Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1999-09-30
2001-10-23
Nguyen, Anhtuan T. (Department: 3734)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S101030, C604S118000, C604S101040, C600S018000
Reexamination Certificate
active
06306116
ABSTRACT:
FIELD OF THE INVENTION
The invention pertains to a method and apparatus for pumping blood (from one or both of the superior and inferior vena cava) into the right atrium or right ventricle of a beating heart. Typically, the apparatus is used to assist the cardiac function of a beating heart during surgery thereon.
BACKGROUND OF THE INVENTION
Coronary artery bypass grafting (CABG) has traditionally been performed with the use of a cardiopulmonary bypass (CPB) machine to oxygenate and perfuse the body during surgery. Recently, techniques have been developed to allow for performing CABG without the use of CPB by stabilizing the epicardial surface of a beating heart at the coronary anastomotic site with a stabilizer (e.g., stabilizing feet) to allow placement of sutures through the graft vessel and recipient coronary artery. This procedure may be performed through a partial or full sternotomy, or via a thoracotomy (which is an incision between two adjacent ribs).
A challenge to beating heart surgery is that some hearts do not tolerate the necessary manipulation (e.g., movement of the beating heart into position for surgery and stabilization of the site on which surgery is performed) well from a hemodynamic standpoint. Currently, when the beating heart is lifted or twisted (to access the portion thereof on which surgery will be performed), the cardiac output drops, often to dangerously low levels.
There is a need for a pumping apparatus capable of assisting the beating heart during surgery, to compensate for decreased hemodynamic function (including decreased ventricular function) that results from manipulation. The inventive pumping apparatus is designed to perform this function.
Some pumping systems have been used to assist the beating heart during surgery. However, such conventional systems are subject to significant limitations and disadvantages.
For example, pumps (such as the Medtronic “Bio-Pump” centrifugal pump available from Medtronic, Inc.) have been used to pump blood from the vena cava during beating heart surgery. It has been proposed to use a system including such a pump (and an intake cannula and outflow cannula connected to the pump) as follows: the intake cannula is inserted into the vena cava, the outflow cannula is inserted into the pulmonary artery, and blood is then pumped through the cannulae from the vena cava and back into the pulmonary artery during surgery. However, this technique requires two incisions in the patient: one to allow insertion of the intake cannula in the vena cava; the other in the pulmonary artery to allow insertion of the outflow cannula therein. Undesirably, the latter incision must be made in a high pressure zone (the pulmonary artery).
As another example, the Hemopump Cardiac Assist System (sponsored by Medtronic, Inc.) includes a cannula for insertion through an incision in the ascending aorta into the left ventricle of a beating heart. The cannula includes (and encloses) a pump. The pump is a rotating Archimedes screw whose intake is the distal end of the cannula (which is positioned in the left ventricle) and whose outlet is positioned in the ascending aorta. In use, the pump continuously pumps blood from the left ventricle into the aorta. However, this apparatus assists the left heart, rather than the right heart (which is weaker than the left heart). The apparatus does not inflate the right atrium or right ventricle, and thus does not provide the hemodynamic benefits which result from inflation of the right atrium or right ventricle during beating heart surgery.
SUMMARY OF THE INVENTION
In a class of embodiments, the inventive apparatus includes an intake tube (for insertion into the inferior vena cava or superior vena cava), a return tube (for insertion into the right atrium or right ventricle), and a pump coupled between the intake and return tube. In operation, blood is pumped from the vena cava into an intake port of the intake tube, from the intake tube (through the pump) to the return tube, and from the return tube to the right atrium or right ventricle. Preferably, the pump is configured to pump blood from the vena cava into at least one intake port of the intake tube, from the intake tube to the return tube, and from the return tube to the right atrium or right ventricle. Preferably, a balloon is mounted around the distal end of the intake tube near the intake port, and the balloon is inflated when the intake port has been inserted into the vena cava in order to prevent backflow and resultant pressure loss during the systolic phase of the heart beat (and preferably also to center the intake port in the vena cava).
Preferably, the pump has an input port coupled to the intake tube and an output port coupled to the return tube, and is configured to pump blood in one direction (from input port to output port, and thus from intake tube to return tube). A peristaltic pump is an example of such a pump. Alternatively, the intake and return tubes are branches of a single Y-tube, the pump has one port coupled to the tube, and the pump has two-stage cycle: a first stage in which it draws blood in from the tube through the pump's port; and a second stage in which it returns blood from within the pump, back through the pump's port in the opposite direction to the tube.
Preferably, the apparatus includes a return manifold at the distal end of the return tube, and the intake tube extends through the return manifold. The return manifold defines a chamber that is sealed from the intake tube (but is in fluid communication with the return tube) and is perforated by one or more outflow ports, the outflow ports being positioned so that blood can flow into the right atrium (or right ventricle) through them when the intake tube's intake port is positioned in the vena cava. Blood returning from the pump flows through the return tube into the return manifold's chamber. Since the returning blood in the chamber is at high pressure, it flows out of the chamber's outflow ports (or port) into the right atrium or right ventricle. The returned blood flows from the right atrium into the right ventricle (or from the right ventricle to beyond the right ventricle), as occurs in normal functioning of a beating heart.
Preferably, the apparatus includes an atrial pressure sensor which measures the pressure of the blood which has flowed into the right atrium from the pump. In preferred implementations of such embodiments, the output of the sensor is provided to a control unit for the pump, and the stroke volume of the pump is controlled in response to the measured pressure to achieve a desired time-varying atrial pressure (a desired atrial pressure as a function of time). A typical stroke volume is less than 20 cc (but the optimal stroke volume may be greater in some applications).
In preferred embodiments, the intake port of the inventive apparatus is positioned (during use) in the inferior vena cava. In alternative embodiments, the intake port is positioned in the superior vena cava, or the inventive apparatus has a Y-shaped distal end having two intake ports, each of which is positioned in a different one of the inferior vena cava and the superior vena cava during use.
In other embodiments, the invention is a method for pressurizing the right atrium of a beating heart during surgery (to assist cardiac function). One example of such surgery is a coronary bypass grafting procedure on the beating heart. The method includes the steps of: (a) inserting a distal portion of an intake tube into at least one of the inferior vena cava and superior vena cava so that at least one intake port (defined by the distal portion of the intake tube) is positioned to receive blood from at least one of the inferior vena cava and the superior vena cava, and inserting a distal portion of a return tube into the right atrium or right ventricle so that at least one return port (defined by the distal portion of the return tube) is positioned to permit blood flow from the return tube into the right atrium (or right ventricle); and (b) pumping blood from the at l
Girard & Equitz LLP
Maynard Jennifer
Nguyen Anhtuan T.
Origin Medsystems Inc.
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