Meta‐analysis of the effects of venous super‐drainage in deep inferior epigastric artery perforator flaps for breast reconstruction

Venous congestion is the most common vascular complication of the deep inferior epigastric artery perforator (DIEP) flaps. Adding a second venous drainage by anastomosing a flap vein and a recipient vein (super‐drainage) is considered the solution of choice. Evidence to support this procedure, had not yet been confirmed by an analysis of the literature. We aimed to provide this evidence.


| INTRODUCTION
The Deep Inferior Epigastric artery Perforator (DIEP) flap, is considered the gold standard for autologous breast reconstruction (Bartlett et al., 2018). Flap failure is reported to occur in 1 to 5% of cases (Lie et al., 2013). However, the frequency of partial failures and their consequences is higher (Santanelli et al., 2015). The unsatisfactory results are frequently due to perfusion-related complications, developing in F I G U R E 1 Flow diagram that shows selection of articles T A B L E 1 Studies included in our meta-analysis Note: "Cases": flaps with a second venous anastomosis. "Controls": flaps with a single venous anastomosis. In bold are the seven studies that were not analyzed in the previously published meta-analysis by Lee (Lee & Mun, 2017 up to 17% of DIEP flaps (Peeters et al., 2009). Venous congestion is the most common of the above-mentioned perfusion-related complications, with a reported incidence ranging from 2 to 20% (Kim et al., 2015;Sbitany et al., 2012) representing one of the main causes of fat necrosis, partial flap necrosis and, less frequently, complete necrosis of the flap (Santanelli et al., 2015). The etiology of venous congestion is multifactorial (Blondeel et al., 2000;Lundberg & Mark, 2006;Nahabedian et al., 2005;Rozen et al., 2009;Schaverien et al., 2010;Tran et al., 2007) with reversible and nonreversible causes.

| Statistical analysis
The Mantel-Haenszel test in R was used to calculate Pooled RRs and corresponding 95% confidence intervals (CI) for perfusion-related complications. The heterogeneity among studies was analyzed by using the I 2 test. We used a fixed-effects model for I 2 ranging from 0 to 30%; in the case of I 2 > 30%, we applied a random effect model using the DerSimonian and Liard method.
For each test p value ≤.05 was set for significance.

| RESULTS
After  Ochoa et al., 2013;Santanelli et al., 2015;Unukovych et al., 2016;Xin et al., 2012) and were included in our study. All the studies that we reviewed were retrospective, except the one by Ayestaray (Ayestaray et al., 2016), which is prospective and randomized.
Overall, our study analyzed 3,094 DIEPs, of which, 1,279 received a second venous anastomosis ("case group"); and 1815 received only one venous anastomosis ("control group"). Venous congestion F I G U R E 3 Partial necrosis in DIEP flaps. Articles and related forest plots dealing with the complication. PN: number of flaps presenting Partial Necrosis occurred in 38 of 1,121 flaps, with an overall mean rate of 3.4%. The venous congestion rate in each study ranged from 0.9 to 36.5%.
In physiologic conditions, the dominant venous drainage to the lower abdominal skin and fat is provided by the superficial venous system through the inferior epigastric vein (SIEV) (Enajat et al., 2010;Sbitany et al., 2012). All the papers included in our meta-analysis used the SIEV as a second vein of the flap to increase venous output.  (Eom et al., 2011).
Unfavorable anatomy of the venous system is considered among the most important, not-reversible, causes of venous congestion. Several studies (Kim et al., 2015;Rozen et al., 2009;Sbitany et al., 2012;Schaverien et al., 2008)  Once venous congestion occurs, and intraoperatively the reversible causes have been excluded, it is necessary to treat the venous congestion itself, by venous super-drainage.
One previously published meta-analysis, from Lee et al (Lee & Mun, 2017) showed that the use of super-drainage has a statistical advantage over venous congestion but only a trend toward a decreased risk of congestion-related complications. Further studies were, therefore, suggested. A detailed comparison with that previous meta-analysis (Lee & Mun, 2017), is presented in Table 2. Our analysis includes the six articles examined by Lee and seven additional ones, reporting on large groups of patients (Ochoa et al., 2013;Unukovych et al., 2016) and on a prospective randomized study (Ayestaray et al., 2016). (Table 1). Statistical methods were comparable but the larger amount of data, allowed us to achieve statistical evidence that the use of super-drainage, employing a second venous anastomosis between the SIEV and a recipient vein, reduces venous congestion, prevents partial and total flap necrosis, and the need to take the patient back to surgery. Unfortunately, the available data did not show a statistically significant advantage of a second venous anastomosis to prevent fat necrosis, a common complication (6 to 17.4%) in DIEP flaps.
However, from the results of our meta-analysis, there seems to be an advantage also in performing a second venous anastomo-  (Table 1). However, our study follows the PRISMA guidelines (Moher et al., 2009), which warrant the quality of a meta-analysis.
Our study is the first to report statistically significant results on

| CONCLUSIONS
In conclusion, our meta-analysis shows that venous super-drainage, that is, performing a second venous anastomosis between the superficial venous system and a recipient vein, provides a statistically significant advantage in terms of venous congestion and related complications in DIEP flaps for breast reconstruction.

CONFLICT OF INTEREST
The authors do not have any conflict of interest to disclose.
T A B L E 2 Comparison between our meta-analysis and the one from Lee and Mun Lee and Mun, 2017 Pignatti et al, 2020 Articles included Enajat, 2010Lee, 2012Xin, 2012Santanelli, 2015Boutros, 2013Al-Dhamin, 2014Ali, 2010Enajat, 2010Eom, 2011Lee, 2012Xin, 2012Boutros, 2013Ochoa, 2013 Al Conclusion "The present review demonstrated that superdrainage using SIEV reduces the risk of flap congestion notably, while having little influence on flap survival. With regard to partial flap necrosis including partial flap loss and fat necrosis, general trends toward decreased risks were observed. However, statistical significance was not achieved and further studies would be needed." "In conclusion, our meta-analysis shows, that venous super-drainage, that is, performing a second venous anastomosis between the superficial venous system and a recipient vein, provides a statistical advantage in terms of venous congestion and related complications in DIEP flaps for breast reconstruction." Note: Cases: flaps with a second venous anastomosis. Controls: only one venous anastomosis. In bold are the seven studies that were not analyzed in the previously published meta-analysis by Lee (Lee & Mun, 2017), "Cases": flaps with a second venous anastomosis. "Controls": flaps with a single venous anastomosis. Abbreviation: RR, risk ratio.