title: Crimping and deployment of balloon-expandable valved stents are responsible for the increase in the hydraulic conductance of leaflets.
abstract: OBJECTIVE
  Leaflet injury has been documented to occur during the deployment of valved stents (VSs). The pathological aspects, however, of this injury are difficult to quantify. Conversely, the hydraulic conductance of a (pericardial) membrane may be easily determined. The impact of crimping and deployment of VS on this parameter was therefore investigated.
  
  
  METHODS
  Bovine pericardial square (25 × 25 mm) patches were placed within a pressure chamber and their hydraulic conductance was determined. The influence of the pressure gradient and tissue thickness on this parameter was analysed. Six balloon-expandable VS were constructed. The hydraulic conductance of their bovine pericardial leaflets was determined before and after VS crimping and deployment in four of them. Pericardial leaflets of non-crimped VS were used as controls.
  
  
  RESULTS
  Hydraulic conductance increased insignificantly with the pressure level within the chamber: from 128 ± 26.9 ml/h/m(2)/mmHg at a pressure of 50 mmHg to 232.3 ± 51.9 ml/h/m(2)/mmHg at a pressure of 250 mmHg (P = 0.117). Hydraulic conductance was not correlated to pericardial thickness, for thickness measurements ranging from 0.34 to 0.76 mm. The hydraulic conductance of VS leaflets significantly increased immediately after crimping from 45.2 ± 7.6 to 667.9.0 ± 527.2 ml/h/m(2)/mmHg (P < 0.001). This increase was still observed 24 h after VS deployment. No change in hydraulic conductance occurred in the control group.
  
  
  CONCLUSIONS
  The determination of the hydraulic conductance of pericardial patches was easy to perform, reproducible and not influenced by tissue thickness. The hydraulic conductance of pericardial leaflets dramatically increased after VS crimping and deployment. This parameter might be, in the future, a useful noninvasive tool in studying leaflet trauma.
authors.affiliation: Inserm U970, Paris V, Paris, France.
authors.forename: Channing
authors.initials: C
authors.lastname: Convelbo
authors.forename: Pierre
authors.initials: P
authors.lastname: Guetat
authors.forename: Michèle
authors.initials: M
authors.lastname: Cambillau
authors.forename: Bachir
authors.initials: B
authors.lastname: Allam
authors.forename: Patrick
authors.initials: P
authors.lastname: Bruneval
authors.forename: Antoine
authors.initials: A
authors.lastname: Lafont
authors.forename: Rachid
authors.initials: R
authors.lastname: Zegdi
mesh_terms: D000818:Animals; D001669:Biochemical Phenomena; D002417:Cattle; D008422:Materials Testing; D010496:Pericardium / Q000502:physiology*; D011312:Pressure; D011474:Prosthesis Design; D012212:Rheology; D015607:Stents
keywords: Hydraulic conductance; Injury; Leaflets; Percutaneous valves; Pericardium