Surgery – Miscellaneous – Devices placed entirely within body and means used therewith
Reexamination Certificate
2002-06-14
2003-08-12
Gilbert, Samuel G. (Department: 3736)
Surgery
Miscellaneous
Devices placed entirely within body and means used therewith
C600S017000, C600S016000
Reexamination Certificate
active
06604529
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of artificially assisting heart function. More particularly, the invention relates to a device and a method for electromagnetically assisting the function of the ventricles in the heart.
2. Description of the Related Art
Despite the significant progress in prevention and medical treatment of cardiovascular disease, congestive heart failure (CHF) affects about 1 percent of adults in the United States (i.e. approximately 4-5 million patients), with 400,000 new cases occurring each year. CHF is the primary diagnosis for about 1 million hospitalizations each year and is a contributing factor in over 250,000 deaths annually. The age-adjusted death rate from CHF is 106.4 per 100,000. The median survival, after diagnosis, is 1.7 years for men and 3.2 years for women; the five year survival rate is less than 50 percent. It is estimated that nearly 60,000 patients annually in the United States could benefit from heart transplantation or long-term mechanical support. Evaluation and care of CHF patients costs our society in excess of $11 billion each year.
Currently, heart transplantation is considered the most effective therapy for end-stage CHF. However, heart transplantation presents multiple problems, including: (1) a shortage of donor hearts; (2) a significant perioperative morbidity/mortality rate; (3) the requirement of immune suppression; and (4) a less than ideal long-term survival rate. Accordingly, there is a crucial need for the development of alternatives to heart transplantation.
Mechanical support by means of implantable ventricular assist devices presently is the most promising alternative to heart transplantation. Currently available assist devices include extracorporeal oxygenators, univentricular and biventricular extracorporeal devices, and total artificial hearts. Most of these devices require the patients to be connected to cumbersome drive systems which makes their use limited only to hospital in-patients.
Lately, the development of an implantable left ventricular assist device (LVAD) and the development of wearable power supplies for this device has made the following possible: (1) a patient's rehabilitation; (2) unrestricted patient mobility; (3) patient discharge to the home; and (4) a patient's ability to return to work. However, while an LVAD may have some advantages over heart transplantation, an LVAD still presents many serious limitations for long-term use. These limitations include: (1) selection of patients (i.e., an LVAD is only available to patients without end-organ failure and qualification for an LVAD is as restricted as heart transplantation); (2) an LVAD is unavailable for patients on long-term glucocorticoid therapy or patients with a small body surface area; (3) it is difficult to assess a patient's ability to manage an LVAD; (4) early post-operative complications such as bleeding, right heart failure, air embolism, and multiple organ failure are possible; and (5) late post-operative complications such as infection, thromboembolism. In addition, most LVADs are designed to assist systolic pumping ability only whereas impairment of diastolic relaxation ability is a major component of CHF.
For these and other reasons, a new device is needed which can assist systolic and diatolic function of the ventricles, which is available to a wide variety of patients, and which does not cause at least some of the early and late post-operative complications previously mentioned.
SUMMARY OF THE INVENTION
A virtual ventricular assist device (VVAD), herein disclosed, is designed to overcome many of the aforementioned limitations of an LVAD. For long-term use, the VVAD: (1) can assist systolic pumping and diastolic relaxation of CHF patients without structural defects (i.e., congenital or acquired valvular diseases); (2) requires no major surgery to implant and, therefore, avoids the early complications mentioned above; (3) requires no foreign materials to interact with the surface of the ventricular cavity or conduit vessels and, therefore, avoids the late complications mentioned above; (4) can be used for the right as well as the left ventricle; and (5) eliminates the need for anticoagulants.
The VVAD consists of essentially two components: (a) implantable magnetic pellets implanted through a delivery catheter; and (b) an external electromagnetic device which, when cyclically charged, attracts or repels the pellets depending on their corresponding charge. The term “pellet” is not to be limited to ball shaped materials; it is to be construed to include many other shapes including that of a plate or umbrella. Moreover, the pellets are “magnetic” in the sense that they react to magnetic fields in a manner similar to metals due to the presence of free electrons which orient themselves in response to a magnetic field; the pellets themselves are not charged.
The implantable pellets are spring-winged, contain materials which are responsive to magnetic fields, and are vacuum-sealed within a polyurethane membrane (or any other biologically inert, synthetic material). The pellets have a myocardial wall contact portion to which a plurality of wings is hingedly connected. Preferably, the pellets are deployed percutaneously to the mid-layer of the targeted myocardial wall through a major artery using a delivery catheter. It is also possible to implant the pellets through the chest wall and into a mid-layer of the targeted myocardium; this transthoracic implantation requires a minimally invasive surgical procedure using a thoracic endoscope. It is also possible to fix the pellets to the outside of the myocardial wall. Pellets made of diamagnetic metals (e.g., bismuth or antimony) are implanted in or on the posterior wall of the left ventricle (LV) whereas pellets made of ferromagnetic metals (e.g., iron or cobalt) are implanted in or on the anterior wall of the left ventricle. The shape of the pellet will depend on the location in which they are fixed and by the method by which they are introduced into the ventricle. For example, in a transthoracic approach, the implantable magnetic pellets can be plate shaped or umbrella shaped like a shell so that they can be implanted on the surface of the targeted myocardium.
The external electromagnetic device (which is battery operated and light enough to be worn in the chest wall) generates an electromagnetic force which is synchronized with an EKG, at least one lead of which monitors the user's heart rate. This electromagnetic device may be external or internal to the chest wall. Onset of the force corresponds to the EKG's R wave whereas offset of the force corresponds to the EKG's T wave. Due to the charge of the electromagnetic field, pellets implanted in the posterior wall of the left ventricle will be pulled toward the electromagnetic device while the pellets in the anterior wall of the left ventricle will be correspondingly pushed away from the electromagnetic device. Due to this opposite motion, a compression of the left ventricle occurs. When the electromagnetic field is discontinued (due to the occurrence of the EKG T wave), the anterior and posterior walls of the left ventricle (which hold the magnetic pellets) return to their original positions. In this fashion, a cyclical compression of the left ventricle occurs thereby allowing the left ventricle to beat as if it were normal and healthy. This synchronized generation of electromagnetic force is designed to boost systolic pumping only during the early half of systole. Moreover, the magnitude of the electromagnetic force generated and its domain are adjusted to boost systolic function by 10-20 percent.
Pellets are implanted into the myocardium after being introduced into the body via a delivery catheter. The delivery catheter contains a mobile electromagnetic rod which is approximately 7 mm in length. The delivery catheter (preferably size 7 FOD, 120 cm) can be introduced into the body by means of a introducer catheter set which can be any commercially
Foley & Lardner
Gilbert Samuel G.
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