Myocardial infarct extension during reperfusion after coronary artery occlusion: Pathologic evidence

AbstractObjectives. The goal of this study was to demonstrate myocardial infarct extension during reperfusion within the same animal.Background. Whether myocardial reperfusion can result in the extension of myocardial necrosis remains controversial. The transformation of reversibly injured myocytes into irreversibly damaged cells after reperfusion has been difficult to demonstrate pathologically.Methods. New Zealand White rabbits (Group I, n = 10) were subjected to 30 min of coronary artery occlusion and 180 min of reperfusion. Horseradish peroxidase, a tracer protein that permeates the sarcolemma of irreversibly injured myocytes, was used to quantitate myocyte necrosis at the beginning of reperfusion. Within the same heart, infarct size was measured after 180 min of reperfusion by triphenyttetrazolium chloride (TTC) staining. In separate experiments to demonstrate the validity of the model, rabbits were subjected to 30 min of coronary occlusion, followed by intravenous infusion of horseradish peroxidase and rapid induction of death (Group II) or 30 min of occlusion, 180 min of reperfusion with horseradish peroxidase administered after 180 min of reperfusion and TTC staining after induced death (Group III).Results. In Group I, infarct size at the onset of reperfusion, delineated by horseradish peroxidase, measured 45.3 ± 2.8% of the area of risk and was significantly less than TTC-delineated infarct size after 189 min of re perfusion (59.8 ± 33%, p = 0.0002). By electron microscopy, border areas within the ischemic bed demonstrated irreversibly injured horseradish peroxidasepositive myocytes adjacent to irreversibly injured horseradish peroxidase-negative myocytes, suggesting that farther cell death occurred during reperfusion. In Group II, infarcts delineated by horseradish peroxidase after 30 min of coronary occlusion were similar in size to infarcts measured by this tracer in Group I. In Group III, infarcts delineated by horseradish peroxidase at 180 min of reperfusion were similar in size to infarcts measured by TTC and similar to TTC-delineated infarcts measured at 180 min of reperfusion in Group I.Conclusions. These results provide evidence that there is a subset of myocytes in border areas within the ischemic region that are viable at the beginning of reperfusion but subsequently progress to irreversible injury during the reperfusion period

Coronary Responses and Differential Mechanisms of Late Stent Thrombosis Attributed to First-Generation Sirolimus- and Paclitaxel-Eluting Stents

ObjectivesThe 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).BackgroundRecent 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.MethodsThe 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.ResultsBoth 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.ConclusionsDifferential 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

Incidence and Predictors of Drug-Eluting Stent Fracture in Human Coronary Artery A Pathologic Analysis

ObjectivesThe aim of this study was to perform pathologic assessment on stent fracture.BackgroundClinically, stent fracture has been reported in 1% to 2% of patients after drug-eluting stent (DES) implantation.MethodsHigh-contrast film-based radiographs of 177 consecutive lesions from the CVPath DES autopsy registry were reviewed. Stent fracture was graded as I (single-strut fracture), II (≥2 struts), III (≥2 struts with deformation), IV (with transection without gap), and V (with transection causing gap in stent segment). The incidence of adverse pathologic findings (thrombosis and restenosis) was assessed histologically.ResultsStent fracture was documented in 51 lesions (29%; grade I = 10, II = 14, III = 12, IV = 6, and V = 9). Lesions with stent fracture had longer duration after implantation (172 days [interquartile range (IQR) 31 to 630 days] vs. 44 days [IQR 7 to 270 days], p = 0.004), a higher rate of Cypher (Cordis Corp., Miami Lakes, Florida) stent usage (63% vs. 36%, p = 0.001), longer stent length (30.0 mm [IQR 22.0 to 40.0 mm] vs. 20.0 mm [IQR 14.0 to 27.3 mm], p < 0.0001), and a higher rate of overlapping stents (45% vs. 22%, p = 0.003). Although fracture with grade I to IV did not have significant impact on the occurrence of adverse pathologic findings such as thrombosis and restenosis, 67% of the grade V fracture lesions were associated with adverse pathologic findings at fracture sites. Longer stent length, use of Cypher, and longer duration of implant were identified as independent risk factors of stent fracture by logistic regression analysis.ConclusionsThe incidence of stent fracture was 29% lesions at autopsy, which is much higher than clinically reported. A high rate of adverse pathologic findings was observed in lesions with grade V stent fracture, whereas fracture with grade I to IV did not have a significant impact on the pathological outcome

The Pathology of Neoatherosclerosis in Human Coronary Implants Bare-Metal and Drug-Eluting Stents

ObjectivesHuman coronary bare-metal stents (BMS) and drug-eluting stents (DES) from autopsy cases with implant duration >30 days were examined for the presence of neointimal atherosclerotic disease.BackgroundNeointimal atherosclerotic change (neoatherosclerosis) after BMS implantation is rarely reported and usually occurs beyond 5 years. The incidence of neoatherosclerosis after DES implantation has not been reported.MethodsAll available cases from the CVPath stent registry (n = 299 autopsies), which includes a total of 406 lesions—197 BMS, 209 DES (103 sirolimus-eluting stents [SES] and 106 paclitaxel-eluting stents [PES])—with implant duration >30 days were examined. Neoatherosclerosis was recognized as clusters of lipid-laden foamy macrophages within the neointima with or without necrotic core formation.ResultsThe incidence of neoatherosclerosis was significantly greater in DES lesions (31%) than BMS lesions (16%; p < 0.001). The median stent duration with neoatherosclerosis was shorter in DES than BMS (DES, 420 days [interquartile range [IQR]: 361 to 683 days]; BMS, 2,160 days [IQR: 1,800 to 2,880 days], p < 0.001). Unstable lesions characterized as thin-cap fibroatheromas or plaque rupture were more frequent in BMS (n = 7, 4%) than in DES (n = 3, 1%; p = 0.17), with relatively shorter implant durations for DES (1.5 ± 0.4 years) compared to BMS (6.1 ± 1.5 years). Independent determinants of neoatherosclerosis identified by multiple logistic regression included younger age (p < 0.001), longer implant durations (p < 0.001), SES usage (p < 0.001), PES usage (p = 0.001), and underlying unstable plaques (p = 0.004).ConclusionsNeoatherosclerosis is a frequent finding in DES and occurs earlier than in BMS. Unstable features of neoatherosclerosis are identified for both BMS and DES with shorter implant durations for the latter. The development of neoatherosclerosis may be yet another rare contributing factor to late thrombotic events

Sentry bioconvertible inferior vena cava filter: Study of stages of incorporation in an experimental ovine model

The Sentry inferior vena cava (IVC) filter is designed to provide temporary protection from pulmonary embolism (PE) and then bioconvert to become incorporated in the vessel wall, leaving a patent IVC lumen. Objective. To evaluate the performance and stages of incorporation of the Sentry IVC filter in an ovine model. Methods. Twenty-four bioconvertible devices and 1 control retrievable filter were implanted in the infrarenal IVC of 25 sheep, with extensive daily monitoring and intensive imaging. Vessels and devices were analyzed at early (≤98 days, n = 10) and late (180 ± 30 days, n = 14 study devices, 1 control) termination and necropsy time-points. Results. Deployment success was 100% with all devices confirmed in filtering configuration, there were no filter-related complications, and bioconversion was 100% at termination with vessels widely patent. By 98 days for all early-incorporation analysis animals, the stabilizing cylindrical part of the Sentry frame was incorporated in the vessel wall, and the filter arms were retracted. By 180 days for all late-incorporation analysis animals, the filter arms as well as frames were stably incorporated. Conclusions. Through 180 days, there were no filter-related complications, and the study devices were all bioconverted and stably incorporated, leaving all IVCs patent

Methodological Standardization for the Pre-Clinical Evaluation of Renal Sympathetic Denervation

Transcatheter ablation of renal autonomic nerves is a viable option for the treatment of resistant arterial hypertension; however, structured pre-clinical evaluation with standardization of analytical procedures remains a clear gap in this field. Here we discuss the topics relevant to the pre-clinical model for the evaluation of renal denervation (RDN) devices and report methodologies and criteria toward standardization of the safety and efficacy assessment, including histopathological evaluations of the renal artery, periarterial nerves, and associated periadventitial tissues. The pre-clinical swine renal artery model can be used effectively to assess both the safety and efficacy of RDN technologies. Assessment of the efficacy of RDN modalities primarily focuses on the determination of the depth of penetration of treatment-related injury (e.g., necrosis) of the periarterial tissues and its relationship (i.e., location and distance) and the effect on the associated renal nerves and the correlation thereof with proxy biomarkers including renal norepinephrine concentrations and nerve-specific immunohistochemical stains (e.g., tyrosine hydroxylase). The safety evaluation of RDN technologies involves assessing for adverse effects on tissues local to the site of treatment (i.e., on the arterial wall) as well as tissues at a distance (e.g., soft tissue, veins, arterial branches, skeletal muscle, adrenal gland, ureters). Increasing experience will help to create a standardized means of examining all arterial beds subject to ablative energy and in doing so enable us to proceed to optimize the development and assessment of these emerging technologies

Acute Thrombogenicity of a Durable Polymer Everolimus-Eluting Stent Relative to Contemporary Drug-Eluting Stents With Biodegradable Polymer Coatings Assessed Ex Vivo in a Swine Shunt Model

AbstractObjectivesThis study sought to evaluate whether the permanent fluoropolymer-coated Xience Xpedition everolimus-eluting stent (Xience-EES) exhibits lower acute thrombogenicity compared with contemporary drug-eluting stents (DES) with biodegradable polymer coatings in an acute swine shunt model.BackgroundPrevious pre-clinical and clinical experience suggests that several factors may influence the predisposition for acute thrombus formation of polymer-coated DES, including stent design and the polymer coating technology. It remains unclear whether relevant differences exist with respect to acute thrombogenicity, particularly between current commercial stent designs using permanent polymers and those using biodegradable polymers.MethodsAn ex vivo carotid to jugular arteriovenous porcine shunt model involving a test circuit of 3 in-line stents, was used to test acute thrombogenicity, where Xience-EES (n = 24) was compared with 4 CE-marked DES with biodegradable polymer coatings (BioMatrix Flex, Synergy, Nobori, and Orsiro [n = 6 each]). After 1 h of circulation, platelet aggregation in whole mount stents was evaluated by confocal microscopy with immunofluorescent staining against dual platelet markers (CD61/CD42b) along with scanning electron microscopy.ResultsXience-EES showed the least percentage of thrombus-occupied area as compared with the biodegradable polymer-coated DES, with a significant difference compared with BioMatrix Flex and Synergy (mean differences: [BioMatrix Flex: 15.54, 95% confidence interval [CI]: 11.34 to 19.75, p < 0.001; Synergy: 8.64, 95% CI: 4.43 to 12.84, p < 0.001; Nobori: 4.22, 95% CI: -0.06 to 8.49, p = 0.055; Orsiro: 2.95, 95% CI: -1.26 to 7.15, p = 0.286). The number of cell nuclei on strut surfaces was also the least in Xience-EES, with a significant difference relative to BioMatrix Flex, Nobori, and Orsiro (mean ratios: BioMatrix Flex: 4.73, 95% CI: 2.46 to 9.08, p < 0.001; Synergy: 1.44, 95% CI: 0.75 to 2.76, p = 0.51; Nobori: 5.97, 95% CI: 3.11 to 11.44, p < 0.001; Orsiro: 5.16, 95% CI: 2.69 to 9.91, p < 0.001).ConclusionsXience-EES’s overall design confers acute thromboresistance relative to contemporary DES with biodegradable coatings, with less platelet aggregation versus BioMatrix Flex and Synergy, and less inflammatory cell attachment versus BioMatrix Flex, Nobori, and Orsiro, in an ex vivo swine shunt model, which lends support to reported clinical findings of lower early stent thrombosis