Predictive and Protective Factors for Partial Necrosis in DIEP Flap Breast Reconstruction. Does Nulliparity Bias Flap Viability?

Although success rate of deep inferior epigastric perforator (DIEP) flap breast reconstruction has greatly improved, complications still occasionally occur. Perfusion-related complications (PRCs) (ie, fat necrosis and partial flap necrosis) are the most frequent concern, affecting aesthetic final result of the reconstructed breast.The aim of our study was to retrospectively investigate 287 consecutive DIEP flap breast reconstructions to investigate predictive and protective factors for PRCs.From May 2004 to February 2012, 287 DIEP flap breast reconstructions were performed on 270 patients; 247 unilateral flaps, including Holm vascular zones I to III, were retrospectively selected and analyzed. Tobacco use, mean blood pressure over the first postoperative 48 hours, superficial epigastric vein drainage, medial/lateral row perforator, nulliparity, crystalloid versus combined crystalloid/colloid intravenous fluid infusion therapy, and learning curve were evaluated by univariate and multivariate logistic regression analyses.Perfusion-related complications occurred 32 (12.9%) times, 79 (31.9%) patients were smokers, 48 (19.4%) showed postoperative mean blood pressure less than 75 mm Hg, 29 (11.7%) were nulliparous, and 173 (70%) had superficial epigastric vein drainage. Selected perforators were 110 (44.5%) from lateral row, 137 (55.5%) from medial row; 91 (36.8%) received crystalloid fluid infusion, whereas 156 (63.2%) combined crystalloid/colloid fluid infusion. From univariate analysis emerged significance of nulliparity, perforator row and intravenous fluid infusion for PRC. Nevertheless, multivariate model confirmed only nulliparity as a significant risk factor (P = 0.029), although variable correlations to other predictors were found: both medial row perforator and combined crystalloid/colloid fluid infusion potentially decrease the PRC risk of 11.6% and 27.6%, respectively. Learning curve did not show significant decrease of PRC risk over time.Our study first proved nulliparity as a statistically significant predictor for PRCs in DIEP flap breast reconstruction, possibly due to different superficial abdominal perfusion between pluriparous and nulliparous women, with potential weaker pattern of perforators and smaller angiosomes in the latter. The choice of medial row perforators and combined crystalloid/colloid fluid infusion might reduce PRC risk

Interest Rate Rules with Heterogeneous Expectations

Recent macroeconomic literature stressed the importance of expectations heterogeneity in the formulation of monetary policy. We use a stylized macro model of Howitt (1992) to investigate the dynamical consequences of alternative interest rate rules when agents have heterogeneous expectations and update their beliefs over time along the lines of Brock and Hommes (1997). We find that the outcome of different monetary policies in terms of stability crucially depends on the ecology of forecasting rules and on the intensity of choice among different predictors. We also show that, when agents have heterogeneous expectations, an interest rate rule that obeys the Taylor principle does not always lead the system to converge to the rational expectations equilibrium but multiple equilibria may persist.