Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1999-05-26
2001-10-16
Layno, Carl (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S001000, C607S009000
Reexamination Certificate
active
06304777
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to invasive devices and methods for treatment of the heart, and specifically to devices and methods for controlling the heart muscle during surgery.
BACKGROUND OF THE INVENTION
Induction of cardioplegia is known in the art as a means for the temporary and elective stopping of cardiac activity by injection of chemicals, selective hypothermia, mechanical stabilization, or electrical stimuli. It is most commonly used in preparation for cardiac surgery.
PCT patent application PCT/IL97/00012, published as WO 97/25098, to Ben-Haim et al., which is incorporated herein by reference, describes methods for modifying the force of contraction of at least a portion of a heart chamber by applying a non-excitatory electrical signal to the heart at a delay after electrical activation of the portion. The signal may be applied in combination with a pacemaker or defibrillator, which also applies an excitatory signal (i.e., pacing or defibrillation pulses) to the heart muscle.
PCT patent application PCT/IL97/00236, which is also incorporated herein by reference, describes a pacemaker that modifies cardiac output. This pacemaker applies both excitatory (pacing) and non-excitatory electrical signals to the heart. By applying non-excitatory signals of suitable strength, appropriately timed with respect to the heart's electrical activation, the contraction of selected segments of the heart muscle can be increased or decreased, thus increasing or decreasing the stroke volume of the heart. The PCT application suggests that pacing electrodes may be placed in two, three or all four chambers of the heart, in accordance with methods of multi-chamber pacing known in the art.
U.S. Pat. No. 5,651,378 to Matheny et al., and an article entitled, “Vagus Nerve Stimulation as a Method to Temporarily Slow or Arrest the Heart,” by Matheny and Shaar,
Annals of Thoracic Surqery
, 63 (6) Supplement (June 1997), pp. S28-29, which are both incorporated herein by reference, describe a method to stimulate the vagus nerve in order to slow or stop a patient's heart during coronary artery bypass grafting surgery. While these methods describe electrically-stimulating the vagus nerve, they are, overall, substantially similar to chemical means of inducing cardioplegia, and are therefore characterized by a generally slow time constant following application and removal of the vagal nerve stimulation.
SUMMARY OF THE INVENTION
It is an object of some aspects of the present invention to provide improved methods and apparatus for regulating motion of the heart.
It is a further object of some aspects of the present invention to provide improved methods and apparatus for reducing motion of the heart during open-heart surgery.
In preferred embodiments of the present invention, an electrical cardiac stimulator for inducing cardioplegia comprises one or more electrodes, placed at multiple sites in or on the heart of a patient, and an electrical control unit. The control unit administers a signal comprising a sequence of pulses to at least one of the electrodes in order to reduce or substantially stop motion of the heart for the duration of signal application. Termination of signal application allows the heart to resume normal beating. Preferably, the level of paralysis of the heart produced during the pulse application is sufficiently complete to allow a surgeon to perform open-heart surgery or minimally-invasive surgery on the substantially non-moving heart. Further preferably, the high rate of response of the heart to application and termination of the signal enables the surgeon to perform the surgery without using cardiopulmonary bypass. Still further preferably, termination of signal application is not characterized by fibrillation of the heart. Fibrillation, in the context of the present patent application, refers to the disorganized, rapid, and agitated contraction of fibrils of a muscle, and is not generally characterized by spontaneous recovery.
Preferably, the signal comprises a sequence of rapid pacing pulses, applied through one or more of the electrodes, in order to induce a state of generally constant contraction of most or substantially all of the heart muscle. For example, a plurality of endocardial electrodes may be used to apply a signal above 5 Hz to the heart, in order to induce cardioplegia.
Typically, short periods of pulse application are separated by longer periods wherein cardioplegia is not induced. Preferably, the durations of the pulse application and non-application periods are set to maximize the surgeon's time for performing surgery, while continuing to generally assure that the patient's systemic oxygen needs are satisfied.
In some preferred embodiments of the present invention, at least some of the electrodes are placed at multiple sites on the epicardium and/or endocardium of the left and right ventricles. Alternatively or additionally, some of the electrodes are trans-venous and/or trans-arterial electrodes, and are typically inserted through a catheter into epicardial or other blood vessels in a vicinity of the heart.
Typically, each electrode coupled to the control unit conveys a particular waveform to the heart, which may differ in certain aspects from the waveforms applied to other electrodes. The particular waveform is preferably determined by the unit under the control or supervision of a human operator. Aspects of the waveforms which are set by the control unit typically include, but are not limited to, parameters such as time shifts between application of signals at different electrodes, signal shapes, amplitudes, DC offsets, pulse durations, frequencies and duty cycles.
In some preferred embodiments of the present invention, a “fencing” signal is additionally applied at one or more locations in or on the heart, in order to inhibit an action potential from developing, and/or to prevent an action potential from propagating from one region of the heart to another. Such fencing is described in PCT patent application PCT/IL97/00233 and in a U.S. patent application filed in the national phase thereof, which are incorporated herein by reference. Fencing is typically used, according to these embodiments, to block or reduce the normal transmission of signals, generally yielding thereby a reduction of the force of contraction of the heart.
In some preferred embodiments of the present invention, one or more motion sensors, e.g., accelerometers, are coupled to or disposed near the heart, and send signals to the control unit indicative of cardiac motion. The motion signals serve as feedback, to enable the control unit to adjust some or all of the above-described electrical stimuli responsive to the signals. Preferably, the motion sensors allow the control unit to calibrate the electrical stimuli which it delivers to the heart, in order to attain a desired level of stabilization of the heart.
In some preferred embodiments of the present invention, one or more sensors, e.g., local electrical activity sensors and/or a Left Ventricular Pressure (LVP) sensor, monitor the heart's behavior to detect an abnormal, potentially-dangerous condition, such as fibrillation. Algorithms and/or circuitry associated with the control unit which detect the condition preferably discontinue signal application and initiate defibrillation and/or cardioversion procedures.
Preferably, application of the electrical stimuli in accordance with the present invention stabilizes the heart within a very short period, typically about 1 second, and can maintain the stability of the heart for prolonged periods, for example, 100 seconds, in order to allow a surgeon to perform surgery on a substantially non-moving heart. The heart typically returns to normal function within about 2 seconds of removal of the electrical stimuli.
There is therefore provided, in accordance with a preferred embodiment of the present invention, a method for controlling activity of a heart of a living person during a medical procedure, including applying electrical signals to the hea
Ben-Haim Shlomo
Darvish Nissim
Felzen Bella
Mika Yuval
Rousso Benny
Cowen, Liebowitz & Latman, P.C.
Dippert William H.
Impulse Dynamics N.V.
Layno Carl
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