BACKGROUND: Catheter directed thrombolysis (CDT) delivering Tissue Plasminogen Activator (tPA) and Ultrasound (US) has shown clinical benefit, but the additional in vivo impact of US warrants further research. Here we quantify clot lysis in a pig model of pulmonary embolism (PE) after CDT using the same catheter with and without US.

METHODS: Per swine, up to 3 contrast-enhanced clots of controlled morphology (prepared >2 days in advance) were delivered to the pulmonary arteries through an introducer sheath via the external jugular vein. Angiography confirmed successful delivery of all clots, one in the left pulmonary artery/swine and one or two in the right pulmonary artery/swine, with occlusion ranging from partial to full. Subsequently, EkoSonic (Ekos) catheters (Boston Scientific, Marlborough, MA, USA) with US core were deployed under fluoroscopic guidance into one pulmonary artery/swine, near the clot locations, and 2 mg/h tPA infused from the catheters for 4h with (2 swine) or without US activation (2 swine). Clots in contralateral pulmonary arteries served as untreated controls. Residual clots were collected at necropsy, weighed and measured.

RESULTS: All swine survived in good health to experiment conclusion, and residual clots were identified in the distal regions of the treated and untreated pulmonary arteries. tPA alone or with US reduced clot weights by, 4±6% and 38±26% relative to controls. Treatment with tPA+US reduced clot length by 53±3% relative to the contralateral controls, whereas the lengths of control and tPA-treated clots were indistinguishable.

CONCLUSIONS: Ultrasound enhanced CDT of model clots.