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BACKGROUND: Necrosis of mastectomy skin flaps is a common complication occurring in up to 15% percent of all breast reconstructions (1). Intraoperative perfusion mapping with laser-assisted indocyanine green (ICG) angiography has recently been utilized to assist reconstructive surgeons in identifying ischemia and predicting areas that will develop necrosis (2). Our study aims to identify specific perfusion values that accurately predict mastectomy flap necrosis.
METHODS: In a prospective clinical trial of 42 patients undergoing autologous or implant-based breast reconstruction, mastectomy flaps were imaged using laser-assisted ICG angiography. Perfusion was videotaped at the completion of the reconstruction and absolute perfusion values were obtained at 90 seconds post-ICG injection using SPY-Q quantitative analysis. All patients were followed clinically and intraoperative perfusion numbers were correlated with skin flap outcomes. Risk factors for abnormal perfusion, including smoking, diabetes, intraoperative hypotension, hypothermia, and intraoperative use of epinephrine were recorded and analyzed.
RESULTS: Sixty-two breast reconstructions were imaged, including 48 tissue expander reconstructions (77%), 6 TRAM flaps (10%), 6 DIEP flaps (10%), and 2 direct-to-implant reconstructions (3%). Eight cases (13%) of full-thickness skin necrosis were identified postoperatively. A SPY value of 7 or below on quantitative analysis accurately predicted the development of flap necrosis in 7 of these 8 reconstructions, yielding an overall sensitivity of 87.5% and a specificity of 83.3%. False positives cases (those with perfusion values ≤7 which did not develop postoperative flap necrosis) were more likely than our other cases to have a smoking history and/or to have had an epinephrine-containing tumescent solution injected by the breast surgeon prior to reconstruction [8 out of 9 false positives (88.9%) vs. 8 out of the other 53 cases (15.1%)]. Excluding our patients with smoking or epinephrine use, a SPY value of 7 or below predicted flap necrosis with a sensitivity of 83% and specificity of 98%.
CONCLUSION: Specific measurements generated from intraoperative perfusion mapping with laser-assisted ICG angiography correlate well with postoperative outcomes. In our series, a SPY value of 7 or below correlated well with flap necrosis. Furthermore, factors that alter perfusion, such as smoking and intraoperative injections containing epinephrine, should be considered when evaluating low perfusion values as they can lead to false positive test results.