The invention relates to an intracardiac blood pump and in particular to a blood pump which can be completely inserted through adjacent vessels into the heart to support the natural pumping function of the heart or replace it by continuous pumping operation.
A pump device for supporting the heart function is described in WO94/09835 (Jarvik). Said pump device comprises pumps operating independently of each other, each pump being provided with a pump section and a drive section rigidly connected with the pump device. The pump section of the one pump is inserted through an apecal operation opening into the left ventricle such that it delivers from the left ventrical into the aorta. The other pump section is inserted through another preferably apecal operation opening into the right-ventricle so that it delivers from the right atrium into the pulmonary artery. Each of the pumps is extended at its pump outlet by a hose-type outlet canula which may be guided through the respective heart valve.
An intracardiac blood pump which is inserted from the aorta through the aortic valve into the left ventricle is known from WO97/37696 (Rau et al). Here the pump inlet is extended by a hose passing through the aortic valve.
From WO97/37697 (Rau et al.) an intravascular blood pump is known which can moved through a blood vessel. This blood pump, too, is, extended at its outlet end by an intake hose. Said intake hose comprises an inflatable balloon serving as isolating device and preventing blood from flowing laterally along the outside of the intake hose.
Finally, U.S. Pat. No. 4,753,221 (Kensey et al.) describes a pump catheter having a pump to be placed in the heart. Said pump comprises an impeller and a pump casing surrounding said impeller. The pump casing can be placed in the heart when the former is in the collapsed condition and subsequently unfolded by inflating a balloon connected with the pump casing.
Further, small-lumen catheters for pressure and volumetric flow measurement are known which serve for diagnostic purposes and comprise an inflatable balloon at the distal catheter end. Said balloon is used for positioning the catheter tip in the pulmonary artery.
Intracardiac blood pumps which are inserted through a blood vessel into the heart are difficult to correctly place in the heart. In particular when the blood pump is inserted through the upper vena cava to pump blood from the right atrium into the pulmonary artery, correct placing of the blood pump is difficult since the pump must perform a bend of approximately 180xc2x0 to ensure that the intake opening is located in the right atrium and the outlet opening in the pulmonary artery. Further, numerous fibres and tendines exist in the right ventricle, which retain the tricuspid valve, protect the leaflet of the valve against bulging inside out and ensure inherent stability of the heart. A blood pump inserted through a vena cava must be guided between such fibres and tendines.
It is the object of the invention to provide an intracardiac blood pump which can be relatively easily placed in the heart.
According to the invention this object is solved by means of the features stated in claim 1.
A flexible hose is attached to the pump outlet of the blood pump according to the invention with the distal end of the hose comprising a balloon acting as guide element in the blood flow. The invention utilizes the fact that the blood naturally flows in the heart from the vena cava into the right atrium and through the right ventricle into the pulmonary artery. The blood pump which comprises a balloon at the distal end of the hose is inserted along this path with the balloon floating in the blood flow automatically finds its way from the right atrium into the pulmonary artery. The hose outlet is subsequently stabilized in the pulmonary artery wheras the pump section is positioned in the right atrium. The pump hose performs a bend of approximately 180xc2x0. In this way it is possible to correctly place the blood pump including the pump hose in the heart without the hose outlet pushing against the ventricular septa or diagnostic aids (X-rays or ultrasound) being required.
The term intracardiac within the meaning of the present invention includes the heart chambers (ventricles), the atria and the adjacent vascular stumps.
The pump hose should prefably be prebent according to its final position which it will assume in the heart. This requires bending by at least approximately 150xc2x0. Although the pump hose must be capable of being elongated for insertion through the vena cava it should assume a U-form or a V-form in the slackened condition. It would be particularly preferred that the pump hose displays a flexural rigidity which decreases from the proximal end to the distal end. In this way the distal end as path finder can be easily moved so that the balloon can better follow the natural blood flow.
The balloon must not necessarily be directly attached to the pump hose. It may also be fixed to a catheter which forms part of the pump hose and extends on the inside or the outside of the latter. In any case a lumen must extend towards the balloon via which the balloon can be inflated. A second lumen may additionally be provided into which a guide wire is inserted which facilitates advancing of the pump hose through the vascular system. After removal of the guide wire said second lumen may be used as pressure measuring lumen.
According to a preferred embodiment the balloon is configured as annular balloon and surrounds the pump hose. The advantage of such a configuration is that owing to the presence of the balloon the distal hose end has an increased outside diameter and is thus retained by the pulmonary valve. In this way the balloon helps to anchor the hose end to the pulmonary valve while the hose outlet is located in the pulmonary artery. This prevents the hose outlet from slipping out the pulmonary artery. Another advantage is that the annular balloon forms a rounded blunt end of the pump hose so that the pump hose cannot damage the vascular or heart walls or other parts of the heart. Finally, the hose end is prevented from hooking at the valve margin or tendines in the heart.
Since the pump section pumps into the pump hose, the pump hose is automatically kept open. Thus a collapsible hose can be used as pump hose, e. g. a hose made of sheet material, whose wall is not inherently stable. Through this hose a catheter may extend to the balloon arranged at the distal end.
When an intracardiac blood pump with a flexible pump hose is used there is the danger that the blood leaving the hose outlet causes a recoil at the hose, which may result in a retrograde displacement of the hose. Thus the hose may slip out of the pulmonary valve. It is thus a further object of the invention to provide an intracardiac blood pump in which displacements of the hose due to hydraulic reaction forces are prevented.
According to the invention this object is solved by means of the features stated in claim 13. To the distal end of the hose a traction element is fixed to which the pumped flow is directed. Said traction element may be a leaflet or a balloon. The blood flow leaving the hose end pushes against the traction element, which produces a forward directed force acting against the retraction force of the hose. In this way the traction element serves for a stabilized positioning of the pump hose.