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Page 6 of 15 Inchauste. Plast Aesthet Res 2023;10:27 https://dx.doi.org/10.20517/2347-9264.2022.139

[39]
Studies have shown that size of the right and left internal mammary arteries did not differ significantly .
[39]
However, studies have shown left internal mammary vein is significantly smaller than the right . The left
internal mammary vein has been shown to have higher rates of thrombosis, venous thrombosis-related flap
[39]
loss, and higher rates of conversion to an alternate vein compared to the right internal mammary vein .
Studies have shown higher rates of venous thrombosis associated with smaller vein diameters.

If a small caliber vein is seen, the first step is to dissect the vessel more proximal to look for a larger caliber.
Consideration should be taken if the recipient vein diameter is less than 2 mm, particularly in delayed
reconstruction in an irradiated chest, to look for an alternate recipient vessel. Alternate recipient vessels
include the vena comitans, retrograde IM vein, contralateral IM vein, or thoracodorsal vein. Other
[40]
alternative recipient venous outflow options include cephalic vein transposition . Cephalic vein
transposition (CVT) is used more frequently in patients undergoing delayed reconstruction and with a
history of radiation . CVT can be used as an alternative for the primary recipient vessel or to supplement
[40]
flap venous insufficiency. Contralateral internal mammary vessels are another option in the setting of
unilateral reconstruction [Figure 1], which requires adequate pedicle length or vein graft in flaps with
shorter pedicles such as a transverse upper gracilis flap (TUG). Adequate dissection is needed to avoid
kinking the vessel and one should appropriately line the course of the pedicle with adipose tissue to prevent
compression from the underlying sternum. Thoracodorsal vessels were the original recipient vessel choice
of free flap breast reconstruction and are often considered a reliable alternative vessel choice when the IM
vessels are not usable, but it does require a longer pedicle. The use of the thoracodorsal vein as an
alternative recipient vessel when the IMA anastomosis is patent may require a long vein graft. It can also
potentially limit the use of a pedicled latissimus dorsi myocutaneous flap for salvage reconstruction. The
thoracodorsal vessels may not be usable in up to a third of all patients with a history of axillary
lymphadenectomy and radiation .
[35]

Venous insufficiency:

After the primary microvascular anastomosis, the flap can demonstrate venous outflow insufficiency with
hyperemic appearance of the flap skin and dark red bleeding from the edges. If the flap demonstrates
venous congestion, the first step is a complete evaluation of the arterial and venous anastomosis for patency.
If the anastomoses are patented, the next step is to augment the venous drainage of flaps with additional
venous anastomosis. If the recipient vein is small and the concern is inadequate deep venous flow, the
primary option is augmentation of the deep venous system by completing a second venous anastomosis to
the other vena comitans of the deep venous system of the flap to IM vena comitans, retrograde IM vein or
an alternate vein.

It is rare to develop intraoperative venous congestion in the setting of patent adequate deep venous
anastomosis, as this occurs less than 1% of the time . This is most commonly due to superficial dominant
[41]
venous drainage of the flap [Figure 2]. Most surgeons routinely dissect the superficial inferior epigastric vein
at a length of 5-8 cm during DIEP flap harvest. In the setting of flap venous congestion, if the SIEV is
engorged and congestion improves with drainage of the superficial system, then augmenting the venous
outflow with a separate venous anastomosis to the SIEV is necessary. A second recipient vein such as
second IMV, retrograde IMV, internal mammary or intercostal perforator, lateral thoracic vein,
thoracoacromial vein, external jugular, cephalic vein transposition, thoracodorsal vein or to a proximally
dissected vena comitans of the flap with and without vein graft has all been described [40-43] . Early recognition
of flap venous insufficiency at the time of primary reconstruction with intraoperative correction has shown
[41]
exceptional intraoperative salvage rates .