Left Internal Mammary Vein Size and Its Impact on Microsurgical Breast Reconstruction.

[UNLABELLED] The internal mammary vessels are the preferred recipient during free-flap breast reconstruction (FFBR). Previous studies have demonstrated that the left internal mammary vein (IMV) is consistently smaller than the right, but with unclear clinical implications. This study explores the impact of IMV size difference on FFBR complication rates.

[METHODS] Abdominal-based FFBRs were retrospectively reviewed. Venous coupler size was considered a proxy for IMV diameter. Outcomes of three patient cohorts (all, unilateral, and bilateral reconstructions) were analyzed with univariate and multivariate analysis.

[RESULTS] Our cohort consisted of 582 patients who underwent 874 abdominal-based FFBR, with a similar number of unilateral (n = 290) and bilateral (n = 292), and right (n = 424) and left (n = 450) reconstructions. Mean follow-up was over 4-years. For all reconstructions, the left IMV (2.7 ± 0.4 mm) was smaller than the right (3.0 ± 0.4 mm) ( < 0.0001). Complication rates between left- and right-sided FFBR were similar, but with a trend toward increased fat necrosis on the left (n = 17, 3.8% versus n = 8, 1.9%). Further subgroup analysis showed significantly higher fat necrosis in unilateral left-sided FFBR (n = 12 versus n = 2, = 0.02), with left-sided FFBR being an independent risk factor for fat necrosis on multivariate analysis.

[CONCLUSIONS] The left-side IMV is significantly smaller than the right IMV. In bilateral reconstructions, the smaller size of the left IMV did not result in a greater risk of complications; however, in unilateral FFBR, fat necrosis was significantly higher on the left side.