Abstract:
A method of treating cardiac arrhythmias resulting from errant electrical signals conducted through the cardiac tissue from a source location. The magnitude of the errant signals is reduced by shunting electrical signals from the source location with an electrically conductive element having a sufficiently low impedance.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/698,438, filed Jul. 11, 2005, the entire disclosure of which is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   This invention relates to the treatment of cardiac arrhythmias, including but not limited to atrial fibrillation. 
   A healthy heart typically beats rhythmically and at a predictable rate. However, in some individuals, often those who have underlying heart disease, the heart beats arrhythmically: either too quickly (a condition called tachycardia) or too slowly (a condition called bradycardia). These rhythm abnormalities can occur in the upper chambers of the heart (the atria) or the lower chambers (the ventricles). 
   One of the most common arrhythmias is atrial fibrillation, which affects more than two million Americans. Atrial fibrillation is associated with symptoms such as palpitations and shortness of breath, an increased risk of blood clots and stroke, and in some patient&#39;s congestive heart failure. There are several options for the treatment of atrial fibrillation, including medications, implantable atrial defibrillators, the surgical maze procedure which physically interrupts conduction paths with incisions, or catheter-based procedures such as radiofrequency ablation to interrupt conduction paths. Unfortunately, many of these treatments do not offer a cure and all have significant limitations. 
   SUMMARY OF THE INVENTION 
   Generally, the methods of the preferred embodiment provide a method of treating cardiac arrhythmias resulting from errant electrical signals or areas of conduction block associated with non-conductive tissue, such as scar. In the former example, rather than isolating the errant signals by conventional methods employing incisions or lines of ablation, the methods of the preferred embodiment shunt the electrical signals from their source. In the latter, the electrical signals are shunted to the area downstream from the scar to restore natural conduction. In these methods the electrical signals can either be shunted directly to a location which restores proper heart function, or the signals are shunted to a neutral location, and proper heart function can then be restored with a pacemaker. The electrical signals can be shunted with an electrically conductive element that has sufficiently low impedance that it substantially reduces the conduction of errant signals through the heart tissue. The ends of the element preferably have connectors for mechanically and electrically anchoring the element to the cardiac tissue. To be effective, both the shunts and the tissue connections (anchors) must have relatively low electrical resistance. 
   Thus, embodiments of the present invention can provide relief from cardiac arrhythmias, such as atrial fibrillation, by providing an electrical bypass for errant signal patents. In some embodiments the signals are conducted from their source to a location which results in proper cardiac function. In other embodiments the signals are conducted to a location that does not affect cardiac function, and proper function may be restored with a pacemaker. This procedure is less invasive than many of the conventional treatments for cardiac arrhythmias, such as the maze procedure, which involves cutting the cardiac tissue, or ablation procedures, which involve ablating cardiac tissue. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram of the steps of a preferred embodiment of the methods of this invention; 
       FIG. 2  is a plan view of a conductive element adapted for use with the first and second preferred embodiments of the methods of this invention; 
       FIG. 3  is a plan view of a conductive element adapted for use with a third preferred embodiment of the methods of this invention; 
       FIG. 4  is a schematic view of a heart showing a single conductor connecting a signal source with the heart tissue to bypass errant signal paths; 
       FIG. 5  is a schematic view of the heart showing two conductors connecting a signal source with the heart tissue to bypass errant signal paths; 
       FIG. 6  is a schematic view showing one method of placing a conductor in accordance with this invention; and 
       FIG. 7  is a schematic view of a device for placing conductors in accordance with this invention. 
   

   Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   In accordance with a preferred embodiment of the methods of this invention, at least one electrically conductive element shunts errant electrical signals from a signal source, by providing a lower impedance path than the errant paths through the cardiac tissue, eliminating the errant signals, or at least reducing them to a level that does not interfere with proper cardiac function. The conductive element can either shunt the electrical signals from the source to a location(s) in the heart which causes proper heart function, or the element can shunt the electrical signals from the source to a location in the heart where the signal does not interfere with the proper function of the heart. In the latter, case, proper heart function may have to be restored using a pacemaker. 
   More specifically, as indicated in  FIG. 1 , at step  22  the source of the electrical signals in the heart is located by moving an electrophysiology catheter over the surface of the heart to sense local electrical activity. While this can be done manually, it is most conveniently done using a remote medical navigation system, such as a Niobe® magnetic medical navigation system available from Stereotaxis, Inc., St. Louis, Mo. A remote medical navigation system provides a number of advantages over manual navigation, including the ability to automatically move a medical device in a planned pattern over the surface of the heart; the ability to intelligently search to quickly focus on a signal source, and the ability to return to locations previously visited. A method of using sensed physiological information to control navigation is disclosed in U.S. Provisional Patent Application Ser. No. 60/642,853, filed Jan. 11, 2005, entitled “Use of Sensed Local Physiologic Data in Positioning A Remotely Navigable Medical Device”, incorporated herein by reference. 
   After the source of the electrical signals is identified, an electrically conductive element  100  ( FIG. 2 ) having at least first and second ends  102  and  104  can be used to bypass or shunt the errant electrical signals being transmitted through the surrounding cardiac tissue. 
   As indicated at step  24  in  FIG. 1 , the first end  102  of the electrically conductive element  100  ( FIG. 2 ) is connected to the source location. In the preferred embodiment the first end  102  is provided with threaded anchor  106 , which is threaded into the tissue at the signal source to make a mechanical and electrical connection to the tissue. The second end  104  of the electrically conductive element  100  is connected to at least one destination location to bypass the errant signal paths. 
   In a first preferred embodiment, this destination position is a location where the conducted electrical signal can help establish normal beating of the heart. This location can be found located by moving the second end  104  of the conductor  100  over the surface of the heart to find a location where substantially normal heart beat is restored. This can be done manually or with the assistance of a remote medical navigation system, such as the Niobe® remote medical navigation system. Alternatively, this location can be found by moving an electrophysiology catheter over the surface of the heart and applying a pacing signal to the electrodes of the catheter to determine where a substantially normal heart beat is established. The second end  104  can then be moved to the identified location. As indicated at step  26  in  FIG. 1 , the second end is then connected to tissue to bypass the errant signals. Like the first end  102 , the second end  104  preferably has a threaded anchor  108  ( FIG. 2 ) or other device for making mechanical and electrical connection with the cardiac tissue. 
   Once both ends  102  and  104  of the electrically conductive element  100  are secured, electrical signals from the source are conducted to a location where the signals establish a substantially normal heart beat. The impedance of the electrically conductive element  100  is sufficiently low that the conduction of errant signals from the signal source are eliminated or at least reduced to a level that they do not significantly impair normal cardiac function. 
   In a second preferred embodiment, the destination position is a location where the conducted electrical signal does not interfere with the normal beating of the heart. This location can be found located by moving the second end  104  of the conductor  100  over the surface of the heart to find a location where an electrical signal has no impact on the normal beating of the heart. This can be done manually or with the assistance of a remote medical navigation system, such as the Niobe® remote medical navigation system. Alternatively, this location can be found by moving an electrophysiology catheter over the surface of the heart and applying a pacing signal to the electrodes of the catheter to determine where a signal does not substantially affect a normal heart beat. The second end  104  can then be moved to the identified location. Like the first end  102 , the second end  104  preferably has a threaded anchor  108  or other device for making mechanical and electrical connection with the cardiac tissue. 
   Once both ends  102  and  104  of the electrically conductive element  100  are secured, electrical signals from the source are conducted to a location where the signals do not interfere with a substantially normal heart beat. The impedance of the electrically conductive element  100  is sufficiently low that the conduction of errant signals from the signal source are eliminated or at least reduced to a level that they do not significantly impair normal cardiac function. Normal heart activity may be restored by the placement of a pacemaker to replace the now shunted signals. 
   In accordance with a third embodiment, shown in  FIG. 3 , an electrically conductive element  120  has a first contact end  122 , and at least two Oust two are shown in  FIG. 3 ) contact ends  124  and  126 . The contact ends  124  and  126  allow the electrical signals from a source connected to end  122  to be shunted to more than one location, either to establish a normal heart function using the electrical signals, or to dissipate the signals. Each of the ends  122 ,  124 , and  126 , can have a suitable anchor, such as a threaded anchor  128  to facilitate mechanical and electrical contact with the tissue. 
   Operation 
   In operation the source of electrical signals in the heart is located. In the first or second embodiments, the first end  102  of element  100  is connected with tissue at the location, for example by threading anchor  106  into the tissue. The destination position is then located. Once the destination position is located, the second end  104  of the element  100  is connected with tissue at the location, for example by threading anchor  106  into the tissue. The element  100  provides a low impedance by passes for the errant electrical signals, hopefully eliminating such signals, or at least reducing them to a level that decreases their impact on normal cardiac function. 
   In the third embodiment two or more destination positions are located, instead of just one as in the first and second embodiments, and the ends  124  and  126  (and others if desired) are connected with the tissue at their respective locations, for example by threading anchor  128  into the tissue. 
   The electrically conductive element  100  can be introduced into the body, and placed using interventional medicine techniques, and thereby eliminating the need for open heart surgery, as is required with maze procedures. It also eliminates the cutting of the heart tissue that is done as part of maze procedures, and eliminates ablation that is part of conventional ablation therapies. Installation of the electrically conductive element can thus be done with a minimum of patient trauma, and interference with the heart. 
   As shown in  FIG. 4 , an element  100  has been placed in the heart, with end one  102  attached to a local source of electrical signals, and a second end  104  attached to a portion of the heart where the electrical signal triggers substantially normal activity. As shown in  FIG. 5 , two elements  100  have been placed in the heart, with one end  102  attached to a local source of electrical signals, and a second end  104  attached to a portion of the heart where the electrical signals trigger substantially normal activity. The elements anchors  106  and  108  on the ends  102  and  104  of the elements  100  are preferably oppositely threaded so that when the element  20  is rotated, both anchors  106  and  108  engage and twist into the tissue. A device  200  (shown schematically in  FIG. 7 , can be provided to simultaneously turn the ends of the element  100  to attach the anchors  106  and  108  to secure the element  100 , as shown in  FIG. 6 ).