Dr. Adrian Chan has been named a Fellow of the Canadian Medical and Biological Engineering Society (CMBES).

Photo of Varsha Chaugai Figure showing Finite Element Method (FEM) mesh of a human thorax Photo of Varsha Chaugai

varsha chaugai

role of thoracic impedance and current in successful synchronized electrical cardioversion

The objective of this research is to examine the effect of transthoracic impedance (TTI) and current on the efficacy of synchronized cardioversion. Synchronized electrical cardioversion is a treatment that applies an electrical pulse to the cardiac tissue to restore normal sinus rhythm in patients presenting atrial fibrillation, atrial flutter and ventricular tachycardia. The success of this treatment is largely dependent on the current density at the heart, which is inversely related to TTI. Hence, during cardioversion it is desirable to have lower TTI and deliver an "optimal" current based on the patient's impedance; that is, the minimum current density that provides a successful cardioversion. Relative to a monophasic electric pulse, the "impedance compensating" biphasic pulse used in the defibrillation technology today is understood to compensate for variation in impedance. While the biphasic technology efficiently compensates for the variation in impedance, the extent of its influence on positive outcomes for patients exhibiting high TTI is still unclear. This was the motivation behind our project where we implement statistical methods on clinical cardioversion data to understand the relationship between TTI, current and success rate of cardioversion treatment. We have also used finite element method to uncover the electrical activity in the thorax and heart during defibrillation for different patient types/sizes and pad position. We believe that this understanding of current distribution in the human body will aid in formulating new strategies to improve the success rate of this treatment especially in large patients with high TTI.

This research is in collaboration with University of Ottawa Heart Institute.

Thesis supervisors Andy Adler, Adrian D. C. Chan, and Timothy Zakutney (Director of Biomedical Engineering ,University of Ottawa Heart Institute)


Varsha Chaugai graduated with her Master's degree in Biomedical Engineering from Carleton University in 2012. She is from Nepal and is currently working as a Research Assistant at Systems and Computer Engineering at Carleton. Her research interests lies in Medical Instrumentation, Bio-Signal Processing and Modelling, Finite Element Methods, and Machine Learning. She has worked as Biomedical Engineer/Instructor for Government of Nepal and Verification Engineer (Intern) at Diablo Technologies, Ottawa.


  1. Chaugai V, Birnie D, Sadek M, Zakutney T, Cleland M, Chan ADC, Adler A, "Effect of transthoracic impedance on the cariodversion success rates using biphasic defibrillators", 34th Annual Scientific Sessions, Heart Rhythm, Denver, CO, USA, 2013.
  2. Chaugai V, Zakutney, Chan ADC, Adler A, "Academic programs in clinical engineering in Canada", 36th Conference of the Canadian Medical & Biological Engineering Society, Ottawa, Canada, 2013.
  3. Chaugai V, Adler A, Chan ADC, Zakutney T, "Estimation of effective pad positions during cardioversion using 3-dimensional finite element model ", 35th Conference of the Canadian Medical & Biological Engineering Society, Halifax, Canada, June 20-22, 2012.

Last updated October 30, 2012