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EPSRC Reference: EP/D500338/1
Title: Feedback control of resonant drift as a tool for low voltage defibrillation
Principal Investigator: Biktashev, Professor VN
Other Investigators:
Biktasheva, Dr IV
Researcher Co-Investigators:
Project Partners:
Department: Mathematical Sciences
Organisation: University of Liverpool
Scheme: Standard Research (Pre-FEC)
Starts: 12 December 2005 Ends: 11 December 2008 Value (£): 78,572
EPSRC Research Topic Classifications:
Medical science & disease Non-linear Systems Mathematics
EPSRC Industrial Sector Classifications:
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Summary on Grant Application Form
There are more than 100 thousand premature cardiac deaths every year in the UK alone. Most of these are associated with re-entrant cardiac arrhythmias. Normally, the contraction of the heart muscle is synchronized by a wave of electric excitation, which is initiated by a group of cells called sinus node and propagates in an orderly fashion through the heart. If propagation of this wave is temporarily blocked in one place but is allowed in others, it may form a re-entrant circuit. This re-entrant wave overrides the sinus rhythm, hijacks the control over the cardiac muscle, causes rapid and uncoordinated contractions of its parts, and disrupts the heart's function of pumping the blood. Milder forms of re-entrant arrhythmias, such as paroxysmal tachycardia or atrial flutter, seriously decrease quality of life. The extreme form is the ventricle fibrillation, which is related to persistent re-entrant waves in the larger chambers of the heart, and is usually lethal.The last line of defence against re-entrant arrhythmias and fibrillation is electrical defibrillation, which is a powerful electric shock aiming at resetting all the excitable cells in the heart to the same state and thus stopping any electric activity, including the re-entrant wave. The most traditional method is transthoracic delivery, i.e. through large electrodes applied to the chest of the patient. It is also one of the functions of the implantable defibrillators, which are used by high-risk cardiac patients and can deliver defibrillating shocks automatically when they detect dangerous patterns of activity.Unfortunately, the defibrillation is not always effective. Shocks have to be really powerful in order to ensure excitation of all cells in the heart. Defibrillating shocks if applied to conscious patients are extremely painful. In any case the powerful electric shocks cause damage to the heart itself and surrounding tissues. Thus there is a high demand in clinics on alternative methods of defibrillation which would work with smaller voltages. Such methods exist and are sometimes attempted by the implantable devices or on the operating table, and then high-voltage shocks are delivered only if the milder methods fail. They fail too often, so search for more efficient low-voltage defibrillation algorithms continues.We suggest that delocalized electric stimulation similar to that used in defibrillation, but delivered by many weak shocks instead of one strong shock, can do the job. If the shocks are properly timed, they can make the locations of re-entrant circuits move, cycle after cycle, inside the muscle in the desired direction and eventually exterminate them. This is the meaning of the term resonant drift . This method works nicely on simple mathematical models, and also on a chemical model , the Belousov-Zhabotinsky reaction, a mixture of chemicals whose properties resemble those of cardiac muscle, with chemical instead of electric excitation. However, it has never been tested on real cardiac tissue. Real heart is much more complicated than the models on which the method has been tried so far, and experimentalists doubt so much that it will work they do not want to risk the expenses and lives of experimental animals. The theory of resonant drift is not developed enough so if, and most probably when, the resonant drift does not work, there will be no obvious way to say why, and thus no ways to see how to modify the experiment to make it work.So the idea of this project is to diminish the need in the real experiments by doing more mathematical modelling and numeric experiments instead. We will test various versions of resonant drift control by computer simulations the most realistic mathematical models of heart known to date, in order to foresee possible difficulties that may be encountered by experimentalists, and ways to overcome those difficulties.
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Organisation Website: http://www.liv.ac.uk