Endovascular therapy has been used to treat different conditions, such treatments including control of internal bleeding, occlusion of blood supply to tumors, and occlusion of aneurysm. Often the target site of the malady is difficult to reach. Because of their ability to access remote regions of the human body and deliver diagnostic or therapeutic agents, catheters are increasingly becoming components of endovascular therapies. Vascular catheters may be introduced into large arteries, such as those in the groin or in the neck, and then pass through narrowing regions of the arterial system until the catheter's distal tip reaches the selected delivery site. To be properly utilized, catheters are often stiffer at their proximal end to allow the pushing and manipulation of the catheter as it progresses through the body but sufficiently flexible at the distal end to allow passage of the catheter tip through the body's blood vessels without causing significant trauma to the vessel or surrounding tissue.
Microcatheters, such as those shown in U.S. Pat. Nos. 4,884,579 and 4,739,768, each to Engleson, allow navigation through the body's tortuous vasculature to access such remote sites as the liver and the arteries of the brain. Although other methods of causing a catheter to proceed through the human vasculature exist (e.g., flow directed catheters), a guidewire-aided catheter is considered to be both quicker and more accurate than other procedures. Catheters with deflectable or variable stiffness distal ends (which increase the flexibility of the catheter's distal end) have been disclosed in U.S. Pat. No. 6,083,222, to Klein et al; U.S. Pat. No. 4,983,169, to Furukawa; U.S. Pat. No. 5,499,973, Saab; and U.S. Pat. No. 5,911,715, to Berg et al.
The addition of a fluid-expandable balloon on the distal end of the catheter and a coupler on the proximal end allows various percutaneous medical treatments such as pressure monitoring, cardiac output and flow monitoring, angioplasty, artificial vaso-occlusion, and cardiac support. Balloon catheters generally include a lumen that extends from the proximal end and provides fluid to the balloon for inflation. Examples of balloon catheters are disclosed in U.S. Pat. No. 4,813,934 to Engleson et al and U.S. Pat. No. 5,437,632 to Engelson et al. A balloon catheter with an adjustable shaft is shown in U.S. Pat. No. 5,968,012, to Ren et al.
For certain vascular malformations and aneurysms, it may be desirable to create an endovascular occlusion at the treatment site. A catheter is typically used to place a vaso-occlusive device or agent within the vasculature of the body either to block the flow of blood through a vessel by forming an embolus or to form such an embolus within an aneurysm stemming from the vessel. Formation of an embolus may also involve the injection of a fluid embolic agent such as microfibrillar collagen, Silastic beads, or polymeric resins such as cyanoacrylate. Ideally, the embolizing agent adapts itself to the irregular shape of the internal walls of the malformation or aneurysm. Inadvertent embolism due to an inability to contain the fluid agent within the aneurysm is one risk which may occur when using fluid embolic agents.
Mechanical vaso-occlusive devices may also be used for embolus formation. A commonly used vaso-occlusive device is a wire coil or braid which may be introduced through a delivery catheter in a stretched linear form and which assumes an irregular shape upon discharge of the device from the end of the catheter to fill an open space such as an aneurysm. U.S. Pat. No. 4,994,069, to Ritchart et al, discloses a flexible, preferably coiled, wire for use in a small vessel vaso-occlusion.
Some embolic coils are subject to the same placement risks as that of fluid embolic agents in that it is difficult to contain the occlusive coil within the open space of the aneurysm. A need exists for a delivery system which accurately places the occluding coil or fluid and ensures that the occluding coil or fluid does not migrate from the open space within the aneurysm. The delivery catheter must have a small diameter, have a highly flexible construction which permits movement along a small-diameter, tortuous vessel path, have a flexible method of placement to ensure accuracy, and must have a method to prevent coil or embolizing agent leakage.