Patent Application
20070010780
1. Field of the Invention
This invention relates broadly to surgical methods and surgical devices. More particularly, this invention relates to methods for treating an ischemic heart by permanent perfusion of the coronary sinus and shunts therefor.
2. State of the Art
When significant diffuse stenotic coronary artery disease exists, flow through the coronary arteries is diminished. There are two conventional treatments for such a condition. One therapeutic modality to deal with this coronary arterial insufficiency is to deploy metal stents into the coronary arteries at the sites of such stenoses to improve flow. The other treatment is to surgically anastomose a detouring conduit on the coronary artery to bypass the stenosed segment; i.e., coronary artery bypass surgery. In either situation, it is not uncommon for stenoses to again appear below the treatment site, and which again require therapeutic intervention to increase blood flow through coronary arteries to nourish the myocardium.
The coronary sinus is the confluence and the final conduit for a group of cardiac veins before they empty into the right atrium. Coronary arterial blood, after passing through the myocardial bed is emptied into the right atrium in a deoxygenated state via the coronary sinus. So, in contrast to the high pressure coronary arterial system, the coronary sinus is a low pressure bed.
Previously, the coronary sinus has been used as a pathway to increase perfusion of the myocardium. An experimental modality of blocking the egress of blood flow from the coronary arterial bed, by tying off the mouth of the coronary sinus as it enters the right atrial cavity, has been employed with limited success because no new blood was delivered to the coronary sinus. Mohl W. et al., “Clinical evaluation of pressure-controlled intermittent coronary sinus occlusion: randomized trial during coronary artery surgery”, Ann Thorac Surg, 46(2):192-201 (August 1988). In another experimental animal model, anastomosis of a vein conduit (harvested from the leg) from a high pressure location on the aorta to the coronary sinus was performed. See Louis J. Acierno, The History of Cardiology, pp. 658-60 (1994) (discussing the ‘Beck I’ operation). The treatment provided long-term retrograde perfusion to the myocardium and blocked egress from the coronary sinus into the atrium. However, the procedure described is highly invasive open heart surgery, and the thinness of the coronary sinus wall is not equipped for graft anastomosis which may lead to complications such as leakage, tearing or hemorrhage.
In addition, during invasive cardiology procedures, a temporary exterior shunt from the femoral artery to the coronary sinus, accomplished on the cardiologist's catheterization table by a connecting catheter supported by a pump, has been employed to provide perfusion of the coronary artery. See Kar S et al., “Myocardial protection by diastolic coronary venous retroperfusion during PTCA” [Abstr], Proceedings of the Third International Symposium on Myocardial Protection via the Coronary Sinus (June 1988; Boston, USA) and Kar S et al., “Synchronized Coronary Venous Retroperfusion for Support and Salvage of Ischemic Myocardium During Elective and Failed Angioplasty,” J Amer. Coll. Cardio., 18(1):271-282 (1991). Similar temporary exterior shunts have also been tried by surgeons in the operating room to augment coronary bed perfusion during coronary bypass surgery. See Harinder S et al., Retrograde Coronary Sinus Perfusion for Management of Coexistent Critical Unstable Carotid and Coronary Artery Disease, Indian Heart J, 54: 717-719 (2002); Castella M et al., “Reduction of Systolic and Diastolic Dysfunction by Retrograde Coronary Sinus Perfusion During Off-Pump Surgery”, J Thoracic and Cardiovascular S, 127:1018-1025 (2004); and Harinder S, “Efficacy of Retrograde Coronary Sinus Perfusion In Off-Pump Surgery”, J Thoracic and Cardiovascular S, 129(2):476-477 (2005).
It is therefore an object of the invention to provide methods for permanent retrograde perfusion from the aorta to the coronary sinus to provide perfusion to the heart.
It is also an object of the invention to provide methods which are less invasive than open heart surgery.
It is a further object of the invention to provide a method for permanent retrograde perfusion from the aorta to the coronary sinus which can be performed percutaneously and methods which can be performed thoracoscopically.
It is another object of the invention to provide permanently implantable shunts for implantation between the aorta and the coronary sinus.
It is an additional object of the invention to provide suitable shunts which can be implanted percutaneously and shunts which can be implanted thoracoscopically.
In accord with these objects, which will be discussed in detail below, in a minimally invasive manner, a permanent shunt is implanted to carry arterial blood from the aorta into the relatively lower pressure venous bed of the coronary sinus. Since egress from the coronary sinus into the right atrium is blocked, the higher pressure arterial blood is forced through the coronary sinus venous bed in a retrograde fashion thus accomplishing perfusion of those arterial beds that are deprived of normal antegrade coronary arterial blood flow on account of coronary arterial stenoses.
In one embodiment, the shunt is delivered percutaneously via a catheter-based delivery system. A guidewire is introduced from the lumen of the aorta, through the right atrial cavity and into the mouth of the coronary sinus, and the delivery system is delivered thereover.
In another embodiment, the shunt is delivered in a minimally invasive, preferably thoracoscopic, manner. A scope is inserted through the chest wall to gain access to the right side of the heart, the pericardium is opened, and using guidewires access to the coronary sinus and the aorta is established (from outside the right atrial cavity). The shunt is threaded into the coronary sinus and the aorta, over preferably two guidewires. Thus, most of the body of the shunt comes to lie in the pericardial sac, outside the cavity of the right atrium.
In each embodiment, the shunt must be anchored at both ends, kink-resistant, and permanently implantable. The shunt will carry high pressure arterial blood into the coronary sinus and normal egress of blood from the coronary sinus into the right atrium will be at least partially blocked resulting in retrograde perfusion of the myocardium.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.
In accord with the invention methods are provided for introducing and implanting a permanent shunt between the aorta and the coronary sinus. The shunt then carries arterial blood from the relatively higher pressure aorta into the relatively lower pressure venous bed of the coronary sinus. As discussed in more detail below, in one embodiment, the shunt preferably has an insertion point in the lumen of the aorta and most preferably the sinus of valsalva which has fluid dynamic conditions placing it in substantially more consistent pressure than the upper tubular portion of the aorta from which prior art temporary shunts have extended. Since egress from the coronary sinus into the right atrium is blocked, the higher pressure arterial blood is forced through the coronary sinus venous bed in a retrograde fashion, thus accomplishing perfusion of those arterial beds that are deprived of normal antegrade coronary arterial blood flow on account of coronary arterial stenoses. Upon permanent retrograde perfusion, thebesian veins (micropores) within the right side of the heart become active to perfuse the myocardium of the right side of the heart. In addition, thebesian veins on the left side of the heart, which open only when the coronary sinus is blocked over an extended period of time, also open and perfuse the myocardium of the left side of the heart.
Referring now to
The guiding catheter 16 has a channel that allows passage of a guidewire 30. Under ultrasound, fluoroscopy, or other radiological modality, the guidewire 30 is guided into the mouth 32 and lumen of the coronary sinus 36.
A shunt 40 is provided on a delivery catheter 42 within the guiding catheter 16. The delivery catheter 42 is threaded over the guidewire 30, into the lumen of the coronary sinus 36, via the sinus of valsalva 14 and right atrium 24. Alternately, the entire guiding catheter 16 may be introduced into the coronary sinus 36, so that an anchoring mechanism, described below, on the distal end 46 of the unexpanded end of the shunt 40 is protected from causing injury to the structures of the heart, as the shunt is threaded over the guidewire.
Once the appropriate position of the distal end 46 of the shunt 40 is confirmed in the mouth 32 of the coronary sinus 36, the anchoring mechanism at the distal end is deployed, e.g., by expanding the distal end 46 of the shunt 40, to cause the distal end of the shunt to completely occupy the inside of the mouth 32 of the coronary sinus 36. Each of the distal (coronary sinus end) and the proximal (aortic sinus of valsalva end) ends 46, 48 of the shunt are equipped with anchoring mechanisms such as barbs 50, hooks, coils, inflatable cuffs, etc. to allow proximal and distal anchoring of the shunt to the inside of their respective anatomical fixation sites.
In one embodiment, expansion is effected by self expansion, e.g., accomplished by release of tension on a resilient material as it is advanced out of the catheter sheath. Such resilient materials may be spring metals, shape memory alloys (SMA), polymers, and/or combinations thereof, covered with a polymeric or fabric material to effect a blood carrying conduit. Alternately or additionally, where the shunt has a shape memory alloy (SMA) wound or woven into a fabric or polymeric lumen, the shunt may be expandable upon application of a predetermined amount of energy. In particular, referring to
Referring to
The body 50 of the shunt (that portion between the distal and proximal ends 46, 48) is preferably designed to be patent once the delivery system is removed. Such may be via the materials used for the shunt, e.g., non-kinking skeletal frames with a polymeric or biologic covering (e.g., PTFE, woven Dacron, cell cultures, albumin, collagen, etc.), or a non-kinking polymeric tubular construct without a skeletal frame. Where a frame is used, it may be self-expanding upon the withdrawal of the catheter sheath, mechanically expandable, or expandable upon the application of a predetermined temperature (e.g., where the frame is constructed of a shape memory alloy (SMA)). Alternatively, the shunt may be an implantable natural construct (human or animal vein, artery, etc.). As yet another alternative, the central portion of the shunt may be balloon expandable and expanded to its full, open configuration after securement of the distal end or the proximal end. The guidewire 30 is removed at the end of the procedure.
The length of the shunt 40 for a percutaneous approach is preferably approximately 4 to 6 cm, the diameter of a central portion of the shunt of the preferably approximately 3 to 6 mm, the diameter at the distal end, in the expanded state, is approximately 1 to 3 cm, and the diameter at the proximal end, in the expanded state, is approximately 0.6 to 1.5 cm.
Thus, an unexpanded shunt 40 is deployed percutaneously into the coronary sinus through the aortic sinus via the right atrial cavity and anchored there distally and anchored proximally in the aorta using a catheter-based shunt delivery system. This forms a shunt, from the relatively high pressure sinus of valsalva (80-100 mmHg) with arterial blood, to the lower pressure venous coronary sinus (5-20 mmHg) via the right atrium. The shunt is an internal shunt, lying within the right atrium. Since, the mouth of the coronary sinus is completely occupied by the expanded and anchored distal opening of the conduit, egress from the coronary sinus into the right atrium is blocked.
In an alternative embodiment, after expansion of the distal end of the shunt, the distal end is secured within the mouth of the coronary sinus but egress from the coronary sinus is only partially blocked. This is advantageous and desirable in certain clinical conditions in order to avoid the temporary edema of the heart tissue that may occur with complete blockage of egress (i.e., until thebesian veins open).
In another approach a shunt between the aorta and coronary sinus is delivered in a minimally invasive, preferably thoracoscopic manner. Prior to discussing the procedure, the shunt will now be described. Referring to
With respect to expanding the first and second ends of the shunt, the ends are preferably balloon (or otherwise mechanically) expandable. Alternatively, referring to
The length of the shunt is preferably approximately 10 to 12 cm, the diameter of a central portion of the shunt of the preferably approximately 4 to 6 mm, the diameter at the distal end, in an expanded state, is approximately 1 to 3 cm, and the diameter at the proximal end, in an expanded state, is approximately 0.6 to 1.5 cm.
Now, in accord with another minimally invasive, preferably thoracoscopic method of the invention, the patient is anaesthetized and an appropriate amount of heparin is administered to prevent coagulation on the guidewires, the use of which is discussed below. The patient is positioned, prepped and draped. Referring to
A needle 408 is introduced through the first cannula 402 and the tip of the needle is used to pierce a hole 409 through the right atrial wall 406. The location of the tip of the needle in the right atrial cavity may be confirmed by aspirating blood through the needle. Once the location is confirmed, a first guidewire 410 is introduced through the needle and directed into the mouth 412 of the coronary sinus 414. Once confirmation of the distal end of the guidewire 410 is assured, e.g., via echocardiogram, the needle 408 and first cannula 402 are withdrawn leaving the first guidewire 410 in position.
The first cannula 402 is then reinserted into the chest wall in the same hole 416 as before adjacent the first guidewire 410. The first cannula 402 is directed toward the lower ascending aorta 418. This location is chosen because access to the sinus of valsalva 420 is difficult to reach and blocked by the right atrial wall 422. Thus feeding the coronary sinus from the sinus of valsalva is less practical in a thoracoscopic approach than in a percutaneous approach. The needle 408 is inserted through the first cannula 402 to pierce the ascending aorta 418. Blood is preferably aspirated to confirm needle location within the aortic lumen. A second guidewire 424 is introduced through the needle 408 and its distal end is positioned within the aorta 418. The needle 408 and first cannula 402 are withdrawn, leaving the first and second guidewires 410, 424 exiting the chest from the same hole 416, as shown in
Referring to
Referring to
The grasper/pusher 430 is then directed to the second end 104 of the shunt 100. The second end 104 is advanced along the second guidewire 424 and inserted into the hole pierced in the aorta 418. The second end 104 is then expanded, as discussed above, to effect its retention within the aorta. The second guidewire 424 is then also removed from the patient. It is recognized that the shunt 100 is now an open conduit between the aorta 418 and the mouth 412 of the coronary sinus 414 with blood being forced under pressure in a retrograde manner into the coronary sinus. As such, there may be leakage of blood at the access port 108. Initially, this provides an avenue for any potential clot to escape. However, the access port 108 must be sealed. Therefore, referring to
Referring to
According to an alternative minimally invasive embodiment of the invention, the first end of the shunt is modified such that, upon expansion of the first end, the first end is smaller than the mouth of the coronary sinus. As such, egress from the coronary sinus is only partially blocked. This is advantageous and desirable in certain clinical conditions in order to avoid the temporary edema of the heart tissue that may occur with complete blockage of egress (i.e., until thebesian veins open).
There have been described and illustrated herein several embodiments of shunts and methods of permanently and minimally invasively implanting shunts between the aorta and the coronary sinus. While particular embodiments of the invention have been described, it is not intended that the invention be limited thereto, as it is intended that the invention be as broad in scope as the art will allow and that the specification be read likewise. Thus, while particular shunt constructs have been disclosed, it will be appreciated that other constructs, including materials, configurations, means for end expansion and tissue retention, etc. can be used as well. It will therefore be appreciated by those skilled in the art that yet other modifications could be made to the provided invention without deviating from its spirit and scope as claimed.
