Minimally invasive mitral surgery: less inflammation than sternotomy

MIMVS vs Sternotomy: the challenge of mitral surgery in Pakistan

For the cardiac surgeon, the adoption of minimally invasive mitral valve surgery (MIMVS) represents a major technical turning point, requiring a rigorous evaluation of its safety compared to conventional sternotomy. This prospective cohort study, conducted at the Punjab Institute of Cardiology in Lahore (Pakistan) between September 1, 2025, and January 28, 2026, specifically addresses this issue. In a tertiary care setting, the authors examine the viability of the minimally invasive approach for treating degenerative mitral pathology within a specific local population.

The objective of this study, including 240 consecutive patients (145 MIMVS and 95 sternotomies), is to compare early postoperative outcomes in terms of morbi-mortality, length of stay, and biological response. The study tests the hypothesis that MIMVS, although technically more demanding with expected longer cardiopulmonary bypass and aortic clamping times, offers clinical benefits comparable to sternotomy while attenuating the systemic inflammatory response. To validate this postulate, researchers monitored not only classic clinical indicators such as stroke or 30-day mortality, but also specific biomarkers such as C-reactive protein (CRP) and creatine kinase (CK).

Study methodology

The Department of Cardiac Surgery at the Punjab Institute of Cardiology (Lahore) conducted this prospective cohort study between September 1, 2025, and January 28, 2026. The team recruited 240 consecutive patients suffering from degenerative mitral valve disease requiring surgical intervention.

L'étude répartit les participants en deux groupes distincts pour comparer les approches chirurgicales :

• MIMVS Group (n=145): patients undergoing minimally invasive mitral surgery.
• Sternotomy Group (n=95): patients undergoing conventional sternotomy.

Les chercheurs ont scrupuleusement documenté les variables préopératoires et les paramètres peropératoires, notamment le temps de circulation extracorporelle (CEC) et de clampage aortique. Le protocole incluait un suivi rigoureux des résultats postopératoires précoces, avec une attention particulière portée aux biomarqueurs d'atteinte organique : le dosage de la protéine C-réactive (CRP) et de la créatine kinase (CK) au deuxième jour postopératoire (J2).

For data analysis, the authors used SPSS software. They considered any result with a p-value < 0.05 to be statistically significant.

Analysis of results: Operative complexity versus biological benefit

The prospective study conducted on 240 patients (145 MIMVS and 95 sternotomies) reveals a clear dichotomy between the intraoperative technical workload and the systemic inflammatory response. While minimally invasive surgery extends operative times, it appears to better preserve patient homeostasis.

Perioperative parameters and techniques

L'approche mini-invasive (MIMVS) se caractérise par une durée d'intervention significativement plus élevée. Le temps de circulation extracorporelle (CEC) atteint 140,9 ± 39,4 min contre 95,7 ± 38,3 min pour la sternotomie (p < 0,001). Le clampage aortique suit la même tendance (88,7 ± 30,6 min vs 60,2 ± 23,0 min ; p < 0,001).

Surgical strategies also differ according to the approach:

• Isolated annuloplasty: More frequent in MIMVS (29.0% vs 13.7%; p = 0.007).
• Valve replacement: Predominant in the sternotomy group (33.7% vs 11.0%; p < 0.001).
• Concomitant tricuspid surgery: More frequently associated with sternotomy (36.8% vs 19.8%; p = 0.001).

Clinical results and biomarkers

Despite prolonged clamping times, major clinical outcomes at 30 days are comparable between the two groups. No statistically significant difference was observed regarding mortality, stroke rate, or length of hospital stay.

The most notable biological observation lies in the drastic drop in CRP at D2 in the MIMVS group, suggesting a major reduction in inflammatory stress related to the surgical approach. Conversely, creatine kinase levels are higher in MIMVS (932.9 vs 609.1 U/L), a result that warrants attention regarding the local muscular impact of the minimally invasive approach.

Clinical analysis of results: a controlled benefit-risk balance

Data collected at the Punjab Institute of Cardiology highlights a classic paradox of minimally invasive surgery (MIMVS): the significant lengthening of operative times does not compromise clinical safety. With significantly higher cardiopulmonary bypass (140.9 vs 95.7 min; p<0.001) and aortic cross-clamp (88.7 vs 60.2 min; p<0.001) durations, the MIMVS group could have presented increased morbidity. However, 30-day mortality (3.4% vs 1.1%) and stroke rates (2.8% vs 3.3%) remain statistically comparable to conventional sternotomy. Notably, the CRP level at day 2 is drastically reduced in MIMVS (18.5 mg/L versus 168.3 mg/L), confirming a blunting of the systemic inflammatory response, despite a more marked elevation of creatine kinases (932.9 vs 609.1 U/L) suggesting a different localized tissue trauma.

Limits and perspective

The major weakness of this study lies in the heterogeneity of the groups. Sternotomy patients presented more complex pathologies, with an increased prevalence of valve replacements (33.7% vs 11.0%) and concomitant tricuspid surgeries (36.8% vs 19.8%). This selection bias necessarily influences the length of hospital stay (14 vs 15 days) and operative times. While these results align with international literature regarding the safety of MIMVS, they highlight that, in this Pakistani context, the choice of approach remains closely linked to the patient's anatomical and pathological complexity.

Implications for practice

This study demonstrates that the learning curve and technical constraints of MIMVS do not prevent achieving excellent results in a tertiary center. The massive reduction in postoperative inflammatory syndrome argues for the generalization of the minimally invasive approach for isolated mitral pathologies, particularly annuloplasties (29% of MIMVS cases here), where the physiological benefit is most evident.

Summary of results

This prospective study (n=240) demonstrates that minimally invasive mitral valve surgery (MIMVS) massively reduces the systemic inflammatory response (CRP at 18.5 vs 168.3 mg/L, p<0.001) compared to sternotomy, despite longer aortic cross-clamp (88.7 vs 60.2 min) and cardiopulmonary bypass (140.9 vs 95.7 min) durations. Major clinical outcomes, including 30-day mortality (3.4% vs 1.1%) and stroke risk (2.8% vs 3.3%), remain statistically comparable between the two techniques.

In concrete terms, for the practitioner:

• Optimize biological recovery: prioritize MIMVS, particularly for isolated annuloplasties (29% of cases here), to benefit from a significantly lower postoperative inflammatory response.
• Manage operative expectations: do not be deterred by the extension of clamping time; the study confirms that it impacts neither the length of stay in intensive care (1.4 days) nor the total duration of hospitalisation.
• Interpret biomarkers with discernment: anticipate a more marked elevation of creatine kinase (932.9 U/L vs 609.1 U/L) inherent to the minimally invasive approach, without this translating into an unfavorable clinical outcome.

Technical lexicon of the study

MIMVS (Minimally Invasive Mitral Valve Surgery): Mitral valve surgery via a minimally invasive approach, generally using a lateral minithoracotomy to avoid complete opening of the sternum.

Conventional sternotomy: Standard surgical procedure consisting of a median vertical incision of the sternum to access the heart and great vessels.

Cardiopulmonary bypass (CPB) : Système de circulation extra-corporelle (CEC) prenant temporairement le relais des fonctions cardiaque et pulmonaire pendant l'intervention.

Aortic cross-clamp time: Duration of aortic clamping interrupting coronary perfusion to allow valve repair or replacement on a motionless heart.

Annuloplasty: Valve repair technique consisting of fixing a synthetic ring around the mitral annulus to restore its geometry and competence.

C-reactive protein (CRP): Plasma protein used as a biomarker of systemic inflammation, whose levels at postoperative day 2 are used here to measure the post-surgical inflammatory response.

Creatine kinase (CK): Enzyme whose elevation in the blood indicates cell lysis or stress (muscular or myocardial), quantified in the study to compare tissue trauma between the two techniques.

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