BLOOD VESSEL GRAFT QUALITY EVALUATION

Abstract: A method for measuring the flow rate of a liquid, saline or blood, through a blood vessel to be used as graft on a patient in need thereof, where a certain quantity of this fluid is passed under controlled conditions through this vessel, thus establishing whether it is suitable for use as a graft. There is also provided a system for effecting such measurement which essentially comprises a large syringe connected to a pump, which passes the fluid through the blood vessel intended for use as graft, under exactly defined conditions, and means for calculating the flow rate and whether the vessel is suitable for the intended patient.

Description: DESCRIPTION BLOOD VESSEL GRAFT QUALITY EVALUATION FIELD OF THE INVENTION The invention relates to the evaluation of Coronary Artery Bypass Graft (CABG) surgery and other medical procedures, which involve blood vessel surgery. There are provided a process for the evaluation of graft patency and means for carrying out such process. The invention enables to evaluate grafts and anastomotic site occlusions, leakage and proper location. BACKGROUND OF THE INVENTION While myocardial revascularization has been employed for many years, the graft patency depends to a large extent on the location and quality of the anastomosis. The determination of possible blood flow through such a vessel is of cardinal importance, and exact determination of this parameter is critical for various types of surgery, and especially of coronary artery bypass grafts (CABG) surgery. There are several methods known today to measure the blood flow rate through grafts including electromagnetic flow-meters, ultrasonic flow-meters, thermal imaging etc. The prior art does not provide direct flow measuring systems, and most of the evaluations can be carried out only towards the end of the operation, after the proximal side of the graft is connected to the aorta, and blood start flow through the graft as the result of blood pressure produced by the heart SUMMARY OF THE INVENTION The invention relates to the determination of flow rates through blood vessels involved in surgery Means and methods for effecting such measurements are provided which are exceedingly simple, yet highly efficient and which provide real time data for the surgeon performing surgery Coronary bypass surgery of the type referred to in the present invention generally involves the attachment (anastomosis) of a graft blood vessel to an existing blood vessel of the patient, which is of the order of diameter of a few millimeters, carrying out the control and evaluation according to the invention, and after ascertaining that such attachment is in order, attaching the second end of the graft to the aorta The device of the invention and the method of evaluation is also applicable to other types of blood vessel surgery, such as that of blood vessels of the feet etc There is provided a device for measuring the flow rate of a liquid through the graft to be used in surgery while it is already connected with a blood vessel of the patient, which fluid can be saline, a buffered solution or blood. The device comprises a liquid container provided at one end with means for applying a predetermined pressure, and at another end with exit means, means for applying controlled pressure (continuous or in pulsed form) to a liquid (saline, blood) in said container, where the pressure is applied to the free end (proximal end) of the blood vessel used as graft, after the anastomosis to the coronary artery is made to the other end (distal end) of the graft, means being provided for the accurate measurement of the parameters involved such as pressure curve, pressure inside the vessel, liquid volume, time and flow rate calculation. Preferably a syringe or syringe-like container is used, to the piston of which there is applied the desired pressure, which can be essentially constant or which can be pulsed, with a pulse rate and form similar to that provided by the human heart. There is provided a closed servo loop which monitors and adjusts the pressure applied to the liquid in said container (syringe). According to the invention the flow rate measurement through the blood vessel intended to be used for the graft is made before connecting the proximal end of the graft to the aorta; it is not required to reactivate the heart to produce pressure and establish the flow through the vessel. Thus, the surgeon is able to determine in real time the graft patency whether the attachment to the artery does not leak or get blocked, and if this is not entirely satisfactory, to repair it or replace it by another graft This determination is made right after the anastomosis to the coronary artery DETAILED DESCRIPTION OF THE INVENTION The invention is described with reference to the schematical drawing, in partial section, and not according to scale, of a device for use in measurements according to the invention In this Figure there is illustrated a device of the invention, which comprises a syringe 11 , having a piston area of about 10 cm2 which is held in holding means 12, which grasp the flange 13 of syringe 11 The syringe piston 14 is attached to a movable pushing plate 15 There is provided a linear motor 16, that moves the pushing plate 15, which is used for pushing piston 14 into the body of the syringe 1 1 To the tip 17 of the syringe 11 there is attached a 3- way stopcock 18, to which there are attached tubes 20 and 21 , tube 20 being connected with pressure transducer 19, the other tube, 21 being attached to the blood vessel to be used as graft 22 There can be applied a constant pressure on the syringe piston, thus ejecting liquid from said syringe, through the vessels to be used as graft to the patient arteries, the pressure and displacement of the syringe piston are measured automatically, for a predetermined time interval, thus indicating flow rate versus applied pressure and testing the graft patency Instead, there can be applied to the piston of the syringe a pulsatile pressure This can be of values which correspond to natural pressure applied to blood in blood vessels in the human body For example, a pulsed pressure can be applied to the piston which mimics a systolic pressure of 100 mm Hg and diastolic pressure of 70 mm Hg, at a frequency of 90 per minute Example A 60 ml syringe was connected as part of a device shown in Fig 1 and filled with saline solution A pulsative pressure of 100 mm Hg (mean value) was applied for 10 seconds During this 10 second period the displacement of the piston of the syringe was measured and at the end of this period of time the flow rate through the graft was calculated based on the cross-section of the syringe and the displacement of the piston during this time interval The average expected flow rate through a vein graft is about 75 ml per minute Generally it is convenient to use saline as test liquid, and after measuring the flow rate through a blood vessel intended as graft, the surgeon can decide in real time whether the graft can serve as by-pass

Claims: CLAIMS 1 A device for establishing in real time the graft patency and anastomosis quality of blood vessels such as aortocoronary bypass and other blood vessels, using direct flow-rate measurement, which device comprises in combination a syringe the piston of which is actuated by controllable actuation means imparting to the piston a steady pressure or a pulsed one, a tube connected at the outlet of the syringe, which tube is connected during measurement to the one side of the graft of the patient after anastomosis is made in the other side, and a three-way valve whereby another tube is attached to pressure measurement means which by a feedback control the actuation means, thus measuring the flow rate of the liquid from the syringe through the grafted blood vessel, resulting from the pressure applied on its 2 A device according to claim 1 , comprising a pressure closed loop control, to maintain the predetermined pressure wave, during an injection time interval 3 A device according to claim 1 , where actuation means are used mimicking the pulsatile blood pressure of a patient 4 A method of measuring the rate of flow of a physiologically acceptable liquid through a (vein) graft blood vessel attached by one of its ends to the blood vessel (coronary artery) of a patient, which comprises applying to the piston of a syringe holding such liquid a predetermined pressure using a pressure closed loop control, said syringe being attached to the other end of the graft, and thus measuring the rate of flow through said blood vessel graft as a function of the applied pressure and establishing whether the anastomosis is satisfactory

Inventors: HAIMOVICH DUDU, ROTTENBERG DAN, HAIMOVICH, DUDU, ROTTENBERG, DAN
Applicants: BRAUN ORI, HAIMOVICH DUDU, R D C RAFAEL DEV CORP LTD, ROTTENBERG DAN, BRAUN, ORI, HAIMOVICH, DUDU, R.D.C. - RAFAEL DEVELOPMENT CORPORATION LTD., ROTTENBERG, DAN
Application year: 1995
Main classification: A61B5
IPC codes: A61B5