CT for Electrophysiology Applications

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1 CT for Electrophysiology Applications Harold Litt MD-PhD Associate Professor of Radiology and Medicine, Chief, Cardiovascular Imaging Section, Department of Radiology Perelman School of Medicine of the University of Pennsylvania

2 Disclosures Research grants and travel support from Siemens Medical Solutions for CT-related projects Thanks to Benoit Desjardins for some slides

3 Outline Scope of the problem Atrial Fibrillation Ventricular arrhythmia Other applications

4 Arrhythmia Epidemiology: Affects > 14 million people in US > 800,000 annual hospital visits in US Some are immediately life threatening Sudden cardiac death - acute or remote MI 500,000 deaths per year in US Other are not immediately life threatening Important complications, such as stroke Atrial fibrillation and flutter

5 Atrial Fibrillation Pulmonary vein ablation/isolation is becoming more prevalent method for treatment of atrial fibrillation Cardiac CT is useful prior to and after ablation Evaluate pulmonary venous anatomy prior Navigation guide during ablation Evaluate complications after ablation Several common pitfalls that can complicate interpretation and procedure guidance

6 Atrial fibrillation: ablation Cause: excitable tissue extends into pulmonary veins Treatment: electrical isolation of the PV RF ablations around the PV ostia or deeper in left atrium Modify the left atrial substrate by linear RF ablations

7 Ablation technique for Afib pulmonary veins left atrium

8 Pulmonary vein CT RSPV LAA LSPV RIPV CT venography LIPV Endovascular views

9 Role of imaging Pre-ablation Ostial diameter of each vein Length to first-order branch Extra pulmonary veins Shape of left atrium LAA thrombus During ablation Procedure guidance Post-ablation Complications Scar formation

10 Pre-ablation: sizing PV ostial mean diameter RS: 20 mm LS: 19 mm RI: 16 mm LI: 17 mm Length of trunk: sup: 22 ± 8 mm inf: 14 ± 6 mm Early branching

11 Pre-ablation: variations Anomalous venous return Separate RM PV

12 Pre-ablation: Esophagus location Lemola, Circ 2004 Esophagus in close contact to LA wall May lie within ablation zone Marked variation in the anatomic relationship Layer of adipose tissue may insulate the esophagus from thermal injury

13 Left Atrial Appendage Filling Defects Poor left atrial function in AF Filling defect in LAA True thrombus Pseudothrombus - incomplete filling of contrast during arterial phase imaging Discrimination is important: e.g. it may influence the decision to perform ablation or cardioversion

14 How to Deal with Pseudothrombus Delayed imaging Takes time and radiation Prone imaging Takes more time and radiation Quantitative analysis

15 Delayed Imaging : Pseudothrombus

16 Delayed Imaging : True Thrombus

17 Prone Imaging Tani T, et al. Usefulness of electron beam tomography in the prone position for detecting atrial thrombi in chronic atrial fibrillation. JCAT Jan-Feb;27(1):

18 Quantitative Analysis Metric based upon the normalized rate of change in attenuation at the interface of the LAA and the left atrial appendage filling defect Slope >=0.17 corresponds to thrombus 0.17 < Slope < 0.03 = varying degrees of slow flow (SEC - spontaneous echo contrast or smoke ) Slope <0.03 is normal

19 TEE Shows Clot

20 Arrhythmia at Time of Scan - High Dose Most scanners automatically detect arrhythmia Results in dramatic increase in dose Even for triggered scans Pulmonary Venous Anatomy Imaging with Low-Dose, Prospectively ECG-Triggered, High-Pitch 128-Slice Dual Source Computed Tomography Wai-ee Thai, Bryan Wai, Kaity Lin, Teresa Cheng, E. Kevin Heist, Udo Hoffmann, Jagmeet Singh and Quynh A. Truong Circ Arrhythm Electrophysiol published online May 14, 2012; DOI: /CIRCEP Circulation: Arrhythmia and Electrophysiology is published by the American Heart Association Greenville Avenue, Dallas, TX Copyright 2012 American Heart Association. All rights reserved. Print ISSN: Online ISSN: msv AF, 16.7 SR vs. 1.6 msv high-pitch

21 Arrhythmia : PVCs

22 Arrhythmia : A Fib

23 Options for Dealing with Arrhythmia Teach your techs to recognize atrial fibrillation Perform nongated study Bill as CTA chest - cardiac CT needs ECG Lower mas, without tube current modulation Allows use of any phase, but high dose Turn off arrhythmia correction, trigger 45% Large volume detector or high pitch helical Most important step is recognition

24 Post-ablation: complications Pulmonary Vein - Stenosis ( %) - Thrombosis - Dissection - Pulmonary infarction - Pulmonary HTN (11%) Other - Catheter site hematoma (13%) - AV fistula (1%) - Systemic emboli ( %) Intrathoracic - Pleural effusion - Pericarditis (3 4.8%) - Pericardial effusion - Cardiac perforation Cronin, Acad Rad 2004

25 Post-ablation: PV stenoses pulmonary vein stenosis post abladon therapy

26 Post-ablation: PV stenoses

27 Post-ablation: Esophageal fistula Schley Europace (3): 18

28 BiV pacer implantation: Coronary sinus mapping

29 Ventricular Arrhythmia RF ablation has become more frequent Isolated PVC, monomorphic VT Frequent ICD shocks with polymorphic VT Goals of CT Define anatomy LV thickness Location of previous MI, scar Coronary anatomy Intra-procedure guidance

30 Scar: Delayed Enhancement MRI vs CT Mahnken JACC 2005 infarct size on DE-MRI was 31.2 ± 22.5% per slice compared with 33.3 ± 23.8% per slice for DE-MSCT enhancement patterns showed excellent agreement between DE-MRI and DE-MSCT (kappa = 0.878).

31 How do you do it? Administer iodinated contrast (more is better) Wait 5-15 mins (variable in the literature) ECG-synchronized acquisition Gated vs. triggered Low dose, thick vs. thin slices Low kvp is better (closer to iodine k-edge) Problem for obese patients, other artifacts Dual energy? Mahnken, et. al. Investigative Radiology (2);123-9

32 Imaging tools: electrical activity scar (red) critical site Normal myocardium (purple)

33 Scar: CT vs. Electroanatomic Map Tian Circ EP (5): 496 Abnormal anatomic, dynamic, perfusion data correlated with abnormal endocardial voltages (r=0.77) 3D CT integrated into mapping system allowed prediction of abnormal voltage in 82% of segments CT hypoperfusion correlated best with scar area

34 Patient with Devices ICDs for primary prevention or VT May be placed after MI, but prior to revascularization CT performed for EP ablation guidance

35 Patients with Devices Severe artifacts Can t use lower kvp, so less sensitive to LE Increased dose if using automated tube current modulation Many have frequent ectopy, limiting study quality

Combined Epicardial and Endocardial Ablation for Treatment of Atrial Fibrillation. Ashkan Babaie MD Providence Portland Medical Center

Combined Epicardial and Endocardial Ablation for Treatment of Atrial Fibrillation Ashkan Babaie MD Providence Portland Medical Center 1 Disclosures None 2 Cox-Maze III The Godfather Cure rates > 95% in