Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1999-03-02
2001-09-18
Jastrzab, Jeffrey R. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S017000
Reexamination Certificate
active
06292693
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 pacing and electrical stimulation of the heart muscle.
BACKGROUND OF THE INVENTION
Multi-site and bi-ventricular pacing are known in the art, primarily as methods for enhancing mechanical synchronization of the contraction of different parts of the heart muscle and reducing mitral regurgitation due to poorly-synchronized mechanical contractions. Such pacing is described, for example, in an article by S. Cazeau, et al., entitled “Multisite Pacing for End-Stage Heart Failure: Early Experience,” in
Pacing and Clinical Electrophysiology
19 (November, 1996), Part II, pages 1748-1757, which is incorporated herein by reference.
U.S. Pat. No. 5,800,464 to Kieval, which is incorporated herein by reference, describes an implantable system for effecting hyperpolarization of myocardial cells of a heart chamber, in order to enhance the relaxation thereof in the diastolic phase.
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 electric field to the heart at a delay after electrical activation of the portion. The non-excitatory field is such as does not induce new activation potentials in cardiac muscle cells, but rather modifies the cells' response to the activation. In the context of the present patent application, the use of such a non-excitatory field is referred to as Excitable Tissue Control (ETC). The non-excitatory field may be applied in combination with a pacemaker or defibrillator, which 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 gives cardiac output enhancement. This pacemaker applies both excitatory (pacing) and non-excitatory (ETC) electrical stimulation pulses to the heart. By applying non-excitatory pulses 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.
SUMMARY OF THE INVENTION
It is an object of some aspects of the present invention to provide improved methods and apparatus for applying Excitable Tissue Control (ETC) in order to enhance hemodynamic performance of the heart.
It is a further object of some aspects of the present invention to provide methods and apparatus for multi-site pacing of the heart together with ETC, so as to enhance hemodynamic performance of the paced heart.
It is yet a further object of some aspects of the present invention to provide methods and apparatus for applying ETC together with pacing of the heart, preferably multi-site pacing, so as to reduce or eliminate the possibility of generating undesirable, new propagating action potentials, which can induce arrhythmias.
In preferred embodiments of the present invention, an electrical cardiac stimulator comprises a plurality of electrodes, which are placed at multiple sites in at least two different chambers of the heart, and an electrical control unit. The control unit administers a sequence of pacing pulses to two or more of the electrodes at respective pacing sites in the different chambers. The control unit then applies an ETC signal to one or more of the electrodes, selected from among the two or more electrodes to which the pacing pulses are administered or from other electrodes in a vicinity of one or more of the pacing sites, following administration of the pacing pulse at the respective sites. Application of the ETC signal at a given site occurs during a predetermined time period following the pacing pulse at or near that site, during which period cardiac cells stimulated by the ETC signal generally do not generate propagating action potentials responsive to the ETC.
Preferably, the ETC signal comprises a pulse train, which is delivered to the left ventricle so as to enhance the peak pulsatile pressure generated by the ventricle and/or to achieve greater hemodynamic efficiency, most preferably resulting in larger cardiac output. The inventors have found that when ETC is combined with multi-site pacing, and particularly bi-ventricular pacing, cardiac output generally increases relative to the greatest cardiac output achievable with multi-site pacing alone.
Further preferably, the pacing signal is administered through one or more of the electrodes that are afterwards used to apply the ETC signal. Applying the ETC pulse train using the electrodes that were used a short time previously for pacing the left ventricle ensures that ETC-induced potential changes in the heart tissue will follow substantially the same electrical pathways as were taken by the earlier pacing-induced potentials. Therefore, new action potentials will generally not propagate in the affected tissue due to the ETC.
The present patent application teaches that multi-site pacing can be used to achieve optimal electrical synchronization of the ETC signal, for purposes of enhancing both hemodynamic performance and safety. Methods of multi-site pacing known in the art are concerned only with mechanical synchronization of the contraction of the heart chambers, while ETC stimulation can further increase cardiac performance by increasing cell contractility. The combination of mechanical resynchronization with enhanced contractility can be used to improve hemodynamics of cardiac patients beyond what can be achieved by multi-site pacing alone. The principles of the present invention may be applied in both implanted devices for cardiac pacing and stimulation and in external, bedside devices, primarily for treatment of hospitalized patients.
There is therefore provided, in accordance with a preferred embodiment of the present invention, a method for stimulating cardiac tissue, including:
applying pacing pulses to the heart at multiple sites in at least two different chambers of the heart; and
applying an Excitable Tissue Control (ETC) signal in a vicinity of one or more of the pacing sites following application of the pacing pulse at the site.
Preferably, applying the pacing pulses includes pacing the left ventricle, and applying the ETC signal includes applying the signal in the left ventricle.
Further preferably, applying pacing pulses includes applying pacing pulses through at least one electrode coupled to the heart, and applying the ETC signal includes conveying the ETC signal through the at least one electrode. Preferably, applying the pacing pulses includes applying a pacing pulse to the left ventricle, and applying the ETC signal includes applying the signal in the left ventricle during a time period which begins between about 0 and 100 ms after onset of the pacing pulse applied to the left ventricle. More preferably, the time period begins between about 10 and 50 ms after application of the pulse to the left ventricle. Most preferably, the time period is selected so as to substantially eliminate the possibility that the ETC signal will cause an action potential to propagate in the tissue.
Preferably, applying the ETC signal includes conveying electrical energy to cells of the heart, such that action potentials are generally not generated in the cells responsive to the application of the ETC signal.
Further preferably, the ETC signal is applied in order to improve hemodynamic performance of the heart. Preferably, the ETC signal is applied in order to increase contractility of the heart or, alternatively or additionally, in order to increase systolic pressure generated by the heart.
In a preferred embodiment, applying the E
Darvish Nissim
Shemer Itzhak
Cowan Liebowitz & Latman P.C.
Dippert William H.
Impulse Dynamics N.V.
Jastrzab Jeffrey R.
LandOfFree
Contractility enhancement using excitable tissue control and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Contractility enhancement using excitable tissue control and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Contractility enhancement using excitable tissue control and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2505288