Visualizing Differential Distribution of Balloon Delivered Coating

Background: We developed a preclinical method for imaging and quantifying balloon delivered coating to tissue surfaces.

Methods: Yorkshire swine peripheral arteries received 60sec inflations with a paclitaxel coated balloon catheter (PCB), either conformal-amorphous on a nylon surface (Fig 1A; IN.PACT, Medtronic, Santa Rosa, CA) or micro-crystalline (3.5 µg/mm²) on an ePTFE surface (Fig 1B; MCEP, W.L. Gore, Flagstaff AZ). Animals were euthanized at 1, 24 and 72h (n=4 per time point and device) and treated arteries collected, bisected, mounted and processed for scanning electron microscopy (SEM).

Results SEM images revealed uniform coating on both balloon surfaces (Fig 1C,D) but higher and more uniform tissue coverage@1h for the MCEP (18.7±6.2%, Fig E,G) vs IN.PACT (10.4±2.2%, Fig 1 F,G). Tissue adherent coating at 1h was flaked/amorphous after IN.PACT (Fig 1Ai) and microcrystalline after MCEP (Fig 1Bi). Between 1 and 24h >94% of the coating had cleared from tissue surfaces (%coated area: 1.1±0.5% after MCEP vs 0.2±0.2% after IN.PACT); similar findings were obtained at 72h (0.4±0.3% after MCEP vs 0.2±0.1% after IN.PACT).

Conclusions Microcrystalline coating on ePTFE surfaces transferred more uniformly to porcine peripheral arteries vs amorphous coating on nylon of similar load and initial distribution. The demonstration of differential coating distribution in animal arteries may help explain the lack of a clinical class effect in for PCB while also providing insights as to the potential of lesion preparation strategies to enhance drug uptake from balloons.