Surgery – Instruments – Internal pressure applicator
Reexamination Certificate
2000-12-20
2004-09-14
Milano, Michael J. (Department: 3731)
Surgery
Instruments
Internal pressure applicator
C606S200000
Reexamination Certificate
active
06790218
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device for filling an anatomical defect. In particular, the device of the present invention is formed of a member which includes a shape memory alloy.
BACKGROUND OF THE INVENTION
In various body tissues, defects may occur either congenitally or as a result of operative procedures. Such defects may include abnormal openings, for example, in the cardiovascular system including the heart. Procedures have been developed to introduce devices for closing such abnormal openings. Embolization, the therapeutic introduction of a substance into a vessel in order to occlude it, is a treatment used in cases such as patent ductus arteriosus (PDA), major aortopulmonary collateral arteries, pulmonary arteriovenous malformations, venovenous collaterals following venous re-routing operations, occlusion of Blalock-Taussig (BT) shunts, and occlusion of coronary arteriovenous (AV) fistulas.
For example, a PDA is a congenital defect, and thus is present at and exists from the time of birth. In this abnormality, a persistent embryonic vessel connects the pulmonary artery and the aorta, and intervention is usually required to effect closure. A cardiologist may employ a variety of coils for this purpose, the coils being delivered through a catheter and subsequently placed in the opening to permit proper physiological functioning. In some cases, several coils may be used to occlude the opening.
Another abnormality is an atrial septal defect (ASD), which is a defect in the wall of the heart, known as the septum, that separates the right atrium and left atrium. Such as hole in the septum often requires an invasive procedure for closure of the defect. Similarly, intervention is often required in the case of a ventricular septal defect (VSD), a hole in the wall separating the right and left ventricles.
The use of coils in the intracranial region of the brain for embolizing aneurysms or fistulas is also generally accepted.
Each one of the aforementioned exemplary closure applications requires a specially designed coil which may be introduced into the particular anatomical location. For example, the geometry of the lumen in instances of PDA often requires complicated positioning of the coil for proper functioning. Additionally, an initially indeterminate number of coils may be required to close a given defect, as the decision to deliver multiple coils to a particular defect site is governed by the success of any preceding delivery.
A variety of devices and materials have been used to occlude such abnormal channels. For example, U.S. Pat. No. 4,994,069 to Ritchart et al., the contents of which are herein incorporated by reference, discloses vaso-occulusion wire formed of platinum, tungsten, or gold thread. The wire is advanced through a catheter, and upon release from the catheter into a vessel, it assumes a randomly coiled shape. Although the wire of this development is described as having memory, the type of memory property of these materials is not that of a shape memory material having transition temperatures for various material states.
Additionally, U.S. Pat. No. 5,192,301 to Kamiyama et al., discloses a closing plug for closing a defect in a somatic wall. The plug is formed of a polymer such as polynorbornene, styrene-butadiene coploymer, polyurethane, or transpolyisoprene. Although these polymers are described as “shape memory” polymers, they are unlike metallic materials displaying shape memory behavior. Many polymers display a glass-transition temperature (T
g
) which represents a sharp change that occurs from a hard and glassy state to a rubbery, soft, or flexible thermoplastic state. If deformed by a load at a temperature below its T
g
, a so-called “shape memory” polymer may retain the deformation until heated above the T
g
, at which point the deformation and the original shape are recoverable. This characteristic of some polymers is often described as “elastic memory”.
A variety of other spring coil configurations have been used, although stainless steel and platinum have emerged as the most common materials. U.S. Pat. No. 5,649,949 to Wallace et al., discloses vosoocclusive coils formed from platinum, gold, rhodium, rhenium, palladium, tungsten, and alloys thereof. Wires formed of composites of these metals and polymers are also disclosed. These materials are inappropriate for the present development because they do not have the shape memory properties of materials such as nitinol. Among the several superior properties of nitinol when compared to stainless steel, the most important include strong physiological compatibility, a substantially lower modulus of elasticity, and a much greater tolerance to strain before the onset of permanent, plastic deformation. In fact, nitinol may have an elasticity an order of magnitude greater than that of stainless steel.
U.S. Pat. No. 5,645,558 to Horton discloses an occlusive device formed of super-elastic alloys, such as nitinol. The device is spherical in shape. U.S. Pat. No. 5,382,259 to Phelps et al. further discloses the use of nitinol shape memory wire to form coils. Fibers are also woven to the coils. These coils do not have the shape of the present development.
Various other coil configurations have been proposed. For example, as disclosed in U.S. Pat. No. 6,117,157 to Tekulve, a helically shaped embolization coil includes bent ends. In addition, U.S. Pat. No. 6,126,672 to Berryman et al. discloses a coil for occluding an intracranial blood vessel. The coil has an anchor in the shape of an “M” or “W” for contacting the blood vessel. The free legs of the anchor are blunted and reinforced to prevent perforation of the vessel wall.
The success and extent of coil usage may be partially gauged through analysis of the PDA coil registry, the largest database covering use of coils to occlude ducts, which surveys more than 500 cases. Among those included in the database, patients ranged in age from 15 days to 71 years, with a median of 4.2 years. The median PDA size was 2 mm, with a range of less than one to about 7 mm. The immediate complete occlusion rate was 75%, and partial occlusion or any degree of shunt occurred in about 25% of the cases. Failure to implant occurred in 5% of the cases. Coil embolization occurred in 9.7% of the cases involving the pulmonary artery, and in 2.4% of the cases involving the systemic artery.
Analysis of data from the coil registry has revealed that an acute occlusion rate and failure was significantly related to coil size. Shorter studies with longer follow up show a cumulative occlusion rate of 98%. While the registry does not address the overall success rate of closure of PDA-associated ducts greater than 4 mm in size because of the statistical limitations of the data set, the immediate results of procedures directed to large ducts are encouraging. Initial complete occlusion occurred in 84.2%, or 16 of 19 cases. In addition, small residual shunts which closed spontaneously or required a second procedure occurred in 10.5%, or 2 of 19 cases, and failure of the procedure necessitating further surgical intervention to effectuate closure occurred in only 5.5%, or 1 of 19 cases. Coil embolization occurred in 16.5%, or 3 of 19 cases, and left pulmonary artery stenosis occurred in 11%, or 2 of 19 cases. It should be noted, however, that left artery stenosis and failure of the procedure were associated with attempts on neonates and infants. Thus, the effectiveness of coils appears to be unquestionably demonstrated.
The device of the present development may be used in a variety of applications, including but not limited to pediatric cardiology procedures directed at occluding either congenital defects or defects arising during the growth process. As previously discussed, such defects include PDA, ASD, VSD, major aortopulmonary collateral arteries, pulmonary arteriovenous malformations, venovenous collaterals following venous re-routing operations, occlusion of Blalock-Taussig (BT) shunts, and occlusion of coronary arteriovenous (AV) fistulas. The device is also useful in tr
Baxter Jessica R
Bianco Paul D.
Fleit Martin
Fleit Kain Gibbons Gutman Bongini & Bianco
Milano Michael J.
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