Balloon dissecting instruments

#This invention relates to methods and devices for endoscopic vascular surgery, in particular to methods and devices for dissecting tissue to create a working space adjacent a blood vessel.

#Numerous surgical procedures have been developed to replace arteries that have become blocked by disease. The aortocoronary bypass surgery is perhaps the most important of these bypass operations. The coronary arteries supply blood to the heart. As a result of aging and disease, coronary arteries may become blocked by plaque deposits, stenosis, or cholesterol. In some instances, these blockages can be treated with atherectomy, angioplasty or stent placement, and coronary bypass surgery is not required. Coronary bypass surgery is required when these other methods of treatment cannot be used or have failed to clear the blocked artery. In coronary bypass surgery, a vein is harvested from elsewhere in the body and grafted into place between the aorta and the coronary artery below the point of blockage. An illustration of this surgery is shown in FIG. 1, which shows the heart 1 and the right anterior coronary artery 2 and the left anterior coronary artery 3 which supply blood to the heart. The right anterior coronary artery 2 is blocked in its proximal segment at 2a, as shown. This blockage has been bypassed by grafting a segment of vein 4 between the aorta 5 and the distal segment 2b of the right anterior coronary artery 2. Similarly, the left anterior coronary artery 3 may be blocked, and may require bypass with a length of vein 4a between the aorta and the distal segment 3b of the left anterior artery. The operation requires access to the heart, which means that the chest cavity must be opened completely.

#The coronary bypass surgery requires a length of vein or artery for the graft. It is preferred to use a vein taken from the patient undergoing the bypass surgery. The patient is a ready source of suitable veins that will not be rejected by the body after transplantation and grafting onto the aorta and coronary artery. The saphenous vein in the leg is the best substitute for small arteries such as the coronary arteries, and it is the preferred vein for use in coronary bypass surgery. This is because the saphenous vein is typically 3 to 5 mm in diameter, about the same size as the coronary arteries. Also, the venous system of the legs is sufficiently redundant so that after removal of the saphenous vein, other veins that remain in the leg are adequate to provide return blood flow. The cephalic vein in the arm is an alternative that is sometimes used.

#FIG. 1 is a front view of the heart showing a vein grafted from the aorta to the right anterior coronary artery, bypassing the proximal segment of the right anterior coronary artery.

#FIG. 2 is a view of the leg showing the incisions necessary for harvesting the saphenous vein using a traditional open procedure.

#FIGS. 3, 3a and 3b are views of the leg showing the incisions necessary for harvesting the saphenous vein according to the methods presented herein.

#FIG. 4 shows an embodiment of a balloon loaded blunt dissector 15 in its uninflated state, with a balloon 16 packed inside the device. The balloon 16 is a nonelastic balloon or bladder and is cylindrical or tubular with a central lumen 17. The balloon 16 has two walls 18 and 19 and may be described as a double walled balloon tube. The balloon 16 may be made of polyethylene, polyurethane, polyamide and other nonelastic materials as well as latex and other elastic materials. The balloon 16 may be any suitable length, for example 12 to 24 inches long, to provide of a tunnel of convenient length when harvesting the saphenous vein. The balloon 16 may be any convenient diameter or width, for example 2 to 3 inches, to allow laparoscopic instruments to fit and operate conveniently within the tunnel created by the balloon 16. The balloon tube 16 may have any suitable cross-sectional shape.

#A guide rod 20 with a blunt or rounded tip 21 is disposed in the central lumen 17 of the double walled balloon tube 16. The guide rod 20 is used as a pushing member to push the balloon 16 through body tissue. A support tube 22 may be provided to give some columnar support to the device and provide a stop member or coupling member to translate pushing force applied to the guide rod 20 to pushing action on the balloon tube 16. The support tube 22 may be secured to the inner wall of the balloon tube 16 in any suitable fashion. The support tube 22 may have an overhanging lip 23 which obstructs passage of the guide rod 20 or endoscope 29 (if provided). Alternatively, the guide rod 20 or endoscope 29 can be fitted with a stop collar 30 to engage the support tube 22 (as shown in FIG. 5). The support tube 22 may have a square tip 25 as in FIG. 4 or a rounded tip 26 as shown in FIG. 5. The guide rod 20 and support tube 22 are used to push the balloon 16 along the saphenous vein or other desired pathway between tissue layers.

#The guide rod 20 and support tube 22 are normally straight (as shown in FIG. 4) and are of sufficient rigidity to bluntly dissect between tissue layers. In addition, the guide rod 20 and support tube 22 may be configured such that they are plastically bendable into curved shapes when subjected to bending moments substantially greater than the bending moments encountered when used to dissect between tissue layers (see FIG. 13). The bendable guide rod 20 and/or support tube 22 are made of materials and are proportioned such that they permanently retain the curved shape and have sufficient rigidity in the curved shape to bluntly dissect between tissue layers. In this way, the dissector 15 can be bent into a desired segment of dissection alongside a curved elongate structure or to maneuver the dissector 15 around an obstruction blocking the path to the area to be dissected. It is contemplated that the tunneling members (including tubes, rods, shafts, etc.) in any of the embodiments disclosed herein may have the plastically bendable properties as described for the embodiments of FIGS. 11-13.