Thermodynamic Correlates of Hot Tip Laser Angioplasty

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Surface temperatures of normal human cadaver arteries and polytetrofiuoroethylene grafts were measured in vitro using thermography to assess vascular wall heating from the metal-capped ("hot tip") laser probe. Laser pulse duration, vessel diameter, blood flow, and saline infusion were varied; power from an Argon laser was constant at 10 watts.The surface temperatures resulting in perforation were 76.2 ± 2.2° C for arteries and 90.4 ± 2.1° C for grafts. Blood flow provided an effective heat sink reducing artery and graft wall peak temperatures from 10 watt/5 sec pulses by 12.2 ±1.7 and 14.1 ± 6.1° C at 100 mL/min, and by 16.3 ± 2.4 and 22.4 ± 4.9° C at 500 mL/min, respectively. In the occluded conduit, inflow of saline proximal to the probe tip reduced peak temperatures (° C) from 10 watt/5 sec pulses as follows: 14.0 ± 3.2 (artery) and 23.2 ± 8.5 (graft) at 50 mL/min, and 19.0 ± 0.6 (artery) and 26.6 ± 8.5 (graft) at 100 mL/min.Radial heating by the hot tip probe can cause thermal perforation. Blood flow or saline infusion modifies nontarget heating and may offer significant protection to the vasculature.

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