FIELD OF THE INVENTION
The present invention pertains to medical devices and methods for accessing an anatomic surface, muscle layer, vessel or anatomic space of the body and particularly for entering the pericardium to access pericardial space and the epicardial surface of the heart in a minimally invasive manner.
BACKGROUND OF THE INVENTION
The human heart wall consists of an inner layer of simple squamous epithelium, referred to as the endocardium, overlying a variably thick heart muscle or myocardium and is enveloped within a multi-layer tissue structure referred to as the pericardium. The innermost layer of the pericardium, referred to as the visceral pericardium or epicardium, clothes the myocardium. The epicardium reflects outward at the origin of the aortic arch to form an outer tissue layer, referred to as the parietal pericardium, which is spaced from and forms an enclosed sac extending around the visceral pericardium of the ventricles and atria. An outermost layer of the pericardium, referred to as the fibrous pericardium, attaches the parietal pericardium to the sternum, the great vessels and the diaphragm so that the heart is confined within the middle mediastinum. Normally, the visceral pericardium and parietal pericardium lie in close contact with each other and are separated only by a thin layer of a serous pericardial fluid that enables friction free movement of the heart within the sac. The space (really more of a potential space) between the visceral and parietal pericardia is referred to as the pericardial space. In common parlance, the visceral pericardium is usually referred to as the epicardium, and epicardium will be used hereafter. Similarly, the parietal pericardium is usually referred to as the pericardium, and pericardium will be used hereafter in reference to parietal pericardium.
It is frequently medically necessary to access the pericardial space to treat an injury, infection, disease or defect of the heart, e.g., an occluded coronary artery, a defective heart valve, aberrant electrical pathways causing tachyarrhythmias, bacterial infections, to provide cardiac resynchronization therapy, or to place epicardial pacing or cardioversion/defibrillation electrodes against the epicardium or into the myocardium at selected sites. It is necessary in these procedures to surgically expose and cut through the pericardium to obtain access to the pericardial space.
Highly invasive surgical techniques, referred to as a median sternotomy (open-chest surgical exposure) or a thoracotomy, have been typically employed to provide the surgeon access to the pericardial space and the heart. A median sternotomy incision begins just below the sternal notch and extends slightly below the xyphoid process. A sternal retractor is used to separate the sternal edges for optimal exposure of the heart. Hemostasis of the sternal edges is typically obtained using electrocautery with a ball-tip electrode and a thin layer of bone wax.
The open chest procedure involves making a 20 to 25 cm incision in the chest of the patient, severing the sternum and cutting and peeling back various layers of tissue in order to give access to the heart and arterial sources. As a result, these operations typically require large numbers of sutures or staples to close the incision and 5 to 10 wire hooks to keep the severed sternum together. Such surgery often carries additional complications such as instability of the sternum, post-operative bleeding, and mediastinal infection. The thoracic muscle and ribs are also severely traumatized, and the healing process results in an unattractive scar. Post-operatively, most patients endure significant pain and must forego work or strenuous activity for a long recovery period.
Many minimally invasive surgical techniques and devices have been introduced In order to reduce the risk of morbidity, expense, trauma, patient mortality, infection, and other complications associated with open-chest cardiac surgery. Less traumatic limited open chest techniques using an abdominal (sub-xyphoid) approach or, alternatively, a “Chamberlain” incision (an approximately 8 cm incision at the sternocostal junction), have been developed to lessen the operating area and the associated complications. In recent years, a growing number of surgeons have begun performing coronary artery bypass graft (CABG) procedures using minimally invasive direct coronary artery bypass grafting (MIDCAB) surgical techniques and devices. Using the MIDCAB method, the heart typically is accessed through a mini-thoracotomy (i.e., a 6 to 8 cm incision in the patient's chest) that avoids the sternal splitting incision of conventional cardiac surgery. A MIDCAB technique for performing a CABG procedure is described in U.S. Pat. No. 5,875,782, for example.
Other minimally invasive, percutaneous, coronary surgical procedures have been advanced that employ multiple small trans-thoracic incisions to and through the pericardium, instruments advanced through ports inserted in the incisions, and a thoracoscope to view the accessed cardiac site while the procedure is performed as shown, for example, in U.S. Pat. Nos. 6,332,468, 5,464,447, and 5,716,392. Surgical trocars having a diameter of about 3 mm to 15 mm are fitted into lumens of tubular trocar sleeves, cannulae or ports, and the assemblies are inserted into skin incisions. The trocar tip is advanced to puncture the abdomen or chest to reach the pericardium, and the trocar is then withdrawn leaving the sleeve or port in place. Surgical instruments and other devices such as fiber optic thoracoscopes can be inserted into the body cavity through the sleeve or port lumens. As stated in the '468 patent, instruments advanced through trocars can include electrosurgical tools, graspers, forceps, scalpels, electrocauteries, clip appliers, scissors, etc.
In such procedures, the surgeon can stop the heart by utilizing a series of internal catheters to stop blood flow through the aorta and to administer cardioplegia solution. The endoscopic approach utilizes groin cannulation to establish cardiopulmonary bypass (CPB) and an intraaortic balloon catheter that functions as an internal aortic clamp by means of an expandable balloon at its distal end used to occlude blood flow in the ascending aorta. A full description of an example of one preferred endoscopic technique is found in U.S. Pat. No. 5,452,733, for example.
However, recently developed, beating heart procedures eliminate the need for any form of CPB, the extensive surgical procedures necessary to connect the patient to a CPB machine, and to stop the heart. These beating heart procedures can be performed on a heart exposed in a full or limited thoracotomy or accessed percutaneously as described particularly in reference to FIG. 19 in U.S. Pat. No. 6,394,948, for example.
In such percutaneous procedures, the epicardium of the beating or stopped heart is exposed to view typically by use of grasping and cutting instruments inserted through one port to cut through the pericardium surrounding the heart while the area is viewed through the thoracoscope or endoscope inserted through another port. The thoracoscopic approach typically requires the placement of a chest tube and admission to the hospital for the initial 1-2 post-operative days.
Therefore, much effort has been expended to develop medical devices and techniques to access the pericardial space employing such minimally invasive percutaneous procedures. One difficulty has been that normally the pericardial space is so small or thin that it is difficult to penetrate the pericardium using miniaturized instruments capable of being introduced through a port to the site without also puncturing the underling epicardium and thereby, damaging the myocardium or a coronary vessel. Proliferative adhesions occur between the pericardium and the epicardium in diseased hearts and hamper access to the pericardial space employing such minimally invasive percutaneous procedures. The simple percutaneous approach can be used to penetrate the pericardium to drain a large pericardial effusion, i.e., an accumulation of too much fluid in the pericardial space that widens the pericardial space. A spinal needle (18-20 gauge) and stylet occluding the needle lumen are advanced incrementally in a superior/posterior fashion through a small (2-4 mm) cutaneous incision between the xyphoid and costal cartilage. Periodically, the stylet is removed, and fluid aspiration is attempted through the needle lumen. The advancement is halted when fluid is successfully aspirated, and the pericardial effusion is then relieved.
Methods and apparatus for accessing the pericardial space for the insertion of implantable defibrillation leads are disclosed in U.S. Pat. Nos. 5,071,428 and 6,156,009, wherein a forceps device is used to grip the pericardium and pull it outward to form a “tent”. In the '428 patent, a scissors or scalpel is introduced to cut the pericardium (pericardiotomy) under direct vision through a sub-xyphoid surgical incision. The forceps device disclosed in the '009 patent incorporates a mechanism for introducing electrical leads or guidewires through the outwardly displaced pericardium. It is difficult to introduce and use the forceps through the narrow lumen of a port or sleeve, particularly if the pericardial fluid is under pressure that makes the pericardium taut like an inflated balloon.
Further methods and apparatus for accessing the pericardial space for the insertion of devices or drugs are disclosed in U.S. Pat. No. 6,423,051, wherein an access tube having a device access lumen is provided with a plurality of hooks in the tube distal end that can be used to hook into the pericardium to enable the lifting and “tenting” of the pericardium. A cutting instrument or sharpened tip guidewire or the like can be advanced through the device access lumen to perforate the pericardium.
Other methods and apparatus that are introduced through percutaneously placed ports or directly through small trans-thoracic incisions for accessing the pericardial space employ suction devices to grip the pericardium or epicardium as disclosed, for example, in U.S. Pat. Nos. 4,991,578, 5,336,252, 5,827,216, 5,868,770, 5,972,013, 6,080,175, and 6,231,518 and the above-referenced '948 patent. The suction device is configured like a catheter or tube having a single suction tool lumen and typically having a further instrument delivery lumen. The suction tool lumen terminates in a single suction tool lumen end opening through the device distal end in the '578, '252, '175, '770, and '013 patents and through the device sidewall in the '216 and '518 patents. Certain of these patents recite that the applied suction draws a “bleb,” i.e., a locally expanded region of the pericardium, into the suction tool lumen or a suction chamber at the device distal end. A needle can then be advanced into the bleb and used to draw off fluids or deliver drugs into the pericardial space, or the like. In addition, it is suggested in these patents that treatment devices including catheters, guidewires, and electrodes, e.g., defibrillation electrodes, can be advanced into the pericardial space through a device introduction lumen for a variety of reasons. Although theoretically plausible, the ability to reliably maintain a vacuum seal against the pericardium when such treatment devices are advanced can be problematic.
For these reasons, it would be desirable to provide additional and improved methods and apparatus for the minimally invasive access to a patient's pericardial space (or other anatomic space). The methods and devices should be suitable for a wide variety of minimally invasive approaches to the pericardium, including at least intercostal/transthoracic and subxiphoid approaches, and the like. The methods and devices should further provide for secure and stable capture of the pericardium and permit the opening of a large space or volume between the pericardium and epicardium. Such access methods and apparatus should be useful for a wide variety of procedures to be performed in the pericardial space, including fluid withdrawal, drug delivery, diagnostic and therapeutic electrophysiology procedures, pacemaker lead implantation, defibrillator lead placement, transmyocardial revascularization, transmyocardial revascularization with drug delivery, placement of the left ventricular assist devices, placement of the arterial bypass graphs, in situ bypass, i.e., coronary artery-venous fistulae, placement of drug delivery depots, closure of the left arterial appendage, and the like. At least some of these objectives will be met by the invention described herein.
SUMMARY OF THE INVENTION
One aspect of the present invention provides methods, apparatus, and kits for accessing an anatomic space between an inner tissue layer and an outer tissue layer. The phrase “anatomic space” is meant to include any natural, potential, or created space or cavity within a patient's body where it may be desirable to gain access for surgical, diagnostic, therapeutic, lead delivery, visualization, or any other purpose. The inner tissue layer may consist of a membrane, a capsule or the adventia, muscularis and endothelial layers of a hollow organ or vessel. The methods, apparatus, and kits are particularly useful for minimally invasive access procedures, but could also be used for accessing internal anatomic spaces where initial access to the outer tissue layer is achieved via open surgical procedures. The present invention will be particularly useful for accessing a patient's pericardial space between the epicardium and pericardium for performing a wide variety of procedures, generally as set forth above. Other internal organs that may be accessed include the intestines, fallopian tubes, gall bladder, kidneys, and the like.
Apparatus and methods according to the present invention for accessing such an anatomic space utilize an elongated tubular access sleeve adapted to be advanced through a small incision to dispose an access sleeve distal end in operative relation to the outer tissue layer. An access sleeve working lumen of the tubular access sleeve of the present invention can be used to introduce an instrument or material to the outer tissue layer. The instrument can be a cutting tool for perforating and making an incision through the outer tissue layer so that further instruments or implantable medical devices or drugs or diagnostic agents or the like can be introduced through the sleeve lumen into the anatomic space.
The modified tubular access sleeve incorporates or accommodates a suction tool comprising at least two suction pads at the ends of at least two elongated arms that can be retracted into the tubular access sleeve during introduction and advancement of the tubular access sleeve distal end into operative relation to the outer tissue layer. Then, the suction pads can be advanced from the working lumen and deployed out of the tubular access sleeve lumen and disposed against the outer tissue layer. Suction can be applied through suction tool lumens to suction ports of the suction pads that fix to the outer tissue layer so as to tension the outer tissue layer and/or pull the outer tissue layer away from the inner tissue layer and/or stabilize the outer tissue layer and/or track any movements of the outer tissue layer.
The suction pads advantageously facilitated cutting into or through the outer tissue layer with a cutting instrument. Initially, suction is applied so that the suction pads grasp the surface of the outer tissue layer. A cutting instrument or tool can then be introduced through the working lumen to dispose a cutting element at the tissue surface. The suction pads are also spread apart so that the tissue surface is tensioned during cutting. In this way, the perforation or hole that is cut is widened by the applied tension. The widened hole can then be maintained for passage of further devices into or through the hole.
In a preferred embodiment, a pair of elongated support arms each support an elongated suction pad comprising a plurality of suction ports and a suction manifold connecting the suction ports to a suction tool lumen of the support arm. Suction applied through the suction ports grasps tissue. Each suction pad is coupled to the distal end of the support arm optionally through a flexible wrist. Each support arm comprises a distal forearm extending from the wrist to a flexible elbow and a proximal or upper arm extending from the elbow to a flexible shoulder joint with a common proximal suction tool trunk.
The proximal suction tool trunk extends proximally through an access sleeve suction tool lumen of the tubular access sleeve to a suction fitting at the proximal end of the trunk that can be coupled to an available surgical operating room vacuum source.
The trunk and support arms can be drawn proximally into the access sleeve suction tool lumen to dispose the suction pads within a distal portion of the working lumen during surgical insertion or withdrawal of the tubular access sleeve from the patient's body. The trunk and support arms can be advanced distally through the access sleeve suction tool lumen to extend the support arms and suction pads from the distal end opening of the working lumen.
Each support arm is formed of a flexible tube that has preformed bends at the wrist, elbows, and shoulders that, when unrestrained, dispose the suction pads apart from one another a distance so that the suction pads can cooperatively grasp the outer tissue layer at separated apart locations generally so that the outer tissue layer between the suction pads can be operatively accessed through the working lumen. The preformed bends at the wrists, elbows and shoulders can be overcome to dispose the arms parallel to one another when drawn proximally into the access sleeve suction tool lumen. The elongated suction pads are drawn together and aligned axially with the working lumen so that the suction pads can be drawn into the distal segment of the working lumen.
Due to their redundancy, the suction ports of the suction pads provide more robust fixation to the outer tissue layer than a single large area suction port. At least some of the suction ports readily engage the tissue surface under low suction force to enable lifting of the outer tissue layer or tracking movement of the outer tissue layer. Engagement of tissue surface areas by all of the suction ports is not necessary. Similarly, the loss of engagement of some of suction ports with the tissue surface areas does not result in complete loss of engagement as is the case when an edge of a single large suction port releases from the tissue surface of the outer tissue layer.
A cutting instrument, e.g., a knife, a needle, a stiff guidewire tip, an electrosurgical cutting tool, surgical scissors or other piercing or cutting tool, can then be introduced through the working lumen to perforate the outer tissue layer and form an access hole or perforation there through creating access into the anatomic space while the access tube stabilizes the outer tissue layer. Advantageously, there is no suction applied through the working lumen that is necessary to maintain the attachment to the outer tissue layer while it is being perforated or other instruments are advanced through the perforation. The fixation of the outer tissue layer is not lost when the outer tissue layer is perforated. Moreover, it is simpler to advance instruments through the working lumen from a proximal lumen end opening that is exposed to the atmosphere.
The methods, apparatus and kits of the present invention can advantageously be used to access the pericardial space between the pericardium and epicardium. In a still further aspect of the present invention, various devices are introduced into the pericardial space for temporary treatment of the heart or pericardial space or to complete a surgical procedure or for permanent implantation against the epicardium or within the pericardial space or within the myocardium or within a coronary vein or artery.
The tubular access sleeve can be circular or oval or have any other desirable cross-section shape. The tubular access sleeve can be straight, curved for formed with a bend or formed of a bendable material to be shaped by the user. The tubular access sleeve and the suction tool are formed of non-conductive materials to minimize electrical hazards. The tubular access sleeve and the suction tool can be provided in a range of diameters and lengths to function as described herein to access any desired site in the body of adult and pediatric patients.
This summary of the invention has been presented here simply to point out some of the ways that the invention overcomes difficulties presented in the prior art and to distinguish the invention from the prior art and is not intended to operate in any manner as a limitation on the interpretation of claims that are presented initially in the patent application and that are ultimately granted.