There have recently been important advances in our understanding of asthma mechanisms and treatment. Asthma is now recognized as a disease of the airways which involves a special type of inflammation, characterized by the presence of activated mast cells, eosinophils and T-lymphocytes. There has been a growing recognition that chronic rather than acute inflammatory events are more relevant to understanding the underlying mechanisms in asthma and the role ofcytokines, as mediators of chronic inflammation, has been an area of very rapid development. At the same time the approach to asthma treatment has changed, with a much greater emphasis on the earlier and more widespread use of inhaled anti-inflammatory drugs, and particularly inhaled steroids. There has also been an increased understanding of the mechanisms of action of existing anti-asthma therapies, but at the same time questions have been raised about the safety of some treatments. This has prompted the search for novel anti-asthma therapies, based on our current understanding of pathophysiological mechanisms. The literature on asthma is vast and we do not intend to provide an exhaustive or comprehensive review, but have concentrated on some areas where there have been advances in knowledge which have clinical and therapeutic relevance.
Objectives This study sought to describe the frequency and clinical impact of acute scaffold disruption and late strut discontinuity of the second-generation Absorb bioresorbable polymeric vascular scaffolds (Absorb BVS, Abbott Vascular, Santa Clara, California) in the ABSORB (A Clinical Evaluation of the Bioabsorbable Everolimus Eluting Coronary Stent System in the Treatment of Patients With De Novo Native Coronary Artery Lesions) cohort B study by optical coherence tomography (OCT) post-procedure and at 6, 12, 24, and 36 months. Background Fully bioresorbable scaffolds are a novel approach to treatment for coronary narrowing that provides transient vessel support with drug delivery capability without the long-term limitations of metallic drug-eluting stents. However, a potential drawback of the bioresorbable scaffold is the potential for disruption of the strut network when overexpanded. Conversely, the structural discontinuity of the polymeric struts at a late stage is a biologically programmed fate of the scaffold during the course of bioresorption. Methods The ABSORB cohort B trial is a multicenter single-arm trial assessing the safety and performance of the Absorb BVS in the treatment of 101 patients with de novo native coronary artery lesions. The current analysis included 51 patients with 143 OCT pullbacks who underwent OCT at baseline and follow-up. The presence of acute disruption or late discontinuities was diagnosed by the presence on OCT of stacked, overhung struts or isolated intraluminal struts disconnected from the expected circularity of the device. Results Of 51 patients with OCT imaging post-procedure, acute scaffold disruption was observed in 2 patients (3.9%), which could be related to overexpansion of the scaffold at the time of implantation. One patient had a target lesion revascularization that was presumably related to the disruption. Of 49 patients without acute disruption, late discontinuities were observed in 21 patients. There were no major adverse cardiac events associated with this finding except for 1 patient who had a non-ischemia-driven target lesion revascularization. Conclusions Acute scaffold disruption is a rare iatrogenic phenomenon that has been anecdotally associated with anginal symptoms, whereas late strut discontinuity is observed in approximately 40% of patients and could be viewed as a serendipitous OCT finding of a normal bioresorption process without clinical implications. (ABSORB Clinical Investigation, Cohort B [ABSORB B]; NCT00856856)
There is increasing evidence in many species that vasoactive intestinal peptide (VIP) may be a neurotransmitter in nonadrenergic inhibitory nerves. We have studied the effect of electrical field stimulation (EFS), exogenous VIP, and isoproterenol (Iso) on human airways in vitro. We have also studied a related peptide, peptide histidine methionine (PHM), which coexists with VIP in human airway nerves, and in separate experiments studied fragments of the VIP amino acid sequence (VIP1–10 and VIP16–28) for agonist and antagonist activity. Human airways were obtained at thoracotomy and studied in an organ bath. In bronchi EFS gave an inhibitory response that was unaltered by 10(-6) M propranolol but was blocked by tetrodotoxin, whereas in bronchioles there was little or no nonadrenergic inhibitory response. VIP, PHM, and Iso all caused dose-dependent relaxation of bronchi, VIP and PHM being approximately 50-fold more potent than Iso. VIP, but not Iso, mimicked the time course of nonadrenergic inhibitory nerve stimulation. In contrast bronchioles relaxed to Iso but not to VIP or PHM. Neither propranolol nor indomethacin altered the relaxant effects of VIP or PHM, suggesting a direct effect of these peptides on airway smooth muscle. Neither of the VIP fragments showed either agonist or antagonist activity. We conclude that VIP and PHM are more potent bronchodilators of human bronchi than Iso and that the association between the relaxant effects of these peptides and nonadrenergic inhibitory responses suggests that they may be possible neurotransmitters of nonadrenergic inhibitory nerves in human airways.
To investigate the clinical usefulness of intracoronary Doppler recordings during percutaneous transluminal coronary angioplasty (PTCA), the changes of intracoronary blood flow velocity during PTCA were assessed in 20 patients with single proximal coronary stenosis, using a Doppler probe endmounted on the tip of a PTCA catheter. A mean of 4 inflations was performed in each patient. Intracoronary velocities were measured before and after each inflation and during peak reactive hyperemia after each transluminal occlusion. Quantitative analysis of the coronary stenosis was assessed before and after PTCA, and the dilatation resulted in an increase in minimal luminal cross-sectional area from 1.1 ± 0.8 to 2.7 ± 1.2 mm2. A gradual and significant improvement in velocities was observed after the first 3 dilatations, but in 15 of the 20 patients the resting and hyperemic velocities were not affected by the fourth dilatation. Coronary flow reserve measured during reactive hyperemia after the last dilatation with the PTCA catheter across the lesion was 1.9. This value of coronary flow reserve is compatible with the residual stenosis measured after PTCA when corrected for the presence of the Doppler balloon catheter (0.68 mm2). This application of the Doppler technique may provide a new method of on-line functional monitoring of the PTCA procedure in individual patients, but does not yet allow an accurate prediction of the change in coronary geometry brought about by PTCA.