APPARATUS FOR ARTERIAL REPERFUSION THROUGH NONINVASIVE ULTRASONIC ACTION

Abstract: The invention relates to an invention for arterial reperfusion through ultrasound action, i.e. the acceleration of dissolution of thrombi. By means of the invention reperfusion may be achieved quicker than through intravenous medicine treatment only. The apparatus comprises an energy supply, a control means controlling the supplied energy and a compound ultrasound transmitter transforming the energy to sound energy and adapted to transmit sound energy into the body and providing sound waves through the entire organ in which a blood vessel has been obstructed by thrombus formation.

Description: TITLE OF INVENTION: APPARATUS FOR ARTERIAL REPERFUSION THROUGH NONINVASIVE ULTRASONIC ACTION FIELD OF THE INVENTION The present invention relates to an apparatus for subjecting the coronary arteries of the heart to ultrasound for the purpose of accelerating reperfusion. Today infarct of the heart is a very common disease in the civilized world. In Sweden each year in the range of 35,000 individuals are stricken with acute infarct of the heart, a fourth of which dies even before they reach the hospital. The disease has a course with various types of complications in the acute stage, together yielding a death rate during the stay at the hospital in the range of nearly 15 percent, varying primarily with age and the magnitude of the infarct of the heart . After discharge from the hospital there is a clear excessive mortality, the more pronounced the larger heart muscle injury the patient has experienced because of his infarct. If it is possible to reduce the magnitude of the infarct of the heart in the acute infarct stage it has been found that this results in lower mortality in the poststage of the infarc . The method having most evidently being able to reduce the heart muscle injury has been early reperfusion of the heart muscle by thrombolytic treatment. Hitherto the thrombolytic treatment has been in form of intravenous medication resulting in enzymatic dis- solution of the formation of the thrombus in a coronary artery constituting the immediate cause of the accute infarct of the heart. The earlier the treatment has been able to be performed, the better effect has been achieved with respect to reducing the heart muscle injury and survival rate after the infarct. STATE OF THE ART With the purpose of noninvasively provide reperfusion as fast as possible, hitherto infarct of the heart has been treated with pharmaceuticals initiating enzymatic thrombo- lysis. Intravenous thrombolytic treatment of patients with accute infarct of the heart results in reperfusion after 30- 150 minutes, on the average after approximately 45 minutes. The potential gain in being able to reperfuse the myocardium immediately instead of having to wait 45 minutes is obvious. The possibility of accelerating thrombolysis under experi¬ mental conditions by subjecting the thrombus to ultrasound has been shown by the applican . The present invention sub¬ stantially reduces the time to reperfusion in that this experimentally confirmed principle using the claimed appa- ratus may be applied on patients having a suspected acute infarct of the heart . A known apparatus closely related to the present in¬ vention is a diagnostic apparatus using ultrasound. The apparatus comprises an ultrasound transmitter and a receiver receiving the echo from the ultrasound when this is reflected against various organs of the body. The sound energy emitted is so low that no effect on the organ can be found. Ultrasound apparatus may also be used for heating organs of the body, e.g. joints and muscles, for therapeutic reasons. In this case higher energy levels are used than in the present invention. Another apparatus related to the present invention is renal calculus crushers, which are used to fragmentize renal calculi without surgical operation. The supplied energy, which may be sound energy, is focused such that the power is highly concentrated to the renal calculus itself, which in contrast to a thrombus is easily located using diagnostic ultrasound or X-rays. The difference in hardness between the renal calculus and the surrounding organs promotes the trans- mission of the destructive energy to the renal calculus. SUMMARY OF THE INVENTION The present invention provides an apparatus for reper¬ fusion through accelerated thrombolysis. The apparatus uti- lizes ultrasound to influence a thrombus formed in a blood vessel. By means of the invention reperfusion may be obtained quicker than through enzymatic treatment only. The exact mechanism underlying the desired effect is not completely mapped out but it is believed to be some or more of the known physical effects provided by ultrasound energy in the present form. According to the invention the apparatus comprises an energy supply, a control means controlling the amount and characteristics of the supplied energy and a compound ultra- sound transmitter transforming the energy to sound energy and adapted to subjecting the entire coronary artery tree to ultrasound, i.e. it is not necessary to know the exact loca¬ tion of the thrombus. In order to be able to distribute the desired energy of the sound signal to the entire coronary artery tree, the transmitter utilizes various sound emitting crystals emitting sound of various wavelengths, of various beam directions and variously shaped beam sectors . Sound signals are transmitted intermittently from the individual crystals. Embodiments of the invention are set forth more in detail in the accompanying claims . BRIEF DESCRIPTIONS OF THE DRAWINGS The invention will now be described in detail referring to the enclosed drawings of which: Fig. 1 is a simplified view of the heart seen from the front, Fig. 2 is a block diagram of the components included in the device, Fig. 3 is a schematic view of the ultrasound transmitter according to the the invention, Fig. 4 is a diagram of possible pulse shapes, and Fig. 5 is a diagram of the frequency of the pulses of Fig. 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION It is now totally accepted that most of the infarcts of the heart is caused by thrombus formation in the coronary arteries, of which a few are shown in Fig. 1. These thrombi are derived from an injury of the cells lining the vessel, an endothelial injury. This is caused in turn, partly, by structural vessel transformations caused by a slow athero- matous process. Thrombocytes are aggregated at the injured endothelian surface, whereby a thrombycyte agglutination is formed, complexed by fibrin precipitation and further built- up by means of coagulation. The obliterative process may also contain components of vascular spasms. The initial thrombus consists of a fragile tissue mass, but as fibrin is precipitated succesively the thrombus is even after a few hours more ecanically resistant . The fragile thrombus is a known phenomenon to everybody who has suffered from nosebleed. When this has been stopped it is important not to mechanically irritate the vessel region in which the nosebleed started. A similar influence of a fragile throumbus in a coronary artery in acute infarct of the heart results in the thrombus being fragmentized, embolized and reperfusion is achieved. The present invention provides an apparatus by means of ultrasound transmitting energy from the exterior of the body to the blood vessel containing an obliterative thrombus . By applying sound waves transthoracically and/or via an eso¬ phageal probe a quick action on the thrombus may be achieved. Fig. 2 shows schematically the structure of the appa- ratus according to the invention. It comprises a power supply supplying electrical energy, a control means controlling the power supply to a compound ultrasound transmitter, in turn transforming the energy to sound energy which is distributed so that the whole tissue volume, within which the thrombus is thought to exist, is subjected to sound energy of the ne¬ cessary level. The transmitter is composed of several transmitting units, each comprising at least one piezoelectric crystal. The transmitting units are applied directly against the chest of the patient or is in an esophageal probe to be inserted in the esophagus directly behind the heart . Fig. 3 shows an embodiment of the apparatus used to in¬ fluence a thrombus in the heart of a human . The ultrasound transmitter consists of several transmitting crystals 1 connected by wires 2 to the control means. Three crystals are applied against the chest 3 of the patient shown in cross- section with three ribs 4 visible and one crystal is located in an esophageal probe 5. The esophagus 9 passes close to the rear of the heart enabling irradiation of the heart 6 at this side without the need to raise the power unnecessarily at the front. Each crystal transmits ultrasound in a sector indepen¬ dent of the others . The sectors are directed such that the largest possible part of the heart 6 is subjected to the ultrasound, since it is not known exactly where the thrombus is located. In the figure the thrombus is shown at 7 in a coronary artery 8. The control means controls the transmitter to transmit signals from the various individual crystals in the compound ultrasound transmitter. Because each separate crystal trans- mits an ultrasound signal of a defined energy level and with defined time intervals and in individual directions as well as different impulse propagation of the signal, complete action on the treated organ is achieved. The various crystals are controlled such that they transmit pulses one at a time, i.e. they never transmit simultaneously. The transmitter supplies sound energy in pulses having a pulse frequency which can be varied. Fig. 4 shows a diagram of possible pulse shapes. The pulse frequency may be varied within broad limits, e.g. from 10 Hz to 10 kHz. A pulse frequency of 1 kHz, as calculated for the entire compound transmitter, has yielded good results. The interval between the pulses is then 1 ms, as is shown in Fig. 4. The duration of the pulses may be varied in turn between 1 μs and 50 μs and 10 μs seems to be a suitable value. During the pulses the output power of the transmitter is e.g. 2 W/cm 2 , maximum 3 W/cm 2 . During the silent periods diagnosis may be performed with the transmitter or with a separate transmitter for ultrasound diagnosis (see below) . The sound frequency is suitably in the range of 25 kHz - 5 MHz. The sound frequency may be fixed, as illustrated in the left pulse. However, it may be more advantagous to let the sound frequency sweep over a range, e.g. 25 kHz - 5 MHz. Fig. 5 illustrates schematically the sound frequencies of the pulses in Fig. 4. The frequency sweep may be linear or along a suitable curve. The shape of the sweep is net criti- cal . A person having acute infarct of the heart caused by a thrombus in the coronary arteries has most often a severe, acute felt pain in the chest, agony and seeks, provided he can, generally medical help as soon as possible. The enzyma¬ tic treatment of the thrombus is started immediately by in¬ travenous treatment with medicine, provided contraindications to such treatment are not present . The treatment with the apparatus according to the invention is likewise started as soon as possible. Since it is not known exactly where in the coronary artery the thrombus is present, a sound signal is transmitted passing the whole heart . In an embodiment the apparatus of the invention may be integrated with an ultrasound diagnosis apparatus. One optional transmitting unit is used for the diagnosis . It will then be possible to study simultaneously the effects of the treatment. Thanks to the pulsed sound shape intervals between the therapeutical sound pulses may be used for the diagnostic ultrasound. In connection with therapeutic treatment with ultrasound of joints and muscles and in connection with treatment of renal calculus, the effects of ultrasound on the tissues of the body has been studied. It has been found that the heart is remarkably resistant to possible trauma which may occur. Thus, there is a very little risk that the treatment with the apparatus of the invention will cause any adverse effects in the heart. This possible effect should in that case be com¬ pared to the effect of the infarct itself, which of course can be lethal . Is is appreciated that the apparatus of the invention also can be used for treatment of thrombi located in various types of vessels in various other organs than the heart, e.g. thrombi in the legs. The invention is only limited by the claims below.

Claims: CLAIMS 1. An apparatus for arterial reperfusion through non- invasive ultrasonic action, characterized by: an energy supply; a control means controlling the amount and nature of the supplied energy; and an ultrasound transmitter trans¬ forming the energy to sound energy and adapted to transmit sound energy into a body to influence the dissolution of thrombus in a blood vessel in the body, said transmitter being composed of several transmitting units each comprising at least one piezoelectric crystal, each crystal having a capacity of sending an ultrasound signal with a defined energy level and frequency and in an individual direction. 2. Apparatus according to claim 1, characterized in that the transmitter is adapted to transmit the sound energy in pulses . 3. Apparatus according to claim 2, characterized in that the transmitter has an output power during energy supply up to 3 W/cm 2 . 4. Apparatus according to claim 1, characterized in that the transmitter has a pulse frequency in the range of 10 Hz - 10 kHz, preferably approximately 1 kHz. 5. Apparatus according to claim 4, characterized in that the sound pulse has a duration in the range of 1 μs - 50 μs, preferably approximately 10 μs . 6. Apparatus to any one of the preceding claims, characterized in that the sound frequency/frequencies of the transmitter is in the range of 25 kHz - 5 MHz. 7. Apparatus according to claim 6, characterized in that the sound frequency within each pulse may be swept from 25 kHz - 5 MHz. 8. Apparatus according to any one of the preceding claims, characterized in that a transmitting unit is adapted to be applied against the outside of the body of a patient . 9. Apparatus according to any one of the preceding claims, characterized in that a transmitting unit is placed in an esophageal probe . 10. Apparatus according to any one of the preceding claims, characterized in that the apparatus is included as an integrated part of an ultrasound diagnosis apparatus.

Inventors: OLSSON BERTIL, OLSSON, BERTIL
Applicants: OLSSON BERTIL, OLSSON, BERTIL
Application year: 1993
Main classification: A61B17
IPC codes: A61B17