microscopy (FM) using golden fluorescence (Go) as a specific marker of ceramide in yellow plaques, which were obtained from 23 autopsy subjects and classified by conventional angioscopy and histology. Ceramide was observed by FM in 34 of the 41 yellow plaques with a necrotic core (NC) but rarely in the 28 without. Ceramide and macrophages/foam cells co-deposited mainly in the border zone of the NC and fibrous cap (FC). The Go of ceramide was seen when the fibrous cap thickness was ≤100 µm. FA was performed to detect coronary plaques exhibiting Go in patients with coronary artery disease. Ceramide was also detected by FA in 6 of 18 yellow plaques (33.3%) in 8 patients with stable angina and in 18 of 24 yellow plaques (75.0%, P<0.05 vs. stable angina) in 8 patients with old myocardial infarction. CONCLUSIONS: The Go of ceramide in human coronary plaques is detectable by FA and Go could be used as a marker of vulnerable plaque (i.e., thin FC with NC).

Fluorescent angioscopic imaging of calcium phosphate tribasic: precursor of hydroxyapatite, the major calcium deposit in human coronary plaques.

Coronary calcification is a risk factor for ischemic heart disease. Hydroxyapatite that is formed by polymerization from calcium phosphate tribasic (CPT) is the major constituent of coronary calcium deposits. If CPT could be visualized, coronary calcification could be predicted and prevented. We discovered that when CPT and collagen I, the main constituent of collagen fibers, are mixed with lac dye (LD) and then exposed to fluorescent light excited at 345 ± 15 nm and emitted at 420 nm, a purple fluorescence that is characteristic of CPT only is elicited. So, we examined localization of CPT and its relation to plaque morphology by color fluorescent angioscopy (CFA) or microscopy (CFM) in 24 coronary arteries obtained from 12 autopsy subjects. By CFA, the incidence (%) of CPT as confirmed by purple fluorescence in 15 normal segments, 25 white plaques, 14 yellow plaques without necrotic core (NC) and 8 yellow plaques with NC was 20, 36, 64 and 100 (p < 0.05 vs. normal segments), respectively. By CFM, the CPT was either deposited alone amorphously or surrounded hydroxyapatite that was identified by Oil Red O, methylene blue and von Kossa's stain. The results suggested that CFA using LD is feasible for imaging CPT, that is a precursor of hydroxyapatite, in human coronary plaques, and this technique would help prediction and discovery of a preventive method of coronary calcification.

Recent Advances in Fluorescent Angioscopy for Molecular Imaging of Human Atherosclerotic Coronary Plaque.

PURPOSE OF REVIEW: In vivo imaging of the native substances, including lipoproteins, that comprise human atherosclerotic plaques is currently beyond the scope of any available imaging techniques. Color and near-infrared fluorescent angioscopy (CFA and NIRFA, respectively) systems have been recently developed for molecular imaging of lipoproteins within the human coronary arterial wall ex vivo and/or in vivo. The author reviews recent findings on lipoprotein deposition in human coronary plaques obtained by these imaging techniques. RECENT FINDINGS: Using specific biomarkers, native pro-atherogenic substances such as oxidized low-density lipoprotein (ox-LDL), LDL, triglycerides (TG), apolipoprotein B-100 (ApoB-100), and lysophosphatidylcholine (LPC), and the anti-atherogenic substance such as high-density lipoprotein (HDL) were visualized by CFA, and LDL and cholesterol by NIRFA, in coronary plaques obtained from autopsy subjects. The relationship between incidence and plaque morphology differed for each substance. The incidence of ox-LDL and LDL on color fluorescence microscopy correlated well with that observed using immunohistochemical techniques. During coronary catheterization in patients, ox-LDL, LDL, and HDL in coronary plaques were visualized by CFA or NIRFA. CONCLUSIONS: Using CFA or NIRFA, the distribution of the major native pro-atherogenic and anti-atherogenic lipoproteins and their components within human coronary plaques can be evaluated ex vivo and/or in vivo. Fluorescent angioscopy could help our understanding of the molecular mechanisms of coronary atherosclerosis and in the evaluation of the effects of therapy targeting the substances comprising atherosclerotic coronary plaques.

Human pericoronary adipose tissue as storage and possible supply site for oxidized low-density lipoprotein and high-density lipoprotein in coronary artery.

BACKGROUND: Thickening of the pericoronary adipose tissue (PCAT) is a proven risk factor for coronary artery disease, but it is poorly understood whether PCAT stores pro-atherogenic substances with oxidized low-density lipoprotein (oxLDL) and low-density lipoprotein (LDL), and an anti-atherogenic substance with high-density lipoprotein (HDL) and supply them to the coronary intima. METHODS: Using immunohistochemical techniques, the localization of oxLDL, LDL and HDL in PCAT and its adjacent coronary segments was examined in 30 epicardial coronary arteries excised from 11 human autopsy cases. RESULTS: PCAT stored oxLDL and HDL in all, but LDL rarely, in 77 specimens examined, irrespective of the presence or absence of coronary plaques and underlying disease. The percentage (%) incidence of oxLDL, HDL and LDL deposits in intima was, respectively, 28, 10, 35 in 29 normal segments, 80 (p<0.05 vs. normal segments), 12, 75 in 19 white plaques (growth stage), 57, 36, 90 in 15 yellow plaques without necrotic core (NC; mature stage), and 40, 21, 100 (p<0.05 vs. normal segments) in 14 yellow plaques with NC (end-stage of maturation) as classified by angioscopy and histology. In coronary intima, oxLDL deposited in either a dotted or diffuse pattern whereas HDL and LDL showed diffuse patterns. Dotted oxLDL deposits were contained in CD68(+)-macrophages traversing the border of PCAT and adventitia, external and internal elastic laminae. Diffuse oxLDL and HDL deposits colocalized with intimal vasa vasorum. CONCLUSIONS: The results suggested that, as a hitherto unrecognized supplying route, the human PCAT stores oxLDL and HDL and oxLDL is supplied to coronary intima either by CD68(+)-macrophages or vasa vasorum and HDL by vasa vasorum, and that deposition of oxLDL and HDL in the intima increased with plaque growth but the former decreased while the latter increased further with plaque maturation. Molecular therapy targeting PCAT before plaque maturation could be effective in preventing atherosclerosis.

Imaging of Triglycerides in Human Coronary Plaques by Color Fluorescent Angioscopy and Microscopy.

Native triglycerides (TG) deposited in the human vascular wall is not measurable or visible in vivo to date. We discovered that by exciting fluorescence at 345 nm and emitting at 420 nm, 3-amino-4-hydroxy-5-nitrobenzene sulfonic acid monohydrate (3-ANA) elicits a brown fluorescence that is characteristic of just TG. Therefore, localization of TG in coronary plaques and normal segments that were obtained from 19 human autopsy cases was examined by color fluorescent angioscopy (CFA) and microscopy using 3-ANA as a biomarker of TG. By CFA, the percentage (%) incidence of TG in 23 normal segments, 13 white plaques without lipid deposition, 18 white plaques (growth stage) with lipid deposition, 11 yellow plaques without necrotic core (mature stage), and 12 yellow plaques with necrotic core (advanced mature stage) was 95, 92, 50, 27, and 25, respectively. By color fluorescent microscopy, TG deposited mostly in the fibrotic area of the plaques. Contrary to the general belief that TG amount increases with plaque maturation, the results indicated that TG was deposited in most of the normal coronary segments, but the amount decreased with plaque maturation. If 3-ANA becomes applicable clinically, the CFA system could be used for imaging TG within coronary plaques in patients in vivo.

Pericoronary Adipose Tissue as Storage and Supply Site for Oxidized Low-Density Lipoprotein in Human Coronary Plaques.

OBJECTIVES: It is generally believed that low-density lipoprotein enters the vascular wall from its lumen and oxidized (oxLDL), after which it plays an important role in atherosclerosis. Because voluminous epicardial adipose tissue is a risk factor for coronary events, there is a possibility that the pericoronary adipose tissue (PCAT), which is a part of epicardial adipose tissue, acts as a risk factor by supplying oxLDL to the coronary arterial wall. The present study was performed whether PCAT stores and supplies oxLDL to the coronary wall. METHODS: Localization of oxLDL in PCAT and its relation to plaque morphology were examined by immunohistochemical techniques in 27 epicardial coronary arteries excised from 9 human autopsy cases. RESULTS: OxLDL deposited in all PCAT of the studied cases. The percent (%) incidence of oxLDL in the intima of 25 normal segment, 19 white plaques, 15 yellow plaques without necrotic core (NC) and 10 yellow plaques with NC, was 32, 84, 93 (p<0.05 vs normal segments and yellow plaques with NC), and 30, respectively. OxLDL deposited either in dotted or diffuse pattern. Double immunohistochemical staining revealed that the dotted oxLDL was that contained in CD68(+)-macrophages. The oxLDL-containing macrophages were observed in the interstitial space but not inside of the vasa vasorum, and they traversed PCAT, adventitia, external and internal elastic laminae, suggesting their migration towards the intima. Diffuse oxLDL deposits were observed in 17 preparations, the majority of which were co-localized with the vasa vasorum in outer or in both inner and outer halves of intima, and rarely in the inner half alone. CONCLUSIONS: The results suggested that PCAT is a supply source of oxLDL to coronary intima and acts as a risk factor for coronary events, that oxLDL increasingly deposits in the intima with plaque growth and decreases after plaque maturation, and therefore molecular therapies targeting the PCAT before plaque growth could be effective in preventing human coronary atherosclerosis.

Molecular Imaging of Native Low-Density Lipoprotein by Near-Infrared Fluorescent Angioscopy in Human Coronary Plaques.

Low-density lipoprotein (LDL) is an important risk factor for coronary artery disease, but its localization within the human coronary arterial wall is poorly understood. Imaging of LDL in 30 coronary arteries excised from 15 subjects who underwent autopsy was performed using near-infrared fluorescent angioscopy system and using indocyanine green dye as a biomarker of LDL. The percentage incidence of LDL in 28 normal segments, 24 white plaques (early stage of plaque growth), and 21 yellow plaques (mature stage of plaque) classified by conventional angioscopy, was 14.2, 79.1 (p <0.01 vs normal segments and p <0.05 vs yellow plaques), and 28.5, respectively. Coronary near-infrared fluorescent angioscopy showed similar results in 7 patients in vivo. Our results suggested that LDL begins to deposit in the human coronary arterial wall in the early stage of atherosclerosis, increasingly deposits with plaque growth and decreases in the mature stage; and therefore, molecular therapy targeting LDL should be started before plaque maturation.

Molecular imaging of apolipoprotein B-100 in human coronary plaques by color fluorescent angioscopy and microscopy.

Apolipoprotein B-100 (ApoB-100) is an important risk factor for coronary artery disease. However, its localization in human coronary plaques is not well understood. The present study was performed to visualize ApoB-100 in human coronary artery wall. Deposition of native ApoB-100 in excised human coronary plaques and normal segments classified by conventional angioscopy was investigated by color fluorescent angioscopy (CFA) and microscopy (CFM) using Nile blue dye (NB) which elicits a golden fluorescence characteristic of ApoB-100 as a biomarker. By CFA, the % incidence of ApoB-100 was 20 in 40 normal segments, 38 in 42 white, and 11 in 35 yellow plaques (P < 0.05 versus white plaques). There was no significant difference in detection sensitivity between CFA and luminal surface scan by CFM. By CFM transected surface scan, ApoB-100 deposited in superficial, deep, and/or in both layers. Deposition in both layers was frequently observed in white plaques and yellow plaques without necrotic core (NC), less frequently in normal segments, and rarely in yellow plaques with NC. (1) Taking into consideration the well known process of plaque growth, the results suggest that ApoB-100 begins to deposit before plaque formation, increasingly deposits with plaque growth, and disappears after necrotic core formation. (2) CFA is feasible for imaging of ApoB-100 in human coronary artery wall.

Molecular imaging of low-density lipoprotein in human coronary plaques by color fluorescent angioscopy and microscopy.

OBJECTIVES: Low-density lipoprotein (LDL) is an important risk factor for coronary artery disease. However, its localization in human coronary plaques is not well understood. The present study was performed to visualize LDL in human coronary artery wall. METHODS: (1) The fluorescence characteristic of LDL was investigated by color fluorescent microscopy (CFM) with excitation at 470-nm and emission at 515-nm using Nile blue dye (NB) as a biomarker. (2) Native LDL in 40 normal segments, 42 white plaques and 35 yellow plaques (20 with necrotic core) of human coronary arteries was investigated by color fluorescent angioscopy (CFA) and CFM. RESULTS: (1) NB elicited a brown, golden and red fluorescence characteristic of LDL, apolipoprotein B-100, and lysophosphatidylcholine/triglyceride, respectively. (2) The % incidence of LDL in normal segments, white, and yellow plaques was 25, 38 and 14 by CFA and 42, 42 and 14 by CFM scan of their luminal surface, respectively, indicating lower incidence (p<0.05) of LDL in yellow plaques than white plaques, and no significant differences in detection sensitivity between CFA and CFM. By CFM transected surface scan, LDL deposited more frequently and more diffusely in white plaques and yellow plaques without necrotic core (NC) than normal segments and yellow plaques with NC. LDL was localized to fibrous cap in yellow plaques with NC. Co-deposition of LDL with other lipid components was observed frequently in white plaques and yellow plaques without NC. CONCLUSIONS: (1) Taken into consideration of the well-known process of coronary plaque growth, the results of the present study suggest that LDL begins to deposit before plaque formation; increasingly deposits with plaque growth, often co-depositing with other lipid components; and disappears after necrotic core formation. (2) CFA is feasible for visualization of LDL in human coronary artery wall.

ß-actin-positive mononuclear cells participate in coronary microvascular medial hyperplasia by migrating through adventitia into media, with special reference to microvessel angina.

Coronary microvascular hyperplasia is a cause of microvessel angina, although the underlying cellular mechanisms remain unclear. We examined how mononuclear cells expressing ß-actin (ß-MNCs), which were identified in coronary vessels, induce coronary microvascular hyperplasia.The presence of ß-MNCs in coronary hyperplastic arterial (HAM) and venous microvessels (HVM) was examined by endomyocardial biopsy in 25 patients with suspected microvessel angina. ß-MNCs were identified in 14 HAMs obtained from 11 patients. Basic fibroblast growth factor and heparin sulfate were injected into the infarcted myocardium to induce HAM and HVM in 28 beagles, and then we examined the role of ß-MNCs in the onset of HAM and HVM. The following changes were observed after infarction induction in beagles: (a) migration of ß-MNCs from the existing microvessels into the interstitial space at 1-2 weeks; (b) those traversing the adventitia into the media, but not intima, of microvessels; (c) their transformation to smooth muscle cells (SMCs) and/or connective tissues (collagen and elastin fibers); (d) and medial hyperplasia without intimal hyperplasia. Medial hyperplasia was classified into SMC-proliferative and both SMC- and connective tissue-proliferative types. ß-MNCs expressed CD(34) but did not express other major vessel-related cell markers.ß-MNCs are a vascular progenitor, and migrate out of the adventitia into media, and participate in the etiology of coronary microvascular medial hyperplasia.

Migration of mononuclear cells expressing ß-actin through the adventitia into media and intima in coronary arteriogenesis and venogenesis in ischemic myocardium.

It was previously thought that arteriogenesis and venogenesis are induced not only by proliferation of vessel-resident smooth muscle cells (SMCs) and endothelial cells (ECs) but also by migration of their precursors. However, it is not well understood through what route(s) the precursors migrate into the existing vessels.We examined through what route or routes circulating mononuclear cells expressing ß-actin (ß-MNCs), which we identified in canine coronary vessels, migrate into coronary vessel walls and cause arteriogenesis and venogenesis at 1, 2, 4 and 8 weeks after induction of myocardial infarction.The following changes were observed: (1) The ß-MNCs migrated via coronary microvessels to the interstitial space at one week; (2) ß-MNCs traversed the adventitia into the media and settled in parallel with pre-existing smooth muscle cells (SMCs) in arterioles and arteries and lost ß-actin and acquired α-smooth muscle actin (α-SMA) to become mature SMCs at 2-4 weeks; (3) at the same time, other ß-MNCs migrated across the adventitia and media into the intima and settled in parallel with pre-existing endothelial cells (ECs) and lost ß-actin, while acquiring CD(31), to become mature ECs, resulting in arteriogenesis; (4) Similarly, ß-MNCs migrated into venular and venous walls and became SMCs or ECs, resulting in venogenesis.ß-MNCs in the interstitial space expressed CD(34) but not other major vascular cell markers.ß-MNCs, possibly a vascular progenitor, migrate not from the lumen but across the adventitia into the media or intima of coronary vessels and transit to SMCs or ECs, and participate in arteriogenesis and venogenesis in ischemic myocardium.

Nitroglycerin-induced heterogeneous subendocardial myocardial blood flow observed by cardioscopy in patients with coronary artery disease.

It is controversial as to whether or not nitroglycerin (NTG) increases subendocardial myocardial blood flow (SMBF), and if it does, whether arterial or venous blood flow is increased in patients with coronary artery disease. This study was performed to examine NTG-induced changes in SMBF.Changes in SMBF induced by NTG (200 µg, i.v.) were examined by cardioscopy in 58 left ventricular wall segments of 58 patients with coronary artery disease. NTG-induced red and purple endocardial colors were defined as increased arterial and venous SMBF, respectively. Endocardial color before NTG administration was classified into brown, light brown, pale and white. Endomyocardial biopsy of the observed portion and (201)Tl scintigraphy were performed in 40 of these patients immediately after cardioscopy and several days after cardioscopy, respectively.Upon administration of NTG, SMBF increased in 48 of 58 wall segments; arterial SMBF in 34 and venous SMBF in 12 wall segments; arterial SMBF in all 24 brown to light brown segments; venous SMBF, arterial SMBF and no change in 12, 10 and 5 of pale segments, respectively; and no change in all 10 white wall segments. (201)Tl-scintigraphy and endomyocardial biopsy revealed that brown, light brown, pale and white endocardial color represented no ischemia, mild ischemia, severe ischemia and fibrosis, respectively.NTG caused an increase in either arterial or venous SMBF depending on control endocardial color, wall motion and severity of coronary stenosis.

Recent Advances in Percutaneous Cardioscopy.

Percutaneous cardioscopy, using high-resolution fiberoptic imaging, enables direct visualization of the cardiac interior, thereby enabling macroscopic pathological diagnosis. Percutaneous cardioscopy has demonstrated that the endocardial surface exhibits various colors characteristic of different heart diseases. This imaging modality can now be used for evaluation of the severity of myocardial ischemia, and staging of myocarditis. Myocardial blood flow recovery induced by vasodilating agents or percutaneous coronary interventions can be clearly visualized. Morphological and functional changes in the cardiac valves can also be evaluated. Cardioscope-guided endomyocardial biopsy enables pin-point biopsy of the diseased myocardium. Recently, dye-image cardioscopy and fluorescence cardioscopy were developed for evaluation of the subendocardial microcirculation. Cardioscope-guided intracardiac therapies such as myotomy, myectomy, valvulotomy, and transendocardial angiogenic and myogenic therapy have been trialed using animal models in anticipation of future clinical applications. Percutaneous cardioscopy has the potential to contribute to our understanding of heart disease, and to assist in guidance for intracardiac therapies.

Role of calcium-activated potassium channels in the genesis of 3,4-diaminopyridine-induced periodic contractions in isolated canine coronary artery smooth muscles.

We found that 3,4-diaminopyridine (3,4-DAP), a voltage-gated potassium channel (K(V)) inhibitor, elicits pH-sensitive periodic contractions (PCs) of coronary smooth muscles. Underlying mechanisms of PCs, however, remained to be elucidated. The present study was performed to examine the roles of ion channels in the genesis of PCs. To determine the electromechanical changes of smooth muscles, isolated coronary arterial rings from beagles were suspended in organ chambers filled with Krebs-Henseleit solution, and 10(-2) M 3,4-DAP was added to elicit PCs. 3,4-DAP caused periodic spike-and-plateau depolarization accompanied by contraction. PCs were not produced when the CaCl(2) concentration in the chamber was ≤ 0.3 × 10(-3) or ≥ 10(-2) M. PCs were eliminated by a CaCl(2) concentration ≥ 5 × 10(-3) M or by lowering pH below 7.20 with HCl and recovered by the addition of iberiotoxin or charybdotoxin, which inhibit large-conductance calcium-activated potassium channels (K(Ca)), or by elevating pH above 7.35 with NaOH. PCs, as well as the spike-and-plateau depolarization, were eliminated by nifedipine, which inhibits L-type voltage-gated calcium channels (Ca(V)). Influx of Ca(2+) through L-type Ca(V), which was opened because closing of K(Ca), secondary to 3,4-DAP-induced closing of K(V), resulted in contraction; the intracellular Ca(2+) increased by this influx opened K(Ca), leading to closure of Ca(V) and consequent cessation of Ca(2+) influx with resultant relaxation. These processes were repeated spontaneously to cause PCs. H(+) and OH(-) were considered to act as the opener and closer of K(Ca), respectively.

Histological characteristics of glistening yellow coronary plaques seen on angioscopy. -With special reference to vulnerable plaques-.

BACKGROUND: Glistening yellow coronary plaques (GY) seen on angioscopy are considered vulnerable to disruption. Collagen fiber (CF) is the main substance that protects coronary plaques against mechanical stress. Therefore, whether angioscopically defined vulnerable plaques correlate with those defined histologically was investigated. METHODS AND RESULTS: One hundred and thirty-two excised human coronary plaques were classified by angioscopy into 19 GY, 49 non-glistening yellow plaques (non-GY) and 64 white plaques, and their relation to CF density was examined. CF-dense (>15/100 µm), CF-loose (>5 and <15/100 µm), and CF-scanty (<5/100 µm) plaques were hypothesized to be stable, relatively stable, and vulnerable, respectively. Histologically the plaques were classified into non-lipid deposition, superficial lipid deposition and diffuse lipid deposition groups; the diffuse lipid deposition group was classified into necrotic core (NC) and non-NC types. Nineteen GY were composed of 4 with superficial lipid deposition, 4 with non-NC type of diffuse lipid deposition, and 11 with NC type. Sixteen (84%) of these were CF scanty. Forty-nine (100%) of non-GY and 57 (89%) of white plaques were CF dense or CF loose The sensitivity, specificity and predictive value of GY in detecting histologically vulnerable plaques were 90%, 97% and 84%, respectively, indicating that GY represented histologically vulnerable plaques. CONCLUSIONS: These pathohistological characteristics might indicate that GY, less-protected plaques against mechanical stress, are vulnerable plaques.

Characterization of coronary fibrin thrombus in patients with acute coronary syndrome using dye-staining angioscopy.

OBJECTIVE: Because fibrin is transparent and almost invisible by any conventional imaging methodologies, clinical examinations of coronary fibrin thrombus have been ignored, and little is known about its role in the genesis of acute coronary syndrome (ACS). The present study was performed to visualize coronary fibrin thrombus and to examine its role in ACS. METHODS AND RESULTS: Dye-staining coronary angioscopy using Evans blue dye, which selectively stains fibrin blue but does not stain blood corpuscles, was performed for observation of globular coronary thrombi in 111 ACS patients. The thrombi were aspirated for histological examination. The thrombi were classified by visual appearance into 8 transparent, 3 light-red, 2 frosty glass-like and membranous, 32 white, 8 brown, 34 red, and 19 red-and-white in a mosaic pattern. Transparent thrombi that were not visible by conventional angioscopy were visualized as a blue structure by dye-staining angioscopy, and they were observed in patients with unstable angina (UA) and non-ST elevation myocardial infarction (NSTEMI). The thrombi caused total or subtotal coronary occlusion. The aspirated thrombi were composed of fibrin alone by histology. Fibrin-rich thrombi were visualized using dye-staining angioscopy in 60% of 50 patients with UA+NSTEMI and in 29% of 61 patients with ST-elevation myocardial infarction. By histology of the aspirated thrombi, fibrin-rich thrombi were observed in 71% of 33 patients with UA+NSTEMI and in 28% of 35 patients with ST-elevation myocardial infarction. CONCLUSION: Fibrin-rich coronary thrombi were frequently observed by both dye-staining angioscopy and histology in ACS patients. Rarely, fibrin itself formed a globular thrombus and caused coronary occlusion.

Possible role of damaged neoendothelial cells in the genesis of coronary stent thrombus in chronic phase. A dye staining angioscopic study.

The mechanism(s) underlying formation of coronary stent thrombus (ST) in chronic phase is yet unclear. Endothelial cells are highly antithrombotic, therefore, it is conceivable that neoendothelial cells (NECs) covering stent struts are damaged and cause ST. This study was performed to examine the role of damaged NECs covering coronary stent struts in the genesis of occlusive or nonocclusive ST in chronic phase.(1) Forty-four patients with acute coronary syndrome (17 females and 27 males) underwent dye-staining coronary angioscopy, using Evans blue which selectively stains damaged endothelial cells, 6 months after bare-metal stent (BMS) deployment. Neointimal coverage was classified into not covered (grade 0), covered by a thin layer (grade 1), and buried under neointima (grade 2) groups. (2) In 7 beagles, the relationships between neointimal thickness and ST were examined 6 months after BMS deployment. (3) The NECs on the struts were stained blue in 4 of 25 patients with grade 2 and in 11 of 20 patients with grade 0/1 (P < 0.05). ST was observed in none of the former and in 5 of the latter (P < 0.05). (4) In beagles, neointimal coverage was grade 0/1 when neointimal thickness was 80.2 ± 40.0 µm, whereas grade 2 when thickness was 184 ± 59.4 µm. ST was observed in 9 of 15 struts with neointimal thickness within 100 µm and in one of 17 struts with thickness over 100 µm (P < 0.05). ST arose from damaged NECs covering the stent struts. NECs may have been damaged due to friction between them and struts due to thin interposed neointima which might have acted as a cushion, resulting in ST.