Minimally invasive cardiac surgery (MICS) continues to gain popularity because of its potential to reduce surgical trauma while maintaining excellent clinical outcomes. However, one longstanding concern has been that MICS frequently requires longer cardiopulmonary bypass (CPB) and aortic cross-clamp times, both of which are known contributors to systemic inflammation. The important clinical question has therefore remained whether the advantages of avoiding a full sternotomy outweigh the inflammatory burden created by prolonged bypass.
This original investigation published in Frontiers in Cardiovascular Medicine addresses that question by examining postoperative inflammatory recovery using the Systemic Inflammation Response Index (SIRI), a biomarker calculated from neutrophil, monocyte, and lymphocyte counts. Unlike traditional inflammatory markers such as C-reactive protein or total white blood cell count, SIRI reflects the balance between innate inflammatory activation and adaptive immune function, providing a dynamic assessment of recovery following cardiac surgery.
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The investigators retrospectively reviewed patients undergoing elective mitral valve repair or replacement between February 2022 and February 2024. After exclusions, 235 patients remained eligible. To minimize selection bias, the researchers performed propensity score matching based on important baseline variables including age, sex, body mass index, left ventricular ejection fraction, and NYHA functional class. This process yielded 89 well-matched patients in each treatment group, creating a balanced comparison between minimally invasive surgery and conventional median sternotomy.
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One of the most interesting findings involved the timing of postoperative inflammation. Both surgical approaches produced nearly identical inflammatory surges during the first postoperative day. SIRI increased dramatically after surgery in both groups, indicating that cardiopulmonary bypass and ischemia-reperfusion injury trigger a universal early inflammatory response regardless of incision type.
The picture changed substantially by postoperative day five. Patients undergoing minimally invasive surgery demonstrated significantly faster normalization of SIRI values, indicating more rapid resolution of systemic inflammation. Although inflammatory activation initially appeared similar, recovery occurred much sooner following MICS. This suggests that minimizing tissue injury and preserving the sternum creates a more favorable biological environment during postoperative healing.
Perhaps even more noteworthy was that this improved inflammatory recovery occurred despite significantly longer operative times, longer CPB duration, and longer aortic cross-clamp times in the MICS group. Traditional surgical thinking often assumes that longer bypass directly translates into greater physiological stress. This study challenges that concept by suggesting that tissue trauma itself may contribute more substantially to prolonged inflammation than bypass duration alone.
The authors propose several physiological explanations. Median sternotomy requires division of the sternum, marrow exposure, extensive soft tissue dissection, and greater musculoskeletal injury. These factors release damage-associated molecular patterns (DAMPs) that continue stimulating inflammation well after surgery. In contrast, totally thoracoscopic MICS avoids sternotomy, minimizes skeletal injury, and preserves chest wall integrity, allowing inflammatory resolution to occur more rapidly despite longer technical operating times.
Reduced inflammation has important implications for recovery. A shorter inflammatory window may facilitate earlier mobilization, less postoperative pain, improved pulmonary function, and more efficient rehabilitation. These biological advantages align closely with Enhanced Recovery After Surgery (ERAS) principles, which emphasize minimizing physiological stress to accelerate functional recovery.
The study also explored the usefulness of SIRI as a predictive biomarker for postoperative pulmonary complications (PPCs). Receiver operating characteristic (ROC) analysis demonstrated moderate predictive ability. On postoperative day one, elevated SIRI values identified patients at increased risk for pulmonary complications in both surgical groups. Although predictive accuracy was modest, SIRI may represent an inexpensive and readily available tool for early postoperative risk stratification because it relies only on routine complete blood count measurements.
Importantly, faster inflammatory resolution did not come at the expense of patient safety. Rates of postoperative complications—including ECMO support, continuous renal replacement therapy, low cardiac output syndrome, ventricular fibrillation, pulmonary complications, reoperation for bleeding, and in-hospital mortality—were statistically similar between the two surgical approaches. These findings reinforce that minimally invasive surgery can achieve comparable short-term safety while potentially offering superior biological recovery.
The investigators acknowledge several limitations. The study was retrospective and conducted at a single center, preventing definitive conclusions regarding causality. Medication use before surgery, including statins and corticosteroids, could not be fully evaluated. Important recovery metrics such as exact ventilation duration, pain scores, and standardized functional recovery assessments were unavailable. Additionally, relatively few pulmonary complications limited the precision of ROC analyses.
Nevertheless, the findings contribute an important perspective to the ongoing evolution of minimally invasive cardiac surgery. Rather than focusing exclusively on operative efficiency or bypass duration, the authors encourage surgeons to consider the broader physiological consequences of surgical access. Preserving the sternum appears to shorten the inflammatory recovery period, potentially improving rehabilitation without increasing perioperative risk.
Future prospective multicenter studies incorporating cytokine measurements, longer follow-up, functional recovery endpoints, and patient-reported quality-of-life outcomes will be necessary to validate these observations. If confirmed, SIRI may become an inexpensive perioperative biomarker for monitoring recovery while providing additional biological evidence supporting minimally invasive cardiac surgery.
Overall, this study suggests that reducing surgical trauma may be more important than minimizing bypass duration when optimizing postoperative inflammatory recovery after mitral valve surgery.
