Upside-Down Gore Excluder as an Endoprosthesis for Aortoiliac Aneurysm Exclusion:A Retrospective Multicenter Study

Objective: The upside-down configuration of a Gore Excluder contralateral leg endoprosthesis has been used to overcome diameter differences in the endovascular treatment of aortoiliac aneurysms. Our goal was not to describe the technique but to study the applicability and safety. Material and methods: Patients were retrospectively enrolled. The indication and details of the procedure were at the discretion of the treating physicians. A case report form was completed including baseline characteristics, indication for treatment, procedural data, and outcomes during follow-up. Results: A total of 31 subjects were enrolled with a range of indications, including 3 patients treated in the emergency setting (9.7%). In 64.5% (n=20), it was a primary intervention for a common iliac aneurysm (n=10), internal iliac aneurysm (n=4), or abdominal aortic aneurysm (n=6). In 11 subjects (35.5%), treatment was performed after previous aortoiliac interventions, including anastomotic iliac artery aneurysm (n=5), type III endoleak (n=3), and endograft thrombus (n=3). Median follow-up was 13 months (range=1-142 months). During follow-up, 2 patients required an upside-down contralateral leg–related secondary intervention, one for an occlusion and another for a type Ia endoleak. There was no type Ib or III endoleak, and no migration, kinking/stenosis, or conversion to open repair was observed. The aneurysm-related mortality was 3.3% (n=1). Conclusion: An upside-down contralateral leg is a valuable technique that can be used to achieve adequate aneurysm exclusion or resolve complications. It is associated with a limited number of complications. Clinical impact: This article studies the use of an upside-down iliac endograft. We describe a wide range of indications in which this previously published technique has been applied. In elective and acute settings and as primary and revision intervention an upside-down iliac endograft was performed successfully. Furthermore, follow-up data is presented showing the effectiveness of the technique. Knowledge of this procedure is a valuable addition to the skillset of every interventionalist.</p

Does the Box-Cox transformation help in forecasting macroeconomic time series?

The paper investigates whether transforming a time series leads to an improvement in forecasting accuracy. The class of transformations that is considered is the Box-Cox power transformation, which applies to series measured on a ratio scale. We propose a nonparametric approach for estimating the optimal transformation parameter based on the frequency domain estimation of the prediction error variance, and also conduct an extensive recursive forecast experiment on a large set of seasonal monthly macroeconomic time series related to industrial production and retail turnover. In about one fifth of the series considered the Box-Cox transformation produces forecasts significantly better than the untransformed data at one-step-ahead horizon; in most of the cases the logarithmic transformation is the relevant one. As the forecast horizon increases, the evidence in favour of a transformation becomes less strong. Typically, the naïve predictor that just reverses the transformation leads to a lower mean square error than the optimal predictor at short forecast leads. We also discuss whether the preliminary in-sample frequency domain assessment conducted provides a reliable guidance which series should be transformed for improving significantly the predictive performance