Varsha Chaugai under the supervision of Dr. Andy Adler, Dr. Adrian - PowerPoint PPT Presentation

Role of Transthoracic Impedance on the success of synchronized electrical cardioversion By Varsha Chaugai under the supervision of Dr. Andy Adler, Dr. Adrian D.C. Chan, Timothy Zakutney Masters Thesis Defense Presentation – August 23, 2012 In partial fulfillment of the requirements for the degree of Masters of Applied Science

Motivation Cardioversion setup 2

Motivation • Biphasic defibrillators compensate for the TTI • Low success rate for patients with high TTI. • More shocks for high TTI patients – unbeneficial. • Impedance compensating biphasic defibrillators improve the success rate for high TTI patients - UNCLEAR 3

Thesis Objectives 1. Effect of TTI on the success rate of cardioversion PART II: PART I: Statistical 3-D Finite Element Analysis on Clinical data Modeling (FEM) 4

Thesis Objectives 2. Examine the effect of pad positions using FEM • Pad position clinician specific • No general agreement 5

Overview of Contributions 3. Current density distribution for 2. Current range different patient types (FEM) 1. Statistical 4. Effect of Pad Effect of TTI and Analysis positions method to improve the success rate 6

Contribution #1 : Statistical analysis to examine the effect of TTI on the efficacy of cardioversion . Methodology : • 574 cases (952 shocks) for AF, 112 cases (125 shocks) for AFL, 89 cases (176 shocks) for VT. • Shocks classified as “success” and “failure”. • Divided into categories of low and high energy and impedance. • Chi- square and Fischer’s exact test at  = 0.05 7

100 100 Results : <70 Ω, ≤ 150 J 100 Defibrillation Success(in %) 90 <70 Ω, 200 J 88 90 81 >70 Ω, ≤ 150 J 80 >70 Ω, 200 J 69 69 70 60 60 57 57 50 40 35 30 25 20 10 0 Atrial Atrial Flutter Ventricular Fibrillation Tachycardia • Statistically significant results for AF and VT. 8

Conclusion : • High TTI, lower success rate. 100 Defibrillation Success (in %) • Inefficient impedance 90 n = number of shocks 80 n=62 compensation. n=238 n=372 70 60 n=197 50 n=27 40 30 n= 55 20 10 0 0-45 45-65 65-85 85-105 105-125 >125 Impedance (Ohms) 9

Contribution #2 : Determination of current amplitude for a successful cardioversion Methodology : • Clinical cardioversion data Results : • Optimal current range between 24 A – 48 A Conclusion : • TTI influences  current  the success rate. 10

Contribution #3 : Effect of TTI on current density distribution in the thorax using FEM on different patient types Methodology : Thin 2-D CAT SCAN Normal Large 11

Results : 14 14 1.4 1.5 % Cardiac Damage Current Energy 12 mm 2 ) 0.31% Cardiac Damage 12 1.2 mA/mm 11.5 10 Y (mA/ 10 1 A) 0% Cardiac RRENT (A) Damage Y(J) DENSITY ( ERGY(J 8 8 0.8 7.1 CURRE ENER 6.5 6 0.6 6 EN RRENT DE CU 4 0.4 4 CURRE 2 0.2 2 CU 0 0 0 Thin Normal Large Thin Normal Large PATIENT TYP YPE PATIENT TYPE 12

Thin Conclusion : • Effect of TTI on cardioversion Normal Large 13

Contribution #4 : Effect of pad position on cardioversion Methodology : AL AP1 AP2 • Pad positions modelled using FEM 14

Results : AL • Least current • Low resistance AP2 • Higher uniformity in current AP1 Conclusion: • AP2 - most effective AP2 15

Effect of pad position on patient size: Methodology: • Modelling the three positions on the three patient types. Thin Normal Large Energy for AL Energy for AP1 Energy for AP2 Results: 18 40 16 35 • Less current and energy 14 30 for large patients at AP2 12 25 Energy(J) Current(A) 10 20 8 Conclusion: 15 6 10 4 • Better defibrillation result 5 2 in AP2 0 0 AL AP1 AP2 16 Position

Thesis Conclusion: • TTI plays an important role in success rate of cardioversion. • Pad position also affects the cardioversion efficacy. • One of the ways to increase the success rate for high TTI patients is to change the pad position to AP2 during cardioversion. 17

Publication: Contribution #4: Conference paper • Chaugai V, Adler A, Chan ADC, Zakutney T, “ Estimation of effective pad positions during cardioversion using 3-dimensional finite element model”, 35 th Conference of the Canadian Medical & Biological Engineering Society, Halifax, Canada, 2012. 18

Role of Transthoracic Impedance on the success of synchronized electrical cardioversion By Varsha Chaugai under the supervision of Dr. Andy Adler, Dr. Adrian D.C. Chan, Timothy Zakutney Masters Thesis Defense Presentation – August 23, 2012 In partial fulfillment of the requirements for the degree of Masters of Applied Science

Future work: 1. Prospective Study 2. Current based defibrillators 3. Measurement of the impedance before the cardioversion procedure 4. Refining the FEM model 5. Analysis of pad shape and pad size 6. Finding current in the heart 7. Comparison of FEM results with the clinical data 8. Inclusion of Defibrillation events 20

Questions: - Cardiac arrest – no electrical conduction in the heart VT: rapid ventricular Contractions, no blood Pumped in the heart - Pacemaker : something wrong with SA or AV node or during cardiac block 21

- true null hypothesis was incorrectly rejected (Type I error) or where one fails to reject a false null hypothesis (Type II error). Impedance does not affect but u say impedance affect ( type I error) Results show impedance affect, but u reject it and show the impedance doesnot affect (type II error) - That’s why we use 0.05 as we are less prone to make type II error - Erroneous results if chi-square is used for <5 - Confounding effect – variables that affect dependent & independent Variable (for our case like age, gender, duration of arrhythmia, patient’s Condition, drug(medicine) consumption history. Disadvantage of retrospective analysis 22

Dysfunction – changed into different arrhythmia, harm is temporary Damage/injury- damage to the myocardial cells and it is permanent. – Thromboembolism, ischemia, degeneration of the cells, myocarditis, Cell necrosis How is giving more number of shocks harmful? Causes damage Strength-duration relationship 23