Chemical apparatus and process disinfecting – deodorizing – preser – Blood treating device for transfusible blood
Reexamination Certificate
1997-12-29
2002-10-01
Sykes, Angela D. (Department: 3762)
Chemical apparatus and process disinfecting, deodorizing, preser
Blood treating device for transfusible blood
C604S004010, C604S006110, C604S028000, C600S017000, C600S504000
Reexamination Certificate
active
06458323
ABSTRACT:
The present invention relates to a method and a device for the selective perfusion of fluids through blood vessels, controlled by the pressure in the blood vessels. In particular, the present invention relates, on the one hand, to the suction of a fluid out of, and the retroinfusion of a fluid into, veins, in particular coronary veins, controlled by the pressure in the veins, and, on the other hand, to the perfusion of fluids through arteries, in particular coronary arteries, controlled by the pressure in the arteries.
The nutritive perfusion of coronary arteries and retroinfusion of blood into coronary veins becoming increasingly important, especially in the area of myocardial protection during, short-term coronary artery closure in the context of a cardiac intervention. A typical intervention of this kind is, for example, the balloon dilation of a coronary artery which has become narrowed as a result of arteriosclerosis. In this method, which is also known as percutaneous transluminal coronary angioplasty (PTCA), a balloon catheter is guided, with radiographic monitoring, into the area of the stenosis of the coronary artery, and the arteriosclerotic plaque is compressed by inflating the balloon situated at the end of the catheter. During the dilation of the balloon, there is no supply of oxygenated blood to the tissue in the downstream area of the artery In most cases this does not pose any problem, as long as the dilation lasts only a short time. However, in the case of dilations of more than just 30 seconds' duration, functional changes in the ischaemic area of the myocardium can be detected, for example as ST-changes on the electrocardiogram, as a reduction in regional wall movement by echo cardiography, or else subjectively by the patient as angina pectoris symptoms. In addition, the risk of complications in angioplasty is higher for certain groups of patients, for instance in elderly patients, in cases of unstable angina, in cases of a decreased left-ventricular ejection fraction, or in cases of dilation of a vessel which supplies more than 40% of the left ventricle.
Corresponding problems in protecting against myocardial ischaemia also arise in other operations for coronary vascularization, such as, for example, in atherectomy, coronary endoprostheses and laser applications.
It is known to effect short-term ischaemic protection by machine perfusion of an artery supplying the affected region of the myocardium, for instance the actual artery which is to be dilated, either with arterial blood, which has been taken from the patient, at another site or with other nutritive fluids. In doing so, however, there is a danger of overperfusion of the myocardial tissue, which is particularly the case if the outflow of the perfused fluid from the affected tissue is impeded or completely blocked. In such cases, this may lead to haemorrhagic tissue infarcts in the affected region of the myocardium.
A further possibility for short-term protection against ischaemia, which has been used for some time now in cases where complications are anticipated, is the retroinfusion of arterial blood into a vein of the area of myocardial ischaemia concerned. The arterial blood is in this case pumped through the corresponding vein into the nutritive capillaries of the ischaemic area and so supplies the myocardium in this region with oxygen and substrates.
Devices for retroinfusion of coronary veins have been known for some years. Thus, European Patent Specification EP-B-0 297 723 describes a retroinfusion unit with which arterial blood is taken, for example, from the femoral artery of the patient and is conveyed to a coronary vein of the ischaemic area via a pump system and an inflatable balloon catheter. The pumping of arterial blood into the coronary vein is in this case synchronized with the R wave of the patient's electrocardiogram, so that the pumping interval is adapted to the patient's cardiac cycle. The pumping interval is in this case predefined and begins at 45% of the R—R interval and ends at 950% of the R—R interval. The infused blood flow is in this case essentially constant during the pumping interval. As long as pumping is being carried out, the balloon of the balloon catheter is inflated and blocks the vein, thus ensuring that arterial blood is effectively transported into the ischaemic area during the diastole. The pumping procedure ends at the end of the diastole and the balloon is emptied, so that the flow in the vein is no longer blocked at this point. During the succeeding systole, venous blood can flow off through the vein.
With the device described in EP 0 297 723, the basal metabolism of the ischaemic area can be satisfactorily maintained during a short-term cardiac intervention. It was furthermore observed that the size of myocardial infarction following a coronary artery closure was significantly reduced. However, it was also found that the local myocardial function is not sufficiently maintained. For example, the local myocardial function breaks down completely in the absence of arterial collateralization of the ischaemic area. One cause of this is to be seen primarily in the incomplete exchange of arterial and venous blood in the retroinfused vein system in the course of a cardiac cycle.
In order to improve this blood exchange, with the aim of better maintaining the myocardial function in the ischaemic area, Boekstegers et al. have recently proposed, in
Cardiovascular Research
1990, 24: 456-464, and in
JACC
1994, 23: 459-469, a system for retroinfusion of coronary veins in which, instead of venous blood flowing off passively during the systole, an active suction through the retroinfusion catheter takes place. For this purpose, the balloon of the catheter also remains inflated in the suction interval and blocks the vein during the systole too. When a device of this kind was used in the animal model, improved maintenance of the myocardial function during coronary artery closure was demonstrated.
However, with regard to clinical application in a patient, the system still has disadvantages.
Thus, in this device, in the same way as in the device in EP 0 297 723, although the pumping volume per pump stroke can be adjusted, the flow of the retroinfused blood cannot, however, be influenced during a pumping interval. It has, however, been shown that the intravenous pressure is subject to considerable fluctuations in the course of one pumping interval as a result of this. Even if the intravenous pressure is recorded, although a desired mean pressure can be set in the course of several pumping intervals, the considerable fluctuations in pressure within one pumping interval cannot be eliminated.
There are, however, some problems associated with these considerable changes in the coronary vein pressure. Thus, it has been found that with a low retroinfusion flow, i.e. at a low venous pressure, an adequate supply of oxygen to the myocardium is not guaranteed, with the result that the myocardial function in the ischaemic area cannot be satisfactorily maintained. With a high infusion flow, i.e. at too high a coronary vein pressure, there is a danger, however, of overperfusion occurring, which does not improve the retrograde nutritive capillary filling, but only impedes the contraction of the myocardium and leads to an ineffective outflow of the arterial blood into the systemic circulation. In the case of retro-infusion at too high a coronary vein pressure, there is also a danger of irreversible damage to the vessel wall.
The object of the present invention is therefore to make available a method and a device for the perfusion of blood vessels, in particular coronary vessels, in which method the perfusion is performed at a vascular pressure which is optimum for nutritive capillary filling, and where this set pressure is maintained as constant as possible during pumping. The method according to the invention and the device according to the invention are in this case intended to make it possible to extend the application possibilities of vascular perfusion, in particular art
Bianco P. M.
McDonnell & Boehnen Hulbert & Berghoff
Sykes Angela D.
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