Surgery – Cardiac augmentation
Patent
1998-07-27
2000-02-29
Kamm, William E.
Surgery
Cardiac augmentation
A61M 112
Patent
active
060303352
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an implantable heart-assist pump of the back-pressure balloon type.
The back-pressure intra-aortic balloon technique is well known for providing effective hemodynamic assistance to the left ventricle in the event of congestive heart failure: the balloon which is inserted in the down branch of the aorta is inflated during the diastolic phase of the heart beat cycle, and as a result it injects an additional volume of blood into the arterial network upstream and downstream from its position. Deflated during the following systole of the heart, it decreases the load on the left ventricle and thus makes it possible to increase blood flow. The hemodynamic balance is positive: an increase in the ejection fraction, and a decrease in the telediastolic pressure. In this way, the balloon delivers additional energy which the ventricle is no longer capable of supplying, and the state of the patient is very significantly improved.
Implanted systems have already been proposed enabling said technique to be implemented in entirely self-contained manner, as described for example in U.S. Pat. No. 5,222,980.
That document describes a permanent implantable heart-assist pump inserted in the down aorta, operating on the above-described principle of the back-pressure balloon, and constituted by a flexible and elastic membrane in the form of a sleeve whose axis coincides with that of the aorta and disposed in and replacing a segment of aorta that has been removed. The membrane is contained in a rigid chamber that has substantially the same shape as the membrane at rest, and into which hydraulic fluid is injected from an external generator for the purpose of compressing the membrane and thus reducing the volume of blood that it contains. Conversely, extracting the fluid increases the inside volume and thus fills the pump.
One of the problems encountered in the design of appliances of that type lies in the extremely high level of reliability that they must provide, given that they are implanted. Operating for a duration of five years corresponds to about 300,000,000 cycles, and all of the elements of the implanted system must be capable of being subjected to those cycles without damage and without failure.
To this end, selecting the material for the flexible membrane and defining it become critical aspects of the design of an implantable heart-assist pump.
In addition to a lifetime compatible with long term implantation, it is also essential for the pump to be designed in such a manner as to minimize any risk of incidents of thrombosis, and that constitutes one of the major difficulties presented by cardiovascular prostheses.
To this end, the organization of the pump, and in particular the way in which its flexible membrane is defined, must satisfy the following conditions: thrombosis must be reduced; parts of the membrane or between the membrane and surrounding structures must be eliminated since they give rise to hemolysis; blood on each heart systole; and pharmacological treatment opposing thrombotic and expansive processes, without prejudicing treatment of the inside surface to encourage colonization by autogenous endothelial cells.
One of the objects of the invention is to provide an implantable heart-assist pump enabling all of the above-explained constraints and conditions to be satisfied by a special organization of the various elements of the pump, and most particularly of the flexible membrane.
The pump is of the above-specified known type, i.e. it comprises: an essentially rigid body open at both ends and designed to be inserted in the down aorta artery; a flexible and elastic membrane in the form of a sleeve connected in sealed manner to the body at the periphery of the ends thereof so as to define firstly, between the body and the sleeve, a closed intermediate space of variable volume, and secondly, inside the sleeve, a variable volume through which the blood to be pumped passes; and means for connecting the intermediate space to a source of hydraulic fluid suitable for causing the membrane to pa
REFERENCES:
patent: 3668708 (1972-06-01), Tindal
patent: 4276874 (1981-07-01), Wolugk
patent: 4888011 (1989-12-01), Kung et al.
patent: 5171207 (1992-12-01), Whalgw
Kamm William E.
Synthelabo Biomedical
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