Local drug delivery with porous balloons in the rabbit: assessment of vascular injury for an improvement of application parameters.

Objectives: Sufficient intramural drug concentrations with the use of porous balloon catheters can be achieved with additional vascular trauma only. However, effective delivery of a potent drug even in deeper layers of the vessel wall might outweigh these traumatic side effects. Given the porous balloon catheter, the parameters of injection pressure and applied fluid volume will influence the interventional result.
Methods: We tested a 2.5-mm porous balloon (35 75-micron pores) in the right carotid artery of New Zealand rabbits and used injection pressures of 1, 2, and 5 atm and fluid volumes of 2 and 4 ml of low-molecular-weight heparin solution in combination with the different parameters (n = 5 animals/group). In 50 rabbits, an intimal fibromuscular plaque was induced by using the electrostimulation model. Balloon dilatation and then application of the porous balloon was performed in 30 animals, 10 animals were only electrostimulated, and 10 animals served as a control group with balloon dilatation only. The vessels were excised 7 d after intervention, stained, and analyzed histomorpologically. Anti-Xa assays revealed the extent of systemically escaped drug, and serial cuts allowed for exact determination of vessel wall injuries.
Results: Effective local drug delivery could not be achieved with an injection pressure of less than 2 atm. Specific pressure-driven effects such as jet injuries could be identified. When the pressure was high enough for disruptive drug delivery (> or = 2 atm), fluid volumes of 4 ml led to loose elastic membranes and local thickening within the media.
Conclusions: Sufficient intramural drug distribution using porous balloon catheters can be achieved with low injection pressures. Different fluid volumes strongly determine the extent of additional vascular injury.