Increased time-dose-response (TDR) of suboptimal oxygen delivery (DO₂) during cardiopulmonary bypass (CPB) has been associated with increased postoperative complications. The impact of surgical approach – minimally invasive vs. median sternotomy – on TDR during mitral valve surgery has not been studied.

All patients that underwent isolated mitral valve surgery at our institution between 05/2018–06/2024 were included. Perfusion variables were collected continuously (second-to-second) during CPB with a threshold of DO₂ index <300 mL O₂/min/m₂ (DO₂i^<300) to quantify depth and duration of insufficient oxygen supply. The primary outcomes used for analysis were maximum and total TDR of DO₂i^<300. Logistic regression was used to assess the relationship of TDR with surgical outcomes.

A median sternotomy and right minithoracotomy was performed in 377 (84.1%) and 74 (15.9%) patients, respectively. The maximum and total cross-clamp (XC) TDR of DO₂i^<300 (577.7 vs. 91.7 AUC<300 mL O₂/min/m², p<0.0001; 1116.0 vs. 143.1 AUC<300 mL O₂/min/m², p<0.0001) and post-XC TDR of DO₂i^<300 (472.4 vs. 281.0 AUC<300 mL O₂/min/m², p=0.0004; 606.5 vs. 334.4 AUC<300 mL O₂/min/m², p<0.0001) were significantly higher with a right minithoracotomy. Total post-XC TDR of DO₂i^<300 was independently associated with postoperative AKI (OR: 1.271, CI: 1.01–1.6, p=0.0413).

A right minithoracotomy approach was associated with an increased TDR of DO₂i^<300. Post-XC TDR of DO₂i^<300 was independently associated with postoperative AKI. These findings highlight the importance of goal-directed-perfusion and the pivotal role of perfusionists in minimally invasive mitral valve surgery.