Device and method for providing phototherapy to the heart

A method for treating a patient's heart is provided. The method includes providing a light source which emits light having an initial power density. The method further includes positioning the light source relative to the patient's heart with intervening tissue of the patient between the light source and the patient's heart. The method further includes directing light onto cardiac tissue of the patient's heart from the light source through the intervening tissue without damaging the intervening tissue. The cardiac tissue is irradiated by an efficacious power density of light for an efficacious period of time.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates in general to phototherapy, and more particularly, to novel apparatuses and methods for phototherapy of cardiac tissue.

Description of the Related Art

Myocardial ischemia refers to the condition of oxygen deprivation in heart muscle (“myocardium”) that is produced by some imbalance in the myocardial oxygen supply-demand relationship. Myocardial infarction (“MI”), also known as “heart attack”, refers to the death of cells in an area of heart muscle as a result of oxygen deprivation due to obstruction of the blood supply, typically due to occlusion of one or more coronary arteries or branches. Occlusion usually stems from clots that form upon the sudden rupture of an atheromatous plaque through the sublayers of a blood vessel, or when the narrow, roughened inner lining of a sclerosed artery leads to complete thrombosis. Approximately 1.5 million myocardial infarctions (MIs) occur annually, and nearly 500,000 deaths result from ischemic heart disease. The United States alone loses billions of dollars annually to medical care and lost productivity due to cardiovascular disease including myocardial infarction.

Treatment after MI depends on the extent to which the cells have been deprived of oxygen. Complete oxygen deprivation produces a zone of infarction in which cells die and the tissue becomes necrotic, with irretrievable loss of function. However, immediately surrounding the area of infarction is a less seriously damaged region of tissue, the zone of ischemia, in which cells have not been irretrievably damaged by complete lack of oxygen but instead are merely weakened and at risk of dying. If adequate collateral circulation develops, the extended zone may regain function within 2 to 3 weeks. The zone of infarction and the zone of ischemia, are both identifiable using standard diagnostic techniques such as electrocardiography, echocardiography and radionuclide testing.

Therapeutic strategies in treating MI are directed at reducing the final extent of the infarcted region by preserving viable tissue and if possible retrieving surviving but at-risk cells. Known treatment methods for myocardial infarction include surgical interventions and pharmacologic treatments. A combination of therapeutic approaches is sometimes advisable. Selection of the appropriate therapy depends on a number of factors, including the degree of coronary artery occlusion, the extent of existing damage if any, and fitness of the patient for surgery. Surgical interventions include coronary artery bypass surgery and percutaneous coronary procedures such as angioplasty, artherectomy and endarterectomy. Pharmacologic agents for treating MI include inhibitors of angiotensin converting enzyme (ACE) such as captopril, quinapril and ramipril, thrombolytic agents including aspirin, streptokinase, t-PA and anistreplase, β-adrenergic anatagonists, Ca++channel blockers, and organic nitrates such as nitroglycerin. However, surgical interventions are invasive and can increase the risk of stroke, and pharmacologic agents carry the risk of eliciting serious adverse side effects and immune responses.

High energy laser radiation is now well accepted as a surgical tool for cutting, cauterizing, and ablating biological tissue. High energy lasers are now routinely used for vaporizing superficial skin lesions and, and for making deep cuts. Examples of such procedures include transmyocardial laser revascularization (TMLR) and percutaneous transmyocardial laser revascularization (PTMR). In TMLR, a laser is inserted through a chest incision and used to drill approximately 15-30 transmural channels from the epicardial to the endocardial surfaces through the left ventricular myocardium in an attempt to improve local perfusion to ichemic myocardial territories not being reached by diseased arteries. In PTMR, the laser is introduced via a catheter. Other examples include laser ablation or cauterization of cardiac tissue to stop atrial fibrillation.

For a laser to be suitable for use as a surgical laser, it must provide laser energy at a power sufficient to heat tissue to temperatures over 50° C. Power outputs for surgical lasers vary from 1-5 W for vaporizing superficial tissue, to about 100 W for deep cutting.

In contrast, low level laser therapy involves therapeutic administration of laser energy to a patient at vastly lower power outputs than those used in high energy laser applications, resulting in desirable biostimulatory effects while leaving tissue undamaged. In rat models of myocardial infarction and ischemia-reperfusion injury, low energy laser irradiation reduces infarct size and left ventricular dilation, and enhances angiogenesis in the myocardium. (See, e.g., Yaakobi et al.,J. Appl. Physiol., Vol.90, pp. 2411-19 (2001)).

Against the background, a high level of interest remains in finding new and improved therapeutic methods for the treatment of myocardial infarction. In particular, a need remains for relatively inexpensive and non-invasive approaches to treating myocardial infarction that also avoid the limitations of drug therapy.

SUMMARY OF THE INVENTION

In certain embodiments, a method for treating a patient's heart is provided. The method comprises providing a light source which emits light having an initial power density. The method further comprises positioning the light source relative to the patient's heart with intervening tissue of the patient between the light source and the patient's heart. The method further comprises directing light onto cardiac tissue of the patient's heart from the light source through the intervening tissue without damaging the intervening tissue. The cardiac tissue is irradiated by an efficacious power density of light for an efficacious period of time.

In certain embodiments, a method for treating a patient's heart is provided. The method comprises introducing light of an efficacious power density onto a target area of the heart by directing light having an initial power density through intervening tissue of the patient. The light has a plurality of wavelengths, and the efficacious power density is at least 0.01 mW/cm2at the target area.

In certain embodiments, a method for treating a patient's heart following a myocardial infarction is provided. The method comprises applying low-level light therapy to the heart no earlier than about two hours following the myocardial infarction.

In certain embodiments, a method provides a cardioprotective effect in a patient having a ischemic event in the heart. The method comprises identifying a patient who has experienced an ischemic event in the heart. The method further comprises estimating the time of the ischemic event. The method further comprises commencing administration of a cardioprotective effective amount of light energy to the heart no less than about two hours following the time of the ischemic event.

In certain embodiments, a method for treating a patient's heart is provided. The method comprises directing an efficacious power density of light through intervening tissue of the patient to a target area of the heart concurrently with applying an electromagnetic field to the heart. The electromagnetic field has an efficacious field strength.

In certain embodiments, a method for treating a patient's heart is provided. The method comprises directing an efficacious power density of light through intervening tissue of the patient to a target area of the heart concurrently with applying an efficacious amount of ultrasonic energy to the heart.

In certain embodiments, a therapy apparatus for treating a patient's heart is provided. The therapy apparatus comprises a light source having an output emission area positioned to irradiate a portion of the heart with an efficacious power density and wavelength of light through intervening tissue. The therapy apparatus further comprises an element interposed between the light source and the intervening tissue. The element is configured to inhibit temperature increases at the intervening tissue caused by the light.

In certain embodiments, a therapy apparatus for treating a patient's heart is provided. The therapy apparatus comprises a light source configured to irradiate at least a portion of the heart with an efficacious power density and wavelength of light. The therapy apparatus further comprises a biomedical sensor configured to provide real-time feedback information. The therapy apparatus further comprises a controller coupled to the light source and the biomedical sensor. The controller is configured to adjust said light source in response to the real-time feedback information.

In certain embodiments, a therapy apparatus for treating a patient's heart is provided. The therapy apparatus comprises an implantable light source configured to irradiate at least a portion of the heart with an efficacious power density and wavelength of light.

In certain embodiments, a method of treating a patient's heart is provided. The method comprises implanting a light source within the patient. The method further comprises irradiating at least a portion of the heart with an efficacious power density and wavelength of light from the implanted light source.

In certain embodiments, a therapy apparatus for treating a patient's heart is provided. The therapy apparatus comprises a light source configured to irradiate at least a portion of the patient's blood with an efficacious power density and wavelength of light prior to the blood flowing to the heart.

In certain embodiments, a method of treating a patient's heart is provided. The method comprises irradiating at least a portion of the patient's blood with an efficacious power density and wavelength of light. The method further comprises allowing the irradiated blood to flow to the heart.

For purposes of summarizing the present invention, certain aspects, advantages, and novel features of the present invention have been described herein above. It is to be understood, however, that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the present invention. Thus, the present invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Low level light therapy (“LLLT”) or phototherapy involves therapeutic administration of light energy to a patient at lower power outputs than those used for cutting, cauterizing, or ablating biological tissue, resulting in desirable biostimulatory effects while leaving tissue undamaged. For example, as described by U.S. Pat. No. 6,214,035 to Streeter, which is incorporated in its entirety by reference herein, LLLT can be used to improve cardiac microcirculation after cardiac surgeries, such as coronary bypass or angioplasty, by applying a low level of laser energy directly to a region of ischemic myocardium before closing the surgical incision.

In non-invasive or minimally-invasive phototherapy, it is desirable to apply an efficacious amount of light energy to the internal tissue to be treated without highly traumatic incisions (e.g., using light sources positioned outside the body). However, absorption of the light energy by intervening tissue can limit the amount of light energy delivered to the target tissue site, while heating the intervening tissue. In addition, scattering of the light energy by intervening tissue can limit the power density or energy density delivered to the target tissue site. Brute force attempts to circumvent these effects by increasing the power and/or power density applied to the outside surface of the body can result in damage (e.g., burning) of the intervening tissue.

Non-invasive or minimally-invasive phototherapy methods are circumscribed by setting selected treatment parameters within specified limits so as to preferably avoid damaging the intervening tissue. A review of the existing scientific literature in this field would cast doubt on whether a set of undamaging, yet efficacious, parameters could be found. However, certain embodiments, as described herein, provide devices and methods which can achieve this goal.

FIG. 1is a flow diagram of a method100of treating a patient's heart in accordance with embodiments described herein. In an operational block110, a light source is provided which emits light having an initial power density. In an operational block120, the light source is positioned relative to the patient's heart with intervening tissue of the patient between the light source and the patient's heart. In an operational block130, light from the light source is directed onto cardiac tissue of the patient's heart without damaging the intervening tissue. The cardiac tissue is irradiated by an efficacious power density of light for an efficacious period of time.

Providing a Light Source

The light source provided in the operational block110preferably generates light in the visible to near-infrared wavelength range. In certain embodiments, the light source comprises one or more laser diodes, which each provide coherent light. In embodiments in which the light from the light source is coherent, the emitted light may produce “speckling” due to coherent interference of the light. This speckling comprises intensity spikes which are created by constructive interference and can occur in proximity to the target tissue being treated. For example, while the average power density may be approximately 10 mW/cm2, the power density of one such intensity spike in proximity to the cardiac tissue to be treated may be approximately 300 mW/cm2. In certain embodiments, this increased power density due to speckling can improve the efficacy of treatments using coherent light over those using incoherent light for illumination of deeper tissues.

In other embodiments, the light source provides incoherent light. Exemplary light sources of incoherent light include, but are not limited to, incandescent lamps or light-emitting diodes. A heat sink can be used with the light source (for either coherent or incoherent sources) to remove heat from the light source and to inhibit temperature increases at the torso.

In certain embodiments, the light source generates light which is substantially monochromatic (i.e., light having one wavelength, or light having a narrow band of wavelengths). To maximize the amount of light transmitted to the heart, the wavelength of the light is selected in certain embodiments to be at or near a transmission peak (or at or near an absorption minimum) for the intervening tissue, which in certain embodiments corresponds to a peak in the transmission spectrum of tissue at about 820 nanometers. In certain such embodiments, the light emitted by the light source has a wavelength at which the absorption by intervening tissue is below a damaging level. In other embodiments, the wavelength of the light is preferably between about 590 nanometers and about 3000 nanometers, more preferably between about 780 nanometers and about 1064 nanometers, and most preferably between about 780 nanometers and about 840 nanometers. In still other embodiments, wavelengths of 630, 790, 800, 808, 810, 820, or 830 nanometers can be used. It has also been found that an intermediate wavelength of about 739 nanometers appears to be suitable for penetrating the intervening tissue, although other wavelengths are also suitable and may be used.

In other embodiments, the light source generates light having a plurality of wavelengths. In certain such embodiments, each wavelength is selected so as to work with one or more chromophores within the target tissue. Without being bound by theory, it is believed that irradiation of chromophores increases the production of ATP in the target tissue, thereby producing beneficial effects. In certain embodiments, the light source is configured to generate light having a first wavelength and light having a second wavelength. In certain such embodiments, the light having the first wavelength is transmitted concurrently with the light having the second wavelength to the target cardiac tissue. In certain other such embodiments, the light having the first wavelength is transmitted sequentially with the light having a second wavelength to the target cardiac tissue.

In certain embodiments, the light source includes at least one continuously emitting GaAlAs laser diode having a wavelength of about 830 nanometers. In another embodiment, the light source comprises a laser source having a wavelength of about 808 nanometers. In still other embodiments, the light source includes at least one vertical cavity surface-emitting laser (VCSEL) diode. Other light sources compatible with embodiments described herein include, but are not limited to, light-emitting diodes (LEDs) and filtered lamps.

The light source is capable of emitting light energy at a power sufficient to achieve a predetermined power density at the cardiac target tissue. The subsurface power densities are selected to be effective at producing the desired biostimulative effects on the tissue being treated. In certain embodiments, phototherapy of tissue achieved by irradiating the target cardiac tissue with average power densities of light of at least about 0.01 mW/cm2and up to about 1 W/cm2. In various embodiments, the average power density at the cardiac tissue is at least about 0.01, 0.05, 0.1, 0.5, 1, 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, or 90 mW/cm2, respectively, depending on the desired clinical performance. In certain embodiments, the cardiac tissue is irradiated with an average power density of preferably about 0.01 mW/cm2to about 100 mW/cm2, more preferably about 0.01 mW/cm2to about 50 mW/cm2, and most preferably about 2 mW/cm2to about 20 mW/cm2. In still other embodiments, the efficacious average power density at the cardiac tissue being irradiated is between about 10 mW/cm2and about 150 mW/cm2. Other levels of power densities at the cardiac tissue being irradiated are compatible with embodiments described herein.

Taking into account the attenuation of energy as it propagates from the skin surface, through body tissue, bone, and fluids, to the subdermal target tissue, initial average power densities preferably between about 10 mW/cm2to about 10 W/cm2, or more preferably between about 100 mW/cm2to about 500 mW/cm2, will typically be used to attain the selected power densities at the subdermal target tissue. Higher average power densities can be used in accordance with embodiments described herein. To achieve such surface power densities, the light source is preferably capable of emitting light energy having a total power output of at least about 25 mW to about 100 W. Light sources with higher total power outputs can be used in accordance with embodiments described herein. In various embodiments, the total power output is limited to be no more than about 30, 50, 75, 100, 150, 200, 250, 300, 400, or 500 mW, respectively. Higher total power outputs can be used in accordance with embodiments described herein. In addition, the light sources of certain embodiments are operated in continuous-wave (CW) mode, while in other embodiments, the light sources are pulsed with peak power outputs.

In certain embodiments, the light source comprises a plurality of sources used in combination to provide the total power output. The actual power output of the light source is preferably controllably variable. In this way, the power of the light energy emitted can be adjusted in accordance with a selected average power density at the subdermal tissue being treated.

Certain embodiments utilize a light source that includes only a single laser diode that is capable of providing about 25 mW to about 100 W of total power output. In certain such embodiments, the laser diode can be optically coupled to the patient via an optical fiber or can be configured to provide a sufficiently large spot size to avoid power densities which would burn or otherwise damage the intervening tissue. In other embodiments, the light source utilizes a plurality of sources (e.g., laser diodes) arranged in a grid or array that together are capable of providing at least about 25 mW to about 2000 W of total power output. The light source of other embodiments may also comprise sources having power capacities outside of these limits.

In certain embodiments, the efficacious period of time over which the tissue is being irradiated by the efficacious power density of light is approximately one second, and up to approximately one hour. In various embodiments, the efficacious period of time is at least about 1, 3, 5, 10, 15, 20, 30, 45, 60, 120, 180, 300, 600, 900, 1200, or 3600 seconds, depending on the desired clinical performance. In certain embodiments, the cardiac tissue is irradiated for a time period of preferably about 1 second to about 5 minutes, more preferably about 1 second to about 3 minutes, and most preferably about 3 seconds to about 3 minutes. Other period of time for irradiation are compatible with embodiments described herein. In certain embodiments, the efficacious power density and the efficacious period of time are selected to achieve an efficacious energy density at the target tissue site being treated. In certain such embodiments, the efficacious energy density is in a range between approximately 0.01 mJ/cm2and approximately 27,000 mJ/cm2.

Other parameters can also be varied in the use of phototherapy in accordance with embodiments described herein. These other parameters can contribute to the light energy that is actually delivered to the treated tissue and may play key roles in the efficacy of phototherapy. Certain embodiments include irradiating a selected portion of the heart, while other embodiments irradiate the entire heart. Certain embodiments irradiate the selected portion of the heart or the entire heart by multiple irradiations of selected small portions of the heart in series.

Positioning the Light Source: Outside the Patient's Torso

The phototherapy methods for the treatment of the heart described herein may be practiced and described using, for example, a laser therapy apparatus such as that shown and described in U.S. Pat. Nos. 6,214,035, 6,267,780, 6,273,905 and 6,290,714, which are all incorporated in their entirety by reference herein, as are the references incorporated by reference therein.

FIGS. 2A-2Bschematically illustrate an embodiment of a therapy apparatus200comprising a light source210configured to be placed outside the patient's torso220. In such embodiments, positioning the light source210in the operational block120comprises placing the light source210outside the patient's torso220and interposing an element230between the light source210and the torso220. The element230inhibits temperature increases at the torso220for an efficacious power density at the cardiac tissue being irradiated. In certain embodiments, the element230is part of the therapy apparatus200, while in other embodiments, the element230is separate from the therapy apparatus200.

In certain embodiments, positioning the therapy apparatus200on the patient's chest provides access to irradiate selected anterior portions of the heart. In other embodiments, irradiation access to selected posterior portions of the heart is provided by placing the therapy apparatus200on the patient's back. Other positions of the therapy apparatus200can be used to provide irradiation access to other selected portions of the heart.

In the embodiment illustrated byFIG. 2A, the therapy apparatus200comprises a light source210having an output emission area211positioned to irradiate a portion of the heart222with an efficacious power density and wavelength of light through intervening tissue224. The therapy apparatus200further comprises an element230interposed between the light source210and the intervening tissue224. The element230is configured to inhibit temperature increases at the intervening tissue224caused by the light.

As used herein, the term “element” is used in its broadest sense, including, but not limited to, as a reference to a constituent or distinct part of a composite device. In certain embodiments, the element230is configured to contact at least a portion of the patient's torso220, as schematically illustrated inFIGS. 2A and 2B. In certain such embodiments, the element230is in thermal communication with and covers at least a portion of the torso220. In other embodiments, the element230is spaced away from the torso220and does not contact the torso220.

In certain embodiments, the light passes through the element230prior to reaching the torso220such that the element230is in the optical path of light propagating from the light source210, through the skin221, and through the bones, tissues, organs, arteries, veins, and fluids of the torso220(schematically illustrated inFIG. 2Bby the region223) to the heart222. In certain embodiments, the light passes through a transmissive medium of the element230, while in other embodiments, the light passes through an aperture of the element230. As described more fully below, the element230may be utilized with various embodiments of the therapy apparatus200.

In certain embodiments, the light source210is disposed on the interior surface of a housing240which fits securely onto the patient's torso220. The housing240provides structural integrity for the therapy apparatus200and holds the light source210and element230in place. Exemplary materials for the housing240include, but are not limited to, metal, plastic, or other materials with appropriate structural integrity. The housing240may include an inner lining242comprising a stretchable fabric or mesh material, such as Lycra or nylon. The inner lining242is configured to contact the torso220while remaining outside the propagation path of the light from the light source210to the heart222. In certain embodiments, the light source210is configured to be removably attached to the housing240in a plurality of positions so that the output emission area211of the light source210can be advantageously placed in a selected position for treatment of a selected portion of the heart222. In other embodiments, the light source210can be an integral portion of the housing240.

The light source210illustrated byFIG. 2Acomprises at least one power conduit212coupled to a power source (not shown). In some embodiments, the power conduit212comprises an electrical conduit which is configured to transmit electrical signals and power to an emitter (e.g., laser diode or light-emitting diode). In certain embodiments, the power conduit212comprises an optical conduit (e.g., optical waveguide) which transmits optical signals and power to the output emission area211of the light source210. In certain such embodiments, the light source210comprises optical elements (e.g., lenses, diffusers, and/or waveguides) which transmit at least a portion of the optical power received via the optical conduit212. In still other embodiments, the therapy apparatus200contains a power source (e.g., a battery) and the power conduit212is substantially internal to the therapy apparatus200.

In certain embodiments, the patient's torso220comprises hair and skin which cover the patient's chest. In other embodiments, at least a portion of the hair is removed prior to the phototherapy treatment, so that the therapy apparatus200substantially contacts the skin of the torso220.

In certain embodiments, the element230is configured to contact the patient's torso220, thereby providing an interface between the therapy apparatus200and the patient's torso220. In certain such embodiments, the element230is coupled to the light source210and in other such embodiments, the element230is also configured to conform to the contours of the torso220. In this way, the element230positions the output emission area211of the light source210relative to the torso220. In certain such embodiments, the element230is mechanically adjustable so as to adjust the position of the light source210relative to the torso220. By fitting to the torso220and holding the light source210in place, the element230inhibits temperature increases at the torso220that would otherwise result from misplacement of the light source210relative to the torso220. In addition, in certain embodiments, the element230is mechanically adjustable so as to fit the therapy apparatus200to the patient's torso220.

In certain embodiments, the element230provides a reusable interface between the therapy apparatus200and the patient's torso220. In such embodiments, the element230can be cleaned or sterilized between uses of the therapy apparatus200, particularly between uses by different patients. In other embodiments, the element230provides a disposable and replaceable interface between the therapy apparatus200and the patient's torso220. By using pre-sterilized and pre-packaged replaceable interfaces, certain embodiments can advantageously provide sterilized interfaces without undergoing cleaning or sterilization processing immediately before use.

In certain embodiments, the element230comprises a container (e.g., a cavity or bag) containing a material (e.g., gel). The container can be flexible and configured to conform to the contours of the torso220. Other exemplary materials contained in the container of the element230include, but are not limited to, thermal exchange materials such as glycerol and water. The element230of certain embodiments substantially covers a localized portion of the torso220in proximity to the irradiated portion of the torso220.

In certain embodiments, at least a portion of the element230is within an optical path of the light from the light source210to the torso220. In such embodiments, the element230is substantially optically transmissive at a wavelength of the light emitted by the output emission area211of the light source210and is configured to reduce back reflections of the light. By reducing back reflections, the element230increases the amount of light transmitted to the heart222and reduces the need to use a higher power light source210which may otherwise create temperature increases at the torso220. In certain such embodiments, the element230comprises one or more optical coatings, films, layers, membranes, etc. in the optical path of the transmitted light which are configured to reduce back reflections.

In certain such embodiments, the element230reduces back reflections by fitting to the torso220so as to substantially reduce air gaps between the torso220and the element230in the optical path of the light. The refractive-index mismatches between such an air gap and the element230and/or the torso220would otherwise result in at least a portion of the light propagating from the light source210to the heart222to be reflected back towards the light source210.

In addition, certain embodiments of the element230comprise a material having, at a wavelength of light emitted by the light source210, a refractive index which substantially matches the refractive index of the torso220(e.g., about 1.3), thereby reducing any index-mismatch-generated back reflections between the element230and the torso220. Examples of materials with refractive indices compatible with embodiments described herein include, but are not limited to, glycerol, water, and silica gels. Exemplary index-matching gels include, but are not limited to, gels available from Nye Lubricants, Inc. of Fairhaven, Mass. and “Scan Ultrasound Gel,” Ref. 11-08, from Parker Laboratories, Inc. of Fairfield, N.J.

In certain embodiments, the element230is configured to cool the torso220by removing heat from the torso220so as to inhibit temperature increases at the torso220. In certain such embodiments, the element230comprises a reservoir (e.g., a chamber or a conduit) configured to contain a coolant. The coolant flows through the reservoir near the torso220. The torso220heats the coolant, which flows away from the torso220, thereby removing heat from the torso220by active cooling. The coolant in certain embodiments circulates between the element230and a heat transfer device, such as a chiller, whereby the coolant is heated by the torso220and is cooled by the heat transfer device. Exemplary materials for the coolant include, but are not limited to, water or air.

In certain embodiments, the element230comprises a container231(e.g., a flexible bag) coupled to an inlet conduit232and an outlet conduit233, as schematically illustrated inFIG. 3. A flowing material (e.g., water, air, or glycerol) can flow into the container231from the inlet conduit232, absorb heat from the torso220, and flow out of the container231through the outlet conduit233. Certain such embodiments can provide a mechanical fit of the container231to the torso220and sufficient thermal coupling to prevent excessive heating of the torso220by the light. In certain embodiments, the container231can be disposable and replacement containers231can be used for subsequent patients.

In still other embodiments, the element230comprises a container (e.g., a flexible bag) containing a non-flowing material which does not flow out of the container but is thermally coupled to the torso220so as to remove heat from the torso220by passive cooling. Exemplary materials include, but are not limited to, water, glycerol, and gel. In certain such embodiments, the non-flowing material can be pre-cooled (e.g., by placement in a refrigerator) prior to the phototherapy treatment to facilitate cooling of the torso220.

In certain embodiments, the element230is configured to apply pressure to at least a portion of the skin221of the torso220in the optical path of the light. By applying sufficient pressure, the element230can blanch the portion of the skin221by forcing at least some blood out the optical path of the light. The blood removal resulting from the pressure applied by the element230to the skin221decreases the corresponding absorption of the light by blood in the skin221of the torso220. As a result, temperature increases due to absorption of the light by blood at the skin221of the torso220are reduced. As a further result, in certain embodiments, the fraction of the light transmitted to the subdermal target tissue of the heart222is increased.

FIGS. 4A and 4Bschematically illustrate embodiments of the element230configured to facilitate the blanching of the skin221of the torso220. In the cross-sectional view of a portion of the therapy apparatus200schematically illustrated inFIG. 4A, certain element portions234contact the skin221and other element portions235are spaced away from the skin221. The element portions234contacting the skin221provide an optical path for light to propagate from the light source210to the torso220. The element portions234contacting the skin221also apply pressure to the skin221, thereby forcing blood out from beneath the element portion234.FIG. 4Bschematically illustrates a similar view of an embodiment in which the light source210comprises a plurality of light sources210a,210b,210c.

FIG. 5Aschematically illustrates one embodiment of the cross-section along the line5-5ofFIG. 4B. The element portions234contacting the skin221comprise ridges extending along one direction, and the element portions235spaced away from the skin221comprise troughs extending along the same direction. In certain embodiments, the ridges are substantially parallel to one another and the troughs are substantially parallel to one another.FIG. 5Bschematically illustrates another embodiment of the cross-section along the line5-5ofFIG. 4B. The element portions234contacting the skin221comprise a plurality of projections in the form of a grid or array. More specifically, the portions234are rectangular and are separated by element portions235spaced away from the skin221, which form troughs extending in two substantially perpendicular directions. The portions234of the element230contacting the skin221can be a substantial fraction of the total area of the element230.

FIGS. 6A-6Cschematically illustrate an embodiment in which light emitted by the light sources210propagates from the light sources210through the intervening tissue224, including the skin221, of the torso220to the heart222and disperses in a direction generally parallel to the skin221, as shown inFIG. 6A. WhileFIG. 6Ashows the light sources210and the element230spaced away from the torso220, in other embodiments, the element230contacts the torso220. The light sources210are preferably spaced sufficiently far apart from one another such that the light emitted from each light source210overlaps with the light emitted from the neighboring light sources210at the heart222.FIG. 6Bschematically illustrates this overlap as the overlap of circular spots225at a reference depth at or below the surface of the heart222.FIG. 6Cschematically illustrates this overlap as a graph of the power density at the reference depth of the heart222along the line L-L ofFIGS. 6A and 6B. Summing the power densities from the neighboring light sources210(shown as a dashed line inFIG. 6C) serves to provide a more uniform light distribution at the tissue to be treated. In such embodiments, the summed power density is preferably less than a damage threshold of the heart222and above an efficacy threshold.

In certain embodiments, the element230is configured to diffuse the light prior to reaching the torso220.FIGS. 7A and 7Bschematically illustrate the diffusive effect on the light by the element230. An exemplary energy density profile of the light emitted by a light source210, as illustrated byFIG. 7A, is peaked at a particular emission angle. After being diffused by the element230, as illustrated byFIG. 7B, the energy density profile of the light does not have a substantial peak at any particular emission angle, but is substantially evenly distributed among a range of emission angles. By diffusing the light emitted by the light source210, the element230distributes the light energy substantially evenly over the area to be illuminated, thereby inhibiting “hot spots” which would otherwise create temperature increases at the torso220. In addition, by diffusing the light prior to its reaching the torso220, the element230can effectively increase the spot size of the light impinging the skin221of the torso220, thereby advantageously lowering the power density at the torso220, as described more fully below. In addition, in embodiments with multiple light sources210, the element230can diffuse the light to alter the total light output distribution to reduce inhomogeneities.

In certain embodiments, the element230provides sufficient diffusion of the light such that the power density of the light is less than a maximum tolerable level of the torso220and heart222. In certain other embodiments, the element230provides sufficient diffusion of the light such that the power density of the light equals a therapeutic value at the target tissue. The element230can comprise exemplary diffusers including, but are not limited to, holographic diffusers such as those available from Physical Optics Corp. of Torrance, Calif. and Display Optics P/N SN1333 from Reflexite Corp. of Avon, Conn.

In certain embodiments in which a plurality of light sources210are used, the light sources210are selectively activated individually or in groups to provide predetermined irradiation patterns on the torso220. These irradiation patterns can comprise irradiated areas and non-irradiated areas, which in certain embodiments, are varied as functions of time. In addition, the light sources210can be pulsed in selected groups or all together. This selective irradiation can be used to reduce the thermal load on particular locations of the torso220by limiting the amount of irradiation to any one particular area of the torso220. Thus, the thermal load at the torso220due to the absorption of the light can be distributed across the torso220, thereby avoiding unduly heating one or more portions of the torso220. In certain embodiments, the irradiated area is a substantial fraction of the total area of the heart, and in other embodiments, the irradiated area includes the total area of the heart. As described more fully below, in certain embodiments, the selective irradiation can be used to reduce the amount of scattering and absorption of the light by the lungs during the treatment procedure.

FIG. 8Aschematically illustrates another embodiment of the therapy apparatus300which comprises the housing240and a light source comprising a light-emitting blanket310.FIG. 8Bschematically illustrates an embodiment of the blanket310comprising a flexible substrate311(e.g., flexible circuit board), a power conduit interface312, and a sheet formed by optical fibers314positioned in a fan-like configuration.FIG. 8Cschematically illustrates an embodiment of the blanket310comprising a flexible substrate311, a power conduit interface312, and a sheet formed by a plurality of optical fibers314woven into a mesh. The blanket310is preferably positioned within the housing240so as to cover an area of the torso220corresponding to a portion of the heart222to be treated.

In certain such embodiments, the power conduit interface312is configured to be coupled to an optical fiber conduit313which provides optical power to the blanket310. The optical power interface312of certain embodiments comprises a beam splitter or other optical device which distributes the incoming optical power among the various optical fibers314. In other embodiments, the power conduit interface312is configured to be coupled to an electrical conduit which provides electrical power to the blanket310. In certain such embodiments, the power conduit interface312comprises one or more laser diodes, the output of which is distributed among the various optical fibers314of the blanket310.

In certain other embodiments, the blanket310comprises an electroluminescent sheet which responds to electrical signals from the power conduit interface312by emitting light. In such embodiments, the power conduit interface312comprises circuitry configured to distribute the electrical signals to appropriate portions of the electroluminescent sheet.

The side of the blanket310nearer the torso220is preferably provided with a light scattering surface, such as a roughened surface to increase the amount of light scattered out of the blanket310towards the torso220. The side of the blanket310further from the torso220is preferably covered by a reflective coating so that light emitted away from the torso220is reflected back towards the torso220. This configuration is similar to configurations used for the “back illumination” of liquid-crystal displays (LCDs). Other configurations of the blanket310are compatible with embodiments described herein.

In certain embodiments, the light source210generates light which cause eye damage if viewed by an individual. In such embodiments, the apparatus200can be configured to provide eye protection so as to avoid viewing of the light by individuals. For example, opaque materials can be appropriately placed to block the light from being viewed directly. In addition, interlocks can be provided so that the light source210is not activated unless the apparatus200is in place, or other appropriate safety measures are taken.

Another suitable phototherapy apparatus in accordance with embodiments described here is illustrated inFIG. 9. The illustrated therapy apparatus400includes a light source410, an element430, and a flexible strap440configured for securing the therapy apparatus400over an area of the patient's torso. The light source410can be disposed on the strap440itself, or in a housing450coupled to the strap440. The light source410preferably comprises a plurality of diodes410a,410b, . . . capable of emitting light energy having a wavelength in the visible to near-infrared wavelength range. The element430is configured to be positioned between the light source410and the patient's torso220.

The therapy apparatus400further includes a power supply (not shown) operatively coupled to the light source410, and a programmable controller460operatively coupled to the light source410and to the power supply. The programmable controller460is configured to control the light source410so as to deliver a predetermined power density to the target cardiac tissue. In certain embodiments, as schematically illustrated inFIG. 9, the light source410comprises the programmable controller460. In other embodiments the programmable controller460is a separate component of the therapy apparatus400.

In certain embodiments, the strap440comprises a loop of elastomeric material sized appropriately to fit snugly onto the patient's torso220. In other embodiments, the strap440comprises an elastomeric material to which is secured any suitable securing means470, such as mating Velcro strips, buckles, snaps, hooks, buttons, ties, or the like. The precise configuration of the strap440is subject only to the limitation that the strap440is capable of maintaining the light source410in a selected position so that light energy emitted by the light source410is directed towards the targeted cardiac tissue.

In the exemplary embodiment illustrated inFIG. 9, the housing450comprises a layer of flexible plastic or fabric that is secured to the strap440. In other embodiments, the housing450comprises a plate or an enlarged portion of the strap440. Various strap configurations and spatial distributions of the light sources410are compatible with embodiments described herein so that the therapy apparatus400can treat selected portions of cardiac tissue.

In still other embodiments, a therapy apparatus500for delivering the light energy includes a handheld probe505, as schematically illustrated inFIG. 10. The probe505includes a light source510and an element530as described herein.

Positioning the Light Source: Within the Torso

FIGS. 1A and 11Bschematically illustrate embodiments of a therapy apparatus600configured to be inserted into the esophagus602of the patient. The therapy apparatus600comprises a flexible probe605and a light source610located on a distal end620of the probe605. In certain embodiments, as illustrated byFIG. 11A, the distal end620of the probe605is configured to contact a surface603of the esophagus602. In certain such embodiments, the distal end620of the probe605further comprises an element630interposed between the light source610and the surface603of the esophagus602. As described above in relation to embodiments positioned outside the torso, the element630is configured to inhibit temperature increases at the esophagus602for an efficacious power density at the cardiac tissue.

In certain other embodiments, as illustrated byFIG. 11B, the esophagus602contains a material640which serves as the element630. In certain embodiments, the material640(e.g., water) has a refractive index which substantially matches the refractive index of the inside surface603of the esophagus602, thereby reducing any index-mismatch-generated back reflections between the distal end620and the esophagus602. In addition, the material640can provide cooling to the esophagus602to inhibit temperature increases. The material640can also advantageously diffuse the light from the light source610.

By inserting the therapy apparatus600into the esophagus602, the therapy apparatus600can treat portions of the heart which are not accessible by other embodiments described herein. For example, upon insertion into the esophagus602, the light source610of the therapy apparatus600is closer to the cardiac tissue to be irradiated than in embodiments with a light source positioned outside the torso. Thus, the therapy apparatus600can provide phototherapy using lower initial power densities since there is less intervening tissue to absorb or scatter the light. In addition, such embodiments can more easily irradiate selected posterior portions of the heart.

FIG. 12schematically illustrates an embodiment of a therapy apparatus700configured to be inserted into a blood vessel702of the patient. The therapy apparatus700comprises a catheter705and a light source710located on a distal end720of the catheter705. In certain embodiments, the catheter705is introduced into either an artery or a vein and positioned so that the light source710is in proximity to cardiac tissue. The catheter705is introduced interfemorally in certain embodiments by inserting the catheter705into a femoral artery. The catheter705is introduced interclavicularly in certain other embodiments by inserting the catheter705into a clavicular artery. By placing the light source710in proximity to the cardiac tissue to be irradiated, such embodiments avoid having the light absorbed or scattered by intervening tissue such as the lungs. An exemplary catheter is described by U.S. Pat. No. 6,443,974 issued to Oron et al., which is incorporated in its entirety by reference herein.

FIG. 13Aschematically illustrates an embodiment of a therapy apparatus800configured to avoid a portion of intervening tissue between the therapy apparatus800and the heart222. The therapy apparatus800comprises at least one light source810which comprises at least one needle820. In certain embodiments, the needle820comprises an optical fiber822that has a first end823optically coupled to the light source810, as illustrated inFIG. 13A. The needle820is positioned so that a second end824of the optical fiber822is inserted into the torso220. By transmitting light from the light source810into the torso220, such embodiments avoid scattering or absorption by a portion of the intervening tissue of the torso220.

In certain embodiments, the needle820is inserted through at least a portion of the skin of the patient's torso220. In certain such embodiments, the second end824of the optical fiber822is past the skin221of the torso220, thereby avoiding scattering or absorption by the skin221of light transmitted to the heart222. In other embodiments, the second end824is inserted deeper into the torso220, past portions of bone, muscles, and other tissue, so that these tissues do not scatter or absorb the light transmitted from the therapy apparatus800to the heart222. In still other embodiments, the second end824is inserted such that the needle820does not puncture the pericardium surrounding the heart222. Other positions of the needle820are compatible with embodiments described herein.

FIG. 13Bschematically illustrates an embodiment of the therapy apparatus800with a plurality of transdermal needles820. In the embodiment illustrated byFIG. 13B, each needle820itself is optically transmissive at the wavelength of light from the light source810. Thus, each needle820serves as a portion of an optical fiber822with a second end824inserted into the torso220. In certain embodiments, each needle820comprises a lumen or other conduit through which the light from the light source810is transmitted into the torso220.

Each needle820extends through at least a portion of the skin221of the torso220. In such embodiments, the light emitted from the second end824of the optical fiber822avoids scattering or absorption by the outermost layers of the skin221. In certain such embodiments, the needles820extend approximately halfway through the muscle wall of the chest to be within approximately 3 millimeters of bone. The needles820are preferably biocompatible and strong enough to withstand the insertion process.

Exemplary needles820in accordance with embodiments described herein include silicon microneedles, such as those described by U.S. Pat. No. 5,928,207 issued to Pisano et al. and U.S. Pat. No. 6,187,210 issued to Lebouitz et al., each of which is incorporated by reference herein. Other exemplary microneedles are described by Brazzle et al. in “Active Microneedles with Integrated Functionality,”Technical Digest of the 2000 Solid-State Sensor and Actuator Workshop, Hilton Head Isl., S.C., 06/04-08/00, Transducer Research Foundation, Cleveland (2000), pp. 199-202, which is incorporated in its entirety by reference herein.

In certain embodiments, phototherapy is performed by directly irradiating the cardiac tissue after a sufficient opening has been made in the chest. In certain such embodiments, the opening is made for a cardiac bypass surgical procedure. The phototherapy can provide a cardio-protective, healing-accelerating mechanism. The phototherapy can be performed before, during, after, or a combination thereof, the bypass surgical procedure. In other embodiments, the opening is made expressly for placing the therapy apparatus in proximity to the heart222. In certain such embodiments, the intervening tissue is at a minimum, while in other embodiments in which the therapy apparatus contacts the target cardiac tissue, the intervening tissue is effectively nonexistent.

In still other embodiments, at least a portion of the therapy apparatus is implanted within the torso220in proximity to the heart222. Such “pacemaker”-type embodiments can deliver light to a selected portion of the heart222while minimizing the scattering and absorption by intervening tissue. Such embodiments can implant a light source comprising a small laser or one or more battery-operated light-emitting diodes and use the light source to irradiate a selected portion of the heart.

In other embodiments, the blood can be irradiated within an artery (e.g., by placing a laser or an optical fiber within the artery). The irradiated blood then has more ATP which gets to the heart. In other embodiments, the blood can be removed from the body, irradiated outside the body, and returned to the body to carry ATP to the heart.

Directing Light Onto Cardiac Tissue: Power Density

Phototherapy for the treatment of cardiac tissue after a myocardial infarction (MI) is based in part on the discovery that power density (i.e., power per unit area or number of photons per unit area per unit time) and energy density (i.e., energy per unit area or number of photons per unit area or power density multiplied by the exposure time) of the light energy applied to tissue are significant factors in determining the relative efficacy of low level phototherapy. Contrary to previous understanding in the prior art, efficacy is not as directly related to the total power or the total energy delivered to the tissue. This discovery is particularly applicable with respect to treating and saving surviving but endangered cardiac tissue in a zone of danger surrounding the primary infarct after an MI. Preferred methods described herein are based at least in part on the finding that, given a selected wavelength of light energy, it is the power density and/or the energy density of the light delivered to cardiac tissue (as opposed to the total power or total energy delivered to the cardiac tissue) that appears to be important factors in determining the relative efficacy of phototherapy in treating patients after experiencing an MI.

Without being bound by theory, it is believed that light energy delivered within a certain range of power densities and energy densities provides the desired biostimulative effect on the intracellular environment, such that proper function is returned to previously nonfunctioning or poorly functioning mitochondria in at-risk cardiac cells. The biostimulative effect may include interactions with chromophores within the target tissue, which facilitate production of ATP thereby feeding energy to injured cells which have experienced decreased blood flow due to the MI. Because MIs correspond to blockages or other interruptions of blood flow to portions of the heart, it is thought that any effects of increasing blood flow by phototherapy are of less importance in the efficacy of phototherapy for MI victims. Further information regarding the role of power density and exposure time in phototherapy is described by Hans H.F.I. van Breugel and P. R. Dop Bär in “Power Density and Exposure Time of He—Ne Laser Irradiation Are More Important Than Total Energy Dose in Photo-Biomodulation of Human Fibroblasts In Vitro,” Lasers in Surgery and Medicine, Volume 12, pp. 528-537 (1992), which is incorporated in its entirety by reference herein.

In embodiments described herein, an efficacious power density of light is directed onto cardiac tissue. In certain such embodiments, a cardioprotective-effective power density of light is provided to a patient that has experienced an ischemic event in the heart, thereby providing a cardioprotective effect.

As used herein, the term “cardiodegeneration” refers to the process of cardiac cell destruction resulting from primary destructive events such as MI, as well as from secondary, delayed and progressive destructive mechanisms that are invoked by cells due to the occurrence of the primary destructive event. Primary destructive events include disease processes or physical injury or insult, including MI, but also include other diseases and conditions such as physical trauma or acute injury or insult. Secondary destructive mechanisms include any mechanism that leads to the generation and release of molecules toxic to cardiac cells, including apoptosis, depletion of cellular energy stores because of changes in mitochondrial membrane permeability, release or failure in the reuptake of excessive glutamate, reperfusion injury, and activity of cytokines and inflammation. Both primary and secondary mechanisms contribute to forming a “zone of danger” for cardiac cells, wherein the cardiac cells in the zone have at least temporarily survived the primary destructive event, but are at risk of dying due to processes having delayed effect.

As used herein, the term “cardioprotection” refers to a therapeutic strategy for slowing or preventing the otherwise irreversible loss of cardiac cells due to cardiodegeneration after a primary destructive event, whether the cardiodegeneration loss is due to disease mechanisms associated with the primary destructive event or secondary destructive mechanisms.

As used herein, the term “cardioprotective-effective” refers to a characteristic of an amount of light energy. A cardioprotective-effective amount of light energy achieves the goal of preventing, avoiding, reducing, or eliminating cardiodegeneration. In certain embodiments, a cardioprotective-effective amount is a power density of the light energy measured in mW/cm2, while in other embodiments, a cardioprotective-effective amount is an energy density of the light energy measured in mJ/cm2.

Thus, in certain embodiments, a method of phototherapy involves delivering a cardioprotective-effective amount of light energy having a wavelength in the visible to near-infrared wavelength range to a target area of the patient's heart222. In certain embodiments, the target area of the patient's heart222includes the area of infarct, i.e. to cardiac cells within the “zone of danger.”

In other embodiments, the target area includes portions of the heart222not within the zone of danger. In certain such embodiments, irradiation of healthy cardiac cells outside the zone of danger can treat and save surviving but endangered cardiac cells in the zone of danger surrounding the infarcted area. Without being bound by theory, it is believed that irradiation of healthy tissue in proximity to the zone of danger increases the production of ATP and copper ions in the healthy tissue and which then migrate to the injured cells within the region surrounding the infarct, thereby producing beneficial effects. Additional information regarding the biomedical mechanisms or reactions involved in phototherapy is provided by Tiina I. Karu in “Mechanisms of Low-Power Laser Light Action on Cellular Level”, Proceedings of SPIE Vol. 4159 (2000), Effects of Low-Power Light on Biological Systems V, Ed. Rachel Lubart, pp. 1-17, which is incorporated in its entirety by reference herein.

The significance of the power density used in phototherapy has ramifications with regard to the devices and methods used in phototherapy treatments of cardiac tissue, as schematically illustrated byFIGS. 14A and 14B, which show the effects of scattering by intervening tissue. Further information regarding the scattering of light by tissue is provided by V. Tuchin in “Tissue Optics: Light Scattering Methods and Instruments for Medical Diagnosis,”SPIE Press (2000), Bellingham, Wash., pp. 3-11, which is incorporated in its entirety by reference herein.

FIG. 14Aschematically illustrates a light beam900impinging a portion910of a patient's torso220and propagating through the patient's torso220to irradiate a portion920of the patient's heart222. In the exemplary embodiment ofFIG. 14A, the light beam900impinging the torso220has a circular cross-section with a radius of 2 centimeters and a cross-sectional area of approximately 12.5 cm2. For comparison purposes,FIG. 14Bschematically illustrates a light beam930having a significantly smaller cross-section impinging a smaller portion940of the torso220to irradiate a portion950of the heart222. The light beam930impinging the torso220inFIG. 14Bhas a circular cross-section with a radius of 1 centimeter and a cross-sectional area of approximately 3.1 cm2. The cross-sections and radii of the light beams900,930illustrated inFIGS. 14A and 14Bare exemplary; other light beams with other parameters are also compatible with embodiments described herein. In particular, similar considerations apply to focussed beams, collimated beams, or diverging beams, as they are similarly scattered by the intervening tissue.

As shown inFIGS. 14A and 14B, the cross-sections of the light beams900,930become larger while propagating through the torso220due to scattering from interactions with tissue. The light beams900,930propagate through various tissue portions, each with a characteristic angle of dispersion, with the light beams900,930experiencing an effective angle of dispersion. Assuming that the effective angle of dispersion is 15 degrees and the irradiated cardiac tissue of the heart220is 7 centimeters below the surface of the torso220, the resulting area of the portion920of the heart222irradiated by the light beam900inFIG. 14Ais approximately 45.6 cm2. Similarly, the resulting area of the portion950of the heart222irradiated by the light beam930inFIG. 14Bis approximately 24.8 cm2.

Irradiating the portion920of the heart222with a power density of 10 mW/cm2corresponds to a total power within the portion920of approximately 456 mW (10 mW/cm2×45.6 cm2). Assuming only approximately 0.5% of the light beam900is transmitted between the surface of the torso220and the heart222, the incident light beam900at the surface of the torso220will have a total power of approximately 91200 mW (456 mW/0.005) and a power density of approximately 7300 mW/cm2(91200 mW/12.5 cm2). Similarly, irradiating the portion950of the heart222with a power density of 10 mW/cm2corresponds to a total power within the portion950of approximately 248 mW (10 mW/cm2×24.8 cm2), and with the same 0.5% transmittance, the incident light beam950at the surface of the torso220will have a total power of approximately 49600 mW (248 mW/0.005) and a power density of approximately 15790 mW/cm2(49600 mW/3.1 cm2). These calculations are summarized in Table 1.

These exemplary calculations illustrate that to obtain a desired power density at the heart222, higher total power at the surface of the torso220can be used in conjunction with a larger spot size at the surface of the torso220. Thus, by increasing the spot size at the surface of the torso220, a desired power density at the heart222can be achieved with lower power densities at the surface of the torso220which can reduce the possibility of overheating the torso220. In certain embodiments, the light can be directed through an aperture to define the illumination of the torso220to a selected smaller area.

Directing Light Onto Cardiac Tissue: Other Parameters

In certain embodiments, delivering the cardioprotective amount of light energy includes selecting an initial power density of the light energy at the torso220corresponding to the predetermined efficacious power density at the target area of the heart222. As described above, light propagating through tissue is scattered and absorbed by the tissue. Calculations of the initial power density to be applied to the torso220so as to deliver a predetermined efficacious power density to the selected target area of the heart222preferably take into account the attenuation of the light energy as it propagates through the skin and other tissues, such as bone and lung tissue. Factors known to affect the attenuation of light propagating to the heart222include, but are not limited to, skin pigmentation, the presence and color of hair over the area to be treated, amount of fat tissue, body size, breast size, the presence of bruised or scarred tissue, amount of pericardial fluid, presence of other materials (e.g., sutures) in the intervening tissue, and the location of the target area of the heart222, particularly the depth of the area relative to the surface of the torso220. For example, for higher levels of skin pigmentation (with correspondingly higher absorptions), the power density applied to the torso220should be higher so as to deliver a predetermined power density of light energy to a selected portion of the heart222. In addition, the power density selected to be applied to the target area of the patient's heart222can depend on other factors, including, but not limited to, the wavelength of the applied light, the type and location of the injury to the heart222, and the patient's clinical condition.

The target area of the patient's heart222to be irradiated can be previously identified by using standard medical imaging techniques. In certain embodiments, treatment includes calculating an initial power density which corresponds to a preselected power density at the target area of the patient's heart222. The calculation of certain embodiments includes some or all of the factors listed above that affect the penetration of the light energy through the torso220and thus the power density at the target area. The power density of light energy to be delivered to the target area of the patient's heart222may also be adjusted to be combined with any other therapeutic agent or agents, especially pharmaceutical cardioprotective agents, to achieve the desired biological effect. In such embodiments, the selected power density can also depend on the additional therapeutic agent or agents chosen. The power density and other parameters of the applied light are then adjusted according to the results of the calculation.

These other parameters can include the timing pattern of the phototherapy. In certain embodiments, the light energy is preferably delivered for at least one treatment period of at least about five minutes, and more preferably for at least one treatment period of at least ten minutes. In other embodiments, the treatment proceeds continuously for a period of about 10 seconds to about 2 hours, more preferably for a period of about 1 minute to about 10 minutes, and most preferably for a period of about 1 minute to about 5 minutes.

In certain embodiments, the light energy is pulsed during the treatment period, while in other embodiments, the light energy is continuously applied during the treatment period. If the light is pulsed, the pulse widths are preferably at least about 10 nanoseconds, and are more preferably in a range between approximately 100 microseconds and approximately 20 milliseconds. In certain embodiments, the pulses occur at a frequency of up to about 100 kHz. Continuous wave light may also be used.

In certain embodiments, the treatment may be terminated after one treatment period, while in other embodiments, the treatment may be repeated for at least two treatment periods. The time between subsequent treatment periods is preferably at least about five minutes, more preferably at least about 1 to 2 days, and most preferably at least about one week. In certain embodiments in which treatment is performed over the course of multiple days, the therapy apparatus is wearable over multiple concurrent days. The length of treatment time and frequency of treatment periods can depend on several factors, including the functional recovery of the patient and the results of imaging analysis of the infarct. In certain embodiments, one or more treatment parameters can be adjusted in response to a feedback signal from a device (e.g., electrocardiogram or magnetic resonance imaging) monitoring the patient.

In certain embodiments, the therapy pattern is selected to reduce the amount of scattering and absorption of the light by the lungs during the treatment procedure. Lung tissue surrounds a large fraction of the heart222and the lung tissue can be a significant source of scatter and absorption. For example, the lungs are substantially opaque at wavelengths of approximately 810 nanometers. However, during breathing, the lungs move back and forth such that the fraction of the heart222occluded from a light source by the lungs varies. Thus, in certain embodiments, irradiation occurs during those portions of the breathing cycle at which the lungs comprise a minimum fraction of the intervening tissue between the light source and the heart222.

The thrombolytic therapies currently in use for treatment of MI are typically begun within a few hours of the MI. However, many hours often pass before a person who has suffered an MI receives medical treatment, so the short time limit for initiating thrombolytic therapy excludes many patients from treatment. In contrast, phototherapy treatment of MI appears to be more effective if treatment begins no earlier than several hours after the ischemic event has occurred. Consequently, the present methods of phototherapy may be used to treat a greater percentage of MI patients.

In certain embodiments, a method provides a cardioprotective effect in a patient that had an ischemic event in the heart. The method comprises identifying a patient who has experienced an ischemic event in the heart. The method further comprises estimating the time of the ischemic event. The method further comprises commencing administration of a cardioprotective effective amount of light energy to the heart. The administration of the light energy is commenced no earlier than about two hours following the time of the ischemic event. In certain embodiments, phototherapy treatment can be efficaciously performed preferably within 24 hours after the ischemic event occurs, and more preferably no earlier than three hours following the ischemic event, and most preferably no earlier than five hours following the ischemic event. In certain embodiments, one or more of the treatment parameters can be varied depending on the amount of time that has elapsed since the ischemic event.

Without being bound by theory, it is believed that the benefit in delaying treatment occurs because of the time needed for induction of ATP production, and/or the possible induction of angiogenesis in the region surrounding the infarct. Thus, in accordance with one preferred embodiment, the phototherapy for the treatment of MI occurs preferably about 6 to 24 hours after the onset of MI symptoms, more preferably about 12 to 24 hours after the onset of symptoms. It is believed, however, that if treatment begins after about 2 days, its effectiveness will be greatly reduced.

In certain embodiments, the phototherapy is combined with other types of treatments for an improved therapeutic effect. Treatment can comprise directing light through the torso220of the patient to a target area of the heart222concurrently with applying an electromagnetic field to the heart. In such embodiments, the light has an efficacious power density at the target area and the electromagnetic field has an efficacious field strength. For example, the therapy apparatus can also include systems for electromagnetic treatment, e.g., as described in U.S. Pat. No. 6,042,531 issued to Holcomb, which is incorporated in its entirety by reference herein. In certain embodiments, the electromagnetic field comprises a magnetic field, while in other embodiments, the electromagnetic field comprises a radio-frequency (RF) field. As another example, treatment can comprise directing an efficacious power density of light through the torso220of the patient to a target area of the heart222concurrently with applying an efficacious amount of ultrasonic energy to the heart222. Such a system can include systems for ultrasonic treatment, e.g., as described in U.S. Pat. No. 5,054,470 issued to Fry et al., which is incorporated in its entirety by reference herein.

Directing Light Onto Cardiac Tissue: Therapy Apparatus Control

FIG. 15is a block diagram of a control circuit1000comprising a programmable controller1010coupled to a light source1005according to embodiments described herein. The control circuit1000is configured to adjust the power of the light energy emitted by the light source1005to generate a predetermined energy delivery profile, such as a predetermined subsurface power density, to the target area of the heart222. In certain embodiments, the control circuit1000is also configured to adjust other parameters of the phototherapy, including but not limited to, pulsing of the light, number, frequency, and duration of treatment periods, pattern of irradiation applied to the patient, wavelengths of the light, and the magnitude, timing, and duration of the application of other sources of energy (e.g., magnetic, RF, ultrasonic) to the heart.

In certain embodiments, the programmable controller1010comprises a logic circuit1020, a clock1030coupled to the logic circuit1020, and an interface1040coupled to the logic circuit1020. The clock1030of certain embodiments provides a timing signal to the logic circuit1020so that the logic circuit1020can monitor and control timing intervals of the applied light. Examples of timing intervals include, but are not limited to, total treatment times, pulsewidth times for pulses of applied light, and time intervals between pulses of applied light. In certain embodiments, the light source1005can be selectively turned on and off to reduce the thermal load at the torso220and to deliver a selected power density to the target cardiac tissue. In addition, in embodiments using a plurality of light sources, the light sources can be selectively activated to provide a predetermined pattern of irradiation.

The interface1040of certain embodiments provides signals to the logic circuit1020which the logic circuit1020uses to control the applied light. The interface1040can comprise a user interface or an interface to a sensor monitoring at least one parameter of the treatment. In certain such embodiments, the programmable controller1010is responsive to signals from the sensor to preferably adjust the treatment parameters to optimize the measured response. The programmable controller1010can thus provide closed-loop monitoring and adjustment of various treatment parameters to optimize the phototherapy. The signals provided by the interface1040from a user are indicative of parameters that may include, but are not limited to, patient characteristics (e.g., skin type, fat percentage), selected applied power densities, target time intervals, and power density/timing profiles for the applied light.

In certain embodiments, the logic circuit1020is coupled to a light source driver1050. The light source driver1050is coupled to a power supply1060, which in certain embodiments comprises a battery and in other embodiments comprises an alternating current source. The light source driver1050is also coupled to the light source1005. The logic circuit1020is responsive to the signal from the clock1030and to user input from the user interface1040to transmit a control signal to the light source driver1050. In response to the control signal from the logic circuit1020, the light source driver1050adjust and controls the power applied to the light source1005. Other control circuits besides the control circuit1000ofFIG. 15are compatible with embodiments described herein.

In certain embodiments, the logic circuit1020is responsive to signals from a sensor monitoring at least one parameter of the treatment to control the applied light. For example, certain embodiments comprise a temperature sensor thermally coupled to the torso220to provide information regarding the temperature of the torso220to the logic circuit1020. In such embodiments, the logic circuit1020is responsive to the information from the temperature sensor to transmit a control signal to the light source driver1050so as to adjust the parameters of the applied light to maintain the temperature at the torso220below a predetermined level. Other embodiments include exemplary biomedical sensors including, but not limited to, an electrocardiograph sensor, a blood flow sensor, a blood gas (e.g., oxygenation) sensor, an ATP production sensor, or a cellular activity sensor. Such biomedical sensors can provide real-time feedback information to the logic circuit1020. In certain such embodiments, the logic circuit1020is responsive to signals from the sensors to preferably adjust the parameters of the applied light to optimize the measured response. The logic circuit1020can thus provide closed-loop monitoring and adjustment of various parameters of the applied light to optimize the phototherapy.

Example: Phototherapy on Neurons

While the following description recounts the irradiation of neurons with an efficacious power density of light, it serves as an example of the phototherapy technique in general. An in vitro experiment was done to demonstrate one effect of phototherapy on neurons, namely the effect on ATP production. Normal Human Neural Progenitor (NHNP) cells were obtained cryopreserved through Clonetics of Baltimore, Md., catalog # CC-2599. The NHNP cells were thawed and cultured on polyethyleneimine (PEI) with reagents provided with the cells, following the manufacturers' instructions. The cells were plated into 96 well plates (black plastic with clear bottoms, Becton Dickinson of Franklin Lakes, N.J.) as spheroids and allowed to differentiate into mature neurons over a period of two weeks.

A Photo Dosing Assembly (PDA) was used to provide precisely metered doses of laser light to the NHNP cells in the 96 well plates. The PDA included a Nikon Diaphot inverted microscope (Nikon of Melville, N.Y.) with a LUDL motorized x,y,z stage (Ludl Electronic Products of Hawthorne, N.Y.). An 808 nanometer laser was routed into the rear epi-fluorescent port on the microscope using a custom designed adapter and a fiber optic cable. Diffusing lenses were mounted in the path of the beam to create a “speckled” pattern, which was intended to mimic in vivo conditions after a laser beam passed through human skin. The beam diverged to a 25 millimeter diameter circle when it reached the bottom of the 96 well plates. This dimension was chosen so that a cluster of four adjacent wells could be lased at the same time. Cells were plated in a pattern such that a total of 12 clusters could be lased per 96 well plate. Stage positioning was controlled by a Silicon Graphics workstation and laser timing was performed by hand using a digital timer. The measured power density passing through the plate for the NHNP cells was 50 mW/cm2.

Two independent assays were used to measure the effects of 808 nanometer laser light on the NHNP cells. The first was the CellTiter-Glo Luminescent Cell Viability Assay (Promega of Madison, Wis.). This assay generates a “glow-type” luminescent signal produced by a luciferase reaction with cellular ATP. The CellTiter-Glo reagent is added in an amount equal to the volume of media in the well and results in cell lysis followed by a sustained luminescent reaction that was measured using a Reporter luminometer (Turner Biosystems of Sunnyvale, Calif.). Amounts of ATP present in the NHNP cells were quantified in Relative Luminescent Units (RLUs) by the luminometer.

The second assay used was the alamarBlue assay (Biosource of Camarillo, Calif.). The internal environment of a proliferating cell is more reduced than that of a non-proliferating cell. Specifically, the ratios of NADPH/NADP, FADH/FAD, FMNH/FMN and NADH/NAD, increase during proliferation. Laser irradiation is also thought to have an effect on these ratios. Compounds such as alamarBlue are reduced by these metabolic intermediates and can be used to monitor cellular states. The oxidization of alamarBlue is accompanied by a measurable shift in color. In its unoxidized state, alamarBlue appears blue; when oxidized, the color changes to red. To quantify this shift, a 340PC microplate reading spectrophotometer (Molecular Devices of Sunnyvale, Calif.) was used to measure the absorbance of a well containing NHNP cells, media and alamarBlue diluted 10% v/v. The absorbance of each well was measured at 570 nanometers and 600 nanometers and the percent reduction of alamarBlue was calculated using an equation provided by the manufacturer.

The two metrics described above, (RLUs and % Reduction) were then used to compare NHNP culture wells that had been lased with 50 mW/cm2at a wavelength of 808 nanometers. For the CellTiter-Glo assay, 20 wells were lased for 1 second and compared to an unlased control group of 20 wells. The CellTiter-Glo reagent was added 10 minutes after lasing completed and the plate was read after the cells had lysed and the luciferase reaction had stabilized. The average RLUs measured for the control wells was 3808+/−3394 while the laser group showed a two-fold increase in ATP content to 7513+/−6109. The standard deviations were somewhat high due to the relatively small number of NHNP cells in the wells (approximately 100 per well from visual observation), but a student's unpaired t-test was performed on the data with a resulting p-value of 0.02 indicating that the two-fold change is statistically significant.

The alamarBlue assay was performed with a higher cell density and a lasing time of 5 seconds. The plating density (calculated to be between 7,500-26,000 cells per well based on the certificate of analysis provided by the manufacturer) was difficult to determine since some of the cells had remained in the spheroids and had not completely differentiated. Wells from the same plate can still be compared though, since plating conditions were identical. The alamarBlue was added immediately after lasing and the absorbance was measured 9.5 hours later. The average measured values for percent reduction were 22%+/−7.3% for the 8 lased wells and 12.4%+/−5.9% for the 3 unlased control wells (p-value=0.076). These alamarBlue results support the earlier findings in that they show a similar positive effect of the laser treatment on the cells.

Increases in cellular ATP concentration and a more reduced state within the cell are both related to cellular metabolism and are considered to be indications that the cell is viable and healthy. These results are novel and significant in that they show the positive effects of laser irradiation on cellular metabolism in in-vitro neuronal cell cultures.

The explanations and illustrations presented herein are intended to acquaint others skilled in the art with the invention, its principles, and its practical application. Those skilled in the art may adapt and apply the invention in its numerous forms, as may be best suited to the requirements of a particular use. Accordingly, the specific embodiments of the present invention as set forth are not intended as being exhaustive or limiting of the invention.