Evolution of Femoral Cannulation Techniques in Minimally Invasive Mitral Valve Surgery: A 10-Year Experience

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for allowing me to review your paper on femoral cannulation techniques in minimally invasive mitral valve surgery. I feel this is a well written paper and shows how much improvement has been made in this area over the last decade. 

I do have a question in regards to the 4 MANTA related complications. Were they noted sporadically throughout the 5 years of percutaneous cannulation or were they noted early on during the experience suggesting there is need for more training prior to utilization of this technique?

Also, how much do you think the surgical times are improved by better surgical technique rather than the type of cannulation performed as the cannulation time is not included in the overall surgical times?

Author Response

please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

2. Major Comments

2.1 Potential Era Bias

The comparison between cut-down and percutaneous cannulation appears to correspond largely to different time periods (cut-down earlier vs percutaneous later).

This introduces era bias, where improvements may reflect:

• Increased surgical experience
• Improved perioperative care
• Changes in patient selection

Although propensity score matching was performed, time was not included as a covariate.

Suggestion

The authors should acknowledge more clearly that:

• Improvements in operative times
• Reduced ICU stay

may partly reflect institutional maturation rather than access technique alone.

Suggested addition:

“Because the transition to percutaneous cannulation occurred later in the study period, improvements in operative efficiency and ICU stay may partially reflect temporal improvements in surgical workflow and perioperative management.”

 

2.2 Interpretation of ICU Length of Stay

The regression model reports:

β −3.5 days (95% CI −5.5 to −1.6)

However, the observed median difference appears to be approximately 1 day.

This discrepancy requires clarification.

Possible issues:

• Regression performed on log-transformed data
• Modeling artifact
• Misinterpretation of β coefficient

Suggestion

Clarify:

• The scale used in regression
• Whether ICU stay was transformed

Example clarification:

“ICU stay was log-transformed before regression modeling.”

Without clarification, the reported −3.5 days effect size appears inconsistent with descriptive statistics.

 

2.3 Re-exploration Rate

Re-exploration was significantly higher in the percutaneous group (12.1% vs 4.5%).

The authors attribute this to:

• procedural complexity
• anticoagulation strategies
• learning curve

However, no statistical adjustment was performed.

Suggested improvement:

• Provide multivariable analysis for re-exploration
  OR
• Clearly state it was not independently analyzed.

 

2.4 Patient Selection for Percutaneous Access

The manuscript states:

“Due to the retrospective character, it is not possible find out how many patients were excluded due to peripheral arterial disease.”

This is an important limitation because preoperative CT screening strongly affects eligibility.

The authors should clarify:

• Whether all patients underwent CT angiography
• The criteria used for exclusion

Example improvement:

“All patients underwent routine preoperative CT angiography to evaluate femoral vessel suitability; however, the number of patients excluded due to peripheral arterial disease could not be retrospectively determined.”

 

3. Statistical Comments

3.1 Table Formatting

Several issues appear in Table 5:

Example:

Cross-clamp time
68.0 [56.0–83.0]
68.0 [56.0–83.0]

The value appears duplicated.

This likely represents a formatting error.

 

3.2 Confidence Intervals

Confidence intervals are inconsistently reported.

Example:

2.8 % [0.3-9.6%]

Spacing and formatting should be standardized.

Suggested format:

2.8% (95% CI 0.3–9.6)

Comments for author File: Comments.pdf

Author Response

please see the attachment

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript reports a 10-year single-center experience comparing surgical femoral cut-down and ultrasound-guided percutaneous femoral cannulation in minimally invasive mitral valve surgery (MIMVS). The study includes a large cohort and addresses a relevant technical aspect of minimally invasive cardiac surgery. Overall, the manuscript is well structured and the data are interesting; however, several points should be clarified before publication. First, the comparison between the two strategies is strongly influenced by a temporal (era) effect, since the cut-down technique was used before 2021 and the percutaneous approach afterward. Improvements in operative times, ICU stay, and workflow efficiency may therefore reflect increasing surgical experience rather than the cannulation strategy itself. This limitation should be more clearly acknowledged and discussed. Second, although propensity score matching was performed, the matched cohort includes only 72 pairs, which represents a substantial reduction from the original population. The authors should discuss the potential impact of this reduction on statistical power and representativeness. Third, the significantly higher re-exploration for bleeding in the percutaneous group (12.1% vs 4.5%) deserves deeper discussion. Even if the authors report that these events were intrathoracic and not access-site related, this finding remains clinically relevant. In the context of vascular access strategies, the risk of bleeding complications remains a central issue, as highlighted in previous literature emphasizing the relationship between access strategy and hemorrhagic events (Cesaro et al., PMID: 31213156). The authors should clarify whether perioperative anticoagulation strategies, procedural complexity, or learning-curve effects may have contributed to this difference. Finally, the reporting of vascular complications could be improved by providing a more detailed breakdown of access-site events, rather than only the composite endpoint of groin complications. In summary, the manuscript addresses an important technical topic and presents valuable real-world data. However, clarification of the methodological limitations and a more balanced discussion of bleeding outcomes would strengthen the scientific message of the study.

Comments on the Quality of English Language

The overall meaning of the manuscript is understandable, but the English language requires revision. Several grammatical inaccuracies and stylistic issues are present throughout the text. Professional language editing is recommended to improve clarity and readability.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

WELL DONE

Author Response

Thank you for your valuable time you dedicated to review this article.

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have carefully revised the manuscript and have appropriately addressed most of the previously raised concerns. In particular, the clarification regarding the potential era effect, the limitations of propensity score matching, and the more balanced discussion of bleeding events have improved the overall quality and transparency of the study.

The additional details on re-exploration for bleeding and the expanded reporting of vascular complications are also appreciated and enhance the clinical interpretability of the results.

However, one point remains insufficiently addressed. The suggested reference discussing the relationship between vascular access strategies and bleeding risk (PMID: 31213156) has not been incorporated, nor has a rationale for its omission been provided. Given the relevance of bleeding complications in the present study, especially considering the observed differences in re-exploration rates, this reference appears directly pertinent to the discussion. The authors are encouraged to either include it or briefly justify its exclusion.

Aside from this point, the manuscript is scientifically sound and well presented. Minor refinements could further strengthen the discussion, particularly by maintaining a cautious interpretation of bleeding outcomes in light of potential confounding factors such as procedural complexity and learning curve effects.

In conclusion, I believe the manuscript is suitable for publication after minor revision.

Comments on the Quality of English Language

The quality of English has improved compared to the previous version and is generally clear and understandable. Minor residual issues in phrasing and sentence structure remain, but these do not affect the scientific content and can be addressed during the editorial process.

Author Response

We thank the Reviewer for this helpful suggestion. We agree with the general concept that vascular access strategy can influence bleeding risk. However, the proposed article (PMID: 31213156) primarily addresses transradial versus transfemoral access in percutaneous coronary interventions and focuses on access-site bleeding outcomes in an interventional cardiology setting. Because our study evaluates peripheral cannulation techniques for minimally invasive mitral valve surgery and the observed re-explorations were intrathoracic rather than access-site related, we considered that this reference might be only indirectly applicable. Nevertheless, we are happy to add the reference if the Reviewer and Editor consider it appropriate despite the contextual differences.