Perfusion assessment techniques following mastectomy and reconstruction

History

It is fascinating to examine the evolution of implant-based reconstruction when considering the merits of perfusion imaging. Implant-based reconstructions were originally performed in one stage, with the implant sitting in the subcutaneous pocket, above the pectoralis muscle. These procedures were fraught with high capsular contracture and explantation rates. Later, upon introduction of the tissue expander by Radovan, two-stage, submuscular reconstructions became the new standard of care, and complication rates significantly declined.

It is no surprise that incorporating well-vascularized, muscular tissue contributed to increased success with implant-based reconstructions. However, with the introduction of acellular dermal matrices in the early 2000s as well as improved mastectomy techniques and autologous fat grafting, complete submuscular dissection has become less necessary, and many surgeons have now returned to performing their reconstructions within the prepectoral space. Though this technique improves postoperative discomfort and eliminates post-reconstruction animation deformity, it does create an increased need for well-perfused skin and subcutaneous tissues around the implant.

Detecting ischemic tissue after mastectomy has always been a challenging task, relying primarily on subjective observations of skin color, capillary refill, and mastectomy flap thickness. Unfortunately, the predictive ability of this approach is suboptimal, and highly variable between clinicians, as demonstrated by that fact that skin and nipple necrosis can affect up to 37% of nipple-sparing mastectomy operations. However, the intra-operative use of fluorescence angiography has recently emerged as an objective tool in the evaluation of tissue perfusion with consistent correlation to clinical outcomes.

The most common contrast agent for this application is indocyanine green (ICG), an intravenous dye that binds to plasma proteins and fluoresces in the near infrared spectrum upon excitation by a laser light source. When coupled with a camera capable of detecting these wavelengths, such as the SPY-PHI (Stryker) or FLUOBEAM (FLUOPTICS) systems, this allows for the real-time visualization of tissue perfusion, with well-perfused areas of the image appearing bright, and poorly perfused areas appearing dark ( Fig. 18.1 ). Furthermore, the dye has a low potential for causing adverse reactions, and a short plasma half-life of just 2–3 min, allowing for repeated use within a relatively short timeframe.

This technology has gained popularity among breast reconstruction surgeons primarily for its ability to assess skin and nipple viability following mastectomy. In a case series of 24 breasts, Komorowska-Timek and Gurtner showed that incorporating SPY values into surgical decision-making was associated with a decrease in the rate of mastectomy skin necrosis, from 15% to 4%. Similarly, in a larger study of 184 patients, Duggal et al . observed a lower incidence of skin necrosis (13%) in those for whom ICG angiography was utilized, versus those without use of the technology (24%) ( Fig. 18.2 ).