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Mechanical Properties and Biological Interaction of Aortic Clamps: Are All Minimally Invasive?
Giacomo Bianchi1, Angela Pucci2, Marco Matteucci3, Egidio Varone1, Simone L. Romano3, Vincenzo Lionetti3, Mattia Glauber1.
1Hospital & Research Institute CREAS IFC CNR - Massa - G.Pasquinucci Heart Hospital, Massa, Italy, 2Cardiovascular Pathology Section - University of Pisa, Pisa, Italy, 3Sector of Medicine, Scuola Superiore Sant’Anna, Pisa, Italy.
OBJECTIVE:
Although specifically-designed aortic clamps are mainstay of minimally invasive cardiac surgery, no comparative reports about their mechanical properties and interaction with the aortic wall are present. In this study the generated force in the clamp’s jaws and the biological response of the aorta after clamping, i.e. endothelial layer destruption and muscle cell layer shrinking, are evaluated.
METHODS:
The jaw force of five commercially available clamps (Geister, Cygnet, Cardiovision/Chitwood 195.10, Cardiovision 195.40 and Cardiovision 195.81) was assesses by clamping a 2.2 mm compression load cell (Interface Advanced Force Measurement, Scottsdale, Arizona) with dedicated computer USB interface. The test was conducted at proximal, middle and distal site from the fulcrum with a closing force equal to the one used in clinical setting. Biological response of the aortic wall was assessed in five minipigs (weight 38-40 kg) that underwent thoracic aorta clamping under general anesthesia through left thoracotomy. After 45 min, the animals were euthanatized and the aorta removed. Immunochemistry and morphometric analysis were carried out for each aortic segment
RESULTS:
Each clamp showed a peculiar pattern of force generation, being higher in the proximal and middle portion and lower in the distal part. One clamp (Cygnet) exhibits homogeneous maximal force generation at all the three sites. Two clamp exhibited similar aortic wall shrinkage (CV195.81 and CV195.10, 25,6% and 24,9%; p=NS), while the others had higher values. Variable degree of endothelial layer disruption occurred in all clamping test; three clamps (CV195.10, Cygnet, Geister) had the lower amount of intact endothelium. Interestingly, endothelial disruption and media shrinkage does not correlate with generated force in the clamping portion (p=NS), but relates with the Δshrink (p<0,001), that is specific of the clamp design itself.
CONCLUSIONS:
Minimally invasive aortic clamps present unique pattern of force generation and peculiar interaction with the aorta. Choice of a clamp that is minimally invasive not only in the design, but also “biologically”, will lead to improve surgical results, thus avoiding complications of aortic manipulation.
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