Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1999-05-26
2002-08-27
Layno, Carl (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S009000
Reexamination Certificate
active
06442424
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
Heart surgery is often accompanied by the induction of cardioplegia (elective stopping of essentially all cardiac activity by injection of chemicals, selective hypothermia, mechanical stabilization, or electrical stimuli). In humans, induced global cardioplegia is nearly always practiced in conjunction with cardiopulmonary bypass.
Recently, minimally-invasive methods of cardiac surgery have been developed, in which the heart is approached through an incision made between the ribs, without sternotomy. It is sometimes preferred that, rather than inducing cardioplegia, the surgeon mechanically restrains a portion of the heart on which a surgical procedure, such as a bypass graft, is to be performed. Various tools and methods have been developed for this purpose, such as: (a) a suction cup-based stabilization platform (e.g., the Utrecht Octopus); (b) mechanical stabilization devices, such as the CTS Access Ultima System, produced by Cardiothoracic System, Cupertino, Calif.; (c) the Octopus
2
or the EndoOctopus device, both produced by Medtronic, Minneapolis, Minn.; (d) a U-shaped metal foot and other stabilizers produced by Genzyme Surgical Products, Tucker, Ga.; (e) the Octopus Suction stabilizer, produced by fedtronic GmbH, Germany; and (f) CardioVations mechanical stabilizers produced by Ethicon Endo-Surgery, Cincinnati, Ohio.
Such mechanical restraint of the heart muscle requires that substantial force, e.g., pressure or vacuum, be applied, which can cause tissue trauma; and the implements involved interfere with the surgeon's work. This interference typically includes reducing the surgeon's free workspace and limiting the extent of tissue stabilization, due to concerns about tissue injury. Other effects of mechanical stabilization are described in an article, “The effects of mechanical stabilization on left ventricular performance,” by Burfeind et al.,
European Journal of Cardio
-
Thoracic Surgery
, 14 (1998), pp. 285-289, which is incorporated herein by reference,.
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.
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 Surgery
, 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, their operation is, 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 minimally-invasive and open-chest surgery.
In preferred embodiments of the present invention, an electrical cardiac stimulator allows a patient's heart to pump blood while inhibiting motion of a segment of the heart. The stimulator comprises one or more electrodes, preferably placed at multiple sites in or on the heart, and a control unit. The control unit administers electrical signals to at least one of the electrodes in order to reduce or substantially stop motion of the segment for the duration of signal application. Termination of signal application allows the segment, as well as the heart as a whole, to resume normal motion. Preferably, the reduction in motion of the segment, as provided by the present invention, is used to enable a surgeon to perform minimally-invasive surgery or open-chest surgery, generally without inducing global cardioplegia or requiring cardiopulmonary bypass.
In some preferred embodiments of the present invention, administration of the electrical signals is accompanied by use of a stabilizer, typically a mechanical stabilizer, in conjunction with the electrical signals to further reduce motion of the segment. Similarly, for some applications, electrical signals as provided by embodiments of the present invention are used to reduce the force applied—and thus the injury produced—by a stabilizer, while maintaining a desired level of motion reduction.
In some preferred embodiments of the present invention, one or more motion sensors, e.g., accelerometers, are coupled to the heart, and send motion signals to the control unit indicative of the segment's motion and, optionally, of the motion of other areas of the heart. Preferably, the motion signals serve as feedback to enable the control unit to adjust the electrical signals applied to the heart, in order to reduce the detected motion of the segment. In a preferred embodiment, one of the motion sensors is coupled to the segment of the heart, adjacent to a surgical location within the segment, and is in a vicinity of at least one motion-reduction electrode. The control unit receives motion signals from the sensor, and actuates the motion-reduction electrode to apply the electrical signals, referred to herein as “motion-reduction pulses,” in order to change contractility and contraction timing of muscle in the segment.
The motion-reduction pulses preferably comprise one or more of: regular pacing pulses, rapid pacing pulses, a fencing signal, and an enhancement signal. The enhancement signal is typically similar to signals used for Excitable Tissue Control, as described in U.S. Pat. application Ser. No. 09/260,369, which is assigned to the assignee of the present patent application and incorporated herein by reference. Most preferably, the motion-reduction pulses are synchronized with the overall heartbeat, and have timing, shape, and magnitude characteristics which are determined during a calibration period of the control unit. During the calibration period, a high degree of stabilization is preferably achieved, while maintaining adequate safety margins, e.g., acceptable standard patient vital signs, and avoidance of fibrillation and arrhythmia.
Generally, motion of the segment is characterized by a sum of: (a) a first component, consisting of motion resulting from general contraction and relaxation of the heart, which may depend on parameters of stimulation applied through the one or more motion-reduction electrodes and the contraction force generated thereby; and (b) a second component, consisting of local motion resulting from that part of the heart which is substantially stimulated by the motion-reduction electrodes. It is a goal of this embodiment of the present invention to apply motion-reduction pulses which alter the motion of the first and second components, particularly with respect to the timi
Ben-Haim Shlomo
Darvish Nissim
Felzen Bella
Malonek Dov
Mika Yuval
Cowan Liebowitz & Latman P.C.
Dippert William H.
Impulse Dynamics N.V.
Layno Carl
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