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Page 2 of 26 Chen et al. Plast Aesthet Res 2023;10:24 https://dx.doi.org/10.20517/2347-9264.2022.136

INTRODUCTION
Microsurgical autologous free tissue transfer has become a widely practiced technique for breast
[1-3]
reconstruction with improved patient satisfaction and quality of life . With advances in flap monitoring
techniques and medical and surgical management, autologous free tissue transfer is now a safe and effective
[4,5]
procedure with high success rates . While uncommon, microvascular thrombosis remains a serious
complication, occurring in 1.5%-6.2% of breast reconstruction cases, with up to 75% of those cases
[6,7]
ultimately resulting in flap failure . In this review, we present an overview of the risk factors associated
with microvascular thrombosis in free tissue transfer as well as its diagnosis and treatment to facilitate a
comprehensive understanding of this potentially devastating complication.

PREOPERATIVE CONSIDERATIONS
Risk factors
Risk factors for flap thrombosis can be categorized by their association with one of the three components of
Virchow's triad: stasis, endothelial injury, and hypercoagulability. While flap thrombosis is usually
attributed to suboptimal intraoperative technique and flap monitoring, acquired or inherited factors that
influence the coagulation cascade must be accounted for during patient selection and preoperative
optimization. Preoperative consultation should therefore always pay close attention to family and prior
medical history suggestive of coagulopathy, potential secondary causes of bleeding disorders, and
medications.

While the impact of patient factors on venous thromboembolism has been well studied, data on
microvascular thrombosis rates in breast reconstruction are less robust and often discordant. Many studies
are limited by small samples and event numbers, inclusion of a single institution, heterogeneity of
reconstruction technique, or insufficient controlling of confounding variables . In this section, we
[8]
summarize the current literature available for commonly encountered patient factors that are often thought
to be associated with flap thrombosis, and review management strategies for each.

Hereditary thrombophilia
While there have been individual case reports of thrombosis with flap loss in Factor V Leiden patients
undergoing microsurgical breast reconstruction, they cannot be used to accurately estimate thrombotic
risk [9-11] . In a retrospective study of 2032 consecutive free flaps (not limited to breast reconstruction), 58 of
which were performed on patients with prior macrovascular thrombosis and/or known thrombophilia,
Wang et al. found significantly higher rates of flap thrombosis and flap failure among the hypercoagulable
group . However, Pannucci et al. noted that this study failed to recognize that flap thrombosis occurred
[12]
only among hypercoagulable patients with prior history of macrovascular thrombosis or another acquired
hypercoagulable disorder . Flap thrombosis did not occur in patients who had known hereditary
[13]
thrombophilia without any additional history, suggesting that hereditary thrombophilias are less predictive
of flap outcomes than acquired thrombophilias or prior history of thrombosis.

Based on these findings, Pannucci et al. recommend preoperative screening according to personal and
family history of thrombosis, acquired risk factors, and Caprini score; if the patient has elevated risk
determined by the screening, they should be referred to a hematologist . This approach deviates from the
[13]
algorithm previously proposed by Friedman et al., who suggest that surgeons should order thrombophilia
testing if there is a concern for thrombosis risk and refer to hematology only if the testing is positive .
[14]
Pannucci et al. argue that decisions on thrombophilia testing should be deferred to the hematologist,
because there is no evidence supporting hereditary thrombophilia as a risk factor for flap thrombosis . At
[13]
our institution, all patients with a history of VTE or hereditary thrombophilia are routinely evaluated by