Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
2000-07-11
2004-06-08
Denion, Thomas (Department: 3748)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S096010
Reexamination Certificate
active
06746426
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to medical devices and methods, and more particularly to transluminally implantable vascular blocking devices and methods for causing retrograde flow of arterial blood through veins to treat ischemia caused by insufficient arterial blood flow.
BACKGROUND OF THE INVENTION
Atherosclerotic cardiovascular disease remains a major cause of premature death and morbidity, in most regions of the world. In addition to drug therapy, there currently exist a number of surgical and interventional techniques for treating atherosclerotic cardiovascular disease. Among these are a number of revascularization procedures wherein arterial or oxygenated blood (i.e., blood that generally has a pO
2
of at least 50 and typically 75-100 while the patient is breathing room air) is rerouted or caused to flow in a manner that provides improved perfusion of ischemic tissues.
1. Surgical Bypass of Diseased Coronary or Peripheral Arteries
An arterial bypass graft operation is a type of surgery that is done to reroute or “bypass” blood around clogged arteries, thereby improving the supply of blood and oxygen to tissues that have become ischemic due to blockage(s) in the affected artery. During bypass surgery, surgeons take a blood vessel from another part of the body, or a synthetic or natural vascular graft, and construct a detour around the blocked part of a coronary or peripheral artery. In coronary artery bypass graft surgery (CABG) procedures performed to remedy an obstructed coronary artery, an artery (e.g., the right internal mammary artery or left internal mammary artery) may be detached from the chest wall and the open end of that detached artery is then attached to the coronary artery below the blocked area. Alternatively, a segment of a long vein may be harvested from the patient's leg (e.g, Saphenous Vein) or other area of the body and one end of that vein segment connected to the aorta and its other end is attached or “grafted” to the coronary artery below the blocked area.
Occasionally, because many coronary or cardiac veins are substantially parallel to coronary arteries, it happens that arterial bypass grafts are accidentally attached to a coronary or cardiac vein instead of the desired coronary artery. This results in the formation of inadvertent arterio-venous fistulas and resultant steal of arterial blood from the affected coronary vein due to shunt effect (i.e., oxygenated blood that has entered the vein flowing in the direction of normal venous bloodflow back to the right atrium instead of flowing in a direction opposite normal venous blood flow and perfusing the ischemic myocardium). These inadvertent arterio-venous fistulas have required corrective surgery to ligate the erroneously placed graft (thereby eliminating the shunt) and to create a new bypass graft that is connected to the intended coronary artery. see, Lawrie, G. M. et al.,
Aortocoronary Saphenous Vein Autograft Accidentally Attached to a Coronary Vein: Follow
-
up Angiography and Surgical Correction of the Resultant Arteriovenous Fistula
, Ann. Thorac. Surg. 22:1 87-90 (1976).
Cardiovascular surgeons have also experimented with the purposeful use of cardiac veins for coronary revascularization. These coronary vein bypass graft (CVBG) procedures were typically performed on patients who had severely diffuse stenotic coronary artery disease that rendered them not to be candidates for mainstream CABG surgery. This CVBG technique involved using an intervening graft from the internal mammary artery or an aortic attachment to a saphenous vein graft. Instead of anastomosing the grafts to the distal coronary artery, the grafts were attached to coronary or cardiac veins that are generally parallel to the obstructed arteries. The coronary vein to which the graft is attached is then ligated proximal to the graft attachment to prevent a shunt. Thus, the veins were ‘arterialized’, allowing arterial blood to flow through the vein in a retrograde fashion in a effort to bring oxygenated blood to the venules and capillaries of the heart. However, the ligating of the vein proximal to the graft attachment (i.e., between the location at which the graft is anastomosed to the vein and the coronary venous sinus) often required dissection of the vein or tunneling under the vein to free the region of vein that is to be ligated from the myocardium. Such dissection and freeing of the vein can cause undesirable trauma to the myocardium. see, Hochberg, M. S., et al.,
Selective Arterialization of Coronary Veins: Clinical Experience of
55
American Heart Surgeons
; Clinics of CSI; 1986, 1:195-201 (1986).
Furthermore, accomplishing a specific degree of partial or total closure of the vein can be difficult to accomplish by merely tying a ligature or suture around the vein. Indeed, if the ligature is drawn and tied too tightly the vein may be severed or perforated causing hemorrhage. On the other hand, if the ligature is drawn and tied too loosely the vein lumen may not become or remain permanently closed and the ligature may fail to stop the undesirable steal of arterial blood from the vein.
2. Catheter-Based Transluminal Procedures for Bypass of Diseased Coronary or Peripheral Arteries:
Included among the newer interventional techniques are certain percutaneous, transluminal techniques for bypassing obstructions in coronary or peripheral arteries through the use of the adjacent vein(s) as in situ bypass conduit(s); (e.g. using catheters to perform extraluminal procedures outside the diseased vessel lumen). These are proprietary procedures being developed by Transvascular, Inc. of Menlo Park, Calif. and are described in various publications including U.S. Pat. No. 5,830,222 (Makower) and U.S. Pat. No. 6,068,638 (Makower), as well as in published PCT Applications WO 98/16161 and WO 98/46119.
In one such procedure known as a Percutaneous In Situ Coronary Venous Arterialization (PICVA™), catheters are used to form an interstitial channel between a coronary artery or chamber of the heart and a coronary vein such that arterial or oxygenated blood (i.e., blood that generally has a pO
2
of at least 50 and typically 75-100 while the patient is breathing room air) will flow from the artery or chamber of the heart and into the vein. A blocker delivery catheter is advanced into the vein, proximal to the location at which the channel is formed (i.e., between the location at which the channel is formed and the coronary venous sinus), and a radially expandable vessel blocking device is deployed from the catheter such that it becomes implanted in the lumen of the vein. This vessel blocking device serves to substantially block the flow of blood through the vein in the proximal direction (i.e., the direction in which venous blood normally flows through the vein, thereby eliminating the shunt effect and causing the arterial blood to flow through the vein in the distal direction (i.e., the direction opposite normal venous blood flow).
In another procedure known as Percutaneous In Situ Coronary Artery Bypass (PICAB™), catheters are used to form a first interstitial channel between a coronary artery or chamber of the heart and a coronary vein such that arterial or oxygenated blood (i.e., blood that generally has a pO
2
of at least 50 and typically 75-100 while the patient is breathing room air) will flow from the artery or chamber of the heart and into the vein and a second interstitial channel between the vein into which the oxygenated blood is flowing and a distal segment of the obstructed coronary artery, downstream of the obstruction. A blocker delivery catheter is advanced into the vein and used to implant two (2) radially expandable vessel blockers, one proximal to the first interstitial channel (i.e., between the first channel and the coronary venous sinus) and another distal to the second interstitial channel (i.e., between the second channel and the capillary bed that is drained by the vein). The first vessel blocking device serves to substantially block the flow of blood through the vein in the
Flaherty J. Christopher
Lamson Theodore C.
Buyan Robert D.
Chang Ching
Denion Thomas
Medtronic Vascular Inc.
Stout, Uxa Buyan & Mullins, LLP
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