Systematic review and meta-analysis of the mechanical complications of ischemic heart disease: papillary muscle rupture, left ventricle rupture and post-infarct ventricular septal defect.

Background: Improvements in revascularisation, including pharmacological, catheter-based and surgical, have resulted in improved outcomes for patients with acute myocardial infarction (AMI), leading to decreased frequency of mechanical complications. Improvements in both techniques and technology have permitted select patients to be managed with a purely percutaneous, transcatheter strategy. Through systematic review, this study aims to synthesise the collective experience of percutaneous treatment of the mechanical complications of ischaemic heart disease. Methods: The search strategy queried the electronic databases PubMed, Embase and the Cochrane Central Register of Controlled Trials, from 1 January 2000 to 31 December 2020. Studies highlighting the outcomes of patients receiving percutaneous treatment of post-myocardial infarction papillary muscle rupture (PMR), ventricular septal defect (VSD), left ventricular free wall rupture (FWR) and pseudoaneurysm (PA) were included. A qualitative review of studies was conducted for PMR, FWR and PA. A quantitative analysis was conducted for VSD. Results: Fifteen studies were included in the qualitative synthesis of the percutaneous management of PMR, 4 were included in the qualitative analysis of the percutaneous management of left ventricular FWR, 7 studies defined the outcomes of the percutaneous management of PA and 25 were included in the quantitative meta-analysis of the primary percutaneous management of post-MI VSD. For VSD, there were 43 failed procedures in 314 patients. The proportion of failed procedures was 15.9% and there were 174 deaths in 428 patients. 37.5% of patients experienced early mortality. Conclusions: Although surgical techniques remain the gold standard, we have shown that percutaneous management may be a viable option in certain cases.

Wzx flippases exhibiting complex O-unit preferences require a new model for Wzx-substrate interactions.

The Wzx flippase is a critical component of the O-antigen biosynthesis pathway, being responsible for the translocation of oligosaccharide O units across the inner membrane in Gram-negative bacteria. Recent studies have shown that Wzx has a strong preference for its cognate O unit, but the types of O-unit structural variance that a given Wzx can accommodate are poorly understood. In this study, we identified two Yersinia pseudotuberculosis Wzx that can distinguish between different terminal dideoxyhexose sugars on a common O-unit main-chain, despite both being able to translocate several other structurally-divergent O units. We also identified other Y. pseudotuberculosis Wzx that can translocate a structurally divergent foreign O unit with high efficiency, and thus exhibit an apparently relaxed substrate preference. It now appears that Wzx substrate preference is more complex than previously suggested, and that not all O-unit residues are equally important determinants of translocation efficiency. We propose a new "Structure-Specific Triggering" model in which Wzx translocation proceeds at a low level for a wide variety of substrates, with high-frequency translocation only being triggered by Wzx interacting with one or more preferred O-unit structural elements found on its cognate O unit(s).