An observational study comparing the SPY-Elite® vs. the SPY-PHI QP System in breast reconstructive surgery

Background: Indocyanine green angiography (ICG-A) can be applied to visualize per-operative tissue perfusion. Perfusion cut-off values based on ICG-A are important in guiding the intraoperative decision making. Two modalities able to quantify relative tissue perfusion values exist: the SPY-Elite® and the SPY-PHI QP system. We conducted an observational study comparing the quantitative perfusion values of the SPY-Elite® and the SPY-PHI QP with the postoperative outcomes in breast reconstructive procedures.

Methods: Sixteen consecutive patients undergoing breast reconstructive surgery (20 breasts) were included. The SPY-Elite® and the SPY-PHI QP imaging systems were applied simultaneously during surgery. There exists no international consensus on cut-off values, therefore cut-off was set to 33% as previous reported by Moyer et al.

Results: Five patients had implant-based breast reconstruction, 4 oncoplastic techniques (volume displacement or replacement), 7 autologous tissues (2 pedicled latissimus dorsi flaps and 5 free deep inferior epigastric artery perforator flaps). In 4/16 cases (25%) results of the imaging systems were unequal in quantifying tissue perfusion. The SPY-PHI QP system yielded a sensitivity of 50%, specificity 77%, positive predictive value 25%, negative predictive value 91% and 73% accuracy. The SPY-Elite® had a sensitivity of 50%, specificity 100%, positive predictive value 100%, negative predictive value 93% and 93% accuracy.

Conclusions: Imaging modalities assessing and quantifying real-time tissue perfusion is a valuable tool in breast reconstructive surgery. We tested the SPY-Elite® and the SPY-PHI QP using a perfusion cut-off value of 33%. The results were not comparable in assessing and quantifying tissue perfusion using the chosen cut-off value. Further studies investigating specific cut-off values for the SPY-PHI QP is needed.