Limitations
The limitations of this study are linked to its retrospective design, yielding missing data and incomplete follow-up. Regarding the validity of biomarkers to represent organ function, the low specificity of some biomarkers might impede clear interpretation of some data, as for example, liver enzymes AST, ALT and LDH are known to have other tissue sources. Therefore, this study would have been favored by a prospective design, incorporating the follow-up of organ-specific markers.
Since MIVT was used consecutively for MV surgery since 2009, with a short time overlap to cover the learning phase, there is a historical difference between the study groups. This might include some selection bias, where patients with more complex MV pathology were preferably operated through conventional approach during the transit period. As we found it mandatory to include the learning period, propensity-matching was performed for patient-related conditions but not for MV disease. However, we feel confident that even in a fully 1:1-matched cohort, the clinical outcome and organ function results would be comparable, demonstrating that the port-access approach allows to achieve a qualitatively identical outcome despite longer procedural times.