Coronary chronic total occlusions (CTOs) are severe blockages formed by lipid, fibrous, and calcific material within the artery, halting blood flow for at least three months. Treating CTOs using true-lumen crossing is challenging due to their composition and high tortuosity in coronary arteries. Our study uses intracardiac echocardiography (ICE) catheters to image coronary arteries, introducing a novel 2D and 3D outlining technique. This advancement may improve percutaneous coronary interventions (PCI) for CTOs by providing live imaging feedback during true-lumen crossing procedures, enhancing treatment outcomes.
Percutaneous coronary intervention (PCI) for improving calcified coronary artery compliance remains a challenge and is associated with high rates of complications and adverse outcomes. In addition to traditional rotational atherectomy devices for improving coronary artery compliance, recently, electric discharge plasma mediated shockwave therapy has been introduced to cause calcium fracture and improve coronary compliance. However, this intervention has cardiac pacing limitations. Laser lithotripsy is commonly utilized to fracture kidney stones. High powered laser pulses are transmitted via small diameter optical fibers (200-400 μm core diameter) to the stone surface, where they induce fracture. We implemented a novel catheter device that utilizes indocyanine green (ICG) filled balloon to produce calcium fractures. At 2mg/mL, ICG has greater than 5x higher absorption coefficient (256cm-1, 755nm) than water at 2.1 μm, a typical target of holmium lasers (~40cm-1, 2.1μm) during lithotripsy. To demonstrate the feasibility of laser induced calcium fracture a balloon catheter device (2mm outer diameter un-inflated, 1 meter long) was constructed with a fiber port coupled to alexandrite lasers (755nm) and a balloon port to fill biocompatible ICG in front of the fiber. Different temporal pulse regimes (millisecond to sub-nanosecond) were explored inducing shockwaves pressure amplitudes higher than 50 atm sufficient to cause fracture in coronary artery phantoms made from Ultracal 30® material. This approach does not require cardiac pacing and can markedly improve arterial vessel compliance during stent deployment.
Coronary chronic total occlusions (CTOs) are atherosclerotic plaques comprised of lipid, fibrous and hard calcific material that originate in the vessel wall and extend into the lumen, restricting luminal cross-section by 100% resulting in complete stoppage of blood flow in the affected artery for at least three months. Due to their structure and calcific composition, CTOs are very difficult to treat with existing percutaneous coronary interventional (PCI) techniques. CTOs frequently have a hard fibro-calcific cap on the proximal side with a softer lipidic composition in the interior and distal side. We constructed a novel catheter system with a fiber coupled Ho:YAG laser (2.1um, Coherent Inc) for cutting and a biocompatible CO2 cooling system delivered through a 200um conduit for intravascular cooling. Laser radiation delivered a maximum average power of 20W corresponding to a pulse energy of 300mJ, pulse duration of 200μs, and a pulse repetition rate of 10Hz. Light emitted from the fiber was directed onto ex vivo suspect-calcified CTO arteries (n=3). Successful CTO crossing was achieved in all ex vivo samples. Histological processing showed greater than 50% reduction in residual thermal damage in crossed CTO regions with CO2 cooling compared to no cooling. The miniature device was also used to cross CTOs in an in vivo rabbit femoral CTO model (n=4) under Xray fluoroscopy guidance and subsequent contrast angiography confirmed restoration of blood flow.
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