Surgery – Miscellaneous – Methods
Reexamination Certificate
1999-11-15
2002-11-05
Peffley, Michael (Department: 3739)
Surgery
Miscellaneous
Methods
C606S046000, C607S122000
Reexamination Certificate
active
06474340
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the diagnosis and treatment of electrophysiological diseases of the heart, and more specifically to devices and methods for epicardial mapping and ablation for the treatment of atrial fibrillation.
BACKGROUND OF THE INVENTION
Atrial fibrillation results from disorganized electrical activity in the heart muscle, or myocardium. The surgical maze procedure has been developed for treating atrial fibrillation and involves the creation of a series of surgical incisions through the atrial myocardium in a preselected pattern so as to create conductive corridors of viable tissue bounded by scar tissue. While very effective in treating atrial fibrillation, the maze procedure is highly invasive, high in moribidity and mortality, and difficult to perform by even the most skilled surgeons. The procedure not only requires a median sternotomy or other form of gross thoracotomy for access to the heart, but requires stopping the heart and establishing cardiopulmonary bypass, to which a significant part of the trauma, morbidity and mortality of the maze procedure may be attributed.
As a less invasive alternative to the surgical incisions used in the maze procedure, transmural ablation of the heart wall has been proposed. Such ablation may be performed either from within the chambers of the heart (endocardial ablation) using endovascular devices (e.g. catheters) introduced through arteries or veins, or from outside the heart (epicardial ablation) using devices introduced into the chest through surgical incisions. Various ablation technologies have been proposed, including cryogenic, radiofrequency (RF), laser and microwave. The ablation devices are used to create elongated transmural lesions—that is, lesions extending through a sufficient thickness of the myocardium to block electrical conduction—which form the boundaries of the conductive corridors in the atrial myocardium. Perhaps most advantageous about the use of transmural ablation rather than surgical incisions is the ability to perform the procedure on the beating heart without the use of cardiopulmonary bypass.
In performing the maze procedure and its variants, whether using ablation or surgical incisions, it is generally considered most efficacious to include a transmural incision or lesion that isolates the pulmonary veins from the surrounding myocardium. The pulmonary veins connect the lungs to the left atrium of the heart, and join the left atrial wall on the posterior side of the heart. This location creates significant difficulties for endocardial ablation devices for several reasons. First, while many of the other lesions created in the maze procedure can be created from within the right atrium, the pulmonary venous lesions must be created in the left atrium, requiring either a separate arterial access point or a transeptal puncture from the right atrium. Second, the elongated and flexible endovascular ablation devices are difficult to manipulate into the complex geometries required for forming the pulmonary venous lesions and to maintain in such positions against the wall of the beating heart. This is very time-consuming and can result in lesions which do not completely encircle the pulmonary veins or which contain gaps and discontinuities. Third, visualization of endocardial anatomy and endovascular devices is often inadequate and knowing the precise position of such devices in the heart can be difficult, resulting in misplaced lesions. Fourth, ablation within the blood inside the heart can create thrombus which, in the right chambers, is generally filtered out by the lungs rather than entering the bloodstream. However, on the left side of the heart where the pulmonary venous lesions are formed, thrombus can be carried by the bloodstream into the coronary arteries or the vessels of the head and neck, potentially resulting in myocardial infarction, stroke or other neurologic sequelae. Finally, the heat generated by endocardial devices which flows outward through the myocardium cannot be precisely controlled and can damage extracardiac tissues such as the pericardium, the phrenic nerve and other structures.
If, on the other hand, epicardial ablation devices are utilized to form the pulmonary venous lesions, other challenges are presented. First, the posterior location of the pulmonary veins is extremely difficult to access through thoracic incisions without gross manipulations of the heart. Such manipulations are not generally possible if minimally-invasive techniques are being utilized via small thoracic access ports, or if the procedure is being performed on a beating heart without cardiopulmonary bypass. Further complicating epicardial access are the pericardial reflections, where the pericardium attaches to the heart wall near the pulmonary veins. The pericardial reflections are located so as to prohibit positioning a device completely around the pulmonary veins without cutting away or puncturing through the reflections. Such cutting or puncturing of the pericardial reflections is risky and difficult, particularly if working through small incisions in the chest without a clear view and open access to the posterior side of the heart. Furthermore, surgical repair of any damaged tissue is almost impossible without highly invasive open heart surgery.
What are needed, therefore, are devices and methods for forming transmural lesions that isolate the pulmonary veins from the surrounding myocardium which overcome these problems. The devices and methods will preferably be utilized epicardially to avoid the need for access into the left chambers of the heart and to minimize the risk of producing thrombus. The devices and methods should be useful through small access ports in the chest using minimally invasive techniques. The devices and methods will preferably avoid the need for cutting or puncturing the pericardial reflections, however, the pericardial reflections may be cut without departing from the scope of the invention. The devices and methods should further be useful on the beating heart without requiring the use of cardiopulmonary bypass and should not require significant manipulation or retraction of the heart.
SUMMARY OF THE INVENTION
The present invention meets these and other objectives by providing epicardial ablation devices and methods useful for creating transmural lesions that electrically isolate the pulmonary veins for the treatment of atrial fibrillation. The devices and methods may be utilized through a small access port in the chest, preferably through a subxiphoid penetration, and positioned within the pericardium and around the pulmonary veins. Advantageously, the devices and methods do not require the large thoracic incision used in the conventional maze procedure, and may be used on the beating heart without cardiopulmonary bypass. By eliminating the need for ablation within the left atrium, the risk of thrombus formation is minimized. The devices and methods of the invention are more easily visualized, faster to use, and more accurately positionable than known cardiac ablation catheters and devices, enable the formation of continuous, uninterrupted lesions around the pulmonary veins, and protect extracardiac tissues from injury.
In a first embodiment, a method of forming a transmural lesion in a wall of the heart adjacent to the pulmonary veins comprises the steps of placing at least one ablation device through a thoracic incision and through a pericardial penetration so that the at least one ablation device is disposed in contact with an epicardial surface of the heart wall; positioning the at least one ablation device adjacent to the pulmonary veins on a posterior aspect of the heart while leaving the pericardial reflections intact; and transmurally ablating the heart wall with the at least one ablating device to create at least one transmural lesion adjacent to the pulmonary veins. The ablation device is preferably placed through a small puncture, incision, or access port in the chest, either between the ribs or in a subxiphoid position, for minim
Anderson Scott C.
Gallup David A.
Pless Benjamin
Richman Roxanne L.
Ulstad, Jr. Jack E.
Epicor, Inc.
Hoekendijk & Lynch, LLP
Peffley Michael
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