mapping and ablation of vt in the operating room
TRANSCRIPT
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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
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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
RVLV
Inferior Apical Scar
Mid Septal Scar Inferior Basal Scar
Anterior Septal Scar
Intraseptal VT Substrate: MR Imaging Intra-Septal VT Substrate
Trans Thoracic Intra Cardiac
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ECG Features of VT originating from basal IVS
Left bundle blockwith early precordialtransition (V 1 – V2)
Right bundle blockwith unusual precordial transition
• 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.
• 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
Median Sternotomy providesbest cardiac visualization:
� RV epicardium
� Superior IV Septum
� Anterior LV wall
To visualize posterolateralLV wall, heart has to bephysically lifted.
Partial sternotomy can allowvisualization of RV, anteriorand inferior LV surfaces.
Trans-Aortic View: Basal LV
Plane of Aortic Transaction
LCC
NCC
RCC
AML
Anterior Posterior
Superior
Inferior
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• 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.
Surgical Ablation: Alternative Approaches
• 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).
VT Mapping in the OR
• 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-à-vis 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.
Mapping in EP Lab prior to Surgical Ablation: PENN Approach
Epicardial View
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Trans-Aortic View
Plane of Aortic Transaction
LCC
NCC
RCC
AML
Anterior Posterior
Superior
Inferior
RFA Lesion (old)
Trans-Aortic View
Anterior Posterior
Superior
Inferior
LCC
NCC
RCC
RAA
RV & RVOT
RFA Lesion (recent)
Surgical VT Ablation: Lesion Creation
LV RV
APEX
BASE
LAA
BASE
APEX
SEPLAT
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.
Trans-Aortic Deployment of Cryo Probe
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• Surgical approach utilized median sternotomy with cardio-pulmonary 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.
Cryo Ablation: Final Result
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.
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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 5th year 25% patients had died.
• PENN surgical VT Experience: All patients (n=8) had non-ischemic 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 pre-discharge
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.
• 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.
Surgical VT Ablation: Conclusions
• Surgical ablation remains the treatment of last resort in patients experiencing VT that is refractory to conventional 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
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Ed, we miss you at PENN…………
Visually Identification of
Scar:
• Infero-basal LV
• Lateral LV
LV RV
APEX
BASE
LAA
BASE
APEX
SEPLAT
Epicardial Deployment of Cryo Probe
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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
4 0 Cryotherapy Yes Mitral and Tricuspid valve repair
5 3 Cryotherapy Yes None
6 0 Cryotherapy Yes None
7 0 Cryotherapy No Repair of perforation in RV wall
8 0 Cryotherapy Yes None
Patient#
Clinicalarrhythmia
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 SMVT 1 1 external shock 1 1
5 SMVT 2 12 1 2
6 SMVT 3 16 3 1
7 SMVT 2 6 2 0
8 SMVT 2 4 3 1
Surgical VT Ablation: Case SummaryPatient#
No. of Induced VT
EndocardialLocalization
EpicardialLocalization
EndocardialRF Lesions
EpicardialRF 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
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Epicardial View Trans-Aortic View: Further Retracting AML
Dep
thA
rea
Volu
me
4-mm 6-mm 8-mm
4-mm 6-mm 8-mm
4-mm 6-mm 8-mm
- Rivard, Khairy et al, Heart Rhythm 2008;5:230
• Catheter adhesiveness, • Sharply demarcated lesion,• Preservation of ultrastructure, • Reversible suppression,• Lesion limited by warming blood, • Pain free
Cryothermal Ablation
Limitations of conventional lesion creation
• Diffuse
• Intramural / Epicardial
• Heterogeneous
• Close to critical structures
Hallmarks of Nonischemic Substrate