Abstract:
A method and apparatus for placing an epicardial lead over a desired, predetermined location on the left ventricle using a minimally invasive approach. A thoracoscope having a handle portion and a probe tube defining a central opening is placed through an incision in the patient generally aligned with the desired position for the pacing lead. An introducer and pacing lead are placed within the central opening of the thoracoscope and moved into contact with the pericardium at the desired lead location. An attachment member of the pacing lead attaches an electrode of the pacing lead to the pericardium. The pacing lead includes a mesh disk surrounding the electrode to aid in long term attachment of the electrode to the heart. Alternatively, the pericardium can be incised such that the lead is placed directly over the epicardial surface of the left ventricle.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   The present invention is based on and claims priority to U.S. Provisional Patent Application Ser. No. 60/364,311 filed on Mar. 14, 2002. 

   FIELD OF THE INVENTION 
   The present invention, called “stingray technique”, generally relates to a technique of inserting an epicardial lead in a patient with congestive heart failure (CHF) requiring bi-ventricular pacing. More specifically, the present invention is related to a thoracoscope design and technique of inserting a left ventricular lead using an thoracoscopic approach that places the lead at a specific, known location on the epicardial surface of the left ventricle. 
   BACKGROUND OF THE INVENTION 
   Despite considerable progress in the management of CHF, it remains a major health problem worldwide. It is estimated that there are 6-7 million people with CHF in the United States and Europe alone and approximately 1 million new patients are diagnosed with CHF every year. 
   Despite significant advances in the treatment of CHF using various pharmacological therapies, the quality-of-life in patients with CHF remains poor as these patients are frequently hospitalized, and heart failure in these patients is a common cause of death. In addition, there are significant long-term care costs associated with this problem. 
   Many patients with advanced CHF have a conduction system disease that may play a role in worsening cardiac function. One frequently noted conduction abnormality is left bundle branch block (LBBB), which is present in about 29% of patients with CHF. The presence of LBBB delays left ventricular ejection due to delayed left ventricular activation. 
   Pacing therapies have been introduced in an attempt to improve cardiac function in patients diagnosed with CHF. Cardiac resynchronization, in which bi-ventricular pacing is performed, has shown beneficial results in patients with CHF and LBBB. During bi-ventricular pacing, in addition to the standard right atrial and right ventricular leads, an additional lead is positioned in the coronary sinus. This additional lead is advanced into one of the branches of the coronary sinus overlaying the epicardial surface of the left ventricle. Since the lead is advanced through the coronary sinus, the potential placement positions for the lead are severely limited. 
   Although bi-ventricular pacing has shown beneficial results, numerous problems are associated with this technique. One such problem is the amount of time required for a physician to insert the lead into the desired location on the left ventricle. Further, the placement of the lead on the left ventricle is limited to sites that provide adequate pacing and sensing signals. Further, cannulation of the coronary sinus is often difficult due to either the rotation of the heart or the presence of an enlarged right atrium or Thebesian valve. Further, the placement of a lead on the surface of the left ventricle though the coronary sinus cannot be carried out in some patients with prior bypass surgery or with coronary sinus stenosis. Finally, the coronary sinus lead provides an oftentimes unstable placement and can become detached after installation. 
   Therefore, a need exists for an alternative approach that allows for the easier placement of the left ventricle lead and an apparatus for positioning such a lead in the desired location. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a method and apparatus for placing an epicardial pacing lead on the left ventricle using a minimally invasive approach. 
   A thoracoscope is provided including a handle portion and a hollow probe tube that extends from the handle portion such that the handle portion and the probe tube define a central opening extending along a longitudinal axis. Preferably, a camera and a light source can be positioned through the central opening such that the camera can provide images relating to the placement of the thoracoscope within the chest cavity. 
   The apparatus of the present invention further includes an introducer that is configured for receipt in the central opening of the thoracoscope. The introducer includes a hollow body portion that extends from a proximal end to a distal end. The introducer is movable along the longitudinal axis of the thoracoscope such that the distal end of the introducer can project varying distances from the probe tube. During a lead placement procedure, the distal end of the introducer is brought into contact with the pericardium surrounding the heart for proper lead delivery. 
   A pacing lead having an electrode coupled to a lead wire is positioned within the introducer and is movable along the longitudinal axis of the introducer. The pacing lead includes an electrode surrounded by a mesh disk. The pacing lead further includes an attachment member, such as a screw-like wire, for use in securing the electrode in contact with the desired location on the pericardium. Preferably, the pacing lead is movable along the longitudinal axis of the introducer such that the electrode and mesh disk are movable between a retracted position in which the electrode and mesh disk are contained within the distal end of the introducer and an extended position in which the electrode and mesh disk extend from the distal end of the introducer. 
   The method of placing the pacing lead in contact with the pericardium initially requires the right ventricular lead and the right atrial lead to be placed on the heart in the usual manner. Once the two leads have been placed, the patient is placed on his or her back and the procedure begins. Initially, a double-lumen endotracheal tube is used to selectively ventilate the patient&#39;s right lung while blocking ventilation of the left lung to create space in the left pleural cavity. Once the required space is created, a small incision is made in the left fifth intercostal space or another appropriate site to allow placement of a thoracic port to maintain access to the left pleural cavity. Prior to the incision, an imaging system, such as CT or MR is used to determine the proper lead placement on the epicardial surfaces of the left ventricle. The proper lead placement is the determined location on the epicardial surface of the left ventricle that will provide the optimal delivery point for an electrical signal to aid in heart pacing. Although CT and MR are known techniques for obtaining such images, other imaging techniques are contemplated. 
   Once the incision is made, the probe tube of the thoracoscope is introduced through the port and the left ventricle is visualized using a camera and light source introduced through the thoracoscope. The vessels, fat and phrenic nerve are identified using images received from the thoracoscope. 
   Once the probe tube is properly positioned, the introducer including the retracted epicardial lead, is introduced into the probe tube and extended to the desired position over the pericardium. Once the introducer is properly placed, the lead is extended from the distal end of the introducer. The lead is then rotated such that the screw-like attachment member of the pacing lead penetrates the pericardium over the desired location on the epicardium. If it is not possible to attach the lead directly to the pericardium and deliver the proper pacing signal to the left ventricle, the pericardium can be incised and opened to provide access directly to the epicardial surface of the left ventricle. 
   Once the lead has been anchored in place by the attachment member, the thoracoscope and introducer are removed and tests done to confirm the desired location of the lead. It is contemplated that more than one lead can be placed during the procedure in order to provide a redundant system. 
   Once the thoracoscope has been removed, the lead is tunneled to the left pectoral pocket with the remaining leads and connected to the pacemaker. 
   Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings illustrate the best mode presently contemplated of carrying out the invention. 
     In the drawings: 
       FIG. 1  is a schematic illustration of the standard transvenous leads placed in the right atrium (RA), right ventricle (RV) and the coronary sinus (CS); 
       FIG. 2  is a schematic illustration similar to  FIG. 1  illustrating the transvenous lead placement in the right atrium, right ventricle, and the epicardial lead placement on the left ventricle using the method and technique of the present invention; 
       FIG. 3  is a perspective view of the epicardial lead placement apparatus of the present invention including a thoracoscope, introducer and an epicardial pacing lead of the present invention; 
       FIG. 4  is a perspective view of the introducer with the lead contained therein; 
       FIG. 5  is a perspective view of the introducer used with the thoracoscope of the present invention; 
       FIG. 6  is a perspective view of the epicardial pacing lead of the present invention; 
       FIG. 7  is a magnified view of the distal end of the introducer as viewed along line  7 - 7  of  FIG. 5 ; 
       FIG. 8   a  is a magnified view taken along line  8 - 8  of  FIG. 4  illustrating the distal end of the introducer with the electrode of the epicardial pacing lead contained therein; and 
       FIG. 8   b  is a magnified view taken along line  8 - 8  of  FIG. 4  illustrating the protrusion of the electrode of the epicardial pacing lead extending from the distal end of the introducer. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring first to  FIG. 1 , thereshown is a schematic illustration of a prior art bi-ventricular pacing method and apparatus  10  currently used. The bi-ventricular pacing system  10  shown in  FIG. 1  utilizes a totally transvenous lead system. Specifically, a right atrial lead  12  has one end  14  connected to a pacemaker  16  and a distal end including an electrode  18  in contact with the inner wall of the right atrium  20 . As illustrated in  FIG. 1 , the right atrial lead  12  is fed into the heart through the superior vena cava  22 . 
   A second, right ventricular lead  24  is coupled at its end  26  to the pacemaker  16  and its distal end, including a electrode  26  is placed in contact with the inner wall of the right ventricle  28 . The right ventricular lead  24  also passes through the vena cava  22  and passes through the tricuspid valve  30 . The third lead  32  of the pacing system  10  passes through the vena cava  22  and enters into the coronary sinus  34  through the opening  36  in the right atrium  20 . The third lead  32  is fed through the coronary sinus and includes an electrode  38  positioned in contact with the outer surface of the left ventricle  40  through the coronary sinus. As described previously, the placement of the third lead  32  in the coronary sinus  34  presents both a time-consuming and difficult task to a physician. Additionally, placement of the lead in the coronary sinus  34  is difficult in many cases due to the rotation of the heart and in the presence of an enlarged right atrium or Thebesian valve. Further, patients who have had prior bypass surgery or have coronary sinus stenosis are not candidates for total transvenous lead system incorporating the lead  32  within the coronary sinus  34 . 
   In the pacing system  10  illustrated in  FIG. 1 , sensing of the heart rhythm occurs in the electrode  18  of the right atrial lead  12 . The pacemaker  16  paces the heart through the right atrial lead  12  followed by synchronized pacing between the right ventricular lead  24  and the coronary sinus lead  32 . The synchronized pacing results in narrowing of the QRS complex of the heart rhythm in a known and conventional manner. Although the total transvenous lead pacing system  10  of the prior art shown in  FIG. 1  has proven effective, problems exist in placing the lead in the coronary sinus. 
   Referring now to  FIG. 2 , thereshown is the pacing system  42  of the present invention. As illustrated, the pacing system  42  includes the pacemaker  16  and both the right atrial lead  12  and the right ventricular lead  24 . The right atrial lead  12  includes the electrode  18  in contact with the wall of the right atrium  20  and the right ventricular lead  24  includes electrode  26  in contact with the wall of the right ventricle  28 . However, in accordance with the present invention, the third coronary sinus lead is replaced with a left ventricular lead  44  that, instead of passing through the superior vena cava  22 , is attached directly to the epicardial surface of the left ventricle  40 . The left ventricular lead  44  includes an electrode  46  held in contact with the epicardial surface by a mesh pad  48  and an attachment member (not shown) such that the required electrical signals can be transferred to the left ventricle  40 . 
   Traditionally, the left ventricular lead  44  is placed in contact with the pericardium during thoracotomy in which part of the pericardium is excised to expose the epicardium. Once the epicardium has been exposed, the electrode  46  of the left ventricular lead  44  is placed at the site as appropriate. In the prior art methods of placing the left ventricular lead  44 , only a limited view of the left ventricle is obtained and, because the patient must be tilted sideways to make thoracotomy easier, the left ventricle  40  is somewhat rotated, making it more difficult to position the left ventricular lead  44  in the posterolateral region of the left ventricle. 
   In an attempt to address the problems associated with the placement of the left ventricular lead  44  during thoracotomy, the present invention utilizes a thoracoscopic approach to facilitate the left ventricular lead placement. The present invention eliminates the flaws in the current technique of epicardial left ventricular lead placement during thoracotomy and improves the efficacy of this approach. 
   Referring now to  FIG. 3 , thereshown is a thoracoscope  50  constructed in accordance with the present invention. The thoracoscope  50  includes a hollow handle portion  52  having an inner end  54  and an outer end  56 . The thoracoscope  50  includes a hollow probe tube  58  extending from the inner end  54  of the handle portion  52  to a distal end  60 . In the preferred embodiment of the invention, the probe tube  58  has a hollow, open interior and is formed from a rigid material such that the probe tube  58  can be inserted through an incision in the patient. The probe tube  58  extends along a generally longitudinal axis and defines a central opening along the longitudinal axis that extends through both the probe tube  58  and the handle portion  52  of the thoracoscope  50 . 
   The outer end  56  of the handle portion  52  is designed to receive both a light source  62  and a camera  64  which can be fed through the probe tube  58  to the distal end  60 . The camera  64  and light source  62  allow images to be displayed in real time such that the physician can monitor the procedure through a display device, such as a video monitor. 
   The handle  52  further includes an irrigation port  66  that helps irrigate and aspirate the thoracoscope as needed. The irrigation port  66  is connected to a supply of irrigation fluid, as is conventional. 
   The handle portion  52  of the thoracoscope  50  includes an extended tube  68  having a hollow interior centered along the longitudinal axis of both the probe tube  58  and the handle portion  52 . Thus, the probe tube  58 , handle portion  52  and extended tube  68  are all coaxial with each other to define a continuous central opening through the thoracoscope  50 . 
   Referring now to  FIGS. 3 and 5 , the thoracoscope is sized to receive an introducer  70 . The introducer  70  includes a hollow, tubular body portion  72  that extends from a distal end  74  to a proximal end  76 . The proximal end  76  includes a handle portion  78  having a series of external grooves that allow the introducer  70  to be rotated along its longitudinal axis, as illustrated by arrow  80  in  FIG. 5 . In the preferred embodiment of the invention, the body portion  72  of the introducer  70  has a circular cross-section that slightly tapers from the proximal end  76  to the distal end  74 . Preferably, the outer surface of the body portion includes a matte black non-reflective surface such that light from the light source  62  does not interfere with the lead positioning, as will be described in detail below. 
   Referring now to  FIG. 7 , the distal end  74  of the introducer  70  is open and includes a pair of notches  80  recessed from an outer rim  82 . In the preferred embodiment of the invention, the distal end  74  of the introducer  70  is formed from a somewhat flexible material such that the distal end  74  can be placed into contact with the pericardium of the heart without damaging such surface. 
   Referring now to  FIG. 4 , the hollow introducer  70  includes a hollow, open interior that generally is coaxial with the hollow interior of the probe tube  58  and is sized to receive an epicardial pacing lead  84 . The epicardial pacing lead  84  extends through the hollow interior of the introducer  70  and is movable along the longitudinal axis of the introducer  70 . 
   Referring now to  FIG. 6 , the epicardial pacing lead  84  includes a wire  86  coupled to an electrode  88 . The electrode  88  is centered within a mesh disk  90 . The electrode  88  is coupled to the wire  86 , which in turn is connected at its opposite end to the pacemaker  16 , as shown in  FIG. 2 . Preferably, the outer surface of the wire  86  includes a matte black non-reflective surface such that light from the light source does not interfere with the lead positioning, as will be described in detail below. 
   Referring back now to  FIG. 8   b , when the distal end  92  of the epicardial pacing lead  84  is extended from the distal end  74  of the introducer  70 , the mesh disk  90  extends outward and surrounds the electrode  88 . In the preferred embodiment of the invention, the mesh disk  90  is formed from a resilient material that has a pre-formed shape, as shown. When the mesh disk  90  is extended from the distal end  74  of the introducer  72 , the mesh disk  90  extends to the configuration shown. 
   The electrode  88  includes a screw-like attachment member  94  that is used to hold the electrode  88  in contact with the pericardium after placement of the epicardial pacing lead  84 . As illustrated in  FIG. 8   a , before the epicardial pacing lead  84  is extended, the mesh disk  90  is compressed within the introducer  70  and the attachment member  94  extends slightly from the distal end  94 . As can be understood in  FIGS. 8   a  and  8   b , the epicardial pacing lead  84  is movable longitudinally along the central axis of the introducer  70  to extend and retract the electrode  88  as desired. 
   Although a specific embodiment of the lead and electrode are shown in the Figures of the present invention, it should be understood that other designs and configurations for the lead and electrode  88  are contemplated as being within the scope of the present invention. 
   The procedure for attaching the left ventricular lead  44  using the method and apparatus of the present invention will now be described. Initially, the patient is positioned in a supine position prior to performance of the procedure. With the patient positioned correctly, a double lumen endotracheal tube is inserted to ventilate the right lung while at the same time ventilation is blocked to the left lung to create a space in the left pleural cavity. With the left lung deflated, a small incision is made with a scalpel at the sight identified as adjacent to the left ventricle sight considered most appropriate for left ventricular lead placement. The identification of the desired sight on the left ventricle can be done using various imaging techniques, such as computerized tomography. 
   Once the desired location on the left ventricle is determined, a small 4-5 mm, 3-4 cm long thoracic port is placed over the incision and anchored in place. The thoracic port helps maintain the intercostal space, decreases trauma and maintains pleural access. 
   Once the thoracic port is positioned correctly, the probe tube  58  of the thoracoscope  50  of the present invention is introduced through the thoracic port. The camera  64  and light source  62  of the thoracoscope  50  are used to verify the lack of left lung ventilation and to identify intrapleural and mediastinal anatomies. 
   Once the probe tube  58  of the thoracoscope  50  is properly positioned, the introducer  70  including the epicardial pacing lead  84  is inserted into the probe tube  50  through the extended tube  68  and handle portion  52 . With the introducer  70  extending through the probe tube  58 , the appropriate left ventricle sight, which is devoid of blood vessels, is identified. Additionally, the phrenic nerve can also be identified at this time through use of the thoracoscope  50 . 
   Once the appropriate left ventricle sight is identified, the introducer  70  and the epicardial pacing lead  84  are advanced into contact with the pericardium at the appropriate site. Pressure is placed against the pericardium and, with pressure against the heart, the attachment member  94  of the lead is screwed through the pericardium until the mesh disk  90  contacts the outer surface of the pericardium. Once positioned, the lead is tested to determine whether adequate pacing is achieved. 
   If adequate pacing is not achieved, a small nick is made in the pericardium to expose the epicardial surface. If the pericardium needs to be split for epicardial lead placement, a pericardial holding and incising device (not shown) can be introduced through the introducer  70 . Once the pericardium has been nicked, the lead is positioned directly in contract with the pericardium and pacing thresholds performed to determine stability and the appropriateness of lead location. During this portion of the procedure, more than one lead can be placed in order to provide a redundant system. 
   Once the appropriate lead location on the left ventricle has been identified and the thoracoscope removed, the lead is tunneled to the left pectoral region where a pocket has been created to position the pacemaker  16  or other implantable defibrillator. A suction tube for expansion of the lung can be placed through the same incision if required. Additionally, other leads could be implanted using the same technique and tunneled to the left pectoral pocket if required. 
   While the present invention has been described with reference to bi-ventricular pacing in patients with CHF, it should be understood that the method and apparatus of the present invention could be utilized in other conditions such as children with heart blocks who may need pacing because a transvenous approach is suboptimal due to the complications associated with growth. Different lead designs and different sizes of thoracoscopes including disposable units may also be used while operating within the scope of the present invention. 
   In addition, although the invention has been described with reference to its exemplary embodiments, it should be understood by those skilled in the art that various changes may be made without departing from the scope of the invention. In addition, change and modifications may be made in order to adapt a particular situation or material without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode for carrying out the invention, but that the invention will include all embodiments falling within the scope of the appended claims. 
   It is contemplated by the inventor that a registration and imaging process may be used in which appropriate sites for pacing obtained by imaging techniques, such as CT or MR could be used for placement of leads. Once the appropriate sites are identified, it may be possible to place a lead without the need of an endoscope. Additional navigational tools may be used to position the lead at the appropriate site.