| Methods and systems for providing right and/or left heart support during cardiac surgery -> Monitor Keywords |
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Methods and systems for providing right and/or left heart support during cardiac surgeryRelated Patent Categories: Surgery, Miscellaneous, MethodsMethods and systems for providing right and/or left heart support during cardiac surgery description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20050279370, Methods and systems for providing right and/or left heart support during cardiac surgery. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATIONS [0001] This application is a divisional of co-pending U.S. application Ser. No. 09/481,730, filed Jan. 11, 2000, which is a continuation-in-part of U.S. application Ser. No. 09/462,656, filed Jan. 14, 2000, entitled "Transport Pumps and Organ Stabilization Apparatus Including Related Methods," which is a continuation-in-part of U.S. application Ser. No. 08/933,566, filed Sep. 19, 1997, now U.S. Pat. No. 6,083,260, which is a continuation-in-part of U.S. application Ser. No. 08/891,456, filed Jul. 11, 1997, now U.S. Pat. No. 6,123,725. BACKGROUND OF THE INVENTION [0002] I. Field of the Invention [0003] The present invention involves methods and systems for performing heart surgery. More particularly, the present invention is directed to methods and systems for providing right and/or left heart support during beating heart surgery. [0004] II. Discussion of the Prior Art [0005] Major heart surgery is oftentimes accomplished by procedures that require full cardiopulmonary bypass (CPB) through the use of artificial heart-lung machines and complete cessation of cardiopulmonary activity. While the average mortality rate with this type of procedure is low, it is nonetheless associated with a complication rate that is often much higher compared to when cessation of the heart and CPB are not required. The use of CPB continues to represent a major assault on a host of body systems. For example, there is noticeable degradation of mental faculties following such surgeries in a significant percentage of patients who undergo coronary artery bypass grafting (CABG) procedures. The CABG procedure generally involves open chest surgical techniques to treat diseased vessels. During this procedure, the sternum of the patient is cut in order to spread the chest apart and provide access to the heart. During surgery the heart is stopped, and by the use of CPB blood is diverted from the lungs to an artificial oxygenator. In general CABG procedures, a source of arterial blood is then connected to a coronary artery downstream from the occlusion. The source of blood is often an internal mammary artery, and the target coronary artery is typically among the anterior or posterior arteries which may be narrowed or occluded. The degradation of mental faculties resulting from CABG procedures is commonly attributed to cerebral arterial blockage and emboli from debris in the blood generated by the use of CPB. At the same time, the dramatic increase in the life expectancy of the general population has resulted in patients that are more likely to be older and in poor health, with less cardiovascular, systemic, and neurologic reserve needed to recover from the trauma caused by the use of CPB. As a consequence, inflammatory, hemostatic, endocrinologic, and neurologic stresses are tolerated to a much lesser degree by a significant number of patients today, and play a more significant role in CPB-induced morbidity. [0006] The combined statistics of postoperative morbidity and mortality continue to illustrate the shortcomings of CPB. The extracorporeal shunting and artificially induced oxygenation of blood activates a system wide roster of plasma proteins and blood components in the body including those that were designed to act locally in response to infection or injury. When these potent actors are disseminated throughout the body without normal regulatory controls, the entire body becomes a virtual battleground. The adverse hemostatic consequences of CPB also include prolonged and potentially excessive bleeding. CPB-induced platelet activation, adhesion, and aggregation also contribute to a depletion in platelet number, and is further compounded by the reversibly depressed functioning of platelets remaining in circulation. The coagulation and fibrinolytic systems both contribute to hemostatic disturbances during and following CPB. However, the leading cause of morbidity and disability following cardiac surgery is cerebral complications. Gaseous and solid micro and macro emboli, and less often perioperative cerebral hypoperfusion, produce neurologic effects ranging from subtle neuropsychologic deficits to fatal stroke. Advances in computed tomography, magnetic resonance imaging, ultrasound, and other imaging and diagnostic techniques have added to the understanding of these complications. But with the possible exception of perioperative electroencephalography, these technologies do not yet permit real time surgical adjustments that are capable of preventing emboli or strokes in the making. Doppler and ultrasound evaluation of the carotid artery and ascending aorta, and other diagnostic measures, can help identify surgical patients at elevated risk for stroke and are among the growing list of pharmacologic and procedural measures for reducing that risk. [0007] CPB also affects various endocrine systems, including the thyroid gland, adrenal medulla and cortex, pituitary gland, pancreas, and parathyroid gland. These systems are markedly affected not only by inflammatory processes, but also by physical and biochemical stresses imposed by extracorporeal perfusion. Most notably, CPB is now clearly understood to induce euthyroid-sick syndrome which is marked by profoundly depressed triiodothyronine levels persisting for days following cardiothoracic surgery. The efficacy of hormone replacement regimens to counteract this effect are currently undergoing clinical investigation. By contrast, levels of the stress hormones epinephrine, norepinephrine, and cortisol are markedly elevated during and following CPB, and hyperglycemia is also possible. [0008] Beating heart bypass surgery has been recognized as desirable because it has the possibility of avoiding the necessity of placing the patient on a full CPB system. However, attempts at beating heart bypass surgery have met with limited success and have essentially been limited to surgery on the anterior heart vessels due to problems which develop when the beating heart is lifted or displaced from its normal position in order to perform the beating heart surgery. Typically when the beating heart is lifted or manipulated in order to provide surgical access to posterior heart vessels, a number of difficulties are encountered. When the beating heart is lifted and manipulated, the right side of the heart tends to collapse, particularly the right auricle or atrium and frequently the right ventricle and/or pulmonary artery. When the right side of the heart collapses, pulmonary blood flow either ceases or becomes inadequate, thus forcing the use of CPB. Another difficulty encountered is that, even if the right side of the heart does not collapse, the pulmonary artery and/or the pulmonary vein frequently become crimped or kinked thus also impeding the pulmonary blood flow. Similarly, during the lifting and manipulation of the beating heart for lateral or posterior access, the left side of the heart, particularly the left auricle or left atrium can also collapse or partially collapse, thus impeding aortic circulatory blood flow. Further, when the beating heart is lifted or manipulated for beating heart surgery access or during catheterization or cannulation procedures, the heart may lapse into arrhythmia or disrhythmia or may arrest at least a portion of the time or most of the time that the surgery is being performed thus likewise impeding pulmonary blood flow and arterial circulatory blood flow. As a result, patients undergoing beating heart surgery are at risk of having to be placed on CPB on an emergency basis in the event that the pulmonary and/or circulatory blood flow is compromised during the surgery, which presents the CPB-induced side effects previously described. [0009] The medical community is currently performing more beating heart bypass surgery in an effort to avoid the use of full CPB. The need is increasing for apparatus systems, methods and associated equipment to enhance the capability and versatility of beating heart surgery and to avoid CPB procedures in any heart surgery. The current trend toward thoracoscopic methods of performing bypass surgery, without opening the chest cavity, have resulted in limited success and applicability primarily due to the limited number of heart vessels which can be accessed through thoracoscopic methods. A major limitation of thorascopic bypass surgery methods is due to the fact that only the anterior heart vessels are accessible for surgery. More importantly, even open chest surgery providing full access to the heart also requires CPB when bypass surgery is performed on the lateral or posterior vessels of the heart, due to the fact that in conventional procedures the heart must be stopped when it is lifted or rotated from its normal position and manipulated for surgical access to the various heart vessels. [0010] The present invention addresses this need by providing systems and methods for performing cardiac surgery that eliminate, or at least reduce, the need for full CPB. SUMMARY OF THE INVENTION [0011] The present invention provides methods and systems for performing cardiac surgery wherein the patient's lungs are used for blood oxygenation, thereby avoiding the need for CPB or other external blood oxygenation equipment or procedure. The present invention accomplishes this goal by maintaining at least partial blood flow through a protected blood flow path within the right and/or left side(s) of a beating heart to ensure sufficient pulmonary blood flow to the lungs and/or circulatory blood flow throughout the body during beating heart cardiac surgery. In reference to this invention, the "right side" of the heart refers to and includes the vena cava veins (superior and inferior), the right atrium, the right ventricle, the pulmonary artery and any combination or all thereof. The "right side" of the heart provides the pulmonary blood flow to the lungs. The "left side" of the heart refers to and includes the pulmonary veins, the left atrium, the left ventricle, the aorta and any combination or all thereof. The "left side" of the heart provides the circulatory blood flow to the body. The terms "pulmonary artery" and "pulmonary vein" include all branches thereof, and the term "aorta" includes the aortic vessels which are near the heart and are exposed or manipulated during open chest cardiac surgery or are utilized during minimally invasive cardiac surgery. As will be explained in greater detail below, in accordance with the present invention the protected blood flow path may be established by positioning one or more conduits within at least a portion of the right and/or left sides(s) of the heart, and at least partial blood flow may be maintained through the protected blood flow path by the pumping action of a blood pump communicatively coupled to the conduit or, alternately, by the pumping action of the beating heart itself. [0012] In an important aspect, the present invention ensures sufficient pulmonary and/or circulatory blood flow during beating heart surgery regardless of any compromise in cardiac output or function experienced during beating heart surgery. Generally speaking, such compromise conditions include any situation where the cardiac output of the beating heart is diminished or disrupted from normal levels. As noted above, the cardiac output of a beating heart can become compromised in a multitude of ways during beating heart surgery. For example, when the beating heart is lifted and manipulated to provide surgical access to posterior or lateral heart vessels, portions of the right and/or left side of the heart may collapse, thereby causing the pulmonary and/or circulatory blood flow to either cease or become inadequate. Even if collapse does not occur, portions of the right and/or left side of the heart may nonetheless become crimped or kinked (particularly the pulmonary artery and/or the pulmonary vein) and thereby impede or cease the pulmonary and/or circulatory blood flow during beating heart surgery. The cardiac output of the heart may also become compromised if the heart lapses even briefly into arrhythmia, disrhythmia or arrest during beating heart surgery. Up until now, the above-identified compromise conditions place patients undergoing beating heart surgery at risk of being placed on CPB on an emergency basis in the event that the pulmonary and/or circulatory blood flow is compromised during the surgery. By maintaining at least partial blood flow through the right and/or left sides of the heart during beating heart surgery, the present invention removes this risk and thus avoids the host of adverse side-effects associated with CPB. [0013] The present invention provides, generally speaking, two types of systems for carrying out the methods of this invention, which systems may be selected and employed (individually or in combination) in the right and/or left side(s) of the heart to meet the needs of a particular beating heart surgical procedure. The first system involves a pump and cannula system for selectively augmenting the heart's natural pumping ability during beating heart surgery to ensure sufficient pulmonary and/or circulatory blood flow, thereby avoiding the need for CPB. The second system involves one or more conduits, such as cannulas and/or stents, positioned within the heart to establish a protected blood flow path such that the heart's natural pumping activity will maintain at least partial blood flow therethrough during beating heart surgery, thereby ensuring sufficient pulmonary and/or circulatory blood flow and thus avoiding the need for CPB. [0014] The first system for carrying out the methods of the present invention may take a variety of different forms. Generally speaking, the cannula is positioned to establish a protected blood flow path within a portion of the heart and the pump is selectively operated to maintain at least partial blood flow therethrough during beating heart surgery. For right heart support, the cannula may extend through the tricuspid valve and/or pulmonary valve into the pulmonary artery. For left heart support, the cannula may extend through the bicuspid valve and/or aortic valve into the aorta. In either embodiment, the pump is communicatively coupled to the cannula to selectively (i.e. automatically or on-demand) transport blood past the valve(s) through which the cannula passes to augment the pumping ability of the right and/or left side of the heart. The pump may be adapted as a miniaturized blood pump so it can be positioned close to the heart, either in the open chest cavity or at least in the sterile surgical field, thus providing a minimum priming volume. Alternatively, the cannula can also be adapted to be inserted into the heart in closed chest procedures through the chest wall as part of a thorascopic procedure, through the femoral vein, the jugular vein or any appropriate access point in the venous system. In these instances, the pump is adapted to be positioned as close to the body insertion point as possible in order to keep priming volume to a minimum; for that reason thorascopic or jugular access is preferred when a closed chest procedure is elected. The pump may also comprise an intravascular pump dimensioned to be positioned within the heart itself, having a priming volume of approximately zero. The pump, in all embodiments, is preferably variable output and controlled (automatically or on-demand) in response to one of a variety of appropriate parameters, including but not limited to blood pressure, blood flow, blood oxygen level, and/or blood CO2 level. [0015] In all embodiments, the pump and cannula system may be used in both the right and left sides when bypass surgery is initiated. The pump and cannula system of the present invention is particularly useful during beating heart surgery to overcome or prevent situations where cardiac output or outflow may become compromised. As noted above, these situations may stem from, but are not necessarily limited to, instances when the heart is lifted, rotated or otherwise manipulated to access lateral or posterior blood vessels, when the heart outflow is diminished or reduced such as by a collapse, kink, or restriction in the heart chambers or in the veins or arteries, when the heart goes into arrhythmia or malfunctions in any way during the operation, or when the heart is intentionally stopped such as by the application of cardioplegia to perform procedures such as valve surgery, internal surgery or other reason. This system is also desirable in any heart surgery procedure, even for anterior vessel bypass, when lifting or manipulating of the heart is not anticipated. This applies to both open chest and minimally invasive procedures. [0016] By having this system in place before cardiac surgery begins, the present invention thus assures that the patient will at all times during the surgery have adequate pulmonary blood flow through the lungs and/or circulatory blood flow throughout the body. More importantly, it will avoid the necessity of being placed on a CPB machine in the event of an unexpected failure of the beating heart to sustain adequate pulmonary or circulatory blood flow during beating heart surgery. This allows the heart to continue to beat and provide pulmonary and circulatory blood flow to the extent it is capable, until there is a cardiac output compromise (such as by collapse, kink, arrhythmia or arrest, etc.) which decreases or stops the blood flow output by the heart. When that occurs, the pump(s) in either or both sides of the heart may be engaged to augment and/or replace the blood flow produced by the heart such that the patient's pulmonary and/or circulatory blood flows are maintained at sufficient levels to sustain them during the surgery. By having this system in place at the beginning of the beating heart surgery, even for anterior vessel surgery when no need is anticipated, it can merely be engaged or turned on to provide pump assisted blood flow if needed on an unexpected or emergency basis, thus assuring that emergency CPB procedures are avoided. Thus, this system assures that the patient's lungs are utilized for oxygenation of the blood during the entire surgical procedure, even if an unexpected compromise in blood flow from the beating heart occurs. [0017] In one embodiment, the pump and cannula system is provided wherein the cannula portion is adapted for insertion through at least the pulmonary valve and a sufficient length into the pulmonary artery to provide a protected blood flow path within one or more of the right atrium, right ventricle, and pulmonary artery and the pump may be selectively operated to maintain at least a partial blood flow therethrough during beating heart surgery. Access for insertion of the cannula portion can be through the vena cava, e.g., from a femoral vein incision, through an incision in the wall of the vena cava or in the wall of the right atrium. If the cannula is not inserted through the tricuspid valve, but only through the pulmonary valve and into the pulmonary artery, access could be through an incision in the wall of the right ventricle or reverse access can be used by entering through an incision in the wall of the pulmonary artery. Separate cannulas can be employed, i.e., one introduced through the right atrium and through the tricuspid valve but ending in the right ventricle, and a second introduced by any desired access and beginning in the right ventricle and extending through the pulmonary valve and a desired length, according to this invention, into the pulmonary artery. The pump portion of the system is adapted for intake of blood upstream of the pulmonary valve or upstream of the tricuspid valve and output of blood into the right ventricle or into the pulmonary artery during beating heart surgery. The pump system may be integral with the above cannula or cannulas, particularly in a concentric double wall cannula configuration, or can comprise pump cannulas separate from and in addition to the above cannulas which protect the right side from collapse. [0018] In another embodiment, a separate pump and cannula system may be provided for the left side wherein the cannula portion is adapted for insertion through at least the aortic valve and a sufficient length into the aorta to provide a protected blood flow path within one or more of the pulmonary vein, left atrium, left ventricle, and aorta, and the pump may be selectively operated to maintain at least partial blood flow therethrough during beating heart surgery. As indicated above for the right side, access for the left side cannula or cannulas can be from any desired upstream or downstream incision. One or two cannulas may be employed for preventing collapse of the left side. The pump portion of the system, which may have its separate cannulas, is adapted for intake of blood upstream of the aortic valve or the bicuspid valve and output of blood into the left ventricle or the aorta during beating heart surgery. [0019] The pump and cannula systems of the present invention may be used in either the right side system or the left side system or both depending on the particular patient or procedure. Whether the cannula for pump output extends into the pulmonary artery/aorta or extends only into the respective ventricle will similarly depend on the requirements for a particular patient or procedure. In some instances, the beating heart blood flow may be impeded due to partial compression, wrinkling or other distortion of the ventricle muscle. Although the muscle is working, it is unable to both fill the ventricle with blood and expel or pump the blood in sufficient quantity. The pump system of this invention can be used by positioning the pump cannula output end in the ventricle to fill or preload the ventricle with blood, so the heart muscle can then pump or expel the blood from the ventricle, even though the muscle is not in its normal shape or position. In this aspect of the invention, beating heart blood flow can be maintained during surgery without the necessity of the cannula extending through the pulmonary/aortic valve. The heart may be stopped by short acting drugs that which stop the heart for a short period of time, or by electrical means affecting the electrical conduction of the heart or neurological systems or by use of electrical current to paralyze the nerves responsible for heart beating. While the heart is stopped, the pump(s) will deliver 100% of the necessary pulmonary blood flow to and from the lungs and/or 100% of the necessary circulatory blood flow to and from the body without any assistance from the heart. In the event the heart is stopped, and particularly when the heart is opened (such as for valve surgery), it is preferred to provide a seal by balloon sheath cannula, clamp or otherwise to isolate the heart, or at least one side of the heart, at the intake cannula and output cannula so that the pumped blood is directed from the vein to the artery without leakage or backflow into the heart during the surgery. This will enhance the pulmonary and/or circulatory blood flow provided by the pump in the pump and cannula system. [0020] The pump and cannula systems disclosed herein for use in heart surgery according to the present invention preferably have a priming volume less than about 1,000 ml, and more preferably less than about 100 ml. Optimally, each individual pump/cannula unit will have a priming volume less than about 50 ml, preferably less than about 30 ml and more preferably less than about 10 ml. In one preferred embodiment, the pump and cannula system comprises concentric intake and output conduits (forming a generally coaxial dual cannula assembly), adapted for insertion into a single incision. In another preferred embodiment of this aspect of the invention, the pump and cannula system comprise an intake cannula for insertion in the upstream vessel or heart chamber and an output cannula for insertion downstream into the pulmonary artery or the aorta. In a further preferred embodiment of this aspect, the pump and cannula system may comprise a miniaturized pump having a sterile drive motor suitable for placement of the pump including the drive motor close to the chest and in the sterile zone, or preferably within the chest cavity itself during the heart surgery. In a further preferred embodiment of this aspect, a reverse flow pump and coaxial cannula combination may be employed having a minimum priming volume, although it is to be understood that any number of conventional pumping systems may be employed without departing from the scope of the present invention, including but not limited to a centrifugal pump, a cable driven axial flow pump, and a roller pump. [0021] In another aspect, this invention provides a cannula system for protecting selected portions or all of the right side from collapse or kinking during beating heart surgery, an optional cannula system for protecting selected portions or all of the left side from collapse or kinking, and optional pump systems for use with the right and/or left side protection cannulas, if needed to supplement or augment the blood flow provided by the beating heart. In some patients all that may be required is the protection cannula or cannulas in the right side to allow the beating heart to maintain sufficient pulmonary and circulatory blood flow during the beating heart bypass surgery and it may not be necessary to use the pump system to provide supplemental pulmonary blood flow and may not be necessary to protect the left side or to provide supplemental circulatory blood flow. For such patients, this invention enables beating heart bypass surgery without artificial pumping of the blood and with minimum invasive apparatus. In some patients, beating heart bypass surgery can be started or attempted with only right side protection cannula(s) in place, then right side supplemental pumping of pulmonary blood flow added during the bypass surgery (or after the surgery) by separately inserting the pump system according to this invention. Likewise, left side protection cannula(s) and/or left side supplemental pumping of arterial blood can be added as needed during (or after) the bypass surgery by insertion of the cannula(s) and/or pump systems according to this invention. Thus, this invention provides optional incremental apparatus that may be selected by the surgeon and used only according to particular patient needs in order to minimize the invasiveness of the bypass surgery procedure. Continue reading about Methods and systems for providing right and/or left heart support during cardiac surgery... 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