Hybrid approach improves success of chronic total occlusion angioplasty.

OBJECTIVES: Treatment options for coronary chronic total occlusions (CTO) are limited, with low historical success rates from percutaneous coronary intervention (PCI). We report procedural outcomes of CTO PCI from 7 centres with dedicated CTO operators trained in hybrid approaches comprising antegrade/retrograde wire escalation (AWE/RWE) and dissection re-entry (ADR/RDR) techniques. METHODS: Clinical and procedural data were collected from consecutive unselected patients with CTO between 2012 and 2014. Lesion complexity was graded by the Multicentre CTO Registry of Japan (J-CTO) score, with ≥2 defined as complex. Success was defined as thrombolysis in myocardial infarction 3 flow with <30% residual stenosis, subclassified as at first attempt or overall. Inhospital complications and 30-day major adverse cardiovascular events (MACEs, death/myocardial infarction/unplanned target vessel revascularisation) were recorded. RESULTS: 1156 patients were included. Despite high complexity (mean J-CTO score 2.5±1.3), success rates were 79% (first attempt) and 90% (overall) with 30-day MACE of 1.6%. AWE was highly effective in less complex lesions (J-CTO ≤1 94% success vs 79% in J-CTO score ≥2). ADR/RDR was used more commonly in complex lesions (J-CTO≤1 15% vs J-CTO ≥2 56%). Need for multiple approaches during each attempt increased with lesion complexity (17% J-CTO ≤1 vs 48% J-CTO ≥2). Lesion modification ('investment procedures') at the end of unsuccessful first attempts increased the chance of subsequent success (96% vs 71%). CONCLUSIONS: Hybrid-trained operators can achieve overall success rates of 90% in real world practice with acceptable MACE. Use of dissection re-entry and investment procedures maintains high success rates in complex lesions. The hybrid approach represents a significant advance in CTO treatment.

Endothelial cell-specific ETB receptor knockout: autoradiographic and histological characterisation and crucial role in the clearance of endothelin-1.

Inactivation of endothelin B receptors (ETB), either through selective pharmacological antagonism or genetic mutation, increases the circulating concentration of endothelin-1 (ET-1), suggesting ETB plays an important role in clearance of this peptide. However, the cellular site of ETB-mediated clearance has not yet been determined. We have used a novel mouse model of endothelial cell-specific knockout (KO) of ETB (EC ETB(-/-)) to evaluate the relative contribution of EC-ETB to the clearance of ET-1. Phenotypic evidence of EC-specific ETB KO was confirmed by immunocytochemistry and autoradiography. Binding of the radiolabelled selective ETB ligand BQ3020 was significantly and selectively decreased in EC-rich tissues of EC ETB(-/-) mice, including the lung, liver, and kidney. By contrast, ETA binding was unaltered. RT-PCR confirmed equal expression of ET-1 in tissue from EC ETB(-/-) mice and controls, despite increased concentration of plasma ET-1 in EC ETB(-/-). Clearance of an intravenous bolus of [(125)I]ET-1 was impaired in EC ETB(-/-) mice. Pretreatment with the selective ETB antagonist A192621 impaired [(125)I]ET-1 clearance in control animals to a similar extent, but did not further impair clearance in EC ETB(-/-) mice. These studies suggest that EC-ETB are largely responsible for the clearance of ET-1 from the circulation.

Endothelial ET(B) limits vascular remodelling and development of pulmonary hypertension during hypoxia.

BACKGROUND: We hypothesised that the potential protective effects of endothelial ET(B) are important in limiting pulmonary vascular muscularisation, vasoconstriction and the development of pulmonary arterial hypertension in response to hypoxia. METHODS: EC-specific ET(B) knockout mice (EC ET(B)(-/-)) and control mice (ET(B)(f/f)) were subjected to hypobaric hypoxic (10% FiO2) or normoxic conditions for 14 days before assessment of right ventricular pressure and pulmonary vascular morphology and function. RESULTS: During normoxia, no difference in right ventricular pressure was detected between EC ET(B)(-/-) (23.7 +/- 1.7 mm Hg) and ET(B)(f/f) mice (20.2 +/- 1.5 mm Hg). Hypoxia induced an exaggerated increase in right ventricular pressure in EC ET(B)(-/-) mice (34.4 +/- 1.2 mm Hg vs. 24.6 +/- 1.4 mm Hg), accompanied by an increase in right ventricular mass. No effect was observed in ET(B)(f/f) mice. Endothelin-1 constricted pulmonary arteries from both groups, although maximum response was similar irrespective of inspired oxygen or genotype. Hypoxia increased the percentage of muscularised vessels in both groups of mice, but the percentage increase was significantly greater in EC ET(B)(-/-) mice. CONCLUSIONS: The potential protective effects of endothelial ET(B) are important in limiting pulmonary vascular muscularisation and the development of pulmonary arterial hypertension in response to hypoxia.

The endothelin system as a therapeutic target in cardiovascular disease: great expectations or bleak house?

There is considerable evidence that the potent vasoconstrictor endothelin-1 (ET-1) contributes to the pathogenesis of a variety of cardiovascular diseases. As such, pharmacological manipulation of the ET system might represent a promising therapeutic goal. Many clinical trials have assessed the potential of ET receptor antagonists in cardiovascular disease, the most positive of which have resulted in the licensing of the mixed ET receptor antagonist bosentan, and the selective ET(A) receptor antagonists, sitaxsentan and ambrisentan, for the treatment of pulmonary arterial hypertension (PAH). In contrast, despite encouraging data from in vitro and animal studies, outcomes in human heart failure have been disappointing, perhaps illustrating the risk of extrapolating preclinical work to man. Many further potential applications of these compounds, including resistant hypertension, chronic kidney disease, connective tissue disease and sub-arachnoid haemorrhage are currently being investigated in the clinic. Furthermore, experience from previous studies should enable improved trial design and scope remains for development of improved compounds and alternative therapeutic strategies. Although ET-converting enzyme inhibitors may represent one such alternative, there have been relatively few suitable compounds developed, and consequently, clinical experience with these agents remains extremely limited. Recent advances, together with an increased understanding of the biology of the ET system provided by improved experimental tools (including cell-specific transgenic deletion of ET receptors), should allow further targeting of clinical trials to diseases in which ET is involved and allow the therapeutic potential for targeting the ET system in cardiovascular disease to be fully realized.