Abstract:
A double catheter includes an outer, resilient catheter having shape memory and a hook-shaped distal end, an inner, pliable catheter slidably disposed in the outer catheter and of greater length than the outer catheter so that a distal end portion of the inner catheter can be extended or retracted from a distal end opening of the outer catheter to vary the overall length of the double catheter, the inner catheter preferably having an internal lumen suitable for the introduction of contrast media, and a mechanism operable from the proximal end of the outer catheter for changing the curvature of the hook shaped distal end of the outer catheter. Such a catheter of the invention can cannulate the coronary sinus without significant manipulation.

Description:
[0001]    This application claims priority of U.S. Provisional Application No. 60/195,701, filed Apr. 7, 2000. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates to medical devices, particularly to catheters of the type used to cannulate the coronary sinus.  
         BACKGROUND OF THE INVENTION  
         [0003]    The coronary sinus is a venous structure that is three to four centimeters in length and one centimeter in diameter. It forms a part of the venous drainage of the heart. The coronary sinus arises from the posterior inferior aspect of the right atrium and courses over the posterior surface of the heart, ending in the great cardiac vein. It is the final common venous drainage of most of the heart.  
           [0004]    Cannulation of the coronary sinus has until recently not been considered important from a medical viewpoint. Medical researchers have cannulated the coronary sinus in animals and in humans to obtain information about the functioning of the heart. Cardiac surgeons will, during cardiac surgery, cannulate the coronary sinus for retrograde cardioplegia. However, routine cannulation of the coronary sinus is not performed when there is no therapeutic advantage to performing coronary sinus angiography.  
           [0005]    It has recently become apparent that the coronary sinus and its branches can be used to place catheters (fine pacing catheters) on the epicardium of the left ventricle. The left ventricle can then be paced via these catheters. Preliminary studies show that pacing the left ventricle produces significant benefit in patients with heart failure, especially those with conduction disturbances. Therefore, studies are underway to study the coronary sinus anatomy and place the pacing catheters in the appropriate branch of the coronary sinus. Unlike for coronary arterial circulation, which has been well studied because of its therapeutic benefit, there are no presently available preformed catheters that will slip easily into the coronary sinus. U.S. Pat. No. 5,423,772 exemplifies one proposed device designed for use in the coronary sinus wherein the catheter has a double curve.  
           [0006]    Congestive heart failure is one of the commonest diagnoses leading to hospital admission in the United States. There are 2 to 5 million patients diagnosed with CHF in the U.S. annually, and 15 million worldwide. Treatment of heart failure consists of medications, and cardiac transplantation in severe cases. Other forms of surgery, e.g. valve surgery, are also sometimes helpful. Attention has recently focused on resynchronization therapy. About 30-50% of people with severe CHF have asynchronous contraction of the cardiac chambers. This can be corrected by pacing the right atrium, the right ventricle and the left ventricle at optimal intervals to provide synchrony. Leads to pace the right atrium and right ventricle have been used for years. Recently, leads have been devised to pace the left ventricle by passing the lead through the coronary sinus into a branch vein that overlies the left ventricle. Delivery systems to guide the leads into the appropriate branch veins are now being researched.  
           [0007]    Currently available catheters and catheter systems have several disadvantages which render lead delivery difficult. For example, the anatomy of the right atrium and the coronary sinus origin is different in patients with congestive heart failure than in patients with normal sized hearts. These differences in part form the basis for the design of the delivery system of the present invention. Such differences include that the os of the coronary sinus lies higher in the right atrium in such persons than in normal persons. The eustachian ridge is unusually prominent, and the right atrium is usually larger than normal. Subeustachian fossae are more well developed in the large right atria. There is great variation in the size of the coronary sinus and its shape and direction, and the target coronary branch veins arise at acute angles from the main coronary sinus in many patients. This renders it difficult to pass a lead into these branches. Venous valves obstruct the passage of the lead. These are variably placed, frequently close to the origin of the coronary veins. The present invention provides a catheter especially adapted for use in the coronary sinus, especially in patients suffering from congestive heart failure.  
         SUMMARY OF THE INVENTION  
         [0008]    A double catheter according to one aspect of the invention includes an outer, resilient catheter having shape memory and a hook-shaped distal end configured for cannulation of the coronary sinus, an inner, pliable catheter slidably disposed in the outer catheter and of greater length than the outer catheter so that a distal end portion of the inner catheter can be extended or retracted from a distal end opening of the outer catheter to vary the overall length of the double catheter, the inner catheter preferably having an internal lumen suitable for the introduction of a fluid, such as contrast media, into the coronary sinus and also for passage of a pacing lead, and a mechanism operable from the proximal end of the outer catheter for changing the curvature of the hook shaped distal end of the outer catheter. Such a catheter of the invention can cannulate the coronary sinus without significant manipulation, enable an angiogram of the coronary sinus by means of an occlusive balloon which includes the proximal coronary sinus at the time of contrast media injection, serve as a conduit for the passage of a fine coronary sinus pacing lead (5 French in diameter), provide backup support for introducing this lead over a guide wire into the distal branches, and minimize the steps necessary for the placement of a coronary sinus lead, thereby allowing rapid introduction of such a lead.  
           [0009]    The invention further provides a method of using a catheter to place a pacing lead in a transverse branch of the coronary sinus in order to treat a related condition such as congestive heart failure. Such a method for placing an electrical lead in a lateral branch of a coronary sinus vein using a double catheter includes the steps of inserting the catheter into the coronary sinus, advancing a guide wire through the catheter into a coronary sinus lateral branch vein, advancing the inner catheter out of a front end opening of the outer catheter along the guide wire into the branch vein, inserting the lead through the outer and inner catheters to a target location in the branch vein, and withdrawing the catheter leaving the lead in the branch vein. If necessary, the curvature of the double catheter can be adjusted in order to enter the coronary sinus. These and other aspects of the invention are discussed in the detailed description that follows.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0010]    In the accompanying drawing, wherein like numeral denote like elements:  
         [0011]    [0011]FIG. 1 is a side view of a double catheter of the invention;  
         [0012]    [0012]FIG. 2 is a side view of the outer catheter of FIG. 1;  
         [0013]    [0013]FIG. 3 is a side view a second embodiment of a catheter according to the invention;  
         [0014]    [0014]FIGS. 4 and 5 are diagrams illustrating preferred shapes for the outer guide and obturator of FIG. 3;  
         [0015]    [0015]FIG. 6 is a diagram illustrating an alternative inner catheter for use in the embodiment of FIG. 3; and  
         [0016]    [0016]FIGS. 7 and 8 are diagrams illustrating use of the catheter of FIG. 3 a method of introducing a pacing lead according to the invention. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0017]    [0017]FIGS. 1 and 2 illustrate a double catheter  10  according to the invention having a typical length of 60 cm. An outer catheter  11  is made of a braided silastic or similar material to allow torque control and stiffness. An inner catheter  12 , which slides in and out of outer catheter  11 , is constructed of a more pliable, soft material such as silicone. The combination of outer and inner catheters  11 ,  12  provides a number of advantages, including variability in the reach of the catheter, and outer catheter stiffness necessary for manipulation along with inner catheter softness, which permits safe cannulation of the coronary sinus and advancement of catheter  11  into the distal coronary sinus for purposes of support. It also allows the inner catheter  12  to conform to the torturous course of a coronary sinus.  
         [0018]    Inner catheter  12  fits into lumen  15  of outer catheter  11 , and is preferably coated with a hydrophilic lubricious material which allows catheter  12  to slide in and out of outer catheter  11  with ease. A proximal end  13  of inner catheter  12  terminates in a hemostatic valve  14  having an adjustable diaphragm. Valve  14  prevents leakage of blood when a 5 French pacing lead is introduced through inner catheter  12  into the coronary system. Preferably, a distal end  16  of inner catheter  12  has a tip  17 , for example, about 1 cm long, made of a material softer than the remainder of inner catheter  12 . This may, for example, be accomplished by making tip  17  thinner than the remainder of catheter  12 , or by making a bilayered inner catheter  12  wherein the one layer extends further than the other to form the tip and optionally is made of a material softer than that of the other layer.  
         [0019]    Outer catheter  11  has several functions. Because of its stiffness and torque, it can be manipulated in the right atrium to allow cannulation of the coronary sinus. Such stiffness also lends support to the pacing lead as it is introduced into the distal coronary sinus. A distal end  18  of outer catheter  11  has an external inflatable cuff or balloon  21 . Balloon  21  can be inflated with air by means of a syringe  22  connected to balloon  21  as described below. Inflation of balloon  21  allows occlusion of the proximal coronary sinus, which is necessary for obtaining a coronary sinus angiogram.  
         [0020]    The proximal end of outer catheter  11  has several features. A port  26  including a shutoff valve  30  is provided for introduction of air into balloon  21 . This port  26  is connected by means of a passage  27  in the wall of catheter  11  with the distal balloon  21 . A torque coupling  28  of a type known in the art may be tightened down on inner catheter  12  to prevent it from moving within outer catheter  11 . A torque screw  29  is attached to a cable or wire  31  that runs in the wall of outer catheter  11  and may be wound over one or more small rounded corners or small pulleys  35  set in the wall of catheter  11 . This cable  31  is anchored, as by embedding a enlarged end thereof, at a point  34  close to a tip  32  of outer catheter  11 . Rotation of torque screw  29  causes cable  31  to be retracted, which changes the shape of the outer catheter  11  (making the hooked shape more pronounced as shown by the arrow) and counter-rotation does the opposite. Torque screw  29  may, for example, comprise a spool or reel having an external circumferential groove on which cable  31  is attached and is wound or unwound as needed. A port  36  with an associated shutoff valve  37  is provided through the wall of outer catheter  11  for delivering a saline flush through lumen  15 .  
         [0021]    For optimum deployment in the coronary sinus, inner and outer catheters  11 ,  12  preferably have a predetermined shape and a certain degree of stiffiess to maintain such shape during manipulation in the heart, but still flexible enough to bend when required. As shown in FIG. 2, the hook-shaped distal end of outer catheter  11  may comprise substantially straight segments spanning three bends  41 ,  42  and  43 . First bend  41  adjoining a straight, proximal portion  44  of outer catheter 11  is in the range of about 130° to 180°, especially 130° to 175°. Second, intermediate bend  42  extends in a direction opposite bend  41  and is in the range of about 75° to 100°. Third bend  43  near the distal end of outer catheter  11  extends in the same direction as bend  42  and is in the range of about 130° to 175°. These ranges refer to the angle formed by the straight segments adjacent each bend when the catheter is in an undistorted state. Operation of the deflection device to tighten the cable will reduce these angles, especially for second bend  42 . The material of which outer catheter  11  is made, e.g. silastic, has sufficient shape memory to return to its original shape when undistorted. The undistorted shape of outer catheter  11  can be varied and catheter  10  thereby made in several sizes to accommodate different heart sizes. For example, for a normal size atria with a prominent Eustachian valve, outer catheter  11  may be substantially J-shaped with no first bend (bend  41 =180°), whereas for large atria with a prominent Eustachian valve, it may be useful to make catheter  11  more in a question mark shape (shown inverted in FIGS.  1 - 2 ).  
         [0022]    Coronary sinus catheter  10  may be deployed in the following fashion. Distal balloon  21  is deflated, inner catheter  12  is withdrawn completely into outer catheter  11 , and catheter  10  is inserted through a venous sheath introduced in the left XX subclavian vein. It is guided into the right atrium over a guide wire, and the guide wire and sheath are then removed. Catheter  10  is rotated until tip  17  lies within the tricuspid valve, then advanced until tip  17  is seen to lie in the inferior-most portion of the tricuspid valve. If the reach of catheter  10  in this configuration is not sufficient to cannulate the tricuspid valve, then inner catheter  12  is advanced out of outer catheter  11  to make the entire system longer.  
         [0023]    Subsequent manipulation is carried out in a left anterior fluoroscopic view. Counterclockwise torque is exerted on catheter  10 . At the same time, inner catheter  12  is gradually withdrawn. Eventually, catheter  10  slips over the tricuspid annulus and, because of the counterclockwise torque, twists and pops into the proximal coronary sinus. In some instances, it may come to lie at the mouth of the proximal coronary sinus. In that case, inner catheter  12  is gradually advanced until the coronary sinus is cannulated. Once the coronary sinus is cannulated, inner catheter  12  is advanced as far as it will go into the coronary sinus and/or great cardiac vein. Distal balloon  21  on outer catheter  11  is inflated using syringe  22  to occlude the proximal coronary sinus. Contrast medium is injected via a port  25  through the lumen of inner catheter  12  to obtain a coronary sinus angiogram. Port  36  is then hooked up to a saline flush. A coronary sinus lead is introduced through a hemostasis valve  14  into inner catheter  12 . It is positioned using a guide wire in an appropriate branch of the coronary sinus.  
         [0024]    A triple catheter  50  according to the invention is designed to overcome the obstacles described above that are encountered with congestive heart failure patients and further provide a more economical catheter system that does not rely on specialized miniature adjustment mechanisms. The system includes an outer guide catheter  51 , an inner guide catheter  52  nested therein, an obturator  53  nested inside the inner guide  52 . In one example, outer guiding catheter  51  is 2.9 mm in outer diameter, 2.6 mm inner diameter. It is relatively stiff and has a braided design, which lends support and one-for-one torque control. In this respect, it can resemble an angioplasty guiding catheter. The shape of outer guiding catheter  51  is similar, but not identical, to a left amplatz curve. The proximal end terminates in an screw-adjusted hemostatic valve  56 , to allow introduction of leads or wires of different diameters without leakage of blood. There is also a side-port  58 , preferably with a 3-way valve, to allow injection of contrast medium and saline.  
         [0025]    Inner guiding catheter  52  made of a soft, pliable material such as silicone, and in this example is 2.6 mm in outer diameter and 2.3 mm in inner diameter. It has no longitudinal braiding, which makes it extremely flexible and able to conform to various shapes. Inner catheter  52  is designed to advance over a guide wire into a side branch of the coronary sinus, in conjunction with the obturator  53 . Its flexibility allows it to negotiate tortuous vessels and side branches that originate from the coronary sinus at an acute angle, yet it still possesses the radial strength needed to prevent it from collapsing when obturator  53  is withdrawn. Inner guide  52  is longer than outer guide  51 , e.g., 68 cm in length. The proximal end of guide  52  has a hemostasis valve  57  to prevent back bleeding and a side port  59  to permit contrast medium injection.  
         [0026]    Obturator  53  is preferably made of very pliable silicone, and has a central lumen that will accommodate an 0.038 inch guide wire. Obturator  53  fits into inner guide  52 , and in one embodiment is 70 mm long, 2.1 mm in outer diameter tapering to 1.25 mm diameter at its tip. In use, obturator  53  tracks over a 0.038″ guide wire  81  into a targeted side branch  56 , in concert with the inner guide catheter  52 . A tapered tip  71  of obturator  53  may protrude from the front end opening of inner catheter  52 . Without such a protruding tip  71 , the edge of inner catheter  52  might catch on venous valves or sharp angles. The terminal 7 mm of obturator  53  may have a bend  71  therein of up to about 30 degrees, i.e., defining an angle from 150-180 degrees. This allows tip  71  to function as a guiding device for the 0.038″ guide wire  81 , which can then be directed into acutely angled side branches. The proximal end of obturator  53  terminates in a standard port  60  allowing attachment of a 10 cc syringe.  
         [0027]    Referring to FIGS. 7 and 8, outer guiding catheter  51  is initially connected to a syringe and pressure monitoring system and then inserted into the right atrium  80 . The physician attempts to use it to cannulate the coronary sinus without the use of the other components. If this succeeds, an 0.038″ hydrophillic-coated guide wire  81  is advanced through it, and used to cannulate the target lateral coronary sinus side-branch  56 . (If the side branch  56  cannot be easily cannulated, the angled obturator  53  can be extended and used to direct the guide wire  81  as illustrated in FIG. 7.) The inner guide  52 , with obturator  53  inside, is then passed through outer guide  52  over the 0.038″ wire into the target side branch  56 . Obturator  53  is then withdrawn, and an electrical lead  83  is then advanced through the catheter over a 0.014″ guide wire  82  to its final resting place in the target branch  56 , and ultimately connected to a pacemaker after the catheter is withdrawn in order to apply electrical heart stimulation to that location. Guide wire  82  is only used if needed; it may be possible to place lead  83  without it.  
         [0028]    An advantage of this three-part system is that it allows a standard lead (not an over-the-wire design) to be positioned in a transverse branch  56  which has a relatively sharp angulation at its origin from the main coronary sinus. Although not deflectable using an screw adjustment mechanism as described above in connection with the first embodiment, this embodiment can nevertheless be used to cannulate the coronary sinus whether the latter is placed normally, higher than normal, or lower than normal. The angle of outer guide  51  can be changed by inserting or withdrawing the inner guide  52 . Inserting inner guide  52  without obturator  53  before cannulation straightens outer guide  51 , i.e., makes the angle of the outer guide  51  shallower, allowing engagement of a lower origin of the coronary sinus. Inserting both obturator  53  and inner guide  52  makes the outer guide angle even shallower. Thus, the outer guide alone, the outer guide plus inner guide, and outer guide plus inner guide plus obturator can be used as needed to cannulate coronary sinuses of varying heights of origin.  
         [0029]    This three-part telescoping embodiment thus eliminates the need for a cable system to change the curvature of the catheter during manipulation. As shown in FIG. 4, outer guide catheter  51  preferably has three bends in a manner similar to outer catheter  11 , with the first or proximal bend  61  ranging from about 150-180 degrees, the second (middle) bend  62  ranging from about 120-180 degrees, and the third proximal bend from 90 to 160 degrees in a direction opposite to that of the other two bends, as shown. Inner guide catheter  51  preferably has three bends in a manner similar to the outer catheter  11 , with the first or proximal bend  61  ranging from about 150-180 degrees, the second (middle) bend  62  ranging from about 120-180 degrees, and the third proximal bend from 90 to 160 degrees in a direction opposite to that of the other two bends, as shown. In one preferred form, outer guide  51  is 9 French diameter, 60 cm length, inner guide  52  is made of a soft material 8 French diameter, 68 cm length, and obturator  53  is 5 French diameter, 75 cm length.  
         [0030]    Referring to FIG. 5, obturator  53  stiffens and shapes inner guide  52  when inside of it. It may be pre-formed with a right angle bend  54  as shown to conform more easily to the shape of outer guide  51 , but this is not essential. However, tip  71  of obturator is  53  bent to an angle in the range of about 150-180 degrees to better aid in introducing a lead into a transverse vein as described above. Obturator  53  preferably tapers to a blunt point having a small opening therein just large enough to admit the largest size guide wire to be used in the procedure, in this example, 0.038 inch.  
         [0031]    In an alternative version of catheter  50 , the radial strength of the inner guide or catheter  52  prevents its collapse when obturator  53  is withdrawn. For this purpose, as shown in FIG. 6, a bend  56  in inner guide  52  is reinforced with a helical wire coil  55  that is embedded therein, or a series of spaced wire rings or hoops. These hoop reinforcements prevent inner guide  52  from collapsing during withdrawal of obturator  53  but do not prevent inner guide  52  from bending in a flexible manner.  
         [0032]    The claims which follow define certain aspects of the invention but do not limit the invention. It will be evident, for example, that a catheter according to the invention can be used to reach other hard to access parts of the human body, both in the heart and elsewhere, due to its unique structure.