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Systems and methods for unobstructed visualization and ablation

Systems and methods for unobstructed visualization and ablation description/claims

This application claims the benefit of priority to U.S. Prov. Patent Application 60/870,598 filed Dec. 18, 2006, which is incorporated herein by reference in its entirety.

The present invention relates generally to medical devices used for accessing, visualizing, and/or treating regions of tissue within a body. More particularly, the present invention relates to methods and apparatus for intravascularly accessing, visualizing, and/or treating tissue regions at or around the ostia of the pulmonary veins of the heart, without obstructing blood flow from the pulmonary vein.

Conventional devices for accessing and visualizing interior regions of a body lumen are known. For example, ultrasound devices have been used to produce images from within a body in vivo. Ultrasound has been used both with and without contrast agents, which typically enhance ultrasound-derived images.

Other conventional methods have utilized catheters or probes having position sensors deployed within the body lumen, such as the interior of a cardiac chamber. These types of positional sensors are typically used to determine the movement of a cardiac tissue surface or the electrical activity within the cardiac tissue. When a sufficient number of points have been sampled by the sensors, a “map” of the cardiac tissue may be generated.

Another conventional device utilizes an inflatable balloon which is typically introduced intravascularly in a deflated state and then inflated against the tissue region to be examined. Imaging is typically accomplished by an optical fiber or other apparatus such as electronic chips for viewing the tissue through the membrane(s) of the inflated balloon. Moreover, the balloon must generally be inflated for imaging. Other conventional balloons utilize a cavity or depression formed at a distal end of the inflated balloon. This cavity or depression is pressed against the tissue to be examined and is flushed with a clear fluid to provide a clear pathway through the blood.

However, such imaging balloons have many inherent disadvantages. For instance, such balloons generally require that the balloon be inflated to a relatively large size which may undesirably displace surrounding tissue and interfere with fine positioning of the imaging system against the tissue. Moreover, the working area created by such inflatable balloons are generally cramped and limited in size. Furthermore, inflated balloons may be susceptible to pressure changes in the surrounding fluid. For example, if the environment surrounding the inflated balloon undergoes pressure changes, e.g., during systolic and diastolic pressure cycles in a beating heart, the constant pressure change may affect the inflated balloon volume and its positioning to produce unsteady or undesirable conditions for optimal tissue imaging.

Accordingly, these types of imaging modalities are generally unable to provide desirable images useful for sufficient diagnosis and therapy of the endoluminal structure, due in part to factors such as dynamic forces generated by the natural movement of the heart. Moreover, anatomic structures within the body can occlude or obstruct the image acquisition process. Also, the presence and movement of opaque bodily fluids such as blood generally make in vivo imaging of tissue regions within the heart difficult.

Other external imaging modalities are also conventionally utilized. For example, computed tomography (CT) and magnetic resonance imaging (MRI) are typical modalities which are widely used to obtain images of body lumens such as the interior chambers of the heart. However, such imaging modalities fail to provide real-time imaging for intra-operative therapeutic procedures. Fluoroscopic imaging, for instance, is widely used to identify anatomic landmarks within the heart and other regions of the body. However, fluoroscopy fails to provide an accurate image of the tissue quality or surface and also fails to provide for instrumentation for performing tissue manipulation or other therapeutic procedures upon the visualized tissue regions. In addition, fluoroscopy provides a shadow of the intervening tissue onto a plate or sensor when it may be desirable to view the intraluminal surface of the tissue to diagnose pathologies or to perform some form of therapy on it.

Moreover, many of the conventional imaging systems lack the capability to provide therapeutic treatments or are difficult to manipulate in providing effective therapies. For instance, the treatment in a patient's heart for atrial fibrillation is generally made difficult by a number of factors, such as visualization of the target tissue, access to the target tissue, and instrument articulation and management, amongst others.

Conventional catheter techniques and devices, for example such as those described in U.S. Pat. Nos. 5,895,417; 5,941,845; and 6,129,724, used on the epicardial surface of the heart may be difficult in assuring a transmural lesion or complete blockage of electrical signals. In addition, current devices may have difficulty dealing with varying thickness of tissue through which a transmural lesion desired.

Conventional accompanying imaging devices, such as fluoroscopy, are unable to detect perpendicular electrode orientation, catheter movement during the cardiac cycle, and image catheter position throughout lesion formation. Without real-time visualization, it is difficult to reposition devices to another area that requires transmural lesion ablation. The absence of real-time visualization also poses the risk of incorrect placement and ablation of critical structures such as sinus node tissue which can lead to fatal consequences.

Thus, a tissue imaging system which is able to provide real-time in vivo access to and images of tissue regions within body lumens such as the heart through opaque media such as blood and which also provides instruments for therapeutic procedures such as ablation of the ostia around the pulmonary veins are desirable.

A tissue imaging and manipulation apparatus that may be utilized for procedures within a body lumen, such as the heart, in which visualization of the surrounding tissue is made difficult, if not impossible, by medium contained within the lumen such as blood, is described below. Generally, such a tissue imaging and manipulation apparatus comprises an optional delivery catheter or sheath through which a deployment catheter and imaging hood may be advanced for placement against or adjacent to the tissue to be imaged.

The deployment catheter may define a fluid delivery lumen therethrough as well as an imaging lumen within which an optical imaging fiber or electronic imaging assembly may be disposed for imaging tissue. When deployed, the imaging hood may be expanded into any number of shapes, e.g., cylindrical, conical, semi-spherical, etc., provided that an open area or field is defined by the imaging hood. The open area is the area within which the tissue region of interest may be imaged and which is also defined in part by the contacted tissue region as well. The imaging hood may also define an atraumatic contact lip or edge for placement or abutment, against the tissue region of interest. Moreover, the distal end of the deployment catheter or separate manipulatable catheters may be articulated through various controlling mechanisms such as push-pull wires manually or via computer control

The deployment catheter may also be stabilized relative to the tissue surface through various methods. For instance, inflatable stabilizing balloons positioned along a length of the catheter may be utilized, or tissue engagement anchors may be passed through or along the deployment catheter for temporary engagement of the underlying tissue.

In operation, after the imaging hood has been deployed, fluid may be pumped at a positive pressure through the fluid delivery lumen until the fluid fills the open, area completely and displaces any blood from within the open area. The fluid may comprise any biocompatible fluid, e.g., saline, water, plasma, Fluorinert™, etc., which is sufficiently transparent to allow for relatively undistorted visualization through the fluid. The fluid may be pumped continuously or intermittently to allow for image capture by an optional processor which may be in communication with the assembly.

The imaging hood, may be formed into any number of configurations and the imaging assembly may also be utilized with any number of therapeutic tools, such as tissue ablation instruments, which may be deployed through the deployment catheter. One particular variation may employ an imaging hood having a tissue anchor deployable therethrough and into a portion of a body lumen such as the pulmonary vein. Once the anchor has been temporarily deployed and secured within the pulmonary vein, the hood and ablation instrument may be articulated around a circumference of the vein ostium or several ostia where the tissue may be ablated in a controlled and consistent manner to electrically isolate the tissue such that a conduction block is created.

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