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A new ultrasound device has been developed to create holes in myocardium comparable to lasers. The device consists of 1 mm diameter solid titanium needle in a hand piece vibrating at a frequency of 24 kHz. The characteristics of the ultrasound needle were investigated using high speed and thermal imaging techniques. Similar imaging techniques were employed to investigate the C02, the Holmium, and the Excimer laser. The US needle created cavitation bubbles which rupture the structure of soft tissue and blend the cell matrix in a liquid environment. Shock waves were observed that traveled over 10 mm into the tissue without the evidence of direct tissue damage. During tissue penetration, the channel wall was heated due to the friction. In comparison, pulsed lasers generated explosive vapor bubbles that implode within 1 ms. These bubbles were bigger and appeared at a much lower frequency ( 40 Hz maximum). After vapor condensation the channel wall was heated significantly. The feasibility of the US needle was tested in-vivo in a porcine model. During activation, the US needle could perforate the left ventricular wall within a 2-4 seconds. Histology obtained acutely, showed 1 mm diameter channels with a small zone of thermal denaturation and small fissures along the channel wall similar to the excimer laser. Debris was found inside the channels as plugs of totally blended cell material. The US needle shows to be an effective device to create channels in the myocardium comparable with laser systems. The device is compact, easy to apply and cost effective compared to laser equipment. During surgery the surgeon can apply the US needle as an adjunct to CABG on sites which are unsuitable for bypassing without special precautions. Based on the characteristics the US needle device is expected to be as effective in the reduction of angina as laser systems.
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