A wide variety of diseases and maladies can be treated by surgical intervention. Increasingly, however, less invasive procedures are sought to achieve similar objectives while reducing risks and recovery time associated with more traditional surgical approaches. For example, a variety of thoracic surgical procedures, such as treatment of aortic aneurysms and arterial stenosis, were traditionally performed via a gross thoracotomy. Less invasive procedures, such as balloon-expanded stents and PTCA, have been developed which avoid the need for a gross thoracotomy, requiring instead only a small incision to gain access to the thoracic cavity intravascularly or through an intercostal opening.
Cardiac arrhythmias present a significant health problem. Cardiac arrhythmias include ventricular tachycardias, supra ventricular tachycardias, and atrial fibrillation. Of these, atrial fibrillation is the most common cardiac arrhythmia. It has been estimated that over one million people in the United States alone suffer from atrial fibrillation. Incidence of atrial fibrillation is expected to increase over the next several decades as populations in the United States and Europe trend older because atrial fibrillation tends to become more common with increasing age.
Atrial fibrillation may be treated with medication intended to maintain normal sinus rhythm and/or decrease ventricular response rates. Not all atrial fibrillation may be successfully managed with medication, though. A surgical approach was developed to create an electrical maze in the atrium with the intention of preventing the atria from fibrillating. Known, appropriately, as the “maze” procedure, this technique involves making atrial incisions which interrupt pathways for reentry circuits which can cause atrial fibrillation and instead direct the cardiac electrical impulse through both atria before allowing the signal to activate the ventricles. As a result, virtually the entire atrial myocardium, with the exception of the atrial appendages and the pulmonary veins, can be electrically activated. The maze procedure is very effective in reducing or eliminating atrial fibrillation. Unfortunately, the procedure is difficult to perform and has traditionally required a gross thoracotomy and cardiopulmonary bypass to permit the surgeon appropriate access to the patient's heart.
Several less invasive techniques have been proposed for achieving a similar maze-like effect in the atrial myocardium without requiring direct surgical intervention. For example, U.S. Pat. No. 6,267,760 (Swanson) and U.S. Pat. No. 6,237,605 (Vaska et al.), both of which are incorporated entirely herein by reference, suggest RF ablation devices intended to ablate cardiac tissue and create atrial myocardial lesions to achieve much the same purpose as the surgical incisions of the standard maze procedure. U.S. Pat. No. 6,161,543 (Cox et al.), which is also incorporated entirely herein by reference, suggests that a cryogenic probe be employed to freeze tissue instead of using the RF ablation devices to heat tissue. Each of these approaches leaves something to be desired, however.