1. Field of the Invention
The subject invention is directed to implantable cardiac stimulation leads, and more particularly, to a device and method for delivering one or more implantable cardiac leads to an implantation site while protecting the fixation mechanism at the distal end of the lead.
2. Background of the Related Art
Implantable cardiac stimulation leads, including epicardial and endocardial leads, are well known in the art. In general, these devices have an elongated flexible body with an electrode assembly at one end for contacting and stimulating cardiac tissue and a connector assembly at the other end for mating with an automated stimulation device, such as a pacemaker or defibrillator. The distal end of the lead can include a helical screw to facilitate active fixation of the lead tip or a plurality of flexible tines to facilitate passive fixation of the lead tip.
In the implantation of a cardiac device, and in the replacement of previously implanted cardiac leads, two or more transvenous cardiac leads are typically introduced through the venous system into the chambers or coronary sinus of the heart. To implant an endocardial lead within a heart chamber, a transvenous approach is typically utilized wherein the lead is inserted into and passed through the subclavian, jugular, or cephalic vein and through the superior vena cava into the right atrium or ventricle. A cover or retraction mechanism is generally used to protect the fixation helix on the lead tip during the transvenous advancement into the heart chamber. Once positioned, the helix is rotated into the myocardium to permanently fix the electrode.
Endocardial pacing and cardioversion/defibrillation leads have also been developed that are adapted to be advanced into the coronary sinus and coronary veins branching therefrom in order to locate the distal electrode(s) adjacent to the left ventricle or the left atrium. These leads are advanced through the superior vena cava, the right atrium, the valve of the coronary sinus, the coronary sinus, and into a coronary vein communicating with the coronary sinus, such as the great vein. Typically, coronary sinus leads do not employ any fixation mechanism and instead rely on the close confinement within these vessels to maintain each electrode at a desired site.
There are several known approaches for implanting cardiac leads introduced through the venous system into the right chambers or coronary sinus of the heart, as described above. One approach is disclosed in U.S. Pat. No. 5,246,014, which employs a catheter that surrounds the lead body and engages a distal screw-in electrode. The assembly is advanced to the desired site and rotated to screw the distal screw-in electrode into the myocardium of the right atrium or ventricle. The introducer can also be used to direct a cardiac lead into the coronary sinus opening.
Another approach is disclosed in U.S. Pat. No. 5,003,990, which relies on a guidewire and a carriage that releasably engages the distal screw-in electrode and is pushed along the guidewire as the lead body is pushed along a transvenous path. In yet another approach disclosed in U.S. Pat. No. 5,304,218 a cardiac lead is formed with a channel in the distal tip that receives a guidewire that has already been advanced through the path to the cardiac implantation site. The lead is pushed over the guidewire to the cardiac implantation site where the guidewire is withdrawn and the lead is either fixed in place or left at the cardiac implantation site.
U.S. Pat. No. 6,185,464 discloses a device for introducing and implanting a cardiac lead at an implantation site within a heart chamber or vessel. The device includes an elongated guide body and a tracking mechanism coupled with the distal end of the lead for receiving and slidingly engaging the guide. A pusher mechanism is provided, which engages the cardiac lead at or near the distal end thereof, to advance the guide body tracking mechanism and the cardiac lead distally along the guide body to the implantation site. Then, the lead body is released from the lead engaging mechanism and the pusher mechanism is retracted along with the pusher body. This device does not provide means to protect the fixation mechanism at the distal end of the lead, nor is it suited to deliver more than one lead at a time to the site of implantation.
It would be beneficial therefore, to provide a lead delivery device that facilitates the safe and efficient introduction of one or more endocardial cardiac leads into a heart chamber or vein while protecting the delicate fixation mechanism at the distal end of the lead.