Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2002-04-25
2004-04-20
Getzow, Scott M. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06725092
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to tissue and organ stimulating and sensing devices, and more particularly, to a medical adapter for providing connectivity between a cardiac pacer and associated pacer leads and for controlling the operation of the cardiac pacer. The present invention also relates to a medical adapter capable of sending stimulating signals to and receiving sensing signals from a patient's heart.
BACKGROUND OF THE PRESENT INVENTION
Cardiac pacers, which provide stimulation to a patient's heart, by means of amplitude and frequency modulated electrical pulses, have been developed for permanent or temporary applications. The two most common types of cardiac pacers currently in use are pacemakers and implantable cardioverter-defibrillators (ICD). Cardiac pacers can be implanted in a suitable location inside the patient's body or located outside the patient's body. Cardiac pacers operate with one or more conductive leads, which carry stimulating, low voltage electrical pulses, generated by the pacer, to selected sites within the patient's heart, to communicate sensing signals from those sites back to the cardiac pacer, and to carry high energy pulses, generated by an ICD, to defibrillate the heart, if required.
Furthermore, it is often necessary to provide stimulation of a patient's heart using a cardiac pacer located outside the patient's body or to provide temporary stimulation of the patient's heart.
Such is the case, when a physician might want to try more than one cardiac pacer before selecting the most appropriate one for permanent implantation. To enable the physician to try more than one cardiac pacer before selecting the most appropriate one for permanent implantation, medical cardiac adapters have been developed. These adapters allow a physician to connect various pacers to the patient's hearts via implanted leads wherein the various pacers may have different interfaces for connecting to the leads. The adapters provide the universal interface between the implanted leads and the pacer so as to provide interchangeability between the pacers. Examples of such previously proposed adapters are disclosed in the following patents.
The Bourney et al. Patent (U.S. Pat. No. 4,545,381) discloses and claims an adapter for converting an implantable cardiac pacer to an externally worn cardiac pacer. This adapter provides a housing to which a cardiac pacer can be secured. It also provides compatibility with a plurality of cardiac pacers.
The Fain et al. Patent (U.S. Pat. No. 5,679,026) discloses and claims a header adapter, which is designed to fit onto the header and case of a cardiac pacer. This header adapter provides a plurality of lead connector configurations, thereby allowing the use of different types of leads and compatibility between leads and cardiac pacers from different manufacturers.
It is also often necessary to maintain proper stimulation of a patient's heart with an external pacer while the patient is undergoing medical procedures. However, certain medical procedures, such as Magnetic Resonance Imaging (MRI), can interfere with the proper stimulation of a patient's heart with an external pacer and implanted leads.
MRI is an imaging technique adapted to obtain both images of anatomical features of human patients as well as some aspects of the functional activities of biological tissue. These images have medical diagnostic value in determining the state of the health of the tissue examined.
In an MRI procedure, a patient is typically aligned to place the portion of the patient's anatomy to be examined in the imaging volume of the MRI apparatus. Such an MRI apparatus typically comprises a primary magnet for supplying a constant magnetic field (B
0
) which, by convention, is along the z-axis and is substantially homogeneous over the imaging volume and secondary magnets that can provide linear magnetic field gradients along each of three principal Cartesian axes in space (generally x, y, and z, or x
1
, x
2
and x
3
, respectively). A magnetic field gradient (B
0
/ x
i
) refers to the variation of the field along the direction parallel to B
0
with respect to each of the three principal Cartesian axes, x
i
. The apparatus also comprises one or more RF (radio frequency) coils which provide excitation and detection of the MRI signal.
The use of MRI with patients who require medical assist devices, such as external cardiac assist devices or other external medical assist devices that also utilize implanted leads to stimulate a certain tissue region or organ, often presents problems. As is known to those skilled in the art, devices such as pulse generators (IPGs) and cardioverter/defibrillator/pacemakers (CDPs) are sensitive to a variety of forms of electromagnetic interference (EMI) because these enumerated devices include sensing and logic systems that respond to low-level electrical signals emanating from the monitored tissue region of the patient. Since the sensing systems and conductive elements of these devices are responsive to changes in local electromagnetic fields, the devices are vulnerable to external sources of severe electromagnetic noise, and in particular, to electromagnetic fields emitted during the MRI procedure. Thus, patients with such devices are generally advised not to undergo MRI procedures.
To more appreciate the problem, the use of a cardiac assist device during a MRI process will be briefly discussed.
The human heart may suffer from two classes of rhythmic disorders or arrhythmias: bradycardia and tachyarrhythmia. Bradycardia occurs when the heart beats too slowly, and may be treated by a common pacemaker delivering low voltage (about 3 V) pacing pulses having a duration of about 1 millisecond.
The common pacemaker operates in conjunction with one or more electrically conductive leads, adapted to conduct electrical stimulating pulses to sites within the patient's heart, and to communicate sensed signals from those sites back to the device.
Furthermore, the common pacemaker typically has a metal case and a connector block mounted to the metal case that includes receptacles for leads which may be used for electrical stimulation or which may be used for sensing of physiological signals. Electrical interfaces are employed to connect the leads outside the metal case with the medical device circuitry and the battery inside the metal case.
Electrical interfaces serve the purpose of providing an electrical circuit path extending from the interior of a sealed metal case to an external point outside the case while maintaining the seal of the case. A conductive path is provided through the interface by a conductive pin that is electrically insulated from the case itself.
Such interfaces typically include a ferrule that permits attachment of the interface to the case, the conductive pin, and a hermetic glass or ceramic seal that supports the pin within the ferrule and isolates the pin from the metal case.
A common pacemaker can, under some circumstances, be susceptible to electrical interference such that the desired functionality of the pacemaker is impaired. For example, common pacemaker requires protection against electrical interference from electromagnetic interference (EMI), defibrillation pulses, electrostatic discharge, or other generally large voltages or currents generated by other devices external to the medical device. As noted above, more recently, it has become crucial that cardiac assist systems be protected from intense magnetic and radio frequency (RF) fields associated with MRI.
Such electrical interference can damage the circuitry of the cardiac assist systems or cause interference in the proper operation or functionality of the cardiac assist systems. For example, damage may occur due to high voltages or excessive currents introduced into the cardiac assist system.
Therefore, it is required that such voltages and currents be limited at the input of such cardiac assist systems, e.g., at the interface. Protection from such voltages and cu
Helfer Jeffrey L.
MacDonald Stuart G.
Weiner Michael L.
Basch & Nickerson LLP
Biophan Technologies Inc.
Getzow Scott M.
Nickerson Michael J.
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