Advances in procedural techniques--antegrade.

There have been many technological advances in antegrade CTO PCI, but perhaps most importantly has been the evolution of the "hybrid' approach where ideally there exists a seamless interplay of antegrade wiring, antegrade dissection re-entry and retrograde approaches as dictated by procedural factors. Antegrade wire escalation with intimal tracking remains the preferred initial strategy in short CTOs without proximal cap ambiguity. More complex CTOs, however, usually require either a retrograde or an antegrade dissection re-entry approach, or both. Antegrade dissection re-entry is well suited to long occlusions where there is a healthy distal vessel and limited "interventional" collaterals. Early use of a dissection re-entry strategy will increase success rates, reduce complications, and minimise radiation exposure, contrast use as well as procedural times. Antegrade dissection can be achieved with a knuckle wire technique or the CrossBoss catheter whilst re-entry will be achieved in the most reproducible and reliable fashion by the Stingray balloon/wire. It should be avoided where there is potential for loss of large side branches. It remains to be seen whether use of newer dissection re-entry strategies will be associated with lower restenosis rates compared with the more uncontrolled subintimal tracking strategies such as STAR and whether stent insertion in the subintimal space is associated with higher rates of late stent malapposition and stent thrombosis. It is to be hoped that the algorithms, which have been developed to guide CTO operators, allow for a better transfer of knowledge and skills to increase uptake and acceptance of CTO PCI as a whole

Adjunctive strategies in the management of resistant, 'undilatable' coronary lesions after successfully crossing a CTO with a guidewire.

Successful revascularisation of chronic total occlusions (CTOs) remains one of the greatest challenges in the era of contemporary percutaneous coronary intervention (PCI). Such lesions are encountered with increasing frequency in current clinical practice. A predictable increase in the future burden of CTO management can be anticipated given the ageing population, increased rates of renal failure, graft failure and diabetes mellitus. Given recent advances and developments in CTO PCI management, successful recanalisation can be anticipated in the majority of procedures undertaken at high-volume centres when performed by expert operators. Despite advances in device technology, the management of resistant, calcific lesions remains one of the greatest challenges in successful CTO intervention. Established techniques to modify calcific lesions include the use of high-pressure non-compliant balloon dilation, cutting-balloons, anchor balloons and high speed rotational atherectomy (HSRA). Novel approaches have proven to be safe and technically feasible where standard approaches have failed. A step-wise progression of strategies is demonstrated, from well-recognised techniques to techniques that should only be considered when standard manoeuvres have proven unsuccessful. These methods will be described in the setting of clinical examples and include use of very high-pressure non-compliant balloon dilation, intentional balloon rupture with vessel dissection or balloon assisted micro-dissection (BAM), excimer coronary laser atherectomy (ECLA) and use of HSRA in various 'offlabel' settings

Arterial pathology in canine mucopolysaccharidosis-I and response to therapy.

Mucopolysaccharidosis-I (MPS-I) is an inherited deficiency of α-L-iduronidase (IdU) that causes lysosomal accumulation of glycosaminoglycans (GAG) in a variety of parenchymal cell types and connective tissues. The fundamental link between genetic mutation and tissue GAG accumulation is clear, but relatively little attention has been given to the morphology or pathogenesis of associated lesions, particularly those affecting the vascular system. The terminal parietal branches of the abdominal aorta were examined from a colony of dogs homozygous (MPS-I affected) or heterozygous (unaffected carrier) for an IdU mutation that eliminated all enzyme activity, and in affected animals treated with human recombinant IdU. High-resolution computed tomography showed that vascular wall thickenings occurred in affected animals near branch points, and associated with low endothelial shear stress. Histologically these asymmetric 'plaques' entailed extensive intimal thickening with disruption of the internal elastic lamina, occluding more than 50% of the vascular lumen in some cases. Immunohistochemistry was used to show that areas of sclerosis contained foamy (GAG laden) macrophages, fibroblasts and smooth muscle cells, with loss of overlying endothelial basement membrane and claudin-5 expression. Lesions contained scattered cells expressing nuclear factor-κβ (p65), increased fibronectin and transforming growth factor β-1 signaling (with nuclear Smad3 accumulation) in comparison to unaffected vessels. Intimal lesion development and morphology was improved by intravenous recombinant enzyme treatment, particularly with immune tolerance to this exogenous protein. The progressive sclerotic vasculopathy of MPS-I shares some morphological and molecular similarities to atherosclerosis, including formation in areas of low shear stress near branch points, and can be reduced or inhibited by intravenous administration of recombinant IdU

Npp1 promotes atherosclerosis in ApoE knockout mice.

Ecto-nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) generates inorganic pyrophosphate (PP(i)), a physiologic inhibitor of hydroxyapatite deposition. In a previous study, we found NPP1 expression to be inversely correlated with the degree of atherosclerotic plaque calcification. Moreover, function-impairing mutations of ENPP1, the gene encoding for NPP1, are associated with severe, artery tunica media calcification and myointimal hyperplasia with infantile onset in human beings. NPP1 and PP(i) have the potential to modulate atherogenesis by regulating arterial smooth muscle cell (SMC) differentiation and function, including increase of pro-atherogenic osteopontin (OPN) expression. Hence, this study tested the hypothesis that NPP1 deficiency modulates both atherogenesis and atherosclerotic intimal plaque calcification. Npp1/ApoE double deficient mice were generated by crossing mice bearing the ttw allele of Enpp1 (that encodes a truncation mutation) with ApoE null mice and fed with high-fat/high-cholesterol atherogenic diet. Atherosclerotic lesion area and calcification were examined at 13, 18, 23 and 28 weeks of age. The aortic SMCs isolated from both ttw/ttw ApoE(-/-) and ttw/+ ApoE(-/-) mice demonstrated decreased Opn expression. The 28-week-old ttw/ttw ApoE(-/-) and ttw/+ ApoE(-/-) had significantly smaller atherosclerotic lesions compared with wild-type congenic ApoE(-/-) mice. Only ttw/ttw but not ttw/+ mice developed artery media calcification. Furthermore in ttw/+ mice, there was a tendency towards increased plaque calcification compared to ApoE(-/-) mice without Npp1 deficiency. We conclude that Npp1 promotes atherosclerosis, potentially mediated by Opn expression in ApoE knockout mice

Macromolecular approaches to prevent thrombosis and intimal hyperplasia following percutaneous coronary intervention.

Cardiovascular disease remains one of the largest contributors to death worldwide. Improvements in cardiovascular technology leading to the current generation of drug-eluting stents, bioresorbable stents, and drug-eluting balloons, coupled with advances in antirestenotic therapeutics developed by pharmaceutical community, have had a profound impact on quality of life and longevity. However, these procedures and devices contribute to both short- and long-term complications. Thus, room for improvement and development of new, alternative strategies exists. Two major approaches have been investigated to improve outcomes following percutaneous coronary intervention including perivascular delivery and luminal paving. For both approaches, polymers play a major role as controlled research vehicles, carriers for cells, and antithrombotic coatings. With improvements in catheter delivery devices and increases in our understanding of the biology of healthy and diseased vessels, the time is ripe for development of novel macromolecular coatings that can protect the vessel lumen following balloon angioplasty and promote healthy vascular healing

Pathogen burden, inflammation, proliferation and apoptosis in human in-stent restenosis - Tissue characteristics compared to primary atherosclerosis

Pathogenic events leading to in-stent restenosis (ISR) are still incompletely understood. Among others, inflammation, immune reactions, deregulated cell death and growth have been suggested. Therefore, atherectomy probes from 21 patients with symptomatic ISR were analyzed by immunohistochemistry for pathogen burden and compared to primary target lesions from 20 stable angina patients. While cytomegalovirus, herpes simplex virus, Epstein-Barr virus and Helicobacter pylori were not found in ISR, acute and/or persistent chlamydial infection were present in 6/21 of these lesions (29%). Expression of human heat shock protein 60 was found in 8/21 of probes (38%). Indicated by distinct signals of CD68, CD40 and CRP, inflammation was present in 5/21 (24%), 3/21 (14%) and 2/21 (10%) of ISR cases. Cell density of ISR was significantly higher than that of primary lesions ( 977 +/- 315 vs. 431 +/- 148 cells/mm(2); p < 0.001). There was no replicating cell as shown by Ki67 or PCNA. TUNEL+ cells indicating apoptosis were seen in 6/21 of ISR specimens (29%). Quantitative analysis revealed lower expression levels for each intimal determinant in ISR compared to primary atheroma (all p < 0.05). In summary, human ISR at the time of clinical presentation is characterized by low frequency of pathogen burden and inflammation, but pronounced hypercellularity, low apoptosis and absence of proliferation. Copyright (C) 2004 S. Karger AG, Basel

Marked mitigation of transplant vascular sclerosis in FasL(gld) (CD95L) mutant recipients. I. The role of alloantibodies in the development of chronic rejection

Background. In the acute rejection of allografts, the interaction between Fas (CD95) and its ligand (FasL; CD95L) has been shown to be involved in mediating apoptotic cell death. The role, however, of these molecules in the pathogenesis of transplant vascular sclerosis is as yet undetermined. The present study was therefore designed to address this issue. Material. C3H/HEJ FasL(gld) (FasL-; H2(k)) spontaneously mutant mice were used either as donors or recipients of aortic allografts; wild-type C57BI/6 (B6; H2b) were used as corresponding recipients or donors (n=6/group), respectively. Controls included aortas transplanted across appropriate allogeneic and syngeneic strain combinations. For histopathological evaluations, the grafts were harvested at day 40 after transplantation, at which time, splenocytes and sera were also obtained for mixed leukocyte reaction and complement- mediated microcytotoxicity assays, respectively. Results. Similar to aortas obtained from allogeneic controls, allografts harvested from FasL-→B6 recipients had morphological evidence of chronic rejection characterized by circumferential intimal thickening with partial disruption of the elastic membranes. Correspondingly, heightened antidonor cellular reactivity was also witnessed in these recipients. On the contrary, B6 allografts harvested from the majority of C3H→FasL- recipients exhibited marked preservation of aortic morphology. Although these recipients had diminished antidonor cellular proliferation, the titers of alloantibodies were markedly elevated. Conclusion. The presence of FasL-expressing functional cytotoxic T cells is required for the pathogenesis of transplant vascular sclerosis. The significant reduction and/or absence of chronic rejection with the concomitant retention of antidonor humoral response in C3H FasL- recipients of B6 aortas prompt us to suggest that perhaps posttransplantation vasculopathy is initiated by cell-mediated cytotoxicity with its perpetuation facilitated by alloantibodies

The non-obligatory role of endothelial cells in the relaxation of arterial smooth muscle by acetylcholine

The concept of Endothelium Derived Relaxing Factor (EDRF), put forward by Furchgott in the earlier 80s of the past century, implies that nitric oxide (NO) produced by NO synthase (NOS) in the endothelium in response to acetylcholine (ACh) passively diffuses to the underlying vascular smooth muscle cells (VSMC) thereby reducing vascular tension. It was thought that VSMC do not express NOS by themselves, but to the time of those studies immunohistochemical techniques were not what they are now. State-of-the-art immunohistochemistry permits nowadays to localize NOS both to the endothelium and to VSMC. However, the principal question remained unanswered, is the NO generation by VSMC physiologically relevant? We hypothesized that the destruction of the vascular wall anatomical integrity by rubbing the blood vessel intimal surface may increase vascular superoxides that, in turn, reduce NO bioactivity. To address this issue, we examined ACh-induced vasorelaxation in endothelium-deprived blood vessels under protection against oxidative stress and found that superoxide scavengers - tempol and N-acetyl-L-cysteine - restored vasodilatory responses to ACh in endothelium-deprived blood vessels without influencing the vascular wall tension in intact blood vessels. Herewith we provided the first evidence that VSMC can release NO in amounts sufficient to account for the vasorelaxatory response to ACh. In contrast to the commonly accepted concept of the obligatory role of endothelial cells in the relaxation of arterial smooth muscle, the local NO generation by VSMC can modulate vascular functions in an endothelium-independent manner