Predicting mastectomy skin flap necrosis with indocyanine green angiography: the gray area defined. 
Preservation of breast skin during mastectomy has improved the cosmetic results of breast reconstruction.  Unfortunately, the incidence of mastectomy skin flap necrosis remains high using conventional evaluation methods; therefore, accurate prediction of flap viability is an important component of postmastectomy reconstruction.  The authors studied a prospective cohort of women who underwent skin-sparing mastectomy and breast reconstruction over a 2-year period at Emory University.  Mastectomy skin flap perfusion was measured intraoperatively using indocyanine green angiography.  Once necrosis matured postoperatively, digital images were taken and superimposed over the intraoperative scan.  Perfusion percentages were measured in healthy and nonviable skin.  One hundred eighteen patients were included, and 14 patients (15 breasts) with postoperative skin necrosis and sufficient image data were analyzed.  The average woman's age was 49.7 years (range, 28 to 73 years) and the average body mass index was 27.7 (range, 21.2 to 42.2).  Skin with 25 percent or less perfusion (perfusion score, ≤ 25) was not viable 90 percent of the time, and areas with greater than or equal to 45 percent perfusion survived 98 percent of the time.  A 33 percent perfusion score had a positive predictive value of removing nonviable skin of 88 percent and a negative predictive value of removing healthy skin of 16 percent.  Indocyanine green angiography is a useful adjunct to assess mastectomy skin flap viability.  A gray zone exists between 25 and 45 percent of maximal skin perfusion in which the ultimate viability remains in question.  By designating the cutoff perfusion score of 33 percent, the surgeon can expect to more accurately remove nonviable skin.  Diagnostic, III.