Sensitivity of cardiac pacemaker to high-voltage electroporation pulses

KRMAC, TADEJ (author), Jarm, Tomaž (mentor), Magjarević, Ratko (co-mentor)

In the master's thesis, we investigated the possible effects of high-voltage electroporation pulses on the functioning of the pacemaker, under various conditions and methods of pulse delivery. We also developed simulation models that would allow us a more systematic study and understanding of physical phenomena and facilitate further research We were interested in how the influence of the pulses depends on the horizontal distance of the electrodes of the Cliniporator to the electrodes of the pacemaker, what are the maximum currents and voltages that can occur on the pacemaker electrodes and what are the effects when the Cliniporator pulses are delivered at different stages of pacing of the pacemaker. Measurements were carried out in a glass container, with a medium for two different values of electrical conductivity. The results obtained can be compared with voltages and currents that are caused in the body by other medical devices, for which it was proven that they cannot damage the pacemaker or cause its malfunction. While carrying out the measurements, we also came to a realization, that during the delivery of the Cliniporator pulses, the property of the media changed locally as evidenced by the sparking observed at the electrodes of the Cliniporator. Using the results of experimental measurements, two simulation models were constructed. The first model was constructed using linear electrical lumped elements, which were calculated by making the assumptions about the physical properties of the experimental setup during the measurements and using the results of these measurements. The second model was a numerical model using the finite element method, which required the proper composition of 3D geometry and the use of the output voltage of the Cliniporator. The Cliniporator pulse can affect the shape and amplitude of the pacemaker pulse, but the pacemaker pulse returns to its normal form in the next delivery cycle. In clinical circumstances, this should not present a problem, as the delivery of Clinipator pulses during electrochemotherapy are synchronized with the heart cycle and as such the Cliniporator pulses can never coincide with the pacemaker pulses. After all experimentation there was no change in the functioning of the pacemaker. The energy of the Cliniporator pulses delivered into the system is comparable to the energy delivered during defibrillation. Therefore, electrochemotherapy should be safe for patients with a pacemaker, taking similar precautions as for defibrillation. In order to confirm this, further examination of standards concerning cardiac pacemaker devices is needed. The simulation models achieved satisfactory results when computed signals were compared with the measured current and voltage signals. However, we should be aware of the inaccuracies introduced into the model with all the assumptions and simplifications used in building the models.

• Language: English
• Keywords: cardiac pacemaker, electroporation, electrochemotherapy, measurements, safety, mathematical modelling.
• Work type: Master's thesis/paper
• Organization: FE - Faculty of Electrical Engineering
• Year: 2018
• PID: 20.500.12556/RUL-102886
• Publication date in RUL: 11.09.2018

Secondary language

• Language: Slovenian
• Title: Občutljivost srčnega spodbujevalnika na visokonapetostne elektroporacijske pulze

Abstract

V magistrski nalogi smo raziskovali možne vplive visoko napetostnih elektroporacijskih pulzov na delovanje srčnega spodbujevalnika, pod različnimi pogoji in načini dovajanja pulzov. Razvili smo tudi simulacijske modele, ki bi omogočili bolj sistematično preučevanje in razumevanje fizikalnih pojavov in olajšali nadaljnje raziskovanje. Zanimalo nas je, kakšen je vpliv pulzov v odvisnosti od horizontalne razdalje Cliniporatorjevih elektrod do elektrod srčnega spodbujevalnika, kakšni so maksimalni tokovi in napetosti, ki se lahko pojavijo na elektrodah spodbujevalnika, in kakšni so vplivi, kadar so Cliniporatorjevi pulzi dovedeni ob različnih fazah delovanja spodbujevalnika. Meritve smo izvajali v stekleni kadi z medijem pri dveh različnih vrednostih električne prevodnosti. Pridobljene rezultate lahko primerjamo z napetostmi in tokovi, ki jih v telesu povzročijo naprave, za katere je dokazano, da ne morejo drastično škodovati srčnemu spodbujevalniku. Pri izvajanju meritev smo prišli tudi do spoznanja, da se med dovajanjem Cliniporatorjevih pulzov, lokalno spreminja lastnost uporabljenega medija, zaradi pojava iskrenja ob Cliniporatorjevih elektrodah. S pomočjo rezultatov eksperimentalnih meritev smo sestavili dva simulacijska modela. Prvi model je sestavljen iz koncentriranih linearnih električnih elementov. Koncentrirane elemente smo poračunali s pomočjo predpostavk o fizikalnih lastnosti merilne postavitve in rezultatov meritev. Drugi model je bil numerični model z uporabo metode končnih elementov, ki je upošteval pravilno 3D geometrijo in izhodno napetost Cliniporatorja. Cliniporatorjevi pulzi lahko pri delujočem srčnem spodbujevalniku vplivajo na obliko in amplitudo dovedenega pulza spodbujevalnika, vendar se ta povrne nazaj na svojo normalno oblika že v naslednjemu ciklu delovanja. V klinični razmerah to ne bi smelo biti problematično, saj je dovajanje Cliniporatorjevih pulzov med elektrokemoterapijo natančno sinhronizirano z delovanjem srca in zato pri pravilni sinhronizaciji Cliniporatorjevi pulzi ne bi bili nikoli dovedeni med stimulacijskim pulzom spodbujevalnika. Po končanih eksperimentalnih meritvah nismo opazili nobenih sprememb v delovanju srčnega spodbujevalnika Dovedene energije Cliniporatorjevih pulzov v sistem so primerljive oziroma manjše kot so energije pri defibrilaciiji. Torej bi elektrokemoterapija s tega vidika morala varna za paciente z vgrajenim spodbujevalnikom ob upoštevanju podobnih previdnostnih ukrepov kot pri defibrilaciji. Za potrditev tega bo potrebno še podrobno preučiti standarde, ki se nanašajo na srčne spodbujevalnike. Simulacijski modeli, so dosegli zadovoljive rezultate, kadar smo izračunane signale primerjali s izmerjenimi signali tokov in napetosti. Vendar se je treba zavedati, kakšne napake smo vnesli v model z vsemi predpostavkami in poenostavitvami.

• Keywords: Srčni spodbujevalnik., elektroporacija, elektrokemoterapija, meritve, varnost matematično modeliranje