US 6974436 B1
The present invention relates to systems and methods for transporting fluid between different locations within a body cavity and, in one particular application, systems and methods for transporting fluids to maintain at least partial blood flow through a protected blood flow path within the right and/or left side of the heart during surgery. 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. At least partial blood flow may be maintained through the protected blood flow path by the pumping action of a blood pump disposed within the conduit.
1. A system for maintaining at least partial blood flow within a heart, comprising:
a conduit having an inner flow path and an outer flow path, the conduit being sized and configured to be introduced into the heart through at least one of the wall of the right atrium, the wall of the right ventricle, the wall of the pulmonary artery, the wall of left atrium, the wall of the left ventricle, and the wall of the aorta;
said conduit including a blood inlet port communicating with one of the inner flow path and the outer flow path and a blood outlet port communicating with the other one of the inner flow path and the outer flow path, said blood inlet port and said blood outlet port being sized and configured to be positioned on either side of at least one of the tricuspid valve, the pulmonary valve, the bicuspid valve, and the aortic valve; and
a blood pump disposed within said conduit for selectively transporting blood from said blood inlet port to said blood outlet port of said conduit.
2. The system of
3. The system of
4. The system of
5. The system of
6. The system of
7. The system of
8. The system of
a control circuit forming part of said conduit to allow a user to manually or automatically control the speed and rotation of said pump.
9. The system of
This application is a continuation-in-part of U.S. patent application Ser. No. 09/462,656, filed Jan. 14, 2000, entitled “Transport Pump and Organ Stabilization Apparatus Including Related Methods,” which is a continuation-in-part of U.S. patent application Ser. No. 08/933,566, filed Sep. 19, 1997, now U.S. Pat. No. 6,083,260.
I. Field of the Invention
The present invention involves systems and methods for transporting fluids between various locations in the body, such as during surgical procedures. More particularly, the present invention is directed to a cannula arrangement having an integrated pump disposed therein for transporting blood between various points in the heart to provide right and/or left heart support cardiac surgery.
II. Discussion of the Prior Art
During most surgical procedures, bodily fluids are directed and transferred to various locations with the assistance of artificial pumping apparatus. Major heart surgery, for example, 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.
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.
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.
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.
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.
The present invention addresses this need by providing systems and methods for transporting blood between various points in the heart to provide right and/or left heart support so as to eliminate, or at least reduce, the need for full CPB.
The present invention provides an integrated pump and cannula system that transports fluid between different regions within the body in order to support a wide variety of surgical procedures. This system finds particular utility during cardiac applications, and will be discussed in detail below within the context of transporting blood within the heart to augment or replace the blood flow of the heart itself. It is to be readily understood, however, that the integrated pump and cannula systems of the present invention may be used in a wide variety of other applications that require the transportation of fluid between different locations within the body. When employed during cardiac surgical procedures, the integrated pump and cannula systems of the present invention are particularly advantageous in that they ensure that the patient's lungs are used for blood oxygenation, thereby avoiding the need for CPB or other external blood oxygenation equipment or procedure.
The pump and cannula system of 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 heart (beating or still) to ensure sufficient pulmonary blood flow to the lungs and/or circulatory blood flow throughout the body during 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 disposed within the conduit.
In an important aspect, the present invention ensures sufficient pulmonary and/or circulatory blood flow during cardiac surgery regardless of any compromise in cardiac output or function experienced during cardiac surgery. Generally speaking, such compromise conditions include any situation where the cardiac output of the heart is diminished or disrupted from normal levels. This includes any and all compromise conditions that occur or result during beating heart surgery or still or stopped heart surgery. In beating heart surgery, the cardiac output of a beating heart can become compromised in a multitude of ways. 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.
The present invention provides, generally speaking, a pump and cannula system for selectively augmenting or replacing the heart's natural pumping to ensure sufficient pulmonary and/or circulatory blood flow during periods when cardiac output may become compromised (including but not limited to cardiac surgery and related procedures) or when the blood flow within the heart needs to be augmented for any reason. The pump and cannula system of the present invention may take a variety of different forms. In all embodiments, the cannula is positioned to establish a protected blood flow path within a portion of the heart (across at least one valve) and the pump may be selectively operated to maintain at least partial blood flow therethrough. 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 disposed within the cannula to selectively transport blood past the valve(s) through which the cannula passes to augment or replace the pumping ability of the right and/or left side of the heart. The pump and cannula system may be used during open-chest procedures, or closed chest procedures through the chest wall as part of a thorascopic procedure. In either event, the pump and cannula system may be introduced into the heart through a single incision the wall of the right atrium, the wall of the right ventricle, the wall of the pulmonary artery, the wall of the left atrium, the wall of the left ventricle, or the wall of the aorta. The pump, being disposed within the heart itself, has priming volume of approximately zero. The pump, in all embodiments, is preferably variable output. It may be controlled automatically 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 C02 level. In another embodiment, the pump may be controlled manually (on-demand) through the use of manual controls configured as part of the integrated pump and cannula system.
In all embodiments, the pump and cannula system may be used in both the right and left sides of the heart. 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, or when the heart goes into arrhythmia or malfunctions in any way during the operation. Cardiac output may also be intentionally compromised, such as during still heart or stopped heart surgery, when the heart is deliberately 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 closed chest, minimally invasive, procedures.
By having this system in place before cardiac surgery begins, the present invention thus assures that is the patient will at all times during 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 occurs.
In one embodiment, the integrated 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 is preferably through an incision in 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.
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 left atrium, left ventricle, and aorta, and the pump may be selectively operated to maintain at least partial blood flow therethrough-during cardiac 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.
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 cardiac output 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, at least partial blood flow may 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 inlet 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 procedure. This will enhance the pulmonary and/or circulatory blood flow provided by the pump in the pump and cannula system.
In one preferred embodiment, the pump and cannula system comprises a pair of concentric conduits (forming a generally coaxial dual cannula assembly), adapted for insertion into a single incision. The outer cannula includes a flow port to provide fluid access to the interior of the outer cannula. The inner cannula has the pump coupled thereto such that, when inserted into the outer cannula, the pump is disposed within the outer cannula. The pump may be driven in one direction to draw blood into the flow port of the outer cannula and into the lumen of the inner cannula for delivery out a flow port at its distal end. Depending upon the application, the pump may be driven is an opposite or reverse direction to draw blood into the flow port at the distal end of the inner cannula for delivery out the flow port of the outer cannula. According to the present invention, the flow ports of the inner and outer cannulas are positioned one either side of a heart valve to forcibly transport blood from one side to the other, such as for providing right and/or left ventricular assist.
The pump and cannula systems of the present invention may be used in conjunction with procedures involving collapsing one lung and/or partially reducing the size of the beating heart to provide additional space in the chest cavity in which the surgeon can work. In this regard, it is noted that one lung is normally sufficient to sustain the patient during surgery. In some procedures the surgeon prefers to collapse one lung to provide additional space inside the chest cavity in which to work. The integrated pump and cannula of the present invention can accommodate such a procedure while sustaining the patient on one lung throughout the surgery and avoiding a CPB machine. Likewise, it is sometimes desired by the surgeon to shrink down the heart by evacuating blood from one or more chambers of the heart, also to provide additional space within the chest cavity in which to work. The pump and cannula system of the present invention accommodates such a procedure because it can sustain adequate pulmonary and circulatory blood flow throughout the surgical procedure.
As is apparent, this invention enables the use of various combinations of the above aspects of this invention to meet the requirements of a particular patient for the successful performance of beating heart surgery while assuring that the patient's lungs (or lung) provides the oxygenated blood to sustain the patient through the surgery and that a CPB machine and procedure is avoided. Selective use of the pump and cannula systems described herein in their various configurations results in minimum invasiveness and minimum contact of the blood with apparatus in or outside the body during beating heart bypass surgery. Thus, this invention enables all beating heart surgical procedures without the use of a CPB machine by providing pump and cannula systems placed through or around the entire right side and/or through or around the entire left side to both protect the beating heart blood flow and to augment, supplement or, when necessary, temporarily replace the beating heart blood flow during the surgery. This invention thus enables various heart surgery procedures (including both beating heart and still heart surgery) to be performed without the use of CPB machines by maintaining sufficient pulmonary blood flow through the patient's lungs (or lung) and sufficient circulatory blood flow through the patient's body to sustain the patient during the surgery.
The present invention addresses the need to eliminate the use of CBP or other external blood oxygenation devices or procedures in cardiac surgery and related procedures. The present invention accomplishes this by providing an integrated pump and cannula system which, in use, is capable of maintaining at least partial blood flow through a protected blood flow path within the right and/or left side of the heart during surgery. The various embodiments of this system (to be described below) can be employed alone or in combination depending upon the cardiac procedure to be undertaken. The common denominator between all embodiments, however, is the combined use of at least one cannula positioned within at least a portion of the right and/or left heart to establish a protected blood flow path, and a pump disposed within the cannula to maintain at least partial blood flow through the protected blood flow path, particularly during periods when cardiac output may become compromised.
The integrated pump and cannula systems of the present invention enables safe heart surgery on anterior lateral and posterior blood vessels, in either beating heart or still heart procedures, without the necessity of using CPB. The pump and cannula systems disclosed herein can provide right heart support during beating heart surgery by pumping blood through or across the right side of the heart to augment or supplement pulmonary blood flow produced by the beating heart during surgery. If the heart temporarily collapses or lapses into arrest or disrhythmia during surgery, the supplemental pulmonary blood flow provided by the pump system of this invention eliminates the necessity of the use of CPB. Similarly, the pump and cannula system of this invention can be used with the left heart to provide sufficient supplemental arterial flow of blood to satisfy patient requirements until any compromise condition, such as heart collapse or disrhythmia, is corrected during beating heart surgery, thereby avoiding the need for CPB. By way of example only, the pump and cannula systems described below are useful in a variety of cardiac applications, including but not limited to procedures involving coronary artery bypass graft (CABG). In addition to avoiding the need for CPB, the pump and cannula systems of the present invention are also advantageous in that, by augmenting or replacing the pumping function of the right and/or left ventricle, the heart naturally decompresses (due to the reduced blood volume) which allows a greater degree of freedom to rotate and manipulate the heart for better access to target bypass vessels. This is particularly important in endoscopic surgery. While the pump and cannula systems disclosed herein are discussed primarily with respect to their usefulness in providing right and/or left heart support during beating heart surgery, it is to be readily understood that these pump and cannula systems also enable still heart surgery, such as valve or other internal heart repair, without the use of CPB.
The integrated pump and cannula system 10 of the present invention defines a fluid flow path which extends between the flow ports 24 in the intermediate portion 16 and the flow port 26 at the end of the distal portion 18. In use, the pump and cannula system 10 operates to transport fluid in one of two directions. With the pump 28 operating in a first (i.e. forward) direction, fluid will be drawn into the flow ports 24 of the intermediate portion 16 and transported through the distal portion 18 for delivery out the flow port 26. With the pump 28 operating in a second (i.e. reverse) direction, fluid will be drawn into the flow port 26 and transported through the distal portion 18 for delivery out the flow ports 24 in the intermediate portion 16. The integrated pump and cannula system 10 finds application in virtually any setting which requires the ability to transport a fluid between different locations, and particularly in surgical procedures where bodily fluids are commonly directed and transferred between various locations within the body with the assistance of artificial pumping apparatus. As will be explained in detail below, cardiac surgery represents a significant area of application for the integrated pump and cannula system 10 of the present invention in that, by maintaining at least partial blood flow within the right and/or left sides of the heart during surgery, the need for CPB during such procedures may be greatly reduced if not eliminated altogether. The system of the present invention is capable of maintaining at least partial blood flow within the right and/or left sides of the heart by inserting the pump and cannula system 10 into the right and/or left sides of the heart such that the flow ports 24 and flow port 26 are disposed on opposite sides of at least one heart valve and the pump 28 operated to transport blood therebetween. Transporting blood in this fashion operates to augment or replace the pumping ability of the heart itself, and ensures that sufficient amounts of pulmonary and/or circulatory blood flows are maintained during surgery to avoid the need for CPB.
As also detailed in
The cannula 12 (i.e. each of its constituent portions 14, 16, 18) can be formed of materials ranging from rigid to flexible, and in the preferred embodiment comprise a semi-rigid transparent material such as polyurethane or silicone having a hardness of between about 30A and 90A on a Shore durometer scale and capable of withstanding sterilization by ethylene oxide (ETO). The portions 14, 16, 18 of cannula 12 may comprise separate elements that are bonded or otherwise secured to one another to form a unitary body. The cannula 12 may also be constructed via injection molding or other known techniques to comprise a single element having the aforementioned portions 14, 16, 18 defined thereon. In either case, structural reinforcement may be provided, such as by molding or embedding spiraling wire (not shown) into the walls 68, 70, which spiraling wire may extend either partially or fully across the length of the cannula 12. As will be readily appreciated, such spiraling wire facilitates handling the cannula 12 and furthermore reduces the possibility of the distal portion 18 collapsing or being otherwise restricted or pinched shut. Other ways of reinforcing the tubular areas of the cannula 12 are known in the art and will adapt equally well to the present invention. Such reinforcement may be omitted if the cannula material is sufficiently rigid or if sufficient fluid flow is present within the cannula 12. The cannula 12 may also contain radiopaque markings (not shown) to aid in determining the placement of the cannula 12 within the patient's body using known imaging techniques.
The pump and cannula system 10 for right heart support enables the heart to continue pumping blood in its normal fashion to provide pulmonary blood flow around cannula 12, to the extent that the heart is capable, during the lifting and manipulation of the heart during surgery. The integrated cannula and pump system 10 assures a supplemented or augmented flow of blood to the pulmonary artery 90, even in the event of compromised cardiac output, such as by disrhythmia or other interruption of pulmonary blood flow by the beating heart. Under normal circumstances, and at most times during the beating heart surgery, the internal support provided by cannula 12 will prevent the collapse of the right side of the heart and enable the heart to continue pumping at least a portion of its normal blood output into pulmonary artery 90. The combined flow of the blood flow produced by the beating heart and the blood flow produced by pump 28 and transported through the cannula 12 is at all times sufficient to sustain adequate pulmonary blood flow to sustain the patient during surgery. In the event of a disrhythmia, the pump 28 can be increased in output to compensate until the disrhythmia is corrected. The pump and cannula system 10 can thus overcome any compromise in right heart function or output during beating heart surgery (such as collapse or kinking that may occur in the vena cava 92, right atrium 82, right-ventricle 86, and/or pulmonary artery 90 when the heart is lifted or manipulated) and thus avoid the need for CPB.
The cannula 12 is preferably sealed within the incision formed in the wall of atrial appendage 80 through the use of a purse-string suture, as well known in the art, or any other suitable sealing mechanisms. The length into which the cannula 12 extends past the pulmonary valve 88 into pulmonary artery 90 will depend on the beating heart surgical procedure being performed and on other factors. In general, the cannula 12 should extend through and past an area defined generally as the “kink zone,” which will vary in size and location depending on condition of the patient, the surgical procedure performed and the extent of movement and manipulation of the heart during surgery. The kink zone will frequently extend up to the point where the pulmonary artery is not moved during surgery. It is generally expected that the cannula 12 will need to extend up to about 15 cm beyond pulmonary valve 88 and into pulmonary artery 90. Such a length is generally sufficient to prevent kinking or collapsing of pulmonary artery 90 during the positioning of the heart for beating heart bypass surgery. Preferably, the length beyond the pulmonary valve 88 will generally be up to about 10 cm, or preferably up to about 7 cm, or about 4 cm but may be as little as about 1 cm depending on the kind and size of cannula used.
One advantage of using the integrated pump and cannula system 10 for right and/or left heart support is that it allows the beating heart to continue to pump whatever blood it is capable of pumping under the conditions of the beating heart surgery. When the right and/or left side(s) of the heart is supported according to this invention to establish a protected blood flow path therein (thus preventing collapse, kinking, or occlusion of the right and/or left sides), the beating heart can provide substantial, if not full or sufficient, pulmonary and/or circulatory blood flow during the beating heart surgery. In an important aspect, the pump and cannula system 10 may be employed in either or both sides of the heart to avoid the need for CPB in such cardiac procedures.
The outer cannula 112 includes a main body portion 118, an intermediate portion 120, and a curved distal portion 122. The main body portion 118, intermediate portion 120 and curved distal portion 122 defined a single continuous lumen extending the entire length of the outer cannula 112. As with the intermediate portion 16 described above, a plurality of apertures defining flow ports 126 are formed in the intermediate portion 120 of the outer cannula 112. The outer cannula 112 has a connector 124 having an internally disposed hemostasis valve (not shown) which is adapted to slideably receive the inner cannula 114 therethrough while preventing the unwanted introduction of air into the outer cannula 112 and leakage of fluids from the outer cannula 112. In practice, the outer cannula 112 is introduced into the heart, and the inner cannula 114 is thereafter introduced through the outer cannula 112 such that the pump 116 is disposed and maintained in position within the curved distal portion 122 of the outer cannula 112.
The inner cannula 114 includes a proximal portion 128 and a distal portion 130 extending on either side of an intermediate portion 132 having flow ports 134 formed therein. The pump 116 disposed within the inner cannula 114 may be of the same construction and operation as the pump 28 described above. As will be described in greater detail below, a drive shaft (not shown) extends from the rotor (not shown) disposed within the pump 116, through the intermediate and proximal portions 132, 128, for connection to a motor (not shown). The inner cannula 114 is dimensioned to be inserted into the outer cannula 112 such that the flow port 136 in the distal end of the distal portion 130 extends, in use, through and past an aperture 138 formed in the distal end of the curved distal portion 122. As shown in
The pump arrangements disclosed herein may be operator-regulated as discussed above with regard to the control circuit 40 disposed on the integrated pump and cannula system 10 shown in
The integrated pump and cannula of the present invention has been discussed above largely with reference to beating heart surgery. However, as mentioned above, the system of the present invention finds applicability in a wide range of other surgical procedures, such as still or stopped heart surgery. In these procedures, after the pump is activated, medication or drugs for slowing or completely stopping the heart may be administered when used to support cardiac functions. The pumping rate of the pump may be adjusted to maintain sufficient circulation or to accommodate changes in circulatory demand. The pump may also be equipped with sensing devices (not shown) for measuring various body conditions such as blood pressure, the presence of blood, blood oxygen content, or other parameters that would suggest the need for altering the flow rate of the integrated pump and cannula system. For example, the apparatus may include pressure sensors along the cannula(s) so that a present pressure change would signal the need to change the pumping capacity of the apparatus. The pump may also include sensors to sense the pressure at the distal end of pump and cannula system so that a present pressure change could signal the need to change the pumping capacity of the pump, also the pressure change could be used to signal to the operator the location of the distal end of the cannulas. When the pressure at the proximal ports of the cannula decreases by a certain increment, which indicates commencement of pump suction, a controller used with the apparatus may provide warning signals or automatically decrease the flow rate of the apparatus until returning to a preset pressure within the main lumen of the integrated pump and cannula system. In the removal of the fluid transport device, the insertion wound may be restored using common surgical techniques.
It is to be readily appreciated that the foregoing pump and cannula systems are presented by way of example, and that any number of alternate cannula configurations and designs may be employed without departing from the scope of the present invention. For example,
The integrated pump and cannula system of the present invention advantageously provides the ability to transport fluids between different locations within a body in a wide variety of applications, most particularly in enabling various types of heart surgery procedures to be performed without the use of CPB machines by maintaining sufficient pulmonary blood flow through the patient's lungs (or lung) and sufficient circulatory blood flow through the patient's body to sustain the patient during the surgery.