Does sternal-sparing outweigh prolonged bypass? inflammatory resolution in MICS versus median sternotomy: a SIRI-based analysis.

BACKGROUND

Systemic inflammatory response is an important biological factor that determines morbidity after cardiac interventions. Minimally invasive cardiac surgery (MICS) was conceived to reduce surgical trauma but the subtle dynamics of its effect on the clearance of systemic inflammation is an ongoing research target. The aim of the present study was to investigate divergent inflammatory recovery trajectories of MICS and traditional MS with a multidimensional surrogate marker of immunological stress, the Systemic Inflammation Response Index (SIRI).

METHODS

This retrospective cohort study reviewed patients undergoing elective mitral valve surgery between February 2022 and February 2024; of 269 initially identified patients, 235 were eligible, and propensity score matching yielded 89 matched pairs for analysis. SIRI (combination of neutrophils ×  monocytes/lymphocytes) was evaluated at baseline, postoperative day (POD) 1 and POD 5. The main endpoint was the "inflammatory resolution velocity" measured by relative change from baseline (ΔSIRI). P < 0.05 was considered statistically significant. In addition, the prognostic value of ΔSIRI in predicting postoperative pulmonary complications (PPCs) was carefully analyzed using Receiver Operating Characteristic (ROC) analysis.

RESULTS

Our data showed that there was an acute and uniform inflammatory surge in both groups on POD 1 with no significant statistical divergence (P = 0.619) in the ΔSIRI values. By POD 5, however, the difference in ΔSIRI was significant between the two groups, with the MICS group demonstrating a greater re-equilibration to baseline levels than MS group (P < 0.001). Interestingly, this improved inflammatory clearance in the MICS group occurred in the context of much longer operative times and cardiopulmonary bypass times (P < 0.001), implying that the decreased inflammatory may effect of less tissue damage in this group overcame the inflammatory impact of longer cardiopulmonary bypass time. In terms of clinical utility, ΔSIRI on POD 1 was a good early-warning biomarker for PPCs for both surgical approaches [AUC: MICS = 0.696 (95% CI: 0.530-0.841); MS = 0.762 (95% CI: 0.483-0.955)]; and the rates of major morbidity and mortality were comparable.

CONCLUSION

MICS may reduce systemic inflammatory resolution time, defined by the kinetic of SIRI, creating optimal physiological environment for systemic inflammatory resolution, which may accelerate functional recovery and cardiac rehabilitation after MICS vs. conventional sternotomy. The data suggests a possible biological basis of sternal sparing techniques with regard to the "inflammatory window" and patient oriented outcomes.