LAUSR

We want to thank Dr. Yoshimatsu and his colleagues for their recent paper entitled “Application of indocyanine green angiography to detect flap congestion in the use of free deep inferior epigastric perforator flaps for breast reconstruction” (Yoshimatsu et al., 2021). As they noted in their manuscript, indocyanine green angiography (ICG) is increasingly used to assess tissue perfusion intraoperatively (Chatterjee et al., 2013). As surgeons who achieve their surgical goals by striking a successful balance between reducing perfusion to tissue in exchange for increasing tissue mobility, ICG is a very valuable modality to augment clinical judgment. While it is easily understood how ICG indicates arterial inflow, venous outflow is more commonly the limiting clinical factor. That has always been the Achilles heel of this modality—it does a better job of showing us the aspect of perfusion that is less likely to be a problem. We conceptually understand that ICG angiography can be used to identify venous outflow insufficiency when used at different intervals (separated by approximately 20 min or more of a “washout” period), such that the prolonged and persistent appearance of ICG in the tissue after a period of time after which we would expect the one-time bolus of ICG to have left the tissue would indicate that some degree of venous outflow insufficiency is present. But this is a clinically unwieldy maneuver that most surgeons do not use. Therefore, the identification of a means of using ICG angiography to identify the presence of venous outflow insufficiency easily and promptly would be clinically advantageous, as it would augment clinical judgment in the determination of whether any venous augmentation maneuvers are warranted to increase the likelihood of clinical success. What Dr. Yoshimatsu et al. importantly contribute in their paper is that ICG angiography can in fact provide clinically actionable information about the state of venous outflow of deep inferior epigastric perforator flap (DIEP) flaps during breast reconstruction. While their paper highlights the fact that this observation is more important for venous outflow insufficiency than it is for arterial inflow insufficiency, they do not elaborate on what appearance specifically indicates the presence of venous outflow insufficiency.