Mapping and Ablation of VT in The Operating Room

Mapping and Ablation of VT in The Operating Room Sanjay Dixit, M.D. Associate Professor, University of Pennsylvania School of Medicine Director, Cardiac Electrophysiology Laboratory, Philadelphia V.A.M.C. Disclosure-of-Relationship Speakers Bureau / Honoraria: Biosense-Webster, Medtronic, St Jude Medical, Acuson, Siemens, Boston Scientific Grant: Boston Scientific, Biosense-Webster, Medtronic Special Disclosure Ed, The Party Animal Surgical VT Ablation: Historical Perspective Resection of dyskinetic / akinetic scar: Aneurysmectomy (success ~40%) Sub-endocardial resection ± Aneurysmectomy (success ~90%) Sub-endocardial resection guided by mapping in OR: epicardial sock, intracardiac basket, bipolar catheters Advent of ICD therapy & Catheter based ablation 1

Surgical VT Ablation: Current Indications Treatment of last resort for patients who have failed multiple catheter ablation attempts. PENN experience: over a 3 year period (2007 2009), 527 patients underwent VT ablation 295 patients (56%) had structural heart disease (non-ischemic substrate in 144; 49%); 8 of these patients (1.5%) needed surgical ablation. All 8 patients has non ischemic cardiomyopathy: 6 with dilated cardiomyopathy and 2 with hypertrophic cardiomyopathy. Patient # Age (yrs) Sex LVEF (%) NICM ICD 1 65 M 15 Yes Yes 2 50 M 70 Yes Yes 3 54 M 58 Yes Yes 4 51 F 25 Yes No 5 51 M 30 Yes Yes 6 74 M 30 Yes Yes 7 74 M 50 Yes Yes 8 48 M 40 Yes Yes MRI identified septal scar in 3 patients; clinical VT was localized to thickened basal septum (>20 mm) in 2 of these subjects Intraseptal VT Substrate: MR Imaging Mid Septal Scar Inferior Basal Scar Intra-Septal VT Substrate Trans Thoracic Intra Cardiac RV LV Anterior Septal Scar Inferior Apical Scar 2

ECG Features of VT originating from basal IVS Left bundle block with early precordial transition (V 1 V 2 ) Endocardial mapping was performed in all (LV in 8, RV in 4); epicardial mapping was performed in 6. A total of 24 VTs (spontaneous / induced) were observed. Right bundle block with unusual precordial transition At conclusion of percutaneous ablation, in 4 patients no VT was inducible, in 3 patients clinical VT remained inducible and 1 patient developed RV perforation requiring urgent surgery. In all 4 patients that were non-inducible, 1 targeted VT recurred within a week of the last percutaneous ablation. Cardiac Access for Surgical VT ablation Trans-Aortic View: Basal LV Median Sternotomy provides best cardiac visualization: AML RV epicardium Superior IV Septum Anterior LV wall LCC NCC RCC To visualize posterolateral LV wall, heart has to be physically lifted. Plane of Aortic Transaction Superior Partial sternotomy can allow visualization of RV, anterior and inferior LV surfaces. Anterior Inferior Posterior 3

Surgical Ablation: Alternative Approaches Trans-mitral approach: This offers best visualization of both papillary muscles, posterior LV endocardium and LV apex. LV Apical approach: In patients with mechanical aortic and mitral valves. Aneurysmectomy site: Access to LV can be obtained through this location prior to aneurysm resection and closure. Accessing RV: Either via the tricuspid valve or the RV free wall. Other approaches for epicardial access only: Partial sternotomy, window via epigastric incision, left anterior thoracotomy. VT Mapping in the OR Finger mounted roving electrode: This was used for mapping critical components of the VT circuit in the early era of surgical ablation. Multipolar mesh / Basket catheter: High resolution so can provide comprehensive activation sequences; require special set-up for signal processing so cumbersome to use. Electro-anatomic mapping: Needs special set up creation of magnetic field, reference catheter (usually sutured to RV or LV epicardium). Mapping in EP Lab prior to Surgical Ablation: PENN Approach Epicardial View A priori detailed endocardial and when indicated, epicardial mapping performed in the EP laboratory. Activation, entrainment and electro-anatomic mapping performed to identify critical components of VT circuit / site of origin vis-àvis the underlying substrate. These locations were targeted by conventional RF energy. In the OR, these RF lesions were identifiable (especially endocardial) and served as targets for cryo-thermy applications. 4

Trans-Aortic View Trans-Aortic View AML LCC RCC RV & RVOT NCC RFA Lesion (old) LCC RCC Plane of Aortic Transaction Anterior Superior Posterior NCC RAA Anterior Superior Posterior Inferior RFA Lesion (recent) Inferior Surgical VT Ablation: Lesion Creation Trans-Aortic Deployment of Cryo Probe Surgifrost Surgical Cryoablation System (Medtronic CryoCath LP, Quebec, Canada): The system uses Argon gas and can cool to -150 C. It utilizes flexible metal probe with adjustable insulation sheath. The standard duration of cryo-application is for a maximum of 3 minutes (cooling and thawing phases) and can create large lesions (~ 60 mm). Best results are achieved under cold cardioplegia which ensures adequate freezing. BASE LAT SEP APEX APEX LV RV BASE LAA 5

Cryo Ablation: Final Result Surgical approach utilized median sternotomy with cardiopulmonary by pass under cold cardioplegia. The epicardial and endocardial (via trans-aortic approach) surfaces were inspected and previously placed radiofrequency ablation lesions were identified. No additional mapping was performed in the OR. Cryothermy (Surgifrost, Medtronic CryoCath LP) was applied to sites manifesting old lesions and / or scar identified in and around critical sites (temperature -150 C; total application time 3 minutes; anticipated lesion of 60 mm); additional cryo application on the opposing surface. Lesion Creation in OR: Other Energy Sources Radiofrequency energy: Infrequently used for surgical VT ablation; may not be as effective in cooled hearts. Laser energy (Nd-YAG, pulsed Argon): Have been used for surgical VT ablation in the past with excellent results; unclear why this modality is no longer used. Microwave technology: Has also been shown to be effective for lesion creation during surgical VT ablation. Cryo-thermy: Remains the most common energy source for surgical VT ablation Surgical VT Ablation: Acute End-points In cases where mapping / ablation are performed during ongoing VT, arrhythmia termination and non-inducibility should be the criteria. In cases where cold-cardioplegia is used during surgical ablation, heart requires rewarming in order to assess inducibility. VT induction can be influenced by deep sedation, anesthetic agents, cardiac filling, etc. Other challenges: In patients undergoing concomitant valve or by-pass surgery and/ or experiencing de-compensation during surgical VT ablation, induction not advisable; lack of standard 12 lead ECG in OR may preclude localization. Surrogates of substrate modification: non-capture, conduction block, etc. Delayed (pre-discharge) assessment of VT inducibility. 6

Surgical VT Ablation: Long-term Outcomes Best long-term follow-up data: Patients who underwent surgical VT ablation in the setting of healed myocardial infarcts: 1-year survival of 80-90% but by 5 th year 25% patients had died. PENN surgical VT Experience: All patients (n=8) had nonischemic cardiomyopathy; 2 patients died during the hospitalization following ablation; in remaining 6 patients over a mean follow-up 23±6 months, 4 patients were free of VT, 1 patient had single VT episode resulting in shock and 1 patient had 3 VT events in the first 3 months post-ablation but none after. Patient # Time from surgery to discharge (days) NIPS predischarge No. of AADs at discharge No. of ICD shocks 1 11 Not performed 2 (Quinidine, Mexiletine) 3 2 5 Non-inducible 1 (Sotalol) 0 3 8 Not performed 0 0 4 Died N/A N/A N/A 5 7 Non-inducible 1 (Amiodarone) 0 6 Died N/A N/A N/A 7 6 Non-inducible 1 (Sotalol) 0 8 7 MMVT Inducible 1 (Mexiletine) 1 Surgical VT Ablation: Future Developments Ability to consistently induce and map VT in the OR setting using the same tools as in the EP Lab: Hybrid OR. Surgical VT Ablation: Conclusions Surgical ablation remains the treatment of last resort in patients experiencing VT that is refractory to conventional ablation. Development of energy sources that can create effective lesions without need for cold cardioplegia. Ability to map and ablate ventricular arrhythmias using a less invasive approach similar to what has been accomplished with surgical AF ablation. Ability to create large cryo lesions in the OR typically under cold cardioplegia is the key to success of surgical VT ablation Although mapping in the OR is ideal, a priori mapping and RF lesions in the EP lab can also guide surgical ablation 7

Ed, we miss you at PENN Visually Identification of Scar: Infero-basal LV Lateral LV Epicardial Deployment of Cryo Probe BASE LAT SEP APEX APEX LV RV BASE LAA 8

Patient # Time from last RFA to surgery (months) Energy used Use of cardioplegia Other procedure performed 1 0 Cryotherapy Yes Mitral valve repair 2 0 Cryotherapy No None 3 0 Cryotherapy Yes Maze Patient # Clinical arrhythmia No. failed AADs No. ICD shocks in preceding 3 months No. of prior endocardial procedures No. of prior epicardial procedures 1 SMVT 3 8 1 0 2 SMVT 2 3 1 1 3 SMVT 3 3 2 2 4 0 Cryotherapy Yes Mitral and Tricuspid valve repair 4 SMVT 1 1 external shock 1 1 5 3 Cryotherapy Yes None 5 SMVT 2 12 1 2 6 0 Cryotherapy Yes None 6 SMVT 3 16 3 1 7 0 Cryotherapy No Repair of perforation in RV wall 7 SMVT 2 6 2 0 8 0 Cryotherapy Yes None 8 SMVT 2 4 3 1 Surgical VT Ablation: Case Summary Patient # No. of Induced VT Endocardial Localization Epicardial Localization Endocardial RF Lesions Epicardial RF Lesions VT mapping/target identification Inducible at end of most recent procedure 1 1 1/1 N/A 28 N/A AM\EM\PM\LP No 2 2 0/2 2/2 0 15 PM\LP No 3 2 1/2 2/2 41 37 AM\EM\PM\LP Yes 4 4 2/4 1/4 12 18 AM\EM\PM\LP No 5 2 1/2 1/2 21 52 EM\PM\LP No 6 8 8/8 8/8 182 53 PM\LP Yes 7 1 0/1 0 0 0 PM\LP N/A *urgent surgery 8 4 4/4 4/4 114 0 PM\LP Yes 9

Epicardial View Trans-Aortic View: Further Retracting AML Limitations of conventional lesion creation Cryothermal Ablation Hallmarks of Nonischemic Substrate Diffuse Depth Intramural / Epicardial 4-mm 6-mm 8-mm Heterogeneous Area Close to critical structures Catheter adhesiveness, Sharply demarcated lesion, Preservation of ultrastructure, Reversible suppression, Lesion limited by warming blood, Pain free Volume 4-mm 6-mm 8-mm 4-mm 6-mm 8-mm - Rivard, Khairy et al, Heart Rhythm 2008;5:230 10

Limitations of conventional lesion creation Radiofrequency Ablation Lesion Creation in Epicardial Scar Epicardial Lesion Endocardial Lesion 11