HRP960392A2

HRP960392A2 - A device for the measurement of blood flow

Info

Publication number: HRP960392A2
Authority: HR
Inventors: Bozidar Ferek-Petric; Branko Breyer
Original assignee: Bozidar Ferek Petric
Priority date: 1996-08-30
Filing date: 1996-08-30
Publication date: 1998-04-30

Description

Područje na koje se izum odnosi The field to which the invention relates

Ovaj se izum odnosi na elektroterapiju srca, a posebno na mjerenje karakteristika protoka krvi unutar srca i u velikim krvnim žilama u svrhu kontrole elektroterapije srca. This invention relates to electrotherapy of the heart, and in particular to the measurement of blood flow characteristics within the heart and in large blood vessels for the purpose of controlling electrotherapy of the heart.

Tehnički problem Technical problem

Privremena i stalna fiziološka elektrostimulacija srca su vrlo važne. Privremena stimulacija se obično primjenjuje nakon operacije srca ili infarkta miokarda zbog prolaznog poremećaja provođenja ili aritmije. Bolesnici u mirovanju imaju bitno bolji srčani udarni volumen kada je ventrikulska kontrakcija sinkrona s atrijskim punjenjem ventrikula. To je važno za brži oporavak nakon operacije ili infarkta miokarda. Osim toga, neke se aritmije poput supraventrikulske tahikardije i ekstrasistola mogu spriječiti fiziološkom elektrostimulacijom srca. Temporary and permanent physiological electrostimulation of the heart are very important. Temporary pacing is usually applied after heart surgery or myocardial infarction due to a transient conduction disturbance or arrhythmia. Patients at rest have significantly better cardiac stroke volume when ventricular contraction is synchronous with atrial filling of the ventricles. This is important for faster recovery after surgery or myocardial infarction. In addition, some arrhythmias such as supraventricular tachycardia and extrasystoles can be prevented by physiological electrostimulation of the heart.

Bolesnici s kroničnim poremećajem provođenja ili ritma moraju dobiti trajno ugrađeni sustav za elektrostimulaciju. Doprinos atrija u poboljšanju hemodinamike je i kod njih važan. Postoje dva osnovna načina fiziološke elektrostimulacije srca: sekvencijski i sinkroni. Sekvencijska atrio-ventrikulska stimulacija se upotrebljava da bi se vratio normalni atrio-ventrikulski odnos. U tom načinu jedan atrij i jedan ventrikul se stimuliraju pomoću dva stimulirajuća impulsa razmaknuta za odgovarajući fiziološki interval. Međutim, frekvenciju otkucaja kontrolira program elektrostimulatora i ona se ne mijenja prema fiziološkim potrebama. Sinkrona elektrostimulacija najbolje se približava normalnom srčanom ritmu. Spontani atrijski elektrogram (P val) se detektira elektrodom koja je obično u kontaktu sa atrijskim endokardom i to se upotrebljava za okidanje ventrikulskog impulsa nakon odgovarajućeg, unaprijed postavljenog, kašnjenja. Budući da se atrijski ritam aktivira prirodnim stimulatorom, tj. sinus-atrijskim čvorom, frekvencija se mijenja fiziološki prema opterećenju tijela. Zbog toga je ventrikulska stimulacija sinkrona sa P-valom (VDD način) najfiziološkiji oblik frekvencijski adaptivne elektrostimulacije. U svrhu pojednostavnjenja kirurškog zahvata razvijeni su sustavi za VDD elektrostimulaciju samo jednim elektrodnim kateterom. Zbog relativno male amplitude atrijskog potencijala bilježenog plutajućom elektrodom, koja nema direktan kontakt sa endokardom, česta je pojava podosjetljivosti i gubitka sinkronizacije. Stoga takvi elektrostimulatori zahtijevaju detekcijska pojačala visoke osjetljivosti. Posljedica toga je da može doći do pojave preosjetljivosti atrijskog pojačala i krive sinkronizacije. Izum u našim SAD patentima br. 5,243,976 i br. 5,316,001 omogućuje novu metodu fiziološke VDD stimulacije srca. Svrha našeg izuma je da omogući elektrostimulator koji će, u normalnom atrijskom ritmu raditi u sinkronom načinu (VDD) te održavati atrio-ventrikulski sinkronizam, ali implantacijom samo jednog elektrodnog katetera. U izvedbi izuma prati se protok krvi u srcu pomoću uređaja za mjerenje brzine protoka krvi montiranog na stimulirajući elektrodni kateter. Za sinkronizaciju i kontrolu ventrikulske stimulacije srca koristi se valni oblik protoka kroz trikuspidni zalistak. Rani val brzog dijastoličkog punjenja (E-val) kao i kasni atrijski val dijastoličkog punjenja (A-val) se detektiraju i mjere se njihovi parametri. Ventrikulska stimulacija se sinkronizira sa A-valom. Sustav omogućuje i senzore za frekvencijski adaptivnu ventrikularnu stimulaciju i pouzdano sredstvo za detekciju atrijske fibrilacije. Drugi je predmet neprestano praćenje dinamike punjenja desnog ventrikula da bi se procijenila funkcionalnost srčanog mišića i automatski reprogramirala maksimalna frekvencija praćenja tako da se spriječi angina pektoris te ishemija izazvana brzom frekvencijom. Naš sustav može detektirati pojedinu prijevremenu srčanu kontrakciju kao i razlikovati sinusnu tahikardiju od patološke tahikardije. Također, daje potvrdu ventrikulskog odgovora kao i detekciju ventrikulske dekompenzacije. Naš sustav koristi ultrazvučnu Doppler metodu mjerenja brzine protoka krvi, koja zahtjeva relativno veliki utrošak energije. Patients with chronic conduction or rhythm disorders must receive a permanently implanted electrostimulation system. The contribution of the atria in improving hemodynamics is also important for them. There are two basic ways of physiological electrostimulation of the heart: sequential and synchronous. Sequential atrio-ventricular stimulation is used to restore normal atrio-ventricular relationship. In this mode, one atrium and one ventricle are stimulated using two pacing pulses separated by the appropriate physiological interval. However, the beat frequency is controlled by the electrostimulator program and does not change according to physiological needs. Synchronous electrostimulation best approximates a normal heart rhythm. The spontaneous atrial electrogram (P wave) is detected by an electrode usually in contact with the atrial endocardium and this is used to trigger a ventricular impulse after an appropriate, preset delay. Since the atrial rhythm is activated by a natural stimulator, i.e. the sinus-atrial node, the frequency changes physiologically according to the load on the body. This is why ventricular stimulation synchronous with the P-wave (VDD mode) is the most physiological form of frequency-adaptive electrostimulation. In order to simplify the surgical procedure, systems were developed for VDD electrostimulation with only one electrode catheter. Due to the relatively small amplitude of the atrial potential recorded by the floating electrode, which does not have direct contact with the endocardium, hyposensitivity and loss of synchronization are common. Therefore, such electrostimulators require high-sensitivity detection amplifiers. As a result, hypersensitivity of the atrial amplifier and incorrect synchronization may occur. Invention in our US Patent No. 5,243,976 and no. 5,316,001 provides a new method of physiological VDD stimulation of the heart. The purpose of our invention is to provide an electrostimulator that, in a normal atrial rhythm, will work in synchronous mode (VDD) and maintain atrio-ventricular synchrony, but with the implantation of only one electrode catheter. In an embodiment of the invention, blood flow in the heart is monitored using a device for measuring the speed of blood flow mounted on a stimulating electrode catheter. The flow waveform through the tricuspid valve is used to synchronize and control the ventricular stimulation of the heart. The early fast diastolic filling wave (E-wave) as well as the late atrial diastolic filling wave (A-wave) are detected and their parameters are measured. Ventricular stimulation is synchronized with the A-wave. The system provides sensors for frequency-adaptive ventricular stimulation and a reliable means of detecting atrial fibrillation. Another subject is continuous monitoring of right ventricular filling dynamics to assess heart muscle functionality and automatically reprogram the maximum monitoring frequency to prevent angina pectoris and ischemia induced by a fast rate. Our system can detect individual premature cardiac contractions as well as distinguish sinus tachycardia from pathological tachycardia. It also provides confirmation of ventricular response as well as detection of ventricular decompensation. Our system uses the ultrasound Doppler method of blood flow velocity measurement, which requires relatively high energy consumption.

Za pravilno funkcioniranje ovog izuma bitno je koristiti točnu metodu mjerenja protoka krvi koja je pouzdana na dugi rok te koristi malo snage, a pogodna je za primjenu u implantabilnim uređajima. Dakle, potrebno je konstruirati elektrodni kateter koji ima pretvornik za brzinu protoka koji troši malo energije te stoga ne povećava struju potrošnje baterije elektrostimulatora srca. Također, ne smije se bitno povećati broj vodiča elektrodnog katetera. Pretvornik mora biti dugotrajno pouzdan i biokompatibilan. For the proper functioning of this invention, it is essential to use an accurate blood flow measurement method that is reliable in the long term and uses little power, and is suitable for use in implantable devices. Therefore, it is necessary to design an electrode catheter that has a flow rate transducer that consumes little energy and therefore does not increase the current consumption of the pacemaker battery. Also, the number of leads of the electrode catheter must not be significantly increased. The transducer must be long-term reliable and biocompatible.

Stanje tehnike State of the art

U struci su poznate brojne metode mjerenja protoka krvi ali su samo neke pogodne za ugradnju u elektrostimulator srca. Poznato je iz struke da metalna elektroda uronjena u ionsku tekućinu proizvodi polućelijski potencijal. Dvije različite elektrode formiraju galvansku ćeliju u kojoj se pozitivna elektroda naziva anodom a negativna katodom. Standardni polućelijski potencijal elektrode se definira u slučaju kada ne postoji električna struja između elektrode i elektrolita. Ako nema struje, mjereni polu-potencijal se mijenja zbog polarizacije elektrode. Numerous methods of measuring blood flow are known in the profession, but only some are suitable for installation in a heart pacemaker. It is known in the art that a metal electrode immersed in an ionic liquid produces a half-cell potential. Two different electrodes form a galvanic cell in which the positive electrode is called the anode and the negative electrode the cathode. The standard half-cell potential of the electrode is defined in the case when there is no electric current between the electrode and the electrolyte. If there is no current, the measured half-potential changes due to the polarization of the electrode.

Teoretski postoje dvije vrste elektroda: one koje su savršeno polarizirajuće i one koje su savršeno nepolarizirajuće. Polarizirajuće elektrode su one u kojima ne prelazi pravi naboj preko sučelja elektroda-elektrolit u slučaju kada teče struja. Ta struja je zapravo struja premještanja jer se polarizirajuća elektroda ponaša kao kondenzator. Nepolarizirajuće elektrode su one u kojima struja slobodno teče kroz sučelje elektrode i elektrolita. Neke praktične elektrode se približavaju ovim karakteristikama. Elektrode napravljene od plemenitih materijala su relativno inertne te ih je teško rastapati i oksidirati. Takva elektroda proizvodi snažan kapacitivni efekt pa je skoro idealna polarizirajuća elektroda. Razlika potencijala između mjerenog polućelijskog potencijala i ravnotežnog polućelijskog potencijala kada nema struje, naziva se nadnapon. Tri su elektrokemijska fenomena koji pridonose razvitku nadnapona te je posljedično on superpozicija triju komponenata: omskog nadnapona, koncentracijskog nadnapona i aktivacijskog nadnapona. Omski nadnapon nastaje zbog otpora elektrolita. Postoji pad napona između dvije elektrode kroz strujnu stazu u elektrolitu. Pad napona je proporcionalan struji te otporu elektrolita. Omski nadnapon se ne odnosi linearno prema struji i zato ova pojava ne slijedi Ohmov zakon. Theoretically, there are two types of electrodes: those that are perfectly polarizing and those that are perfectly non-polarizing. Polarizing electrodes are those in which no real charge passes across the electrode-electrolyte interface when current is flowing. This current is actually a displacement current because the polarizing electrode behaves like a capacitor. Non-polarizing electrodes are those in which current flows freely through the electrode-electrolyte interface. Some practical electrodes approach these characteristics. Electrodes made of precious materials are relatively inert and difficult to dissolve and oxidize. Such an electrode produces a strong capacitive effect, so it is almost an ideal polarizing electrode. The potential difference between the measured half-cell potential and the equilibrium half-cell potential when there is no current is called an overvoltage. There are three electrochemical phenomena that contribute to the development of overvoltage and consequently it is a superposition of three components: ohmic overvoltage, concentration overvoltage and activation overvoltage. Ohmic overvoltage occurs due to the resistance of the electrolyte. There is a voltage drop between the two electrodes through the current path in the electrolyte. The voltage drop is proportional to the current and the resistance of the electrolyte. Ohmic overvoltage does not relate linearly to current and therefore this phenomenon does not follow Ohm's law.

Varijacija raspodjele iona na sučelju metal-elektrolit uzrokuje koncentracijski nadnapon. U ravnoteži, kada ne teče struja između elektrode i elektrolita, su intenziteti oksidacije i redukcije na sučelju jednaki. Kada se uspostavi struja, ili se elektroda pomiče u elektrolitu, ili se pojavi protok elektrolita, ravnoteža više ne postoji. Tako se mijenja koncentracija iona te nastaje razlika polupotencijala uzrokovana koncentracijskim nadnaponom. Oksidacija atoma metala u ione moguća je ako je atom sposoban savladati energetsku barijeru - aktivacijsku energiju. Redukcija kationa elektrolita u atome metala također uključuje aktivacijsku energiju. Kada teče struja između elektrode i elektrolita, bilo koja od navedenih reakcija dominira te su dvije aktivacijske energije za oksidaciju i redukciju različite. Ova razlika energije se manifestira kao razlika napona - aktivacijski nadnapon. Ukupni nadnapon je zbroj svih triju nadnapona. Unatoč tome, nadnapon u elektroda od plemenitih metala je prvobitno rezultat koncentracijskog nadnapona. Pojava nadnapona je temeljito proučena i opisana u brojnim referencama struke. To je stoga, što je primarni cilj konstrukcije elektroda za registriranje biopotencijala raznih primjena umanjiti nadnapon i izobličenja registriranog signala biopotencijala koji su uzrokovani nadnaponom. Protivno tome, pojava nadnapona se koristi u ovom izumu. Očito je da protok elektrolita mijenja raspodjelu iona u okolini sučelja elektroda-elektrolit te tako mijenja koncentracijski nadnapon. Primjenom polarografskog para elektroda tipa Clark moguće je mjerenje brzine protoka krvi kako je opisano u SAD patentu br. 3,930,493 uz primjenu uzbudnog napona veličine 0.4 - 0.9 Volta. The variation of ion distribution at the metal-electrolyte interface causes a concentration overvoltage. In equilibrium, when no current flows between the electrode and the electrolyte, the intensities of oxidation and reduction at the interface are equal. When current is established, or the electrode moves in the electrolyte, or electrolyte flow occurs, equilibrium no longer exists. Thus, the concentration of ions changes and a half-potential difference is created caused by the concentration overvoltage. Oxidation of metal atoms into ions is possible if the atom is able to overcome the energy barrier - activation energy. Reduction of electrolyte cations to metal atoms also involves activation energy. When current flows between the electrode and the electrolyte, any of the mentioned reactions dominates, and the two activation energies for oxidation and reduction are different. This energy difference is manifested as a voltage difference - activation overvoltage. The total overvoltage is the sum of all three overvoltages. Nevertheless, the overvoltage in the noble metal electrode is originally the result of concentration overvoltage. The phenomenon of overvoltage has been thoroughly studied and described in numerous professional references. This is because the primary goal of the construction of biopotential recording electrodes for various applications is to reduce overvoltage and distortions of the registered biopotential signal caused by overvoltage. Conversely, the occurrence of overvoltage is used in the present invention. It is obvious that the electrolyte flow changes the distribution of ions in the environment of the electrode-electrolyte interface and thus changes the concentration overvoltage. By applying a polarographic pair of electrodes of the Clark type, it is possible to measure the speed of blood flow as described in US patent no. 3,930,493 with the application of an excitation voltage of 0.4 - 0.9 Volts.

Također postoji mogućnost mjerenja impedancije pomoću vrlo male jakosti struje kako je prikazano u europskoj patentnoj prijavi br. 94100130.7. Koristi se činjenica daje impedancija dviju elektroda uronjenih u ionsku tekućinu modulirana protokom ionske tekućine tj. kretanjem iona. It is also possible to measure the impedance using a very low current as shown in European patent application no. 94100130.7. The fact that the impedance of two electrodes immersed in the ionic liquid is modulated by the flow of the ionic liquid, i.e. the movement of the ions, is used.

Naš izum opisan u međunarodnoj patentnoj prijavi br. PCT/EP95/01171 koristi mjerenje promjene galvanskog potencijala i koncentracijskog nadnapona u svrhu mjerenja brzine protoka krvi, ali bez primjene uzbudnih napona i struja. U tom izumu koriste se elektrode različitih materijala koje u krvi čine galvanski članak, odnosno polarizirajuća elektroda npr. od zlata čiji se koncentracijski nadnapon mijenja promjenom brzine protoka. Nedostatak je ovog sustava što se implantacijom na dugi vijek mijenjaju elektrokemijska svojstva polarizirajućih elektroda. Posebno rast fibroznog tkiva može u kroničnoj fazi elektrostimulacije smanjiti veličinu kako galvanskog potencijala tako i koncentracijskog nadnapona. To bi moglo izazvati gubitak sinkronizacije što komplicira praćenje bolesnika i zahtjeva mjerenje i kontinuirano praćenje razvitka poremećaja u detekciji signala protoka. Također bi bilo potrebno da elektrostimulator srca ima programabilnu osjetljivost za detekciju signala protoka što zahtjeva složeniju konstrukciju kako pojačala za bilježenje signala brzine protoka tako i pratećih sučelja pojačala i mikroprocesora. Potrebna je i složenija programska podrška kako upravljačkog mikroprocesora elektrostimulatora tako i vanjskog programatora. U proizvodnji elektroda za elektrostimulaciju srca koriste se biokompatibilni nepolarizirajući materijali kao na pr. crna platina, karbon i TiN. Elektrode imaju poroznu površinu da bi se spriječila polarizacija. Our invention described in international patent application no. PCT/EP95/01171 uses the measurement of the change in galvanic potential and concentration overvoltage for the purpose of measuring the blood flow rate, but without the application of excitation voltages and currents. In this invention, electrodes of different materials are used that form a galvanic cell in the blood, i.e. a polarizing electrode, for example, made of gold, whose concentration overvoltage changes by changing the flow rate. The disadvantage of this system is that the electrochemical properties of the polarizing electrodes change after long-term implantation. In particular, the growth of fibrous tissue can reduce the size of both the galvanic potential and the concentration overvoltage in the chronic phase of electrostimulation. This could cause a loss of synchronization, which complicates patient monitoring and requires measurement and continuous monitoring of the development of disturbances in flow signal detection. It would also be necessary for the pacemaker to have a programmable sensitivity for the detection of the flow signal, which requires a more complex construction of both the amplifier for recording the flow rate signal and the accompanying interfaces of the amplifier and the microprocessor. More complex software support is also required for both the control microprocessor of the electrostimulator and the external programmer. In the production of electrodes for electrostimulation of the heart, biocompatible non-polarizing materials are used, such as black platinum, carbon and TiN. The electrodes have a porous surface to prevent polarization.

Da bi funkcija senzora brzine protoka bila nezavisna o rastu fibroznog tkiva oko elektroda te da bi elektrode mogle biti proizvedene od suvremenih nepolarizirajućih materijala, razvijen je novi sustav za mjerenje brzine protoka krvi. In order for the function of the flow rate sensor to be independent of the growth of fibrous tissue around the electrodes and for the electrodes to be manufactured from modern non-polarizing materials, a new system for measuring the blood flow rate was developed.

Opis izuma Description of the invention

Ovi i drugi predmeti ovog izuma biti će jasniji kroz slijedeći opis pripadajućih slika: These and other objects of this invention will be made clearer through the following description of the accompanying drawings:

Slika 1 prikazuje distalni završetak elektrodnog katetera za elektrostimulaciju srca sa dvije elektrode za mjerenje protoka krvi. Figure 1 shows the distal end of an electrode catheter for electrostimulation of the heart with two electrodes for measuring blood flow.

Slika 2 prikazuje kateter sa slike 1 implantiran u ljudsko srce. Figure 2 shows the catheter from Figure 1 implanted in a human heart.

Slika 3 prikazuje elektrodni kateter sa dvije elektrode za mjerenje protoka implantiran u desno srce. Figure 3 shows an electrode catheter with two electrodes for flow measurement implanted in the right heart.

Slika 4 prikazuje distalni završetak elektrodnog katetera sa slike 3. Figure 4 shows the distal end of the electrode catheter from Figure 3.

U izvedbi sa slike 1 prikazan je distalni završetak plastičnog tijela elektrodnog katetera 10 za elektrostimulaciju srca. Tijelo elektrodnog katetera 10 sadrži dvije prstenaste elektrode 11 i 12 napravljene različitih geometrijskih oblika. Elektroda 11 ima geometrijski oblik prstena čiji je vanjski promjer jednak promjeru tijela 10 elektrodnog katetera. Pričvršćena je na tijelo 10 tako da vanjska površina prstena nije izbočena izvan konture tijela elektrodnog katetera. Zbog toga ne čini hidrodinamički diskontinuitet površine tijela elektrodnog katetera koji bi uzrokovao lokalnu promjenu brzine protoka kada se elektrodni kateter uroni u protočni medij čiji je vektor brzine protoka paralelan sa kateterom. Elektroda 12 ima geometrijski oblik prstena unutarnjeg promjera jednakog vanjskom promjeru tijela spomenutog elektrodnog katetera. Navučena je na tijelo 10 i stoga njezina vanjska površina izlazi izvan konture tijela 10. Zbog toga čini hidrodinamički diskontinuitet površine tijela elektrodnog katetera. U ovom primjeru je elektroda 12 napravljena u obliku hidroprofila. Hidroprofil (ili aeroprofil na pr. NACA4512) ubrzava brzinu protoka u svojoj neposrednoj blizini i time stvara uzgonsku silu, kako se to može proračunati Bernoulijevom jednadžbom. Ako je vektor brzine protoka krvi paralelan sa tijelom elektrodnog katetera, brzina uz granicu elektrode 12 i krvi će se povećati. Također će doći i do pojave turbulencija. Kako je poznato u struci, elektrokemijske reakcije na granici metal - elektrolit su različite kod različitih brzina protoka elektrolita. Zato na granicama metal-elektrolit elektroda 11 i 12 dolazi do bitne razlike u koncentraciji iona. Koncentracijski nadnapon dviju elektroda će biti različit, a promjena razlike koncentracijskih nadnapona je proporcionalna promjeni brzine protoka. Na vrhu elektrodnog katetera nalazi se elektroda 13 za elektrostimulaciju srca, koja je spojena pomoću elektrodnog vodiča 16 sa generatorom impulsa elektrostimulatora srca (nije prikazan). Elektrodni vodič 14 je spojen (nije prikazano) unutar tijela katetera 10 sa elektrodom 11, a elektrodni vodič 15 je spojen (nije prikazano) unutar tijela katetera 10 sa elektrodom 12. Spajanjem diferencijalnog pojačala 17 na elektrode 11 i 12 pomoću elektrodnih vodiča 14 i 15, ono može mjeriti razliku koncentracijskog nadnapona elektroda 11 i 12. Pojačalo 17 ima pojasni propust prilagođen frekvencijskom spektru signala proizvedenim protokom krvi. Izlazni signal diferencijalnog pojačala sadrži informaciju o brzini protoka krvi. On je složen od intrakardijalnog elektrograma i koncentracijskog nadnapona elektroda. Odgovarajućom obradom, taj se signal može koristiti za upravljanje elektrostimulacijom srca. In the embodiment from Figure 1, the distal end of the plastic body of the electrode catheter 10 for electrostimulation of the heart is shown. The body of the electrode catheter 10 contains two ring electrodes 11 and 12 made of different geometric shapes. The electrode 11 has the geometric shape of a ring whose outer diameter is equal to the diameter of the body 10 of the electrode catheter. It is attached to the body 10 so that the outer surface of the ring does not protrude beyond the contour of the body of the electrode catheter. Therefore, it does not form a hydrodynamic discontinuity of the electrode catheter body surface that would cause a local change in the flow rate when the electrode catheter is immersed in a flow medium whose flow velocity vector is parallel to the catheter. The electrode 12 has the geometric shape of a ring with an inner diameter equal to the outer diameter of the body of the mentioned electrode catheter. It is pulled onto the body 10 and therefore its outer surface protrudes beyond the contour of the body 10. Therefore, it forms a hydrodynamic discontinuity of the electrode catheter body surface. In this example, the electrode 12 is made in the form of a hydroprofile. Hydrofoil (or aerofoil e.g. NACA4512) accelerates the flow velocity in its immediate vicinity and thus creates a lift force, as can be calculated by the Bernoulli equation. If the blood flow velocity vector is parallel to the body of the electrode catheter, the velocity along the boundary of the electrode 12 and the blood will increase. Turbulence will also occur. As is known in the field, electrochemical reactions at the metal-electrolyte interface are different at different electrolyte flow rates. That is why there is a significant difference in ion concentration at the metal-electrolyte boundaries of electrodes 11 and 12. The concentration overvoltage of the two electrodes will be different, and the change in the concentration overvoltage difference is proportional to the change in the flow rate. At the tip of the electrode catheter there is an electrode 13 for electrostimulation of the heart, which is connected by means of an electrode conductor 16 to the pulse generator of the electrostimulator of the heart (not shown). The electrode conductor 14 is connected (not shown) inside the catheter body 10 to the electrode 11, and the electrode conductor 15 is connected (not shown) inside the catheter body 10 to the electrode 12. By connecting the differential amplifier 17 to the electrodes 11 and 12 by means of the electrode conductors 14 and 15 , it can measure the difference of the concentration overvoltage of the electrodes 11 and 12. The amplifier 17 has a bandpass adapted to the frequency spectrum of the signal produced by the blood flow. The output signal of the differential amplifier contains information about the speed of blood flow. It is composed of the intracardiac electrogram and the concentration overvoltage of the electrodes. With appropriate processing, this signal can be used to control electrical stimulation of the heart.

U izvedbi sa slike 2 prikazana je praktična primjena stimulirajućeg elektrodnog katetera iz slike 1 koji sadrži elektrodni par za mjerenje protoka u blizini trikuspidnog zaliska. Srce je prikazano u presjeku četiri komore a presjek miokarda je vidljiv na stjenci lijevog ventrikula 20, desnog ventrikula 21, interventrikulskog septuma 22, lijevog atrija 23 i desnog atrija 24. Dvije komore lijevog srca, lijevi ventrikul 25 i lijevi atrij 26, su odvojeni mitralnim zaliskom 27. Lijevi ventrikularni izlazni trakt sastoji se od aortnog zaliska 28 i aorte 29. Stimulirajući srčani elektrodni kateter 10 je ugrađen kroz gornju šuplju venu 31 kroz desni atrij 32 u desni ventrikul 33 sa svojom elektrodom za elektrostimulaciju 13 smještenom u apeks desnog ventrikula. U nižem području desnog atrija blizu trikuspidnog zaliska 35 kateter za elektrostimulaciju 10 sadrži dvije elektrode 11 i 12. Elektrode 11 i 12 su napravljene kako je opisano u prethodnoj slici. Dotok krvi iz desnog atrija 32 u desni ventrikul 33 kroz trikuspidni zalistak 35 uzrokuje promjenu koncentracije iona u okolini elektroda 11 i 12. Zato se koncentracijski nadnapon elektroda 11 i 12 mijenja. Diskontinuitet konture katetera također uzrokuje lokalnu promjenu brzine protoka uz granicu elektroda-ionska tekućina elektrode 12. Uz granicu elektroda-ionska tekućina elektrode 12 brzina protoka je veća od brzine protoka uz granicu elektroda-ionska tekućina elektrode 11. Stoga se koncentracijski nadnaponi elektroda 11 i 12 razlikuju. Karakteristika promjene razlike koncentracijskog nadnapona dviju elektroda predstavlja karakteristiku promjene brzine protoka krvi kroz trikuspidni zalistak. Kako se mjeri karakteristika protoka krvi kroz trikuspidni zalistak, mogu se detektirati valovi punjenja desnog ventrikula što omogućuje upravljanje elektrostimulacijom srca. The embodiment from Figure 2 shows the practical application of the stimulating electrode catheter from Figure 1, which contains an electrode pair for measuring flow near the tricuspid valve. The heart is shown in a section of four chambers, and the section of the myocardium is visible on the wall of the left ventricle 20, the right ventricle 21, the interventricular septum 22, the left atrium 23 and the right atrium 24. The two chambers of the left heart, the left ventricle 25 and the left atrium 26, are separated by the mitral valve 27. The left ventricular outflow tract consists of the aortic valve 28 and the aorta 29. The cardiac stimulating electrode catheter 10 is inserted through the superior vena cava 31 through the right atrium 32 into the right ventricle 33 with its electrostimulation electrode 13 located in the apex of the right ventricle. In the lower region of the right atrium near the tricuspid valve 35, the electrostimulation catheter 10 contains two electrodes 11 and 12. The electrodes 11 and 12 are made as described in the previous figure. The flow of blood from the right atrium 32 to the right ventricle 33 through the tricuspid valve 35 causes a change in the concentration of ions in the vicinity of electrodes 11 and 12. That is why the concentration overvoltage of electrodes 11 and 12 changes. The discontinuity of the catheter contour also causes a local change in the flow rate along the electrode-ionic liquid interface of electrode 12. Along the electrode-ionic liquid interface of electrode 12, the flow velocity is higher than the flow velocity along the electrode-ionic liquid interface of electrode 11. Therefore, the concentration overvoltages of electrodes 11 and 12 they differ. The characteristic of the change in the concentration overvoltage difference between the two electrodes represents the characteristic of the change in the speed of blood flow through the tricuspid valve. As the characteristic of the blood flow through the tricuspid valve is measured, the right ventricular filling waves can be detected, which allows the electrical stimulation of the heart to be controlled.

Slika 3 prikazuje srce otvoreno kod aurikule desnog atrija 41. Unutar desnog atrija su trikuspidni zalistak 42, fossa ovalis 43, valvula koronarnog sinusa 44 i crista terminalis 45. Prikazane su gornja šuplja vena 46, donja šuplja vena 47 kao i pulmonalna arterija 48 i aorta 49 sa truncus pulmonalis 50. Vidi se lijevi atrij 51 sa desnom gornjom pulmonalnom venom 52 kao i sa desnom donjom pulmonalnom venom 53. Prikazan je apeks desnog ventrikula 54 kao i ostatak perikarda 55. Elektrodni kateter za stimulaciju 60 je ugrađen kroz gornju šuplju venu 46 i šupljinu desnog atrija kroz trikuspidni zalistak 42 u desni ventrikul sa vrhom (nije prikazan) u području apeksa 54. Elektrodni kateter 60 sadrži dvije istovrsne elektrode 57 i 58 u području trikuspidnog zaliska 42. Figure 3 shows the heart open at the auricle of the right atrium 41. Inside the right atrium are the tricuspid valve 42, the fossa ovalis 43, the valve of the coronary sinus 44 and the crista terminalis 45. The superior vena cava 46, inferior vena cava 47 as well as the pulmonary artery 48 and the aorta are shown. 49 with truncus pulmonalis 50. You can see the left atrium 51 with the right superior pulmonary vein 52 as well as the right inferior pulmonary vein 53. The apex of the right ventricle 54 is shown as well as the rest of the pericardium 55. The stimulation electrode catheter 60 is inserted through the superior vena cava 46 and the cavity of the right atrium through the tricuspid valve 42 into the right ventricle with a tip (not shown) in the region of the apex 54. The electrode catheter 60 contains two identical electrodes 57 and 58 in the region of the tricuspid valve 42.

Slika 4 prikazuje distalni završetak plastičnog tijela elektrodnog katetera sa slike 3. U ovom primjeru tijelo katetera 60 sadrži dvije elektrode 57 i 58 napravljene od istog materijala jednakog geometrijskog oblika. Elektrode 57 i 58 imaju geometrijski oblik polu-prstena čiji je vanjski promjer jednak promjeru tijela 60 katetera. Pričvršćene su na tijelo 60 tako da njihove vanjske površine prstena nisu izbočena izvan konture tijela katetera. Elektrode 57 i 58 su montirane jedna nasuprot drugoj međusobno razmaknute. Vektor dinamičkog tlaka uzrokovan brzinom protoka koji djeluje na površinu elektrode 57 ima jednu komponentu koja djeluje okomito na površinu elektrode i jednu komponentu koja je paralelna sa površinom elektrode. Zbog kružnog presjeka tijela elektrodnog katetera dolazi kako do turbulentnog protoka u okolini tijela katetera kao i povećanja brzine fluida koji teče oko cjevastog profila tijela katetera. Elektroda 58 se nalazi u protoku zaštićena tijelom katetera. Zbog toga na nju djeluje manji dinamički tlak nego na elektrodu 57. Uz površinu elektrode 58 je također brzina protoka veća, ali ne tako velika kao uz površinu elektrode 57. Zbog navedenih razlika na granici metal - elektrolit dviju elektroda dolazi do bitne razlike koncentracije iona, a različiti su i intenziteti elektrokemijskih procesa elektroda 57 i 58 na njihovim granicama metal-elektrolit. Koncentracijski nadnapon dviju elektroda će biti različit, a promjena razlike koncentracijskih nadnapona je proporcionalna promjeni brzine protoka. Na vrhu elektrodnog katetera nalazi se elektroda 61 za elektrostimulaciju srca, koja je spojena pomoću elektrodnog vodiča 62 sa generatorom impulsa elektrostimulatora srca (nije prikazan). Elektrodni vodič 63 je spojen (nije prikazano) unutar tijela katetera 60 sa elektrodom 57, a elektrodni vodič 64 je spojen (nije prikazano) unutar tijela katetera 60 sa elektrodom 58. Spajanjem diferencijalnog pojačala 65 na elektrode 57 i 58 pomoću elektrodnih vodiča 63 i 64, ono može mjeriti razliku koncentracijskog nadnapona. Pojačalo 65 ima pojasni propust prilagođen frekvencijskom spektru signala protoka krvi. Izlazni signal diferencijalnog pojačala sadrži informaciju o brzini protoka krvi. Kako se mjeri karakteristika protoka krvi kroz trikuspidni zalistak, mogu se detektirati valovi punjenja desnog ventrikula što omogućuje upravljanje elektrostimulacijom srca. Figure 4 shows the distal end of the plastic body of the electrode catheter of Figure 3. In this example, the catheter body 60 contains two electrodes 57 and 58 made of the same material and having the same geometric shape. Electrodes 57 and 58 have the geometric shape of a half-ring whose outer diameter is equal to the diameter of the body 60 of the catheter. They are attached to the body 60 so that their outer ring surfaces do not protrude beyond the contour of the catheter body. Electrodes 57 and 58 are mounted opposite each other and spaced apart. The dynamic pressure vector caused by the flow rate acting on the electrode surface 57 has one component acting perpendicular to the electrode surface and one component parallel to the electrode surface. Due to the circular cross-section of the electrode catheter body, there is a turbulent flow around the catheter body as well as an increase in the speed of the fluid flowing around the tubular profile of the catheter body. Electrode 58 is in the flow, protected by the body of the catheter. Because of this, a lower dynamic pressure acts on it than on electrode 57. Along the surface of electrode 58, the flow rate is also higher, but not as high as along the surface of electrode 57. Due to the aforementioned differences at the metal-electrolyte boundary of the two electrodes, there is a significant difference in ion concentration, and the intensities of the electrochemical processes of electrodes 57 and 58 at their metal-electrolyte boundaries are also different. The concentration overvoltage of the two electrodes will be different, and the change in the concentration overvoltage difference is proportional to the change in the flow rate. At the tip of the electrode catheter there is an electrode 61 for electrostimulation of the heart, which is connected by means of an electrode conductor 62 to the pulse generator of the electrostimulator of the heart (not shown). Electrode conductor 63 is connected (not shown) inside the catheter body 60 to electrode 57, and electrode conductor 64 is connected (not shown) inside the catheter body 60 to electrode 58. By connecting the differential amplifier 65 to electrodes 57 and 58 using electrode conductors 63 and 64 , it can measure the concentration overvoltage difference. The amplifier 65 has a bandpass adapted to the frequency spectrum of the blood flow signal. The output signal of the differential amplifier contains information about the speed of blood flow. As the characteristic of the blood flow through the tricuspid valve is measured, the right ventricular filling waves can be detected, which allows the electrical stimulation of the heart to be controlled.

Slika prikazuje idealan slučaj koji je u praksi teško postići. Radijalna orijentacija elektrodnog katetera implantiranog u desno srce je uvijek sasvim slučajna. Bez obzira na to što je položaj elektroda u području trikuspidnog zaliska slučajan, uvijek postoji makar i mala međusobna razlika položaja elektroda u odnosu na vektor brzine protoka. To je dovoljno da se razvije razlika brzina elektrolita uz površine elektroda te stoga i razlika nadnapona između dviju relevantnih elektroda. U praksi, dodatno tome, javljaju se i turbulentna strujanja oko tijela elektrodnog katetera koje stvaraju dodatnu razliku elektrokemijskih stanja dviju elektroda. Također se razlika koncentracijskog nadnapona može registrirati i između bilo koje dvije elektrode u protoku krvi unutar srca jer nije moguće postići jednake hidrodinamičke uvjete na dva različita mjesta u srcu. The figure shows an ideal case that is difficult to achieve in practice. The radial orientation of the electrode catheter implanted in the right heart is always completely random. Regardless of the fact that the position of the electrodes in the area of the tricuspid valve is random, there is always even a small difference between the positions of the electrodes in relation to the flow velocity vector. This is enough to develop a difference in the velocity of the electrolyte along the electrode surfaces and therefore an overvoltage difference between the two relevant electrodes. In practice, in addition to that, turbulent flows occur around the body of the electrode catheter, which create an additional difference in the electrochemical states of the two electrodes. Also, the concentration overvoltage difference can be registered between any two electrodes in the blood flow inside the heart because it is not possible to achieve the same hydrodynamic conditions in two different places in the heart.

Opisana je specifična izvedba ovog pronalaska, ali je razumljivo da je ova izvedba opisana samo kao ilustracija. Prethodni opis ne ograničava ni na koji način predmet ovog pronalaska. Namjera je da se predmet ovog pronalaska ograniči kako je definirano u slijedećim patentnim zahtjevima. A specific embodiment of the present invention is described, but it is to be understood that this embodiment is described by way of illustration only. The foregoing description does not limit the subject matter of the present invention in any way. The subject matter of this invention is intended to be limited as defined in the following claims.

Claims

1. A device for measuring the intracardiac blood flow rate, which contains a catheter (10; 60) adapted to be inserted through a blood vessel (31; 46) into the heart, at least one detection device (11/12; 57/58) for detecting the blood flow rate attached to the catheter in a position located in the desired detection area (35; 42) when said catheter is introduced into the heart, electrical conductors (14/15; 63/64) inside said catheter which are connected with their distal ends to said detection device (11/12; 57/58) and which are connected with their proximal ends to electronic circuits (17; 65) for recording and processing data on the blood flow rate detected in the detection area, characterized by the fact that said detection device contains at least two mutually spaced electrodes (11/12; 57/58) made in such a way that mutually different vectors of the blood flow rate caused by the blood flow rate in the mentioned detection area (35; 42) act along their surfaces.

2. Device according to claim 1, characterized in that said two electrodes (11; 12) are made of the same non-polarizing material and have mutually different geometric shapes so that blood flow velocities along the surfaces of the two mentioned electrodes are mutually different, causing mutually different ion concentrations along the two electrode-blood boundaries of the mentioned two electrodes.

3. Device according to claim 1, characterized by the fact that said two electrodes (57; 58) are made of the same non-polarizing material and have a different place and a different way of attachment to said catheter (60) so that the first electrode (57) is directly exposed to dynamic pressure caused by the flow rate in said detection area, and the second electrode (58) is exposed to reduced dynamic pressure by being mounted protected behind the contour of the body (60) of said catheter in relation to the direction of the vector of said flow rate.

4. Device according to any of the preceding claims, characterized in that said first electrode (12) has a geometric shape such that its outer surface constitutes a hydrodynamic discontinuity of said catheter body (10), which causes a local change in the dynamic pressure acting on the surface of said first electrodes as well as a local change in the flow rate along the electrode-blood boundary of the mentioned first electrode, and the mentioned second electrode (11) has a geometric shape such that its outer surface does not form a hydrodynamic discontinuity of the surface of the body of the mentioned catheter (10) which would cause a local change in the dynamic pressure which acts on the surface of said second electrode and the local change in flow rate along the electrode-blood boundary of said second electrode.

5. Device according to any of the preceding claims, characterized in that said first electrode (12) is a ring with an inner diameter equal to the outer diameter of the body (10) of said catheter and that it has a cross-section of a hydroprofile, and said second electrode (11) is a ring with an outer diameter equal to the outer diameter of the body (10) of the mentioned catheter.

6. A device according to any of the preceding claims, characterized in that said second electrode of any geometric shape is implanted in such an anatomical location anywhere in the human body where the blood flow rate within the heart cannot cause a local change in the dynamic pressure and flow rate at its electrode-blood boundary.

7. Device according to any of the preceding claims, characterized in that said electrodes (57; 58) are semi-rings attached to said body (60) facing each other so that a positive velocity vector acts on the outer surface of said first electrode (57) blood flow, and the negative blood flow velocity vector acts towards the outer surface of the second mentioned electrode (58), which is why the effect of the mentioned flow velocity vector on the electrode-blood boundaries of the two mentioned electrodes is different.

8. The device from any of the previous claims, indicated by the fact that the difference in the mentioned dynamic pressure or the difference in the mentioned blood flow rate at the metal-blood boundaries of the two mentioned electrodes produces a voltage difference between the mentioned electrodes by causing a difference in the intensity of electrochemical reactions at their electrode-blood boundaries.

9. Device according to any of the preceding claims, characterized in that said electronic circuits for recording and processing data on blood flow rate contain a differential amplifier (17; 65) with a band pass.

10. Device according to any one of the preceding claims, characterized in that said two electrodes (11/12; 57/58) are electrically connected to said differential amplifier (17; 65) by means of said two electrical conductors (14/15; 63/ 64) so that one of the mentioned electrodes is connected to the positive input, and the other of the mentioned electrodes to the negative input of the mentioned amplifier.

11. The device according to any of the preceding claims, characterized in that said electronic circuits for recording and processing data on the blood flow rate detected in said detection area (35; 42) contain means for monitoring the change of said voltage difference between said two electrodes through the heart cycle, following the filling of the right ventricle.

12. The device according to any of the preceding claims, characterized in that said electronic circuits for recording and processing data on the blood flow rate detected in said detection area (35; 42) contain means for detecting the first wave of said voltage difference indicating the diastolic wave of fast filling caused by ventricular relaxation and the second wave of the aforementioned voltage difference indicating the late filling wave caused by atrial contraction.

13. Device from any of the preceding claims, characterized in that said electronic circuits for recording and processing data on the blood flow rate detected in said detection area (35; 42) contain means for controlling and synchronizing heart electrotherapy.