Nonlinear phenomena in complex systems

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Prompt percutaneous coronary intervention (PCI) and stenting of the stenosis causing the occlusion reduces the risk of cardiac death and recurrent infarction. Until recently, however, clinical guidelines recommended that PCI be limited to the infarct artery, because of concern that the benefit of preventive PCI may not outweigh the risks of the extended procedure.

In these studies, doctors determined who received preventive PCI and who did not. Figure 1 shows a metaanalysis plot of 16 such studies (42,817 patients, median follow-up 12 months). The use of all-cause rather than cardiac death as an outcome is a limitation, because it includes non-cardiac causes that are not influenced by PCI (e. A more serious limitation, in the non-randomised studies, is selection bias: the extent to which patients who received preventive PCI, for example, were sicker than those receiving infarct artery-only PCI and were therefore heading for a worse outcome regardless of the treatment strategy adopted.

Selection bias is not avoided by increasing study size or by adjusting for confounding, because not all confounding factors are measured or known, so even in large propensity score-matched studies11,14 it is not possible to be sure which treatment is better. Selection bias is avoided in a randomised trial, since the use of preventive PCI is determined by random allocation rather than physician nonlinear phenomena in complex systems. The relative risk of cardiac death or non-fatal MI is 0.

The evidence of benefit in reducing the risk of cardiac death and MI in patients with STEMI is known. There is uncertainty whether nonlinear phenomena in complex systems benefit outweighs the risk of PCI in stenoses 24 nonlinear phenomena in complex systems that both mechanisms may be similarly important in the prevention of future cardiac events.

In the PRAMI trial nonlinear phenomena in complex systems evidence of benefit emerged early on. The same observations were apparent in the Complete Versus culprit-Lesion only PRimary PCI Trial (CVLPRIT) trial22 interdependence which all but about a quarter of patients in the preventive PCI group had immediate preventive PCI, the remainder having a staged procedure within a few days.

Neither of the two trials was designed to compare immediate versus staged nonlinear phenomena in complex systems PCI. The results of PRAMI24 and CvLPRIT22 have prompted a rethink in the way we manage non-infarct artery stenoses in STEMI. The European Revascularisation Guidelines were recently changed (September 2014) and now recommend that immediate preventive PCI be considered in selected patients with STEMI,37 but do not indicate how this selection should be made.

The use of a physiological measure of blood flow, such as fractional flow reserve (FFR), may be better than visual angiographic assessment in guiding preventive PCI,38 but it may also worsen outcomes if non-flow limiting stenoses are nonlinear phenomena in complex systems untreated and become the sites of future infarction.

Three trials of preventive PCI in patients with STEMI are in progress that are using FFR to decide which non-infarct artery stenoses to treat. Further research would be needed to resolve this uncertainty. Some patients will benefit more from preventive PCI than others, nonlinear phenomena in complex systems in the absence of knowing who they are, no special selection can be recommended.

The trials excluded patients with cardiogenic shock, previous coronary artery bypass graft (CABG), significant mens healths of the left main stem or in whom the only non-infarct artery disease was a chronic total occlusion.

Therefore, while prisma statement org benefits of preventive PCI may apply nonlinear phenomena in complex systems these selected groups, there is uncertainty. The primacy of randomised trials reveals the danger of using non-randomised studies, which can, as in this case, give the wrong answer.

Published content on this site is for information purposes and is not a substitute for professional medical advice. Radcliffe Cardiology is part of Radcliffe Medical Media, an independent publisher and the Radcliffe Group Ltd.

It is not affiliated with or is an agent of, the Oxford Heart Centre, the John Radcliffe Hospital or the Oxford University Hospitals NHS Foundation Trust group. Qarawani Young porn little girls, Nahir M, Abboud M, et al.

Crossref Corpus RA, House JA, Marso SP, et al. Estevez-Loureiro R, Rodriguez-Vilela A, Salgado-Fernandez J, et al. Di Mario C, Mara S, Flavio A, et al. Politi L, Sgura F, Rossi R, et al.



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