Experimental coronary artery occlusion: relevance to off-pump cardiac surgery

Atherosclerosis Alters Loading-Induced Arterial Damage: Implications for Robotic Surgery

Background

Lack of intra-operative haptic information during robotic surgery increases the risk for unintended tissue overload and damage. Knowledge about the acute and chronic fundamental relationship between force load and induced damage in healthy and diseased arteries is crucial to enable intra-operative haptic feedback or shared autonomy and improve patient safety.

Methods

Arteries of wildtype and atherosclerotic mice were clamped in vivo for 2 minutes (0.0N, 0.6N or 1.27N). Histological analysis (Verhoeff’s-Van Gieson, Osteopontin, CD45, CD105) was performed immediately, or after 6 hours, 2 weeks or 1 month. Endothelium-dependent and–independent vasodilatation was assessed immediately or 1 month after clamping.

Results

Endothelium dependent vasodilatation is worse after clamping of wildtype arteries, but is restored after one month. Clamping also results in flattening of the innermost elastic membrane of both genotypes, which is reversed over time for wildtype arteries but not for vessels from atherosclerotic mice. Higher osteopontin content in wildtype and LDLR-/- mice after 2 weeks suggests a phenotypic switch of the medial smooth muscle cells (SMCs), an effect that is reversed after 1 month. While inflammation in the intima diminishes, medial CD45 content rises through time in both genotypes. CD105 staining shows that even manipulation without clamping results in endothelial cell loss in both LDLR+/+ and LDLR-/- mice.

Conclusions

Arterial clamping induces different acute and long-term injury to the vessel wall of atherosclerotic and healthy arteries.

Arterial Vasoreactivity is Equally Affected by In Vivo Cross-Clamping with Increasing Loads in Young and Middle-Aged Mice Aortas

PURPOSE

To compensate for the lack of haptic feedback by surgical robots, limitation of exerted forces could be implemented. The limits should be based on the observed relationship between tissue load and induced damage. This study examines whether age-related changes influence this relationship.

METHODS

Descending thoracic aortas of male C57BL/6J mice of 10, 25 and 40 weeks were clamped in vivo (no clamp, 0.5N or 2.0N) for 2 min. Functional integrity was tested in vitro by studying endothelium-dependent and -independent vasoreactivity.

RESULTS

Endothelium-dependent relaxation deteriorated with increased clamping force at all ages. Clamping did not influence endothelium-independent vasodilation. Age (10, 25 and 40 weeks) did not significantly impact on the effect of clamping on endothelium-dependent and independent vasoreactivity.

CONCLUSIONS

Within the tested conditions, mechanical clamping induces damage to the vascular endothelium, but not to the smooth muscle cells. Age has no effect on the obtained results in mice from 10 to 40 weeks old.

Pressure-controlled Vascular Clamp: A Novel Device for Atraumatic Vessel Occlusion

Morphological vessel injury after clamping has been an important problem in vascular surgery. Although various techniques have been employed to occlude a vessel during a surgical procedure, a complete, atraumatic occlusion method has not yet been developed. In the present study, we describe use of a novel pressure-controlled and balloon-jawed vessel clamp to provide atraumatic vessel occlusion. We compared its traumatic effect on femoral arteries with that resulting from use of a conventional De Bakey vascular clamp in a canine model. During surgical application, our clamp provided complete vessel occlusion with no oozing in distal arteriotomy. On histological examination of the clamped vessel segments, we observed no destruction of the vessel wall, compared to widespread injury of the De Bakey vascular clamp. Despite some difficulties in application, we think this technique could be a promising method for vascular procedures.