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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

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Radiofrequency Ablation

Endocardial Lesion

Epicardial Lesion

Lesion Creation in Epicardial Scar

Limitations of conventional lesion creation