High-definition dynamic impedance characterization during defibrillation for cardioversion efficacy assessment
Background and Justification
Atrial fibrillation (AF) is the most commonly encountered cardiac arrhythmia. When atrial fibrillation occurs, there is an increased risk of stroke for the majority of patients. Several options are available to treat AF. These include pharmacological cardioversion, electrical cardioversion, pacemaker based therapies and atrial ablation techniques. Over the past two decades, much research effort has been dedicated into the field of transvenous internal defibrillation. Generally speaking, internal atrial defibrillation is a safe and highly effective procedure. However, the effectiveness of the procedure depends on several factors. One of these factors is the electrical impedance which characterises the endocardial atrium as seen by the internally positioned defibrillation electrodes[1]. At the Royal Victoria Hospital Belfast we have digitally recorded the voltage and current waveforms during internal cardioversion of AF patients using a novel low-tilt monophasic[2] and biphasic[3] waveforms. These voltage-current recordings have been gathered in different experimental settings for clinical trials in animal models[4] and in humans[5].
Description
High voltage (50-300 V) and current waveforms, captured simultaneously using a Tektronix digital oscilloscope during every electrical shock delivered to the atrium via transvenous catheterisation, are available at the CACR laboratory. A signal processing application is required to perform analysis of the dynamic impedance waveform in order to characterise its behaviour and relate it to other variables such as AF type, Atrial fibrillatory frequency (AFF) from ECG before shock, defibrillation electrophysiology, voltage amplitude, cardioversion efficacy assessment and optimum defibrillation threshold energy criteria.
References
[1] - “Effect of electrode position on outcome of low-energy intracardiac cardioversion of atrial fibrillation”. Alt E, Schmitt C, Ammer R, Plewan A, Evans F, Pasquantonio J, Ideker T, Lehmann G, Pütter K, Schömig A. American Journal of Cardiology; 79(5):621-625, 1997.
[2] - “Comparing the Efficacy and Safety of a Novel Monophasic Waveform Delivered by the Passive Implantable Atrial Defibrillator With Biphasic Waveforms in Cardioversion of Atrial Fibrillation”. Ganesh Manoharan, MD; Noel Evans, PhD; Desmond Allen, MD; John Anderson, DPhil; Jennifer Adgey, MD. Circulation. 109:1686-1692, 2004.
[3] - “Radio-frequency powered atrial defibrillation with a biphasic rectangular pulse waveform: a safety study at 3 and 5 Jouls”. Escalona, O.J., Walsh, S.J., Allen, J.D., Anderson, J. McC., Adgey, A.A.J. Proceedings of the Fifth IEEE International Caracas Conference on Devices Circuits and Systems, Dominican Republic, pp. 309-314, ISBN: 0-7803-8777-5, Nov 3-5, 2004.
[4] - “Novel Rectangular Biphasic and Monophasic Waveforms Delivered by a Radiofrequency Powered Defibrillator Compared with Conventional Capacitor Based Waveforms in Transvenous Cardioversion of Atrial Fibrillation”. Simon J. Walsh, Ganesh Manoharan, Omar J. Escalona, José Santos, Noel Evans, John McC Anderson, Mike Stevenson, J Desmond Allen, Jennifer Adgey.EUROPACE, Vol. 8, pp. 873-880, 2006.
[5] - “A pilot study of a low-tilt biphasic waveform for transvenous cardioversion of atrial fibrillation: Improved efficacy compared with conventional capacitor-based waveforms in patients”. Glover, B.M., McCann, C.J., Manoharan, G., Walsh, S.J., Moore, M.J., Allen, J.D., Escalona, O., Adgey, J.A.A.. PACE - Pacing and Clinical Electrophysiology, 31 (8), pp. 1020-1024, 2008.
Personnel Involved
First Supervisor: Escalona, OJ Prof
Second Supervisor: Mariotti, D Dr
Collaborator: Dr David McEneaney
Collaboration: This project does not involve collaboration with another establishment