Micro integrated cardiac pacemaker

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

0001The present invention concerns an ultra miniature integrated cardiac pacemaker and distributed cardiac pacing system. The invention provides an ultra miniature integrated cardiac pacemaker and distributed cardiac pacing system that allows pacing of the heart without the need for conventional lead wires that connect the electrodes and the main body of the pacemaker, and allows implantation by catheter manipulation without incising the chest wall, which avoids imposing an extra burden on the user.

0002In this invention, "ultra miniature" refers to the minute size of the pacemaker to the extent that it can be attached to the tip of a catheter.

DESCRIPTION OF RELATED ART

0003A cardiac pacemaker is a device that controls the rhythm of the heart by delivering electrical impulses to the heart, and is indicated for use in patients with symptoms of bradyarrhythmia.

0004A conventional cardiac pacemaker includes the main body of the cardiac pacemaker (generator), lead wires, and electrodes that transmit a stimulating pulse to the myocardium. The main body of the cardiac pacemaker and the electrodes are connected by lead wires. However, conventional pacemakers have the following problems.

0005Since the main body of the cardiac pacemaker and the electrodes are connected by lead wires, cases of breaking of the lead wires have occurred. Breakage of the lead wires results in defective pacing. In addition, there have been also cases of venous obstruction by the lead wires.

0006Moreover, during the early stages after implantation of the cardiac pacemaker, a shift in position of the electrodes may cause defective pacing. When a shift in position of the electrodes occurs, a second operation has to be performed, which adds extra strain for the patient.

0007Furthermore, if there is a defective hermetic sealing structure at the junction between the cardiac pacemaker main body and the lead wires, this may lead to defective pacemaker movement. Problems with electrical safety have also occurred.

0008In the Unexamined Japanese Patent Publication Heisei No. <patcit id="pcit0001" dnum="JP5245215A"><text>5-245215</text></patcit>, a cardiac pacemaker is described in which the signals for cardiac stimulation are delivered from the cardiac pacemaker main body to the stimulation electrodes by wireless transmission, thus eliminating the lead wires between the cardiac pacemaker main body and the electrodes.

0009However, even for this type of cardiac pacemaker, surgical implantation of the pacemaker cannot be avoided, and there have been cases in which skin necrosis occurred at the cardiac pacemaker implantation site.

0010Also, in the above-mentioned cardiac pacemaker, although wireless communication is conducted between the pacemaker main body and the electrodes, there is no communication between the electrodes. Synchrony between the multiple electrodes being used is controller by the pacemaker main body.

0011The present invention was developed in order to solve the above problems, and to provide an ultra miniature integrated cardiac pacemaker and distributed cardiac pacing system with the following features: the generator function of electric stimulus by the pacemaker main body is integrated with the electrodes, thus allowing pacing of the heart without the need for conventional lead wires connecting the electrodes and pacemaker main body. By integrating the control unit of the pacemaker main body and the electrodes, there is no need to implant the pacemaker main body, which avoids imposing an extra burden on the user.

0012<patcit id="pcit0002" dnum="EP0443496A"><text>EP 0443496</text></patcit> discloses an implantable heart pacemaker including means for monitoring electrical signals generated by the heart and for producing a corresponding electrocardiogram signal in order to stimulate the heart by stimulation means.

0013<patcit id="pcit0003" dnum="GB1422171A"><text>GB 1422171</text></patcit> discloses a fuel cell using an oxidisable organic substance and oxygen both from a body fluid which may be used for the operation of heart pacemakers.

SUMMARY OF THE INVENTION

0014The invention is set out in claim 1.

0015The ultra miniature integrated cardiac pacemaker of the present invention requires no chest incision, and is implanted in the heart by attaching it to the tip of a catheter and extracting the catheter after implanting.

0016In one embodiment, the pacemaker includes a control unit that outputs control signals, a heart stimulating means that responds to the control signal and electrically stimulates the heart tissue, an electrocardiographic information detecting means that detects the electrocardiographic information and outputs it to the control unit, and a power unit that supplies the driving power.

0017The control unit outputs the control signals based on electrocardiographic information.

0018The power unit is preferably a biological fuel cell that extracts electrons from oxidative reactions of biological fuels. The biological fuel cell is composed of an anode electrode and a cathode electrode. The anode electrode is coated with immobilized oxidative enzymes for biological fuels and mediators. The biological fuel cell uses blood and/or body fluid as an electrolyte solution and utilizes biological fuels and oxygen in blood and/or body fluid.

0019In another embodiment of the present invention, an ultra miniature integrated cardiac pacemaker includes a control unit that outputs control signals, a heart stimulating means that responds to the control signal and electrically stimulates the heart tissue, an electrocardiographic information detecting means that detects the electrocardiographic information and outputs it to the control unit, a transmitting means that modulates the electrocardiographic information and control signals to be sent outside, and a power unit that supplies the driving power.

0020The control unit outputs the control signals based on electrocardiographic information.

0021The power unit is preferably a biological fuel cell that extracts electrons from oxidative reactions of biological fuels. The biological fuel cell is composed of an anode electrode and a cathode electrode. The anode electrode is coated with immobilized oxidative enzymes for biological fuels and mediators. The biological fuel cell uses blood and/or body fluid as an electrolyte solution and utilizes biological fuels and oxygen in blood and/or body fluid.

0022In a third embodiment, an ultra miniature integrated cardiac pacemaker includes a control unit that outputs control signals, a heart stimulating means that responds to the control signal and electrically stimulates the heart tissue, an electrocardiographic information detecting means that detects the electrocardiographic information and outputs it to the control unit, a receiving means that receives and demodulates the information sent from outside, and a power unit that supplies the driving power. It is designed such that the information sent from outside is input into the control unit.

0023The control unit outputs control signals based on information sent from outside and/or electrocardiographic information.

0024The power unit is preferably a biological fuel cell that extracts electrons from oxidative reactions of biological fuels. The biological fuel cell is composed of an anode electrode and a cathode electrode. The anode electrode is coated with immobilized oxidative enzymes for biological fuels and mediators. The biological fuel cell uses blood and/or body fluid as an electrolyte solution and utilizes biological fuels and oxygen in blood and/or body fluid.

0025In yet another embodiment, an ultra miniature integrated cardiac pacemaker includes a control unit that outputs control signals, a heart stimulating means that responds to the control signal and electrically stimulates the heart tissue, an electrocardiographic information detecting means that detects the electrocardiographic information and outputs it to the control unit, a transmitting means that modulates the electrocardiographic information and control signals to be sent outside, a receiving means that receives and demodulates the information sent from outside, and a power unit that supplies the driving current. It is designed such that the information sent from outside is input into the control unit.

0026The control unit outputs control signals based on information sent from outside and/or electrocardiographic information.

0027The power unit is preferably a biological fuel cell that extracts electrons from oxidative reactions of biological fuels. The biological fuel cell is composed of an anode electrode and a cathode electrode. The anode electrode is coated with immobilized oxidative enzymes for biological fuels and mediators. The biological fuel cell uses blood and/or body fluid as electrolyte solution and utilizes biological fuels and oxygen in blood and/or body fluid.

0028Another embodiment discloses an ultra miniature integrated cardiac pacemaker placed in the atrial myocardium.

0029The ultra miniature integrated cardiac pacemaker is equipped with a control unit that outputs control signals, a power unit that supplies the driving power, a heart stimulating means that responds to the control signals and electrically stimulates the atrial myocardium, and an electrocardiographic information detecting means that detects the electrocardiographic information including at least intracardiac P wave information.

0030The power unit is preferably a biological fuel cell that extracts electrons from oxidative reactions of biological fuels. The biological fuel cell is composed of an anode electrode and a cathode electrode. The anode electrode is coated with immobilized oxidative enzymes for biological fuels and mediators. The biological fuel cell uses blood and/or body fluid as an electrolyte solution and utilizes biological fuels and oxygen in blood and/or body fluid.

0031The control unit is equipped with a stimulation timing determining means that decides the timing of stimulation to generate control signals, and a stimulation timing changing means that changes the timing of stimulation to generate control signals. It is characterized by the ability to change the timing of stimulation to generate the control signal, in case intracardiac P wave information is detected within a preset time interval.

BRIEF DESCRIPTION OF THE DRAWINGS

0032<dl id="dl0001"><dt>Figure 1</dt><dd>is a simplified block diagram of an ultra miniature integrated cardiac pacemaker in accordance with the first embodiment.</dd><dt>Figure 2</dt><dd>is a simplified block diagram of an ultra miniature integrated cardiac pacemaker in accordance with the first embodiment.</dd><dt>Figure 3</dt><dd>is a simplified block diagram of an ultra miniature integrated cardiac pacemaker in accordance with the second embodiment.</dd><dt>Figure 4</dt><dd>is a simplified block diagram of an ultra miniature integrated cardiac pacemaker in accordance with the third embodiment.</dd><dt>Figure 5</dt><dd>is a simplified block diagram of an ultra miniature integrated cardiac pacemaker in accordance with the fourth embodiment.</dd><dt>Figure 6</dt><dd>is a schematic diagram illustrating a first application of the ultra miniature integrated cardiac pacemaker in accordance with the present invention (the first distributed cardiac pacing system).</dd><dt>Figure 7</dt><dd>is a schematic diagram illustrating a second application of the ultra miniature integrated cardiac pacemaker in accordance with the present invention (the second distributed cardiac pacing system).</dd><dt>Figure 8</dt><dd>is a block diagram illustrating an outline of the electrocardiographic information detection device.</dd><dt>Figure 9</dt><dd>is a schematic diagram illustrating a third application of the ultra miniature integrated cardiac pacemaker in accordance with the present invention (the third distributed cardiac pacing system).</dd><dt>Figure 10</dt><dd>is a schematic diagram illustrating a fourth application of the ultra miniature integrated cardiac pacemaker in accordance with the present invention (the fourth distributed cardiac pacing system).</dd></dl>

DETAILED DESCRIPTION OF THE INVENTION

0033The present invention is described in detail below while referring to the figures. <figref idref="f0001">Figure 1</figref> is a simplified block diagram of an ultra miniature integrated cardiac pacemaker (100) in accordance with a first embodiment of this invention.

0034The ultra miniature integrated cardiac pacemaker (100) in this embodiment is composed of a control unit (2) that outputs control signals, a heart stimulating means (3) that responds to the control signals and electrically stimulates the heart tissue, an electrocardiographic information detecting means (5) that detects the electrocardiographic information and outputs it to the control unit (2), a transmitting means (10) that modulates the control signals output from the control unit (2) and/or electrocardiographic information detected by the electrocardiographic information detecting means (5) and sends the information outside, a receiving means (9) that receives and demodulates the information sent from outside, and a power unit (4) that supplies the driving current.

0035The heart stimulating means (3) responds to the control signal output from the control unit (2) and electrically stimulates the heart tissue. The heart stimulating means (3) as shown in the diagram is able to stimulate the heart tissue. The heart stimulating means (3) includes a stimulating unit (31) that responds to the control signals output from the control unit (2) and outputs heart stimulating pulses to stimulate the heart tissue, and two heart stimulating electrodes (32) that stimulate the heart tissue in response to the output pulses.

0036The electrocardiographic information detecting means (5) detects the electrocardiographic information at the site where the ultra miniature integrated cardiac pacemaker is placed. The detected electrocardiographic information is output to the control unit (2). The electrocardiographic information detected by the electrocardiographic information detecting means (5) includes P wave information, QRS complex information, T wave information, or Q-T time, A-H time, H-V time (where A is atrial potential, H is His bundle potential, and V is ventricular potential).

0037The electrocardiographic information detecting means (5) as shown in the diagram is composed of two electrocardiographic information recording electrodes (53) that detect the applied site electrocardiographic information at the placement site, an amplifying unit (51) that amplifies the electrocardiogram, and an A/D conversion (52) unit that converts the detected electrocardiographic information into digital signals. The electrocardiographic information detecting means (5) is designed such that the converted electrocardiographic information is output to the control unit (2).

0038The transmitting means (10) is composed of a modulating unit (11) that inputs and modulates the control signals output from the control unit (2) and/or electrocardiographic information, and a transmitting unit (12) that sends the modulated control signals to the outside via carrier waves; by which the modulated control signals are sent to the outside (such as to other ultra miniature integrated cardiac pacemakers, not shown in the diagram).

0039By transmitting control signals and electrocardiographic information via carrier waves to outside sites such as other cardiac pacemakers, it is possible, for example, to activate two or more cardiac pacemakers synchronously. Moreover, since carrier waves are used for transmission, there is no need for lead wires, and this method avoids imposing an extra burden on the user.

0040The receiving means (9) is composed of a receiving unit (91) that receives information transmitted from the outside via carrier waves, and a demodulating unit (92) that demodulates the information received. It is designed such that the demodulated information is input into the control unit (2). Based on this information and/or electrocardiographic information, control signals are generated in the control unit (2) and output to the heart stimulating means (3).

0041The information transmitted from the outside includes electrocardiographic information and control signals sent from other cardiac pacemakers.

0042By equipping the receiving means (9) that receives information from, for instance, other cardiac pacemakers, it is possible to activate the cardiac pacemaker synchronously with other cardiac pacemakers. Moreover, since there is no need for lead wires, this method avoids imposing extra burden on the user.

0043Possible modes of communication between pacemakers executed by the transmitting means (10) and receiving means (9) include, but are not limited to, spread spectrum communication using radio waves or ultrasound waves, and ultra wide band communication. There is no restriction on the mode of communication. Any method can be used as long as it provides reliable communication between pacemakers.

0044The power unit (4) is designed to supply a power source necessary to drive the ultra miniature integrated cardiac pacemaker. As a power unit (4), in general, it is possible to use a lithium battery or fuel cells. However, in the conventional cardiac pacemakers, the power unit that supplies the electrical source is the largest component. To ultra-miniaturize the cardiac pacemaker, it is necessary to miniaturize the power unit. For the ultra miniature integrated cardiac pacemaker (100) according to the present invention, a biological fuel cell is preferably used as the power unit (4).

0045If a biological fuel cell is used as the power unit, biological fuels such as glucose and oxygen, which are necessary to drive the biological fuel cell, are available in constant supply inside the body. The volume of the power unit (4) depends only on the size of the electrodes, making it possible to miniaturize the volume of the power unit (4). Moreover, metabolites and intermediate metabolic products of sugars (e.g., glucose), such as water, carbon dioxide and gluconolactone, are safe for the human body and they are rapidly removed from the vicinity of the electrodes by blood flow. Biological fuel cells that use enzymes as catalysts can operate under mild conditions such as neutral pH and room temperature.

0046One example of a biological fuel cell used in this invention is the well-known conventional biological fuel cell that extracts electrons from oxidative reactions of biological fuels. This biological fuel cell uses sugars (such as glucose) and oxygen, both supplied by the body, as fuels, and utilizes enzymes as biological catalysts.

0047An example of the composition of the preferable biological fuel cell (40) for this invention will be explained by referring to the diagram. <figref idref="f0002">Figure 2</figref> is a schematic diagram illustrating the simplified structure of the biological fuel cell (40) as the power unit in the ultra miniature integrated cardiac pacemaker (100) of the first embodiment.

0048The biological fuel cell (40) is composed of an anode (41) and a cathode (42). This biological fuel cell utilizes blood or body fluid as the electrolyte solution, and also utilizes sugars and oxygen in blood and body fluid as biological fuels. Therefore, the anode electrode (41a) and the cathode electrode (42a) are positioned so as to be in contact with blood or body fluid. In <figref idref="f0002">Figure 2</figref>, the anode electrode (41a) and the cathode electrode (42a) are designed to be in contact with blood, and the heart stimulating electrode (32) and the electrocardiographic information recording electrode (53) are in contact with the myocardial tissue.

0049The anode (41) is composed of an anode electrode (41a) and an immobile layer (41b) coating the surface of the anode electrode (41a). A gold electrode, etc. is preferably used as the anode electrode (41a).

0050Oxidative enzymes of biological fuels and mediators necessary for the oxidation of biological fuels are immobilized on the surface of the anode electrode (41a).

0051Carbohydrates are used as biological fuels. Examples of carbohydrates are monosaccharides such as glucose and fructose, disaccharides such as mannitol and sucrose, and pentoses such as xylose and arabinose. Glucose, which can be supplied easily by the body, is preferably used as the fuel.

0052Any oxidative enzymes that oxidize biological fuels can be used in the present invention. For example, enzymes called oxidases and hydrogenases could be used. If glucose is used as the biological fuel, glucose oxidase and glucose dehydrogenase can be used. Glucose dehydrogenase is preferable.

0053Any mediator that can transfer electrons released from the biological fuel to the anode electrode (41a) can be used in the present invention. Some examples include, but are not limited to, the so-called coenzymes such as flavin adenine dinucleotide phosphate, enzymes such as laccase, quinines such as pyrrolo-quinoline quinine, and osmium complex, as well as their combinations.

0054The oxidative enzymes and mediators are immobilized on the surface of the anode electrode (41a) to form an immobile layer (41b). There is no restriction on the method of immobilization, and any method well known to immobilize enzymes onto an electrode surface can be used. For example, a gold disc electrode can be used as the substrate, and aminoethane-thiol is adsorbed on the surface of the gold electrode to form a monomolecular film followed by modification of the amino groups. After that, the method mixes the oxidative enzyme for biological fuel, the mediator and albumin in a beaker. Then glutaraldehyde is added to allow the enzymes and mediators to cross-link with glutaraldehyde and then the mixture is applied to the surface of the gold disc electrode.

0055To ensure that the reaction takes place efficiently at the anode, the immobile layer (41b) should preferably be designed such that the anode electrode (41a) does not come into contact with oxygen present in the body.

0056The cathode (42) is composed of a cathode electrode (42a).

0057An example of the cathode electrode (42a) is a platinum electrode. A catalyst to enhance a reaction involving reduction of oxygen is required on the cathode electrode (42a). The platinum itself can function as the catalyst.

0058To ensure that the reaction takes place efficiently at the cathode, it is desirable to form a coating (42b) on the surface of the cathode electrode, which will prevent permeation of substances other than oxygen that react with the cathode electrode (42a), and at the same time allow permeation of oxygen and hydrogen ions.

0059The biological fuel cell (40) does not have a container filled with electrolyte solution. Instead, the cathode electrode (41a) and the anode electrode (42a) are in contact with the blood or body fluid of the body. The blood and body fluid act as the electrolyte solution. In the electrolyte solution, biological fuel and oxygen are constantly supplied by the blood flow, and at the same time metabolic products are dissolved in blood and removed by the blood flow. The supply of biological fuel and oxygen as well as the removal of metabolic products are maintained constant through the mechanism of homeostasis.

0060Next, the action of the biological fuel cell (40) will be discussed.

0061Biological fuel is dissolved in blood and body fluid and supplied to the anode (41) surface. The biological fuel supplied to the anode (41) surface is oxidized by the action of the biological fuel oxidative enzyme immobilized in the immobile layer (91b), producing carbon dioxide, hydrogen ion and intermediate metabolites, as well as electrons. Carbon dioxide, hydrogen ion and intermediate metabolites are dissolved in blood or body fluid to be excreted. Electrons are transferred to the anode electrode (41a) via mediators.

0062The cathode (42) surface is supplied with oxygen and hydrogen ions dissolved in blood and body fluid, and these ions react in the presence of electrons transmitted from the anode electrode (41a) to the cathode electrode (42a), and form water. This reaction generates an electric current, which is used as the driving power source.

0063Based on the program already saved in the memory (7) as well as on electrocardiographic information output from the electrocardiographic information detecting means (5) and information transmitted from the exterior, the control unit (2) generates control signals and outputs the signals into the heart stimulating means (3).

0064For instance, the control unit (2) is equipped with a stimulation timing determining means that decides the timing of stimulation to generate control signals, and a stimulation timing changing means that changes the timing of stimulation to generate control signals. Usually this unit is programmed to generate control signals at stimulation timing at a predetermined frequency. It is also programmed to change the stimulation timing when certain conditions are fulfilled; for instance, in case intracardiac P wave information is detected within a given time interval.

0065Furthermore, this invention can be equipped with a communication means (6). The communication means (6) communicates with an external programmer (8) installed external to the ultra miniature integrated cardiac pacemaker, and is used to change the pacing program saved in the memory (7). By this means, even after implantation of the ultra miniature integrated cardiac pacemaker in the patient, it is possible to use the external programmer (8) to change the pacing program saved in the memory (7) as appropriate for the particular patient.

0066For communication between the external programmer (8) and communication means (6) when a patient is implanted with multiple ultra miniature integrated cardiac pacemakers, by setting different frequencies for the individual ultra miniature integrated cardiac pacemakers, for example, it is possible to change the pacing program for each ultra miniature integrated cardiac pacemaker. Also, by conducting spread spectrum communication or by giving each pacemaker an ID, it is possible to change the pacing program of each ultra miniature integrated cardiac pacemaker.

0067Next, the ultra miniature integrated cardiac pacemaker of the second embodiment (110) of the present invention will be explained. The difference between the ultra miniature integrated cardiac pacemaker in the second embodiment (110) and the aforementioned ultra miniature integrated cardiac pacemaker of the first embodiment (100) is that the former has no transmitting means (10) or receiving means (9).

0068The ultra miniature integrated cardiac pacemaker of the second embodiment (110) can be used when there is no need to synchronize movements with other cardiac pacemakers.

0069Based on the control program already saved in the memory (7) and on electrocardiographic information output from the electrocardiographic information detecting means (5), the control unit (2) generates control signals and outputs the signals to the heart stimulating means (3).

0070The other components are the same as those in the aforementioned ultra miniature integrated cardiac pacemaker of the first embodiment (100), therefore explanations are omitted. In <figref idref="f0003">Figure 3</figref>, the same numbers are assigned to components identical to those in the first embodiment (100) as shown in <figref idref="f0001">Figure 1</figref>.

0071Next, the ultra miniature integrated cardiac pacemaker of the third embodiment (120) of this invention will be explained. <figref idref="f0004">Figure 4</figref> is a simplified block diagram of the ultra miniature integrated cardiac pacemaker in this embodiment (120). The difference between the ultra miniature integrated cardiac pacemaker in this embodiment (120) and the aforementioned ultra miniature integrated cardiac pacemaker of the first embodiment is that the former has no receiving means (9).

0072By sending the control signals to the exterior (such as other cardiac pacemakers) via carrier waves, the ultra miniature integrated cardiac pacemaker (120) is able to synchronize and operate with, for instance, one or more other cardiac pacemakers.

0073Based on the control program already saved in the memory (7) and electrocardiographic information output from the electrocardiographic information detecting means (5), the control unit (2) generates control signals and outputs the signals to the heart stimulating means (3).

0074The other components are the same as those in the aforementioned ultra miniature integrated cardiac pacemaker of the first embodiment, therefore explanations are omitted. In <figref idref="f0004">Figure 4</figref>, the same numbers are assigned to components identical to those in the ultra miniature integrated cardiac pacemaker in accordance with the first and second embodiments shown in <figref idref="f0001">Figures 1</figref> and <figref idref="f0003">3</figref>.

0075Next, the ultra miniature integrated cardiac pacemaker of the fourth embodiment (130) of this invention will be explained. The difference between the ultra miniature integrated cardiac pacemaker in this embodiment (130) and the aforementioned ultra miniature integrated cardiac pacemaker in the first embodiment is that the former has no transmitting means (10) to send control signals and/or electrocardiographic information to the exterior.

0076Through the receiving means (9) that receives information from the exterior, for example, from other cardiac pacemakers, the ultra miniature integrated cardiac pacemaker (130) is able to synchronize and operate with other cardiac pacemakers.

0077Based on the control program already saved in the memory (7), as well as electrocardiographic information output from the electrocardiographic information detecting means (5) and information transmitted from the exterior, the control unit (2) generates control signals and outputs the signals to the heart stimulating means (3).

0078The other components are the same as those in the aforementioned ultra miniature integrated cardiac pacemaker of the first embodiment, therefore explanations are omitted. In <figref idref="f0005">Figure 5</figref>, the same numbers are assigned to components identical to those in the ultra miniature integrated cardiac pacemakers in accordance with the first three embodiments shown in <figref idref="f0001">Figures 1</figref>, <figref idref="f0003">3</figref> and <figref idref="f0004">4</figref>.

0079In the ultra miniature integrated cardiac pacemakers of the first four embodiments, the electrocardiographic information recording electrodes (53) and the heart stimulating electrode (32) are shown as separate components. In reality, the electrocardiographic information recording electrode (53) and the heart stimulating electrode (32) may be shared.

0080Moreover, the receiving unit (91) and the transmitting unit (12) are shown as separate components; however, the receiving unit (91) and the transmitting unit (12) may also be shared.

0081Furthermore, by installing in the patient a sensor that measures body temperature and blood pressure and outputting the biological information obtained from these sensors to the control unit (2) of the ultra miniature integrated cardiac pacemakers of the first four embodiments, the control unit (2) is able to generate control signals based on the biological data.

0082In addition, for the ultra miniature integrated cardiac pacemakers of the first four embodiments, there is no particular restriction on the method of implanting the pacemaker in the heart and conventional methods for catheterization may be adopted. For instance, implantation may be done by attaching the ultra miniature integrated cardiac pacemaker to the tip of a catheter and inserting it into the predetermined position inside the heart, and then withdrawing only the catheter after fixing the pacemaker in the endocardium. In the ultra miniature integrated cardiac pacemakers of the invention, the generator main body and the electrodes are integrated, thus obviating the need for lead wires. Therefore, the ultra miniature integrated cardiac pacemakers of the invention can be made of a size of only 2 to 3 mm in diameter. There is no need to make a wide incision in the chest wall to implant the generator main body.

0083The present invention provides an ultra miniature integrated cardiac pacemaker which allows pacing of the heart without the need for the conventional lead wires that connect the electrodes with the pacemaker main body, and allow implantation in the heart by catheter manipulation only without incision of the chest wall to reduce burden on the patient.

0084Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.