Steerable catheter

Details Steerable catheter Steerable catheter

2000-07-21

2003-03-11

Casler, Brian L. (Department: 3763)

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

C604S523000, C604S095040

Reexamination Certificate

active

06530913

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to catheters and catheter procedures involving laser energy delivery using fiber optic and other laser delivery systems. More particularly, the invention relates to a steerable catheter and method of use, particularly adapted for laser-assisted transmyocardial revascularization (TMR). The distal tip of a central, hollow flexible center tube for guiding a laser delivery means or other functional device extendable therethrough is deflectable utilizing a semi rigid shim, the shim acted upon by a pull cable for controllably deflecting the distal tip of the steerable catheter in at least one given plane. The steerable catheter can be used in conjunction with a fiber or other laser delivery means advance mechanism, optionally using a depth control mechanism as well.
BACKGROUND OF THE INVENTION
In the treatment of heart disease, one method of improving myocardial blood supply is called transmyocardial revascularization (TMR), the creation of channels in the myocardium of the heart. The procedure using needles in a form of surgical “myocardial acupuncture” has been used clinically since the 1960s. Deckelbaum. L. I., Cardiovascular Applications of Laser Technology,
Lasers in Surgery and Medicine
15:315-341 (1994). The technique relieves ischemia by allowing blood to pass from the ventricle through the channels either directly into other vessels communicating with the channels or into myocardial sinusoids which connect to the myocardial microcirculation.
In the reptilian heart, perfusion occurs via communicating channels between the left ventricle and the coronary arteries. Frazier, O. H., Myocardial Revascularization with Laser—Preliminary Findings,
Circulation
, 1995; 92 [suppl II]:II-58-II-65. There is evidence of these communicating channels in the developing human embryo. In the human heart, myocardial microanatomy involves the presence of myocardial sinusoids. These sinusoidal communications vary in size and structure, but represent a network of direct arterial-luminal, arterial-arterial, arterial-venous, and venous-luminal connections. This vascular mesh forms an important source of myocardial blood supply in reptiles but its role in humans is poorly understood.
Numerous surgical TMR studies have been performed, including early studies using needles to perform myocardial acupuncture, or boring, to mechanically displace and/or remove tissue. Such studies have involved surgically exposing the heart and sequentially inserting needles to form a number of channels through the epicardium, myocardium, and endocardium to allow blood from the ventricle to perfuse the channels. The early studies using needles showed that the newly created channels were subject to acute thrombosis followed by organization and fibrosis of clots resulting in channel closure. Interest in TMR using needles waned with the knowledge that such channels did not remain open. However, interest in TMR procedures has recurred with the advent of medical lasers used to create TMR channels. Histological evidence of patent, endothelium-lined tracts within laser-created channels shows that the lumen of laser channels can become hemocompatible and resists occlusion. A thin zone of charring occurs on the periphery of the laser-created channels through the well-known thermal effects of optical radiation on cardiovascular tissue. Additionally, recent histological evidence shows probable new vessel formation adjacent collagen occluded transmyocardial channels, thereby suggesting benefits from TMR with or without the formation of channels which remain patent.
Surgical TMR procedures using laser energy have been described in the prior art. U.S. Pat. No. 4,658,817 issued Apr. 21, 1987 to Hardy teaches a method and apparatus for surgical TMR using a CO
2
laser connected to an articulated arm having a handpiece attached thereto. The handpiece emits laser energy from a single aperture and is moved around the surface of the heart to create the desired number of channels. U.S. Pat. No. 5,380,316 issued Jan. 10, 1995 to Aita et al. purports to teach the use of a flexible lasing apparatus which is inserted into the open chest cavity in a surgical procedure. A lens at the distal end of the flexible apparatus is used to focus laser energy, and the apparatus is moved about the surface of the heart to create the desired number of channels.
The foregoing discussion relates to surgical procedures, i.e. procedures which access the heart surgically, either via open heart surgery, or perhaps by minimally invasive surgical (MIS) methods if the design and size of the distal ends of the hand pieces are suitable for use in an MIS site. However, since TMR most often involves creating channels through the endocardium into the lower left chamber of the heart, it is desirable to create TMR channels in a percutaneous procedure, i.e. by extending a catheter apparatus through the vasculature into the ventricle and creating the channels through endocardial surfaces and into myocardium. Performing such percutaneous TMR is desirable for a number of reasons. Percutaneous catheter procedures are typically less traumatic to the patient compared to surgical procedures. Adhesions between the pericardial sac and epicardium are eliminated. Percutaneous TMR with a catheter apparatus also offers an alternative solution to persons who are not candidates for surgical procedures.
Because TMR procedures generally involve creating a plurality of channels within the myocardium, performing the procedure percutaneously requires the ability to steer a catheter apparatus through the vasculature and maneuver the apparatus within the ventricle of the beating heart as rapidly as possible to create the channels without subjecting the heart to the undue stress of a lengthy procedure. Additionally, the ability to control and stabilize the catheter apparatus against the beating heart wall while creating channels with a laser is desirable for percutaneous procedures to ensure creation of channels as desired and to ensure that the laser is fired only within the myocardial tissue. MR channels should be spaced and grouped appropriately to achieve the desired result without weakening or rupturing the heart muscle.
The early myocardial acupuncture procedures were not performed percutaneously. The Hardy CO
2
laser delivery system described above is rigid, relatively large, and not adaptable for percutaneous use. The Aita '316 patent does not suggest a method for percutaneous use of the laser delivery device described therein for surgical use.
U.S. Pat. No. 5, 389,096 issued Feb. 14, 1995 to Aita et al. purports to teach one method of percutaneous TMR using an elongated flexible lasing apparatus with control lines and a focusing lens structure at the distal tip. However, the method uses pressure applied manually to attempt to stabilize the apparatus against the wall of the heart, and no central, hollow passageway is described. No handle structure, modular or otherwise, is described nor are deflection, deflection components or a floating center tube.
Several prior art patents describe the use of catheters within the ventricle for percutaneous treatment of ventricular tachycardia. Such devices have a means to locate an arrhythmia site and ablate the site, at or just below the ventricle surface, using an electrode device or laser energy. U.S. Pat. No. 5,104,393 issued Apr. 14, 1992 to Isner teaches a catheter apparatus having a guiding Y-shaped sheath and guide catheter assembly for introducing an optical fiber into the ventricle. Positioning is described to enable a single burst of laser energy from a single aperture to ablate the site. However, positioning or specific steering means sufficient to create one or more TMR channels is not described or suggested.
U.S. Pat. Nos. 5,255,679 issued Oct. 26, 1993 and 5,465,717 issued Nov. 14, 1995 to, respectively, Imran and Imran et al., disclose non-laser, basket-shaped catheter apparatus for mapping and/or ablation of arrhythmia sites within the ventricle. A pull cable

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