METHODS AND APPARATUS FOR DEPLOYING CARDIAC ELECTRODES AND FOR ELECTRICAL TREATMENT

Abstract: A cardiac electrode deployment device (12) comprises an electrode structure (18) for delivering defibrillation energy to the heart, monitoring ECG of the heart, delivering pacing energy, and/or delivering cardioversion energy and is also suitable for performing direct cardiac massage.

Description: METHODS AND APPARATUS FOR DEPLOYING CARDIAC ELECTRODES AND FOR ELECTRICAL TREATMENT BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to medical devices and methods. More particularly, the present invention relates to devices and methods for performing minimally invasive direct cardiac defibriUation, pacing, monitoring, and massage. Sudden cardiac arrest is a leading cause of death in most industrial societies. While in many cases it is possible to re-establish cardiac function, irreversible damage to vital organs, particularly the brain and the heart itself, will usually occur prior to restoration of normal cardiac activity. A number of techniques have been developed to provide artificial circulation of blood to oxygenate the heart and brain during the period between cardiac arrest and restoration of normal cardiac activity. Prior to the 1960's, open chest cardiac massage (OCM) was a standard treatment for sudden cardiac arrest. Open chest cardiac massage, as its name implies, involved opening a patient's chest and manually squeezing the heart to pump blood to the body. In the 1960's, closed chest cardiac massage (CCM) where the heart is externally compressed through the chest wall became the standard of treatment. When CCM is combined with airway support, it is known as cardiopulmonarv resuscitation (CPR). CPR has the advantage that it is much less invasive than OCM and can be performed by less skilled individuals. It has the disadvantage, however, that it is not generally effective at pumping blood for more than a few minutes. In particular, the medical literature shows that CCM provides significantly less cardiac output, neuroperfusion, and cardiac perfusion than achieved with OCM. Methods and devices for performing minimally invasive direct cardiac massage have been described by Buckman et al. and by Drs. Filiberto and Giorgio Zadini in the patent and literature publications listed in the Description of the Background Art below. While the methods of Buckman et al. and the Zadinis differ in a number of respects, they generally rely on introducing a balloon, shoe, or other deployable member to engage the heart through a small incision through an intercostal space above the pericardium. The heart may then be pumped by directly engaging and compressing the pericardium, either by inflating and deflating the member or by reciprocating a shaft attached to the member. Improved devices for performing direct cardiac massage are described in copending, commonly assigned application nos. 09/087,665 and 09/344,440, the full disclosures of which are incorporated herein by reference. Data show that such devices are able to achieve significantly improved hemodynamic parameters when compared to conventional closed chest cardiac massage. Patients in sudden cardiac arrest have various states of dysfunction including ventricular fibrillation, ventricular bradycardia, ventricular tachycardia, electromechanical dissociation, and asystole. Thus, to properly evaluate patients in sudden cardiac arrest, it is necessary to monitor electrical heart function by performing an electrocardiogram (ECG or EKG). Those patients found to be suffering from a heart arrhythmia should also be treated with direct current defibriUation to effect electrical cardioversion to a more stable heart rhythm. Direct current defibriUation is performed using electrical countershock by placing defibrillating pads on the patient's chest. When ventricular fibrillation or other arrhythmia is observed, the patent is treated with a countershock typically in the range from 200 to 300 joules. If the initial countershock is unsuccessful, a second shock in the same energy range is given. If the arrhythmia persists, a third countershock at a higher energy level, typically about 360 joules, is used. The availability of direct current defibriUation has enabled the saving of thousands of lives each year. It is effective in treating patients for whom no alternative therapies would be available. Despite such success, the need to use such high energy levels can itself cause injury to the patient. Many patients who have been successively revived using defibriUation suffer damage to the electrical pathways in the heart and require pacemakers and/or internal cardiac defibrillators for the rest of their lives. Adversely, even the very high energy levels which are used in cardiac defibriUation are not effective for all patients. The significant electrical resistance and broad electrical dispersivity of the patient's chest greatly reduces the energy which is actually delivered to the heart tissue. Thus, a practical limit exists on the ability to deliver effective direct current defibriUation to the heart using external pads. The use of internal electrodes for providing cardiac defibriUation has been proposed in a number of circumstances. As mentioned above, patients having chronic arrhythmias can now be treated with implanted, internal cardiac defibrillators which both sense an arrhythmia and deliver a countershock to correct the arrhythmia. Additionally, small electrical paddles (called "spoons") have been used in open surgical procedures for directly applying defibriUation energy to an exposed heart. Under such circumstances, defibriUation can be achieved with much lower energies than are required with closed chest defibriUation. Neither approach, however, is effective for treating patients in sudden cardiac arrest where the patient has neither an implanted defibrillator nor an exposed heart to permit direct cardiac defibriUation. For these reasons, it would be desirable to provide improved methods, apparatus, and kits, for defibrillating patients in sudden cardiac arrest. In particular, it would be desirable to provide such improved methods and apparatus which enable and facilitate the simultaneous performance of cardiac defibriUation and direct cardiac massage in such patients. It would be particularly desirable if the methods and apparatus could also provide for monitoring of the patient's heart rhythm during emergency resuscitation procedures and/or for providing cardiac pacing during such procedures. Additionally, it would be desirable if the electrode structure(s) used to perform such procedures could be provided on a device suitable for also performing direct cardiac massage and that the electrode structure(s) could be arranged to effectively provide at least two or more of the different electrical functions, including at least monitoring defibriUation. At least some of these objectives will be met by the invention described hereinafter. 2. Description of the Background Art U.S. Patent Nos. 5,582,580; 5,571.074 and 5,484,391 to Buckman, Jr. et al. and 5,683,364 and copending application no. 09/287,230 to Zadini et al., licensed to the assignee of the present application, describe devices and methods for minimally invasive direct cardiac massage through an intercostal space, which optionally incorporate electrodes for defibriUation, pacing, ECG monitoring, and cardioversion. Published PCT application WO 98/05289 and U.S. Patent Nos. 5,466,221 and 5,385,528 describe an inflatable and other devices for performing direct cardiac massage. U.S. Patent No. 3,496,932 describes a sharpened stylet for introducing a cardiac massage device to a space between the sternum and the heart. Cardiac assist devices employing inflatable cuffs and other mechanisms are described in U.S. Patent Nos. 5,256,132; 5,169,381; 4,731,076; 4,690,134; 4,536,893; 4,192,293; 4,048,990; 3,613,672; 3,455,298; and 2,826,193. Dissectors employing inflatable components are descπbed in U.S. Patent Nos. 5,730.756; 5.730.748; 5,716.325; 5,707.390; 5.702.417; 5,702,416; 5,694,951; 5,690,668; 5,685,826; 5,667,520; 5,667,479; 5,653,726; 5,624,381; 5,618,287; 5,607,443; 5,601,590; 5,601,589; 5,601,581; 5,593,418; 5,573,517; 5,540,711; 5,514,153; and 5,496,345. Use of a direct cardiac massage device of the type shown in the Buckman, Jr. et al. patents is described in Buckman et al. (1997) Resuscitation 34:247-253 and (1995) Resuscitation 29:237-248. SUMMARY OF THE INVENTION The present invention provides improved methods, apparatus, and kits, for defibrillating a patient suffering from cardiac arrhythmia, such as ventricular fibrillation, ventricular tachycardia, ventricular bradycardia, electromechanical dissociation, and in some cases, even patients initially presenting in asystole. The present invention is particularly useful for patients in sudden cardiac arrest and even more particularly useful for patients in sudden cardiac arrest who are simultaneously undergoing minimally invasive direct cardiac massage. While the prior art recognizes the desirability of combining direct cardiac massage with defibriUation, pacing, cardioversion, and/or monitoring, the devices described for performance of such combined therapies are far from optimized, at best, the prior art teaches that relatively simple electrode structures can be provided on a direct cardiac massage device or that electrodes which are not optimized for performing direct cardiac massage may be utilized for defibriUation. The present invention provides a number of specific improvements for both the methods and apparatus used for the minimally invasive defibriUation, monitoring, and pacing, of patients in sudden cardiac arrest. The present invention still further provides apparatus and kits which are optimized for performing such methods, particularly where the devices may also be used for direct cardiac compression. In a first aspect, methods according to the present invention comprise defibrillating a patient's heart. An electrode structure having an active electrode surface area of at least 10 cm 2 , preferably at least 20 cm 2 , and most preferably in the range from 25 cm 2 to 80 cm 2 , is percutaneously introduced to a region over the heart. The electrode structure is contacted against the heart, and defibriUation energy applied to the heart through the electrode structure. Utilization of an electrode structure having the above minimum areas is advantageous since it reduces the current density entering the heart through any localized region. The defibriUation energy can be applied in a bipolar fashion, e.g., using electrically isolated regions on the electrode structure where said regions are attached to opposite poles of the direct current defibriUation source. For example, one or more active electrodes could be formed on the region of the device which contacts the heart, while a counter electrode could be formed on a portion which contacts other than the heart, e.g., a counter electrode could be positioned to contact an inside surface of the rib cage or other segment of the inner thoracic cavity wall. Usually, however, the defibriUation energy will be applied to the patient in a monopolar fashion, where the electrode structure contacted against the heart, is attached to one pole of the defibriUation power supply controller and a counter electrode is attached to the other pole of the power supply controller. The counter electrode will usually be placed on the patient's skin, typically on the patient's back or left side so that the direct current countershock can be applied to the heart along an anterior-posterior axis. Optionally, the electrode structure can be divided into two or more electrically isolated regions which can be separately energized. In one instance, the regions can be separately but simultaneously energized from opposite poles of the power supply controller, providing bipolar defibriUation as mentioned above. Alternatively, the isolated regions of the electrode structure can be energized with a common polarity but in a pre-determined time sequence selected to optimize the defibriUation. In particular, the geometry and time sequence will be selected to mimic the normal electrical current flow responsible for heart contraction in the patient. In such instances, the heart will usually be contacted with at least two isolated regions, and frequently as many as four or more isolated electrode regions. The sequential firing of the regions will typically occur within a very short total elapse time, typically less than 500 msec, usually less than 100 msec, with individual defibriUation energy bursts occurring within 50 msec, usually 10 msec or less. A preferred determined time sequence and firing pattern will be selected to match the normal firing pattern of the heart, i.e., with isolated electrode structures engaging and stimulating the right atrium, right ventricle, left atrium, and left ventricle in that order. Thus, preferred electrode structures will have isolated regions which are capable of contacting each of these regions of the heart with minimal or no cross-over to the adjacent regions. In another aspect of the present invention, the electrode structure will have an axis which is intended to be aligned with the heart in a pre-determined manner. Typically, the axis will be intended to be aligned with the apex-to-base axis of the heart, for example, over the primary conductive bundle of the heart. In such instances, the methods of the present invention may further comprise aligning the electrode structure pπor to applying defibriUation energy. For example, alignment may be achieved by providing suitable markings on a handle of the apparatus which carries the electrode structure so that a user can visually align the handle to achieve the proper alignment of the electrode structure. Alternatively, when automated or other more complex electrode supports are utilized, various automatic means can be provided for aligning the electrode structure. In a further particular aspect of the present invention, the electrode structure will include at least two electrode regions with a space therebetween. The space between the electrode structures may be positioned over the primary conductive bundle of the heart so that defibriUation energy being delivered by the electrode structure will not pass directly into the conductive bundle, thus lessening the risk of damaging the conductive bundle. Alternatively, the two regions can be placed generally over the atrial and ventricular regions of the heart, respectively. By applying the electrode structure directly to the surface of the heart, usually directly over the pericardium, the total amount of energy needed for defibriUation is greatly reduced when compared to external defibriUation. Typically, defibriUation according to the present invention will require a total amount of energy in the range from two joules, to 200 joules, usually from 20 joules to 80 joules for biphasic defibriUation. Monophasic defibriUation will usually require more energy, typically about twice the values set forth above. Moreover, by utilizing the relatively large electrode surface areas described above, the energy per unit area is further reduced, greatly reducing the risk of damage to the heart and its electrical conduction system. In a still further aspect of the present invention, methods for defibrillating the heart comprise compressing the heart and selectively applying defibriUation energy to the heart while compressed. In particular, the heart is compressed to a pre-defined maximum level of compression, and the defibriUation energy is applied to the heart only while the heart is compressed at some level close to the maximum level of compression, typically at least 50% of the maximum level of compression, preferably at least 75% of the maximum level of compression, and still more preferably at least 90% of the maximum level of compression. Applying the defibriUation energy while the heart is compressed has a number of advantages. First, the hydraulic load on the heart is reduced since the blood has been substantially expelled from the ventricles. Thus, the load on heart muscle for the next heart beat is lessened. Second, the electrode impedance is significantly reduced so the required current is lessened. The level of compression will typically be measured in terms of the degree to which the ventricular chambers have been emptied. Preferably, the heart will be compressed using an electrode structure contacted against a surface of the heart, typically the pericardium, where the electrode structure can be used to apply the defibriUation energy at the appropriate point of compression. Usually, compression is in the anterior-posterior direction, and the electrode structure is preferably percutaneously introduced, as described elsewhere in this application and in the patents and copending applications which have been incorporated herein by reference. Most preferably, the electrode structure is introduced intercostally in a low-profile configtiration and subsequently expanded over the heart in order to deploy the electrode structure in a desired manner. In preferred embodiments of this method, the heart function will be assessed before and/or after applying defibriUation. Assessment before applying defibriUation can determine whether it is necessary to apply such defibriUation energy. Assessment after applying defibriUation energy will reveal whether electrical function of the heart has been improved or whether further defibriUation energy is necessary. Assessment is typically performed using conventional ECG techniques where the electrode structure used for defibriUation may also be used for monitoring. In a still further aspect of the present invention, methods for defibrillating a patient' s heart comprise contacting a surface of the heart with a plurality of isolated electrode regions and delivering defibriUation energy to the heart by selectively energizing said isolated electrode regions in a pre-determined sequential pattern. The number of isolated electrode regions and nature of the preferred sequential patterns have been discussed above. In a still further aspect of the present invention, cardiac electrode deployment devices comprise a support and an electrode structure attached to the support. The electrode structure will have an active surface area of at least 20 cm " , with preferred surface areas set forth above. The electrode structure is configured to engage against an outer surface of the heart, such as the pericardium, in order to provide electrical contact with the heart. The support may be any assembly, structure, system, or other mechanical framework which is suitable for positioning and manipulating the heart-engaging member so that it can engage and compress the heart. Most simply, the support could be a simple handle or shaft having the heart-engaging member attached at a distal end thereof. Once the heart-engaging member is deployed, cardiac defibriUation and optionally massage can be performed by energizing the electrode structure and by simple manual pumping or reciprocation of the handle or shaft. In the exemplary embodiment described hereinafter, the support comprises a shaft together with a sheath which is coaxially received over the shaft. The shaft and sheath may be manipulated relative to each other to deploy and retract the heart-engaging member, as described in more detail hereinbelow. A wide variety of other supports will also be possible, including supports which comprise powered drivers, such as electric, pneumatic, or other motors. Such drivers can be provided as part of the support, where the driver may be disposed externally, internally, or both externally and internally relative to the patient when the heart-engaging member is deployed over the pericardium. Preferably, the electrode structure on the deployment device will be collapsible, i.e., it will be capable of being shifted between a low profile configuration suitable for intercostal introduction to a region over the patient's heart to an open configuration where the entire active support area of the electrode can be engaged against the heart. In an exemplary embodiment, the electrode structure is mounted on a plurality of struts which are reciprocatably attached to the support. The struts are retractable to a radially contracted configuration and advancable along arcuate, diverging paths to define a surface which non-traumatically engages the pericardium to compress the heart when advanced against the pericardium. The struts will typically be composed of a resilient material, more typically be composed of a shape memory alloy, such as nickel titanium alloy, and will usually be formed to deploy radially outwardly and advance along the desired arcuate, diverging paths as they are advanced from a constraining member, usually a tubular sheath. The struts may be advanced and retracted relative to the sheath using any suitable mechanical system, typically a shaft which reciprocates together with the struts through a lumen of the sheath. In some instances, it will be desirable to provide at least some of the struts with a temperature-responsive memory so that the shape of the struts will change in response to a transition from room temperature to body temperature and/or in response to an induced temperature change after they have been deployed, e.g., by electrically heating or cooling the struts and/or infusing a heated or cooled medium into the space surrounding the struts. In preferred embodiments, the active surface area of the electrode structure comprises a plurality of electrically isolated regions where the support includes separate electrical conduction paths connected to each electrically isolated region. The conduction paths allow the regions to be separately connected to an external power supply controller. Exemplary isolated region geometries include spaced-apart semi-circles, concentric rings, spaced-apart concentric rings, pie-shaped sections, concentric pie-shaped ring sections, rectilinear arrays, and the like. By providing electrically isolated, separately energizable electrode regions, a variety of specific defibriUation, pacing, and monitoring functions, can be performed using the same electrode structure. For example, two, three, or more, of the isolated electrode segments can be chosen to perform ECG monitoring of the patient at any time the electrode structure is in contact with the heart and defibriUation energy is not being applied using the structure. The electrode structures are also suitable for performing defibriUation in a variety of ways. Most simply, all isolated regions could be energized simultaneously at a common plurality or in a bipolar fashion in order to perform a monopolar defibriUation treatment with the advantage that the surface electrode area is maximized. Alternatively, selected isolated regions could be energized in a monopolar or bipolar fashion with regions over the electrically conductive bundle being un-energized. Additionally, the isolated electrode regions could be energized in a progressive, sequential matter in order to perform optimized monopolar and bipolar defibriUation. Moreover, the use of isolated regions on the electrode allows sensitive regions on the heart to be protected. In particular, by spacing apart two or more electrode regions on opposite sides of the conductive bundle, damage to the conductive bundle from electrical discharge is minimized. The present invention still further provides systems employing a cardiac deployment device as described above in combination with a power supply controller which may include the circuitry and programming necessary for performing defibriUation, ECG monitoring, pacing, cardioversion, and the like. Optionally, the systems may further comprise a counter electrode for performing monopolar treatments. The present invention will also comprise kits including a cardiac electrode deployment device in combination with instructions for use setting forth any of the methods described above. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is schematic illustration of a cardiac electrode deployment device constructed in accordance with the principles of the present invention. Figs. 2A-2H illustrate alternative electrode structure configurations for the device of Fig. 1. Fig. 2AA illustrates an exemplary electrically conductive fabric comprising conductive and non-conductive threads. Fig. 3 is a perspective view of an exemplary cardiac electrode deployment device of the present invention. Fig. 4 is a detailed view of the distal end of the device of Fig. 3 shown with the electrode deployment structure in its open or expanded configuration. Figs. 5 and 6 illustrate an alternative, hinged-strut structure in a retracted and deployed configuration, respectively. Figs. 7A-7C illustrate use of the device of Figs. 3 and 4 in the simultaneous cardiac compression and cardiac defibriUation methods of the present invention. Fig. 7D illustrates use of a device having an integral counter electrode configured to engage an interior surface of the patient's rib cage. Fig. 8 is a chart illustrating an exemplary treatment protocol according to the methods of the present invention. Fig. 9 illustrates an exemplary kit constructed in accordance with the principles of the present invention. DESCRIPTION OF THE SPECIFIC EMBODIMENTS The methods, apparatus, and kits, of the present invention rely on contacting an electrode structure directly against a patient's heart to deliver defibriUation energy to the heart. The electrode structures may comprise a wide variety of specific designs, but will typically include an electrically conductive surface which is configured to directly engage the pericardium or other heart surface. The electrically conductive surface will usually, but not necessarily, be compliant (elastic or non-elastic) so that it can conform to the heart tissue when the electrode structure is engaged against the heart. The electrically conductive surface may be formed entirely from a conductive metal or electrically conductive fibers, e.g., be woven from metal filaments, or may be formed from an electrically insulating backing which is coated with an electrically conductive surface material, typically by plating, sputtering, plasma deposition, or the like. The electrically insulating backing may be formed from a mesh, fabric, polymeric film, or the like. The electrically conductive surface will have an area within the ranges set forth above and may have any one of a wide variety of particular geometries, as discussed in more detail below in connection with Figs. 2A-2H. While it is generally preferable that the electrode structures be compliant or otherwise conformable to the heart surface, it is possible in some instances to use electrode structures which are generally rigid and which will cause the heart surface to conform to their geometries when the electrode is pressed against the heart. The present invention will find its greatest use in minimally invasive procedures where the electrode structure is introduced to a region over the heart via a percutaneous access route. A preferred percutaneous access route is intercostal, typically through the fourth or fifth infracostal space and directly over the heart. In such instances, the electrode structure may be introduced in a generally anterior-posterior direction so that direct compression of the heart could be achieved by engaging electrode structure against the heart. More specifically, the electrode structure will usually engage the pericardium covering the heart. For simplicity of explanation, however, the following description will refer to engaging the heart. In come cases it might be possible to engage the epicardium directly, but such an approach will be less preferred. Alternatively, the electrode structure could be introduced via a subxiphoid approach, i.e., from a point below the sternum to a region above the heart. When the anterior-posterior approach is employed, the handle of the device will preferably be introduced through an intercostal space in the patient's left rib cage (over the heart), with the handle of the device inclined in the mid-sagittal plane, typically at an angle in the range from 20° to 45° toward the patient's right side, so that the device compresses the heart toward the patient's spine. Preferably, the handle will have little or no inclination in the cranial-caudal plane. In most cases, the electrode structure will be collapsible, i.e., be shiftable between a low profile configuration where it can easily be introduced in either the intercostal or subxiphoid approach and thereafter deployed at the target region to expand the surface area of the electrode to its desired size. For example, electrodes which are formed from or on a film, mesh, fabric, or other foldable material, electrode structures may be folded or otherwise collapsed prior to introduction and deployment. In other instances, it would be possible to arrange the electrode structures with discreet joints, hinge regions, or other mechanical features which allow otherwise rigid structures to be folded into a low profile configuration. Preferably, the electrode structures will be capable of being collapsed to a profile having a width (or diameter when circular) no greater than 20 mm, preferably no greater than 15 mm. The electrode structures will be used to deliver defibriUation energy directly to the heart. The defibriUation energy may take any of the forms which are conventionally used or which have been suggested for use in external or internal defibriUation. Such waveforms are generally classified as either monophasic or biphasic. In monophasic waveforms, the current travels in only one direction, i.e., from a positive defibrillator electrode to a negative defibrillator electrode. Thus, monophasic waveforms have only one phase and no change in polarity. In biphasic waveforms, the current travels in one direction stops, and then is reversed to travel the opposite direction, biphasic waveforms thus have two phases with polarity changing with the phase change. Current defibriUation waveforms may be further classified as either truncated exponential or damped sine. The present invention will preferably use a biphasic, truncated exponential waveform. Optionally, variable energy could be used, i.e., starting at a low energy level and being raised to a higher energy level. In some cases, automatic sensing of impedance could be provided, allowing for automatic adjustment of energy output. Generally, the defibriUation energy will be applied at levels in the ranges defined above. In addition to delivering defibriUation energy, the electrode structures may be utilized for pacing. Pacing requires at least one isolated electrode region on the heart to deliver an electrical current pulse to induce heart contraction, with a series of such pulses along with and through electrode structures elsewhere on the body delivered at the rate of heart compression. The amplitude of such pacing pulses will be significantly smaller than those utilized for defibriUation, typically being in the range from 5 mA to 200 mA, usually in the range from 10 mA to 100 mA. The pacing pulse may take the form of any conventional cardiac pacing pulse waveform, e.g., square wave, sine wave, BTE, or other suitable waveform including truncated exponential and combination waveforms. The negative pulse of the biphasic waveform is typically shorter than the positive pulse and has a sharp end point that does not tail off to zero. In particular embodiments of the present invention, switching or sensing apparatus can be applied to coordinate the delivery of a pacing shock with the heart compression. For example, a motion or other limit switch could be provided to deliver the pacing shock at a pre- determined, repeatable point in the compression cycle which is being induced by direct cardiac massage, usually at the beginning of a compression cycle. The electrode structures may also be utilized and configured to permit ECG monitoring. The same transmission lines which connect the isolated region(s) of the electrode structure can be connected to conventional ECG monitoπng circuitry within the power supply controller or other control box. Usually, at least two electrode regions, and preferably three or more electrode regions can be used for ECG monitoring. Optionally, additional ECG electrodes could be placed externally on the patient's skin. By providing both ECG monitoring and defibriUation capabilities through the same electrode structure, information can be provided to permit the user to immediately apply defibriUation energy when appropriate. For example, the treating professional can estimate the duration of ventricular fibrillation, in order to determine how the defibriUation shock may best be administered. If it appears that the patient has been in fibrillation for greater than a pre-determined period of time, such as five minutes, the professional may determine that pharmacological or other mechanical therapies are necessary. The ECG could also be used to determine the appropriate timing for pacing the heart. The ECG could further be used to confirm and/or adjust the position of the electrode structure on the heart based on expected waveforms, etc. Referring now to Fig. 1, a cardiac electrode deployment device suitable for performing the methods of the present invention will be described. Cardiac electrode deployment device 12 is part of a system 10 which further includes power supply controller 14 and optionally a counter electrode 16. Power supply controller 14 contains the circuitry necessary for producing the defibriUation energy, pacing energy, ECG monitoring, and optionally cardioversion energy which can be delivered or sensed by the electrode structure 18 which is shown in its deployed configuration in broken line. Electrode structure 18 is preferably shiftable between a low profile configuration (where it is drawn rearwardly) into delivery cannula 20 and the deployed configuration shown in broken line. Most simply, the electrode structure can be formed from a plurality of resilient struts having an active electrode surface 22 at their forward ends. The struts may be collapsed inwardly by drawing shaft 24 rearwardly relative to the cannula 20, thus drawing the electrode structure 18 into the cannula. The electrically conductive surface 22 will be connected to the power supply controller 14 through a connecting cable 26. Usually, at least one connector will be provided for each electrically isolated region within the active electrode area 22, as described in more detail below. The active electrode surface 22 may have a wide variety of configurations. Usually, the electrode surface will have a generally circular periphery, although other peripheral geometries, such as ovoid, rectangular, triangular, irregular, and the like, could also be utilized. The most simple electrode surface geometry is illustrated in Fig. 2A, where the surface 22a compπses a single, continuous electrode covering the entire circular area of the electrode structure. The electrically conductive surface may be formed in any of the ways described above. The electrode can be formed from a wide variety of conformable, electrically conductive materials or composites. Usually, the materials will be flexible but non-distensible, most usually being formed from non-distensible fabrics. In one instance, the fabrics can be metalized, for example by vapor deposition or plating (either electro or electroless) of a conductive metal surface over a fabric matrix. More usually, however, the conductive fabrics will be formed by weaving at least part of the fabric from a metal, preferably in both directions of the weave, but in some cases only in a single direction. The metal filaments in the fabric may be disposed at each strand or fiber, optionally at every other strand or fiber, usually will be placed at least once every 100 strands or fibers, more usually at at least every tenth strand. The other strands or fibers may be formed from electrically non-conductive materials, such as polyester. An exemplary fabric is illustrated in Fig. 2AA. The fabric 400 comprises warp 402 and woof 404 threads which are woven at right angles in a conventional pattern. Preferably, at least some of the warp threads 402 and the woof threads 404 will be electrically conductive, most preferably being a metal, such as gold, silver, stainless steel, or other electrically conductive medically acceptable metal. In the exemplary structure, the conductive and non-conductive threads will be arranged in an alternating pattern as illustrated. Such an alternating construction provides very uniform strength and electrical conductivity characteristics. A first alternative electrode configuration 22b is shown in Fig. 2B, where a pair of semi-circular electrode regions 30 and 32 are spaced-apart on the exposed surface of the electrode structure. The two isolated regions are electrically isolated from each other and connected independently through the shaft 24 by isolated electrical connectors. This way, the electrode regions 30 and 32 can be energized separately or commonly, depending on how the power supply controller 14 is arranged. The isolated electrode configuration of Fig. 2B is particularly useful for applying to the surface of the heart so that the non-electrode region 34 can be placed over the conductive bundle of the heart. In this way, the conductive bundle can be protected from direct delivery of electrical current. A second alternative configuration comprising a pair of concentric ring electrodes is shown in Fig. 2C. The concentric ring electrodes could also be laterally spaced-apart, as shown in the electrode surface 22d shown in Fig. 2D. In particular, the plurality of opposed C-shaped electrode surfaces 40, 42, 44, and 46, may be formed on the electrode support. An electrode surface 22e comprising four pie-shaped isolated electrode regions 50, 52, 54, and 56, is illustrated in Fig. 2E. A similar electrode surface 22f comprising eight pie-shaped isolated electrode regions 62-74 is illustrated in Fig. 2F. An additional electrode configuration 22g comprising four pie-shaped electrodes further divided into concentric rings, for a total of eight isolated electrode regions 80-94 is illustrated in Fig. 2g. Finally, a rectilinear array of electrode regions 22h is illustrated in Fig. 2H. It will be appreciated that such electrode configurations can easily be fabricated using a variety of metal deposition techniques, where an electrically conductive metal, such as titanium, stainless steel, silver, gold, and copper, can be deposited, plated, or otherwise coated and patterned onto a suitable electrode substrate. Referring now to Figs. 3-6, an exemplary cardiac electrode deployment device constructed in accordance with the principles of the present invention comprises a sleeve 102, a shaft 104 slidably mounted in a central lumen of the sleeve 102, and a handle 106 attached to a proximal end of the shaft. The sleeve 102 includes a positioning flange 110 near its distal end, typically spaced proximally of the tip 112 of the device by an optimum distance, generally as set forth above. A blunt cap 120 is positioned at the distal-most end of the device 100 and facilitates entry of the device into the chest cavity by blunt dissection, as described in more detail hereinafter. A flared bell structure 130, as best seen in Figs. 4 and 6, is attached to the distal end of shaft 104 and assumes a trumpeted configuration when fully deployed, as shown in both of those figures. The flared bell structure 130 comprises a plurality of outwardly curving struts 132 (the illustrated embodiment has a total of eight struts, but this number could vary). The struts are preferably formed from a resilient metal, usually formed from a superelastic alloy, such as nitinol. The use of such resilient materials will not always provide the degree of rigidity desired for the forward surface 136 (Fig. 6) of the flared bell structure. To enhance the rigidity and pushability of the structure, re- enforcing beams 138 may be provided. It has been found that the combination of the curved struts with straight beam supports provides a useful combination of stiffness over the proximal portion of the structure and greater flexibility at the tip portions. The blunt cap 120 is mounted on a rod 140 (Fig. 6) having an electrical connector 142 at its proximal end. When the sleeve is advanced distally over the flared bell structure 130. the forward tip of the sleeve will engage the rear of the end cap 120, as best seen in Fig. 18. When the sleeve is retracted and the flared bell structure deployed, as best seen in Fig. 19, end cap 120 will be free to move axially. In use, the end cap will typically be withdrawn proximally into the interior of the structure 130. The distal tips of the struts 130 are preferably connected by a fabric electrode structure 150 having an edge which is folded over and stitched to hold the cover in place. The fabric cover may be a light mesh, composed of polyester or the like, and will help distribute forces quite evenly over the region of the pericardium which is contacted by the flared bell structure. The fabric electrode structure 150 may have any of the configurations set forth above in Figs. 2A-2H. The isolated region(s) on the electrode surface are electrically connected through a plurality of conductors (not shown) which terminate in the electrical connector 142. The connector 142 will typically include an array of plug prongs or receptacles which permit inner connection of the connector with a cable, e.g., cable 26 as shown in Fig. 1. The cable in turn, connects the device to a suitable power supply controller. Referring now to Figs. 7A-7C, the electrode deployment device 100 can be introduced into a region over the heart and used for direct cardiac massage. Initially, a small incision I is made over the heart, preferably on the patient's left side between the forth and fifth ribs (R 4 and R 5 ). After the incision I is made, the device 100 is pushed through the incision with the blunt cap 120 bluntly dissecting tissue until the flange 110 engages the outer chest wall, as illustrated in Fig. 7B. At that point, the flared bell structure is still not deployed. The flared bell structure 130 is then deployed by advancing shaft 104 until a first marker 160 approaches the proximal end 162 of the sleeve 102. Once the structure 130 is fully deployed, the handle 106 may be manually grasped and the device shaft 104 pumped through the sleeve 102. This will cause the deployed flared bell structure 130 to engage the electrode surface against the heart. The structure can then be advanced in a posterior direction to compress the heart, generally shown in broken line in Fig. 7C. Preferably, the handle will be inclined from 20° to 45° toward the patient's left in the mid-sagittal plane while being held generally vertically in the cranial-caudal plane. In this way, the electrode structure compresses the heart toward the patient's spine to maximize compression. Defilation energy is then applied using a power supply 170 connected via a cable 172 to the electrode structure on the flared bell structure 130 and via a cable 174 to a counter electrode 180 which is usually disposed on the patient's back. Energy is applied according to the protocols described below. Once resuscitation has been completed, the device 100 may be withdrawn by retracting the shaft 104 relative to sleeve 102 to draw the structure 130 back into the sleeve. The structure 130 will be sufficiently retracted as soon as the second marker 162 becomes visible out of the proximal end of the sleeve. Once the structure 130 is retracted, the device may be proximally withdrawn through the incision and the incision closed in the conventional manner. A preferred protocol for utilizing the cardiac electrode deployment device to resuscitate a patient in cardiac arrest is shown in Fig. 8. After the device is introduced and deployed, as generally shown in Fig. 7A-7C, the heart may be compressed. Optionally, the electrically conductive surface of the bell structure 130 can be coated with an electrically conductive gel prior to introduction. The gel helps establish electrical contact and reduces the impedance between the electrically conductive surface and the heart. It will be necessary, however, when it is desired to retain electrically isolated regions, to make sure that the conductive gel does not short adjacent regions of the electrode structure. Prior to, during, or immediately following such compression, the electrode structure on the device may be used to monitor the patient ECG. If the ECG is acceptable, the device can be used to perform compression until the situation is resolved, hopefully with the patient being resuscitated. If the observed ECG is not acceptable, the electrode structure can be used to apply defibriUation energy to the heart. Usually, defibriUation energy will be applied in a single step (although the step may be divided into a series of discreet, progressively more energetic applications of energy over a very short time period, as described above). After the single application of energy has been completed, heart function will again be assessed by ECG. If the initial defibriUation has been successful, the treatment can frequently be terminated or continued with compression alone, or compression plus pacing, until the patient is resuscitated. If the initial defibriUation has been unsuccessful, i.e., acceptable ECG has not been achieved, the patient may again be defibrillated following direct cardiac massage. Third and subsequent defibriUation steps can further be provided until restoration of an acceptable ECG is achieved. If defibriUation continues to be unsuccessful, the patient can continue to be compressed until the situation is resolved, further surgical or other interventions are initiated, or there is no reason to continue cardiac compression. Use of a modified device 200 for resuscitating a patient is illustrated in Fig. 7D. The device 200 comprises a sleeve 202 and flared bell structure 230, as generally descπbed above for the device 100. The device 200 differs principally in that it includes an integral second electrode 240 which serves as a counter electrode in performing defibriUation according to the present invention. The electrode 240 is expansible from a low profile configuration to an expanded configuration so that it can engage the interior thoracic wall, e.g., an interior surface of the rib cage, when the device 200 is deployed. The electrode 240 will usually be attached to the sleeve 202 so that the elecfrode 240 remains generally stationary against the interior thoracic wall as the flared bell structure 230 (carrying the primary electrode structure) is reciprocated to compress the heart. DefibriUation current can be applied by any of the protocols described herein, and the current wall will generally follow the flux lines 250 shown in Fig. 7D. Cables 270 at 274 connect the power supply 280 to the primary and counter electrodes on the device 200. Referring now to Fig. 9, a kit 300 according to the present invention comprises a cardiac electrode deployment tool, such as device 100 described in detail previously, in combination with instructions for use IFU setting forth any of the methods described above. Usually, the device and instructions for use will be combined in a suitable package P that can be in the form of any conventional medical device packaging, such as a tray, tube, box, pouch, or the like. The instructions for use will usually be provided on a separate package insert, but could also be printed directly on all or a portion of the packaging P. Additional components, such as a counter electrode, could also be provided as part of the kit. While the above is a complete description of the preferred embodiments of the invention, various alternatives, modifications, and equivalents may be used. Therefore, the above description should not be taken as limiting the scope of the invention which is defined by the appended claims.

Claims: WHAT IS CLAIMED IS: L A method for defibrillating a patient's heart, said method comprising: providing an electrode structure having an active electrode surface area of at least 10 cm 2 ; percutaneously introducing the electrode structure to a region over the heart; contacting the electrode structure against the heart; and applying defibriUation energy to the heart through the electrode structure. 2. A method as in claim 1 , wherein applying defibriUation energy comprises applying bipolar energy through at least two isolated regions of the electrode structure. 3. A method as in claim 1 , wherein applying defibriUation energy comprises contacting the patient's back with a counter electrode and applying monopolar energy between the electrode structure on the heart and the counter electrode on the patient's back. 4. A method as in claim 1, wherein the electrode structure comprises at least two isolated regions in contact with the heart and wherein said regions are energized in a pre-determined sequence. 5. A method as in claim 4, wherein the heart is contacted with at least two isolated electrode regions. 6. A method as in claim 5, wherein the heart is contacted with at least four isolated electrode regions. 7. A method as in claim 1, wherein the active surface of the electrode structure has an axis to be aligned with the heart, further comprising aligning the active surface axis with the heart before applying defibriUation energy to the heart. 8. A method as in claim 1 , wherein applying defibriUation energy comprises applying a total amount of energy in the range from 2 joules to 200 joules in a single defibriUation attempt. 9. A method as in claim 1, further comprising compressing the heart by contacting an electrode structure against the heart and pressing the electrode structure to cause compression of the heart, wherein the defibriUation energy is applied through the electrode structure. 10. A method as in claim 9, wherein compression is in an anterior- posterior direction. 11. A method as in claim 10, wherein the heart is compressed at least 50% along the anterior-posterior axis of the heart. 12. A method as in claim 1, wherein the electrode structure is introduced intercostally in a low profile configuration and subsequently expanded over the heart. 13. A method as in claim 1 , further comprising compressing the heart comprises repetitively compressing the heart at from 40 to 160 repetitions per minute. 14. A method as in claim 1, wherein heart function is assessed after applying defibriUation energy. 15. A method as in claim 14, wherein assessment comprises monitoring EKG using the electrode structure. 16. A method as in claim 14, further comprising selectively applying additional defibriUation to the heart if the assessment indicates that it is needed. 17. A method for defibrillating a patient's heart, said method comprising: compressing the heart to a maximum level of compression; and selectively applying defibriUation energy to the heart when the heart is compressed at at least 50% of the maximum level of compression. 18. A method as in claim 17, wherein compressing the heart comprises contacting an electrode structure against the heart and pressing the electrode structure to cause compression of the heart, wherein the defibriUation energy is applied through the electrode structure. 19. A method as in claim 18, wherein compression is an anterior- posterior direction. 20. A method as in claim 19, wherein the maximum level of compression is at least 50% along the anterior-posterior axis of the heart. 21. A method as in claim 18, wherein the electrode structure is percutaneously introduced. 22. A method as in claim 21 , wherein the electrode structure is introduced intercostally in a low profile configuration and subsequently expanded over the heart. 23. A method as in claim 17, wherein the electrode structure has an active surface area of at least 10 cm . 24. A method as in claim 17, wherein compressing the heart comprises repetitively compressing the heart at from 40 to 160 repetitions per minute. 25. A method as in claim 17, wherein heart function is assessed before and/or after applying defibriUation energy. 26. A method as in claim 25, wherein assessment comprises monitoring EKG using the electrode structure. 27. A method as in claim 25, further comprising selectively applying additional defibriUation to the heart if the assessment indicates that it is needed. 28. A method as in claim 17, wherein applying defibriUation energy comprises applying bipolar energy through at least two isolated regions of the electrode structure. 29. A method as in claim 11, wherein applying defibriUation energy comprises contacting the patient's back with a counter electrode and applying monopolar energy between the electrode structure on the heart and the counter electrode on the patient's back. 30. A method as in claim 17, wherein the electrode structure comprises at least two isolated regions in contact with the heart and wherein said regions are energized in a pre-determined sequence. 31. A method as in claim 17, wherein the active surface of the electrode structure has an axis to be aligned with the heart, further comprising aligning the active surface axis with the heart before applying defibriUation energy to the heart. 32. A method as in claim 17, wherein applying defibriUation energy comprises applying a total amount of energy in the range from 2 joules to 200 joules in a single defibriUation attempt. 33. A method as in claim 1, wherein contacting comprises engaging an electrode structure having a plurality of isolated electrode regions thereon against the heart. 34. A method as in claim 33, wherein the heart is contacted with at least three isolated electrode regions. 35. A method as in claim 34, wherein the heart is contacted with at least four isolated electrode regions. 36. A method as in claim 33, wherein each isolated electrode region delivers from 1 joule to 50 joules to the heart and wherein the total amount of energy delivered to the heart is in the range from 4 joules to 200 joules. 37. A method as in claim 36, wherein isolated regions are energized sequentially and the total amount of energy is delivered within a time period less than or equal to 500 msec. 38. A method for defibriUation of a patient's heart, said method comprising: contacting a surface of the heart with a plurality of isolated electrode regions; and delivering defibriUation energy to the heart by selectively energizing said isolated electrode regions in a pre-determined sequential pattern. 39. A method as in claim 38, wherein the heart is contacted with at least three isolated electrode regions. 40. A method as in claim 38, wherein contacting comprises engaging an electrode structure having said isolated electrode regions thereon against the heart. 41. A method as in claim 38, wherein each isolated electrode region delivers from 1 joule to 50 joules to the heart and wherein the total amount of energy delivered to the heart is in the range from 2 joules to 200 joules. 42. A method as in claim 41 , wherein the total amount of energy is delivered within a time period less than or equal to 500 msec. 43. A method as in claim 38, wherein applying defibriUation energy comprises applying bipolar energy through at least two isolated regions of the electrode structure. 44. A method as in claim 38, wherein applying defibriUation energy comprises contacting the patient's back with a counter electrode and applying monopolar energy between the isolated electrode regions on the elecfrode structure on the heart and the counter electrode on the patient's back. 45. A method as in claim 38, wherein the active surface of the electrode structure has an axis to be aligned with the heart, further comprising aligning the active surface axis with the heart before applying defibriUation energy to the heart. 46. A method as in claim 38, wherein applying defibriUation energy comprises applying a total amount of energy in the range from 2 joules to 200 joules in a single defibriUation attempt. 47. A method as in claim 40, further comprising compressing the heart by contacting the electrode structure against the heart and pressing the electrode structure to cause compression of the heart, wherein the defibriUation energy is applied through the electrode structure. 48. A method as in claim 47, wherein compression is an anterior- posteπor direction. 49. A method as in claim 48, wherein the maximum level of compression is at least 50% along the anterior-posterior axis of the heart. 50. A method as in claim 40, wherein the electrode structure is percutaneously introduced. 51. A method as in claim 50, wherein the electrode structure is introduced intercostally in a low profile configuration and subsequently expanded over the heart. 52. A method as in claim 47, wherein compressing the heart comprises repetitively compressing the heart at from 40 to 160 repetitions per minute. 53. A method as in claim 38, wherein heart function is assessed after applying defibriUation energy. 54. A method as in claim 53, wherein assessment comprises monitoring EKG using the electrode structure. 55. A method as in claim 53, further comprising selectively applying additional defibriUation to the heart if the assessment indicates that it is needed. 56. A cardiac electrode deployment device comprising: a support; and an electrode structure attached to the support and having an active surface area of at least 10 cm 2 , wherein said electrode structure is configured to be engaged against an outer surface of the heart to provide electrical contact therewith. 57. A cardiac electrode deployment device as in claim 56, wherein the electrode structure can be shifted between a low profile configuration where it can be intercostally introduced to a region over the heart to an open configuration where the entire active surface area can be engaged against the heart. 58. A cardiac electrode deployment device as in claim 57, wherein the electrode structure comprises (a) a plurality of struts reciprocatably attached to the support, said struts being retractable to a radially contracted configuration and advancable along arcuate, diverging paths to define a surface which non-traumatically engages the heart when advanced thereagainst; and (b) an electrically conductive web secured to the struts to define the active electrode surface when the struts are advanced. 59. A cardiac electrode deployment device as in claim 56, wherein the active surface area of the electrode structure comprises a plurality of electrically isolated regions and wherein the support includes separate electrical conduction paths for connecting the isolated regions of the electrode structure to an external power supply controller. 60. A cardiac electrode deployment device as in claim 56, wherein the isolated regions of the electrode structure are arranged in a pattern selected from the group consisting of spaced-apart semi-circles, concentric rings, spaced-apart concentric rings, pie-shaped sections, concentric pie-shaped ring sections, and a rectilinear aιτay. 61. A cardiac electrode deployment device as in claim 56, wherein the support comprises a handle having a connector for detachably connecting the electrode structure to an external power supply controller. 62. A system comprising: a power supply controller; and a cardiac electrode deployment device as in claim 56. 63. A system as in claim 62, further comprising a counter electrode. 64. A kit comprising: a cardiac electrode deployment device; and instructions for use setting forth a method according to claim 1. 65. A kit comprising: a cardiac electrode deployment device; and instructions for use setting forth a method according to claim 17. 66. A kit comprising: a cardiac electrode deployment device; and instructions for use setting forth a method according to claim 38.

Inventors: BRENNEMAN RODNEY A, BUCKMAN ROBERT F, HARPER KEEGAN, LAWSON ROBERT A, LENKER JAY A, MASSON STEPHEN C, YOCUM GREGORY T, BRENNEMAN, RODNEY, A., BUCKMAN, ROBERT, F., HARPER, KEEGAN, LAWSON, ROBERT, A., LENKER, JAY, A., MASSON, STEPHEN, C., YOCUM, GREGORY, T.
Applicants: THERACARDIA INC, THERACARDIA, INC.
Application year: 2000
Main classification: A61N1
IPC codes: A61N1