Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
1996-11-18
2001-06-05
Casler, Brian L. (Department: 3737)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C600S373000, C607S122000
Reexamination Certificate
active
06241754
ABSTRACT:
FIELD OF THE INVENTION
In a general sense, the invention is directed to systems and methods for creating lesions the interior regions of the human body. In a more particular sense, the invention is directed to systems and methods for ablating heart tissue for treating cardiac conditions.
BACKGROUND OF THE INVENTION
Normal sinus rhythm of the heart begins with the sinoatrial node (or “SA node”) generating an electrical impulse. The impulse usually propagates uniformly across the right and left atria and the atrial septum to the atrioventricular node (or “AV node”). This propagation causes the atria to contract.
The AV node regulates the propagation delay to the atrioventricular bundle (or “HIS” bundle). This coordination of the electrical activity of the heart causes atrial systole during. ventricular diastole. This, in turn, improves the mechanical function of the heart.
Atrial geometry, atrial anisotropy, and histopathologic changes in the left or right atria can, alone or together, form anatomical obstacles. The obstacles can disrupt the normally uniform propagation of electrical impulses in the atria. These anatomical obstacles (called “conduction blocks) can cause the electrical impulse to degenerate into several circular wavelets that circulate about the obstacles. These wavelets, called “reentry circuits,” disrupt the normally uniform activation of the left and right atria. Abnormal, irregular heart rhythm, called arrhythmia, results. This form of arrhythmia is called atrial fibrillation, which is a very prevalent form of arrhythmia.
Today, as many as 3 million Americans experience atrial fibrillation. These people experience an unpleasant, irregular heart beat. Because of a loss of atrioventricular synchrony, these people also suffer the consequences of impaired hemodynamics and loss of cardiac efficiency. They are more at risk of stroke and other thromboembolic complications because of loss of effective contraction and atrial stasis.
Treatment is available for atrial fibrillation. Still, the treatment is far from perfect.
For example, certain antiarrhythmic drugs, like quinidine and procainamide, can reduce both the incidence and the duration of atrial fibrillation episodes. Yet, these drugs often fail to maintain sinus rhythm in the patient.
Cardioactive drugs, like digitalis, Beta blockers, and calcium channel blockers, can also be given to control the ventricular response. However, many people are intolerant to such drugs.
Anticoagulant therapy also combat thromboembolic complications.
Still, these pharmacologic remedies often do not remedy the subjective symptoms associated with an irregular heartbeat. They also do not restore cardiac hemodynamics to normal and remove the risk of thromboembolism.
Many believe that the only way to really treat all three detrimental results of atrial fibrillation is to actively interrupt all the potential pathways for atrial reentry circuits.
James L. Cox, M.D. and his colleagues at Washington University (St. Louis, Mo.) have pioneered an open heart surgical procedure for treating atrial fibrillation, called the “maze procedure.” The procedure makes a prescribed pattern of incisions to anatomically create a convoluted path, or maze, for electrical propagation within the left and right atria, therefore its name. The incisions direct the electrical impulse from the SA node along a specified route through all regions of both atria, causing uniform contraction required for normal atrial transport function. The incisions finally direct the impulse to the AV node to activate the ventricles, restoring normal atrioventricular synchrony. The incisions are also carefully placed to interrupt the conduction routes of the most common reentry circuits.
The maze procedure has been found very effective in curing atrial fibrillation. Yet, despite its considerable clinical success, the maze procedure is technically difficult to do. It requires open heart surgery and is very expensive. Because of these factors, only a few maze procedures are done each year.
One objective of the invention is to provide catheter-based ablation systems and methods providing beneficial therapeutic results without requiring invasive surgical procedures.
Another objective of the invention is to provide systems and methods that simplify the creation of complex lesions patterns in body tissue, such as in the heart.
SUMMARY OF THE INVENTION
The invention provides new methods and structures for creating specially shaped lesions in heart tissue.
One aspect of the invention provides a method of ablating tissue in the heart to treat atrial fibrillation by introducing into a selected atrium an elongated energy emitting element that can be flexed along its length from a generally straight shape into a variety of curvilinear shapes. The method exposes the element to a region of the atrial wall while flexing the element into a desired shape. The method applies ablating energy to the element to thermally destroy tissue, forming an elongated lesion having a contour that follows the flexure of the element. The method repeats the tissue exposure, element flexing and energy application steps at different spaced regions along the atrial wall. In this way, the method forms a convoluted lesion pattern comprising elongated straight lesions and elongated curvilinear lesions. The pattern directs electrical impulses within the atrial myocardium along a path that activates the atrial myocardium while interrupting reentry circuits that, if not interrupted, would cause fibrillation.
In a preferred embodiment, the method introduces the element through a vascular approach, without opening the heart. In this embodiment, the method applies radiofrequency electromagnetic energy to ablate the tissue.
Another aspect of the invention provides a method of ablating tissue in the heart to treat atrial fibrillation that introduces into a selected atrium an energy emitting element comprising a three-dimensional array of longitudinal main splines. The main splines extend in a circumferentially spaced relationship to form a basket.
According to this aspect of the invention, one or more transverse bridge splines periodically span adjacent main splines. At least some of the main splines have elongated regions of energy emitting material longitudinally spaced among regions of non-energy emitting material. At least one of the bridge splines also has a region of energy emitting material that intersects a region of energy emitting material on a main spline.
According to this aspect of the invention, the method exposes the element to the atrial wall. The method applies ablating energy simultaneously to at least some of the energy emitting regions of the element to thermally destroy tissue. The applied ablating energy forms a convoluted lesion pattern comprising elongated straight and elongated curvilinear lesions. The pattern directs electrical impulses within the atrial myocardium along a path that activates the atrial myocardium while interrupting reentry circuits that, if not interrupted, would cause fibrillation.
In one embodiment, the method introduces into the selected atrium a second elongated energy emitting element that can be flexed along its length from a generally straight shape into a variety of curvilinear shapes. The method exposes the second element to a region of the atrial wall at selected parts of the convoluted lesion pattern, while flexing the element into a desired shape. The method applies ablating energy to the second element to thermally destroy tissue to form an elongated lesion having a contour that follows the flexure of the element. This contoured lesion becomes a part of the convoluted lesion pattern.
In a preferred embodiment, the method introduces the three-dimensional element in a collapsed condition through a vascular approach, without opening the heart. The method returns the element to its three-dimensional shape before exposing it to the atrial wall. In this arrangement, the method applies radiofrequency electromagnetic energy to ablate the tissue.
Another aspect of the invention prov
Fleischman Sidney D.
Kordis Thomas F.
McGee David L.
Swanson David K.
Casler Brian L.
EP Technologies, Inc.
Henricks Slavin & Holmes LLP
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