Mapping and Ablation of Outflow Tract VT

Mapping and Ablation of Outflow Tract VT

Raja Selvaraj, JIPMER

Introduction

Outline

Outflow tract VT - Anatomy
Outflow tract VT - Mapping tips
Outflow tract VT - Ablation tips
Covered in other talks - Summit VT, Safety during VT ablation

Outflow tract VTs - Spectrum of origin

RVOT (70-80%)
- Below the valve
- Above the valve
- In the cusps
LVOT (12-45%)
- Aortic sinus of valsalva - LCC, RCC, NCC
- Below the valve
  - Superior basal septum
  - Aorto-mitral continuity
  - LV summit

ASV PVCs are usually from LCC, less commonly RCC, very rarely NCC

Anatomy

Outflow tract anatomy

Understanding of anatomic relationships especially important in this region
Simplistic models are wrong

We usually carry simple models Needs some mental acrobatics to understand actual anatomy

Anatomic considerations

RVOT is anterior and to left of LVOT
RVOT is a cylinder wrappng around the LVOT
Pulmonary valve is cephalad and in different plane to aortic valve
What we call septal rvot is posterior RVOT,

Anatomy - Short axis view as in Echocardiography

Easiest mental model to work from is echocardiographic short axis view

Makes it easier to understand ECG findings

Lead V1
- Negative for anterior rvot
- Small positive with posterior rvot
- Small positive with origin above pulmonary valve
Lead I
- Negative above the valve
Lead avl
- iso / small pos - peri His region
II/ III ratio
- Higher in III for supravalvar (leftward origin)

Supravalvar Muscle extensions

mostly in rcc and lcc inter-cusp extensions catheter position for inter-cusp

note Long axis views of the pulmonary root, stained with Gomori's trichrome: (A) Discontinuous, adventitial ventricular muscle extensions beyond the ventriculo‐arterial junction are shown by the arrows. Sinotubular junction is shown as a subtle ridge by the star; (B) Continuous, adventitial ventricular muscle extension beyond the ventriculo‐arterial junction is shown by the stars in a different case. A = Adventitia; M = Media; VAJ = Ventriculo‐arterial junction.

Mapping

ECG localization

Limb leads to identify outflow tract origin
Precordial leads to decide chamber to map
Precordial transition - V3

Growing R wave with more posterior position

Correlative Anatomy for the Invasive Electrophysiologist: Outflow Tract and Supravalvar Arrhythmia SAMUEL J. ASIRVATHAM, M.D. J Cardiovasc Electrophysiol, Vol. 20, pp. 955-968, August 2009

V3 transition

CS catheter

Almost always useful to have a deeply placed CS catheter
Triangulation to identify presumptive origin - GCV/AIV junction, LCC and RVOT

Bipolar EGM

Timing of near field EGM is key to mapping
Identify near field / far field

Timing of bipolar near field EGM is key to mapping

Distinct EGM when mapping above the valve

Muscle sleeve with fibrous / fatty tissue acting as substrate
Typically seen above the aortic valve and pulmonary valve
Late in sinus rhythm and early before PVC

Komandoor S. Srivathsan et al. Mechanisms and Utility of Discrete Great Arterial Potentials in the Ablation of Outflow Tract Ventricular Arrhythmias. Circulation: Arrhythmia and Electrophysiology. 2008;1:30–38

Unipolar EGM

Concordant with bipolar for RVOT without prior ablation
May not concur in setting of prior ablation
May not be useful while mapping above the valve

Mapping in LCC. Reversal of potentials in bipolar. Note unipolar reflects the main v muscle activation

Pace mapping

Useful as adjunct to activation mapping
Useful to map faster when PVCs are infrequent
Lacks specificity

LVOT mapping

Patient with PVCs, previous ablation from LV with early recurrence activation and pacemap from best lv not great

GCV mapping

Good match and activation from distal CS

Conflict between pace mapping and activation mapping

Pace mapping identifies exit
Earliest near field signal identifies origin
May not match sometimes
Dead end fascicle remnants
Site of earliest near field signal (origin identified by activation mapping) may be different from site of best match identified by pace mapping (exit)
Dead end fascicle remnants may be involved in this disparity by rapid conduction to other regions

Wavefront spread

Csaba Herczku … Josep Brugada. Mapping Data Predictors of a Left Ventricular Outflow Tract Origin of Idiopathic Ventricular Tachycardia With V3 Transition and Septal Earliest Activation. Circulation: Arrhythmia and Electrophysiology. 2012;5:484–491

Utility of three dimensional mapping

Limited incremental value over conventional mapping
Reduces fluoroscopy time
Useful in tagging sites and reinforcing lesions

Non contact mapping for unstable VT

Fung JWH, Chan HCK, Sanderson JE. Ablation of haemodynamically unstable right ventricular outflow tract ventricular tachycardia guided by non-contact mapping. Heart 2002;87:15.

Paul AFriedman et al. Noncontact mapping to guide ablation of right ventricular outflow tract tachycardia. JACC 2002;39:1808-1812

Ablation

What catheter ?

In supravalvar LVOT non-irrigated may be preferred
LVOT below the valve and RVOT, irrigated may be used

Low powers may be effective in the aortic cusps

15-30 W may suffice
Immediate cessation of PVCs indicator of success

Kabilan … Raja Selvaraj. Low power ablation for left coronary cusp ventricular tachycardia—Efficacy and long-term outcome. Indian Heart Journal 2018;17:S384-S388

Ablation in coronary cusps - Aware of relationship to coronaries

Angiography
Retain catheter
Distance > 5 mm
non-irrigated
LMCA / LAD close to posterior subvalvar RVOT

Difficult cases

Supravalvar RVOT VT

Most from close to pulmonary valve
Can be above the pulmonary valve level (1)

Timmermans C, Rodriguez LM, Crijns HJ, Moorman AF, Wellens HJ. Idiopathic left bundle-branch block-shaped ventricular tachycardia may originate above the pulmonary valve. Circulation 2003; 108: 1960–1967.

PA origin VT

Large amplitude R waves in inferior leads
aVL q > aVR q

Pulmonary sinus cusp VT

Liao Z, Zhan X, Wu S, Xue Y, Fang X, Liao H, et al. Idiopathic ventricular arrhythmias originating from the pulmonary sinus cusp: Prevalence, electrocardiographic/electrophysiological characteristics, and catheter ablation. J Am Coll Cardiol 2015; 66: 2633–2644.

Intramural foci - Venous branches

Hongwu Chen et al. Intramural Outflow Tract Ventricular Tachycardia. Anatomy, Mapping, and Ablation. Circ Arrhythm Electrophysiol. 2014;7:978-981.

Intramural foci - Irrigated bipolar ablation

Bipolar ablation from both sides of the septum may sometimes be effective

Teh AW, Reddy VY, Koruth JS, Miller MA, Choudry S, D’Avila A, et al. Bipolar radiofrequency catheter ablation for refractory ventricular outflow tract arrhythmias. J Cardiovasc Electrophysiol 2014; 25: 1093–1099.

Improve contact - Transseptal approach and reverse S curve

Ouyang F, Mathew S, Wu S, Kamioka M, Metzner A, Xue Y, et al. Ventricular arrhythmias arising from the left ventricular outflow tract below the aortic sinus cusps: Mapping and catheter ablation via transseptal approach and electrocardiographic characteristics. Circ Arrhythm Electrophysiol 2014; 7: 445–455.

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Mapping and Ablation of Outflow Tract VT Raja Selvaraj, JIPMER