Internal mammary vein diameter - Is the left side really smaller? A study of 105 bilateral free flap breast reconstruction patients.

[INTRODUCTION] Autologous free flap breast reconstruction is currently considered as the gold standard in breast reconstruction as it provides a durable, natural result. The internal mammary vessels are the most commonly used recipient vessels in free flap breast reconstruction, and anecdotally we have often observed that the left internal mammary vein (IMV) appears smaller than the right IMV. The aim of this study is to compare the diameters of the right and left IMVs by recording the size of the venous coupler used on each side in a large series of bilateral free flap breast reconstructions.

[METHODS] We searched our free flap database for patients who had breast reconstruction between October 2018 and August 2021. Inclusion criteria for this study were bilateral breast reconstruction patients, where the internal mammary vessels were used. We used a paired t-test for statistical analysis of the data.

[RESULTS] A total of 105 patients who had bilateral breast reconstruction were included in this study. Their mean age was 48.4 years. The mean venous coupler size used on the right was 2.64 mm (SD 0.35), whilst the mean left IMV coupler size was 2.48 (SD 0.32). Using a paired t-test, the p value for the comparison of the right and left IMV size in the cohort was 0.00032, demonstrating a statistically significant difference.

[CONCLUSION] We have confirmed that the right IMV is larger in diameter than the left side, and demonstrated that this translates into a recordable practical difference in the coupler size used. Despite this, we experienced no venous congestion or flap failures in our left-sided flaps, indicating that the IMVs remain a safe choice of recipient vein.