The successful implementation of balloon-catheter procedures involves controlling the flow of fluid to a balloon of a catheter or a treatment area in a vessel of a human body. Medical balloon catheters have been proven efficacious in treating a wide variety of blood vessel disorders such as intravascular restrictions due to atherosclerosis or restenosis. Balloon angioplasty, or percutaneous transluminal coronary angioplasty (PTCA), is commonly used to alleviate stenotic lesions in blood vessels, thereby reducing the need for heart bypass operations.
Balloon catheter and guidewire-deployed treatment systems are used to temporarily occlude a vessel in the coronary vasculature during diagnostic and interventional procedures. Guidewires help guide the insertion of catheters and various medical instruments to a desired treatment location within the vasculature of a human body. A flexible guidewire can be advanced through the blood vessels until the guidewire extends across the vessel segment to be treated. Treatment catheters, such as a balloon dilation catheter for PTCA, may be inserted over the guidewire and similarly advanced through the vasculature until they reach the treatment site.
Areas of vascular stenoses or occlusions in a vessel are often characterized by having a mineral component. A variety of different procedures has been developed for treating vascular diseases with these calcified areas. Some treatment methodologies involve the mechanical removal of the blockage, mechanical debridement, atherectomy, balloon angioplasty, stenting, or bypass surgery procedures.
Intravascular procedures often use one or more catheters, such as balloon catheters to dilate vascular restrictions or atherectomy catheters to remove the restriction. Unfortunately, the intravascular procedures associated with these devices may result in particles being dislodged while the restriction is dilated or cut. Such dislodged particles may move downstream from the area of restriction, possibly causing an embolism, which could compromise the flow of blood to the surrounding tissue.
Treatment procedures employing occlusion balloon catheters and aspiration catheters have been developed to help prevent potentially embolic debris from migrating with the blood stream. The occlusion balloon catheter blocks or impedes blood flow while the aspiration catheter aspirates and removes embolic particles from the area of the stenosis.
In one exemplary method for reducing embolization, the treatment area is continuously aspirated while the aspiration catheter is moved, as described in “Methods for Reducing Distal Embolization,” Imran, U.S. Patent Application 2003/0055398 published Mar. 20, 2003. This method is proposed to prevent embolization of any particles that may be created during the crossing of the intravascular inclusions. An adapter for controlling fluid flow in an exemplary angioplasty balloon catheter is described in “Low Profile Angioplasty Catheter and/or Guide Wire and Method,” Imran et al., U.S. Pat. No. 5,520,645 issued May 28, 1996. The balloon-on-a-wire catheter has a flexible elongate tubular member with proximal and distal extremities and with a lumen extending from the proximal extremity to the distal extremity. A removable inflation fitting is secured to the proximal extremity of the flexible elongate tubular member for supplying an inflation fluid to the lumen for inflating and deflating the balloon. Fluid flow may be controlled with a removable inflation means such as a conventional Tuohy Borst adapter having a tubular member formed of suitable material such as a clear plastic. For example, a Tuohy Borst adapter can provide a temporary fluid or airtight seal with the compression of a silicone ferrule.
During treatment procedures using catheters, it is not uncommon for multiple catheters to be introduced and removed sequentially over a guidewire, the latter acting as a guide for the exchange of one treatment catheter for another. Embolic containment procedures typically employ one or two occlusion balloons in conjunction with an aspiration catheter. One example of an inflatable occlusion catheter includes an occlusion balloon mounted distally on an elongated wire-like shaft that extends through a guidewire lumen of a primary dilation or atherectomy catheter. The balloon is advanced through a vessel, positioned distal to the site of the stenosis, and temporarily inflated to prevent embolic particles from migrating downstream as the occlusive restriction is being dilated or cut. After the restriction has been treated, the primary treatment catheter can be removed from over the guidewire of the occlusion balloon catheter. An aspiration catheter can then be advanced to the treatment site to aspirate any embolic debris generated during the treatment. Once the embolic particles have been aspirated, the occlusion balloon(s) is/are deflated and removed from the patient.
An occlusion catheter is often constructed as a guidewire having a hollow shaft, a flexible, shapeable distal tip, and a deflated elastomeric occlusion balloon attached at the proximal end of the distal tip. During use, the distal tip of the guidewire and the balloon cross the lesion, an inflation device is attached to the proximal end of the catheter, and the occlusion balloon is inflated with dilute contrast agent. Following the inflation of the balloon, an angiogram using fluoroscopy may be taken to ensure complete occlusion by the balloon.
The occlusion guidewire can be used in coordination with other treatment catheters to infuse or deliver fluoroscopic material and therapeutic agents to the treatment site. With the occlusion balloon inflated, balloon angioplasty or stenting may be performed. A handheld inflation device can be removed from the proximal end of the catheter while the occlusion balloon remains inflated, and then a stent-delivery catheter may be exchanged to provide a percutaneous transluminal angioplasty. The embolic particles that are released during a coronary angioplasty or stenting procedure may remain upstream of the inflated occlusion balloon. Following the removal of the angioplasty balloon catheter or stent-delivery catheter, an aspiration catheter may be introduced over the occlusion guidewire to aspirate the particles.
An exemplary occlusion catheter is described by Rauker and others in “Occlusion Device,” U.S. Pat. No. 6,475,185 issued Nov. 5, 2002. The occlusion device includes an elongated tubular shaft having an inflatable balloon disposed near the distal end of the elongate shaft with a proximal seal of a sufficiently small profile to allow a second catheter to pass over the distal occlusion device while the inflatable balloon remains uninflated. One occlusion device includes an elongated fluid displacement rod within the elongated shaft of the occlusion device, providing both a fluid pressure source and a seal.
The flexibility of the catheter as well as the guidewire is important for advancing medical devices over the guidewire. Omaleki and others suggest improvements to the properties of the catheter and the wire on which the balloon is attached, as disclosed in “Flexible Catheter,” U.S. Pat. No. 6,500,147 issued Dec. 31, 2002. In an embodiment of the invention, connecting wires extend through the balloon from the distal end of a catheter body to the proximal end of a core wire. The core wire extends distally away from the connecting wires and the catheter body, having a proximal end extending within the balloon into the catheter tubular body but not mounted therein. The balloon is mounted over a tubular body that is configured to give the catheter longitudinal flexibility.
Controlling the flow of inflation fluid through a catheter is critical to the successful use of balloon catheters. Current occlusion balloon catheters are able to control the flow of inflation and contrast fluid with sealing members such as plugs or valves located at the proximal end of the catheter. An exemplary catheter valve is a plug consisting of a wire that is shaped to provide a friction fit within a hollow guidewire or hypotube, the plug also having a sealing member on the distal end of the wire. The valve is operated by pushing the plug in and out of the catheter shaft, thus moving the sealing member with respect to an inflation hole in the side of the shaft. A valve adapter, or actuator, may be removably mounted on the proximal end of the catheter to control valve operation. The adapter grips the catheter shaft and the plug via frictional pads, which may be moved in conjunction with an adapter knob. An inflation fluid port on the adapter is positioned to line up, or at least fluidly communicate, with the inflation hole in the catheter shaft, providing a continuous fluid path to inflate the occlusion balloon. Fluid is transferred through the hypotube to fill the occlusion balloon.
Several types of sealing mechanisms have been developed to control the flow and seal inflation fluid into the occlusion balloon. Sell and others have used a valve of an inner tube that is closely fit into an outer tube, as disclosed in “Low Profile Valve and Balloon Catheter,” U.S. Pat. No. 6,090,083 issued Jul. 18, 2000. The low-profile inflation valve includes a first thermoplastic tube with at least one region of decreased inner diameter, and a structure, which may be a tube, movably located inside the lumen. The region of decreased inner diameter of the first tube forms a seal with a portion of the structure.
A catheter with a valve on the distal end of the catheter is disclosed in “Single-Lumen Balloon Catheter having a Directional Valve,” Samson, U.S. Pat. No. 5,683,410 issued Nov. 4, 1997. The valve is operated by a control wire having a valve plug disposed on the wire. The valve seat may be engaged by the valve plug from either direction, depending on the installation of the control wire. The guidewire with its integral valve plug may traverse the body of the balloon to engage the valve seat in the distal end of the catheter. Pushing on the control wire will seat the valve, allowing the introduction of fluid through the catheter lumen to inflate the balloon. A valve used with a related catheter is described in “Single-Lumen Balloon Catheter having a Directional Valve,” Samson, U.S. Pat. No. 6,096,055 issued Aug. 1, 2000. This single-lumen balloon catheter assembly has a valve portion extending distal of a balloon portion. A valve plug engages the surface of the valve at the proximal end of the valve, which has a smaller inner diameter than the distal end of the valve. The proximal and distal surfaces of the valve are adapted to engage the plug to form a seal therewith.
A number of improvements to a balloon occlusion catheter and its valve mechanism are proposed in “Low Profile Catheter Valve and Inflation Adaptor,” Zadno-Azizi et al., U.S. Patent Application 2002/0133117 published Sep. 19, 2002; “Exchange Method for Emboli Containment,” Zadno-Azizi et al., U.S. Pat. No. 6,544,276 issued Apr. 8, 2003; “Method of Emboli Protection using a Low Profile Catheter,” Zadno-Azizi et al., U.S. Pat. No. 6,500,166 granted Dec. 31, 2002; “Low Profile Catheter Valve,” Zadno-Azizi et al., U.S. Pat. No. 6,355,014, granted Mar. 12, 2002; “Low Profile Catheter for Angioplasty and Occlusion,” Zadno-Azizi, U.S. Pat. No. 6,231,588 issued May 15, 2001; and in “Guidewire Inflation System,” Zadno-Azizi et al., U.S. Pat. No. 6,050,972 granted Apr. 18, 2000. The catheter includes a low-profile catheter valve with a movable sealer portion positioned within the inflation lumen of a catheter. The sealer portion forms a fluid tight seal with the inflation lumen by firmly contacting the entire circumference of a section of the inflation lumen. The sealer portion is positioned proximate to a side-access inflation port on the catheter, establishing an unrestricted fluid pathway between the inflation port and an inflatable balloon on the distal end of the catheter. The sealer portion can be moved to a position distal of the inflation port, thereby preventing fluid from being introduced into or withdrawn from the balloon via the inflation port. An inflation adaptor can be used for moving the sealer portion within the catheter to establish or close the fluid pathway between the inflation port and the inflatable balloon. In one of the embodiments of the catheter valve, a tubular sealing member is used as a valve mechanism at the distal end of the catheter. The tubular sealer fits tightly within the lumen of the catheter and may rotate within the lumen. Fluid flows through the valve when the tubular sealer rotates within the lumen to align its opening or port to the side-port access of the lumen. The movable sealer for a low-profile catheter is described specifically in “Low profile catheter valve and inflation adaptor,” Zadno-Azizi et al., U.S. Pat. No. 6,325,778 issued Dec. 4, 2001.
Another example of a valved balloon catheter having a wire with a valve plug slidably disposed within the inflation lumen is described in “Balloon Catheter with Delivery Side Holes,” Kupiecki, U.S. Patent Application 2003/0004461 published Jan. 2, 2003. The valve plug forms an adjustable pressure seal at a valve seat on the distal end of the catheter and allows fluid within the inflation lumen to be pressurized by a fluid source in order to facilitate balloon inflation.
Preferred characteristics of a controllable closing device or valve are discussed in “Balloon Catheter with Valve,” Maria van Erp et al., U.S. Pat. No. 6,102,891 issued Aug. 15, 2000. The valve is arranged inside the inflation lumen so that it can selectively close off the lumen. The valve is described as a device controlled by means of pressure or a mechanical connection such as a ball valve, a snap connection, or a membrane having cuts that move apart when a certain threshold value of pressure is reached. The closing device may have two components, whereby the functioning of the valve depends on the positions of the components in relation to one another. Preferably, a portion of the tubular basic body forms one of the valve components, while the other valve component is a second body placed inside the lumen of the tubular basic body, which closes off the lumen or the opening in different axial or radial positions. The components are preferably movable in relation to one another in a rectilinear or rotary direction. Another embodiment of the invention has a one-way valve in the shape of a membrane comprising cuts or a tilting plate inside the lumen placed at a certain angle.
Not only have valves been used to control the flow of inflation fluids to a catheter balloon, but a valve with a sealing member also has been used with a catheter that delivers therapeutic or diagnostic agents through a one or more delivery ports, as disclosed in “Balloon Catheter with Delivery Side Holes,” Kupiecki, U.S. Pat. No. 6,440,097 issued Aug. 27, 2002. In one variation of the catheter, pressurized fluid flows from the proximal end to the distal end of the lumen of the catheter and into an inflatable balloon. Also extending from the proximal end to the distal end, a guidewire inside the lumen may have a valve plug disposed on its distal end for selectively seating against a valve seat at the distal end of the catheter to seal the lumen for balloon inflations.
Catheter manufacturers continue to work on developing valve systems that provide more control over fluid flow to and from an occlusion balloon positioned within a vessel in a body. The desirable valve component has a reliable sealing member with rapid positioning capability into an open or closed position, with minimal constriction of fluid transport through the valve to allow rapid inflation and deflation of the occlusion balloon. Therefore, an improved valve for a balloon catheter system is desirable for catheter-employed treatments for vessels in the body, providing greater control of fluid through a catheter, and increasing utility and performance of associated medical devices used during the treatment of vascular conditions.