1 9/14/2019 Road Map - Innovations to Improve Lesions Back to - - PDF document

9/14/2019 1

Tips and Tricks for Mapping and Ablation of LV Summit and Intramural Substrate

William H. Sauer, MD Chief, Cardiac Arrhythmia Service Brigham and Women’s Hospital Harvard Medical School

Disclosures

• I have disclosed relationships with the following commercial

interests: Biosense-Webster, Grant/Research Support Boston Scientific, Consultant Abbott, Consultant

5 10 15 20 25 30 35 Pap Other Septum LVS Endocardial Epicardial Epi Vein Bipolar

94 Patients with failed VT RFA attempt in the same ablation session

Nguyen, Tzou, Sauer, et al. JACC CEP 2018

Audience Response

When faced with inaccessible LV summit or intramyocardial substrate refractory to high power RF:

• A. Give Up and Try Meds
• B. Refer to Cardiac Surgeon
• C. Refer to Radiation Oncology for SBRT
• D. Keep Giving High Power Lesions
• E. Increase RF Current Delivery to Targeted Tissue

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Road Map - Innovations to Improve Lesions

• Impedance Modification
• Patch Location and Surface Area
• Bipolar Ablation
• Adjacent Metal Heating and RF

Current

• Irrigant Ionic Content

▪ RF ablation is performed by applying alternating current from the tip electrode of an ablation catheter through a resistive volume (myocardial tissue and blood) to a patch located on the patient’s surface.

Back to Basics

▪ The current that passes through the resistive tissue generates heat that raises the tissue temperature

Barkagan M, Anter E, et al Circ AEP 2018

Case and Slide Courtesy of Elad Anter, MD

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Myocardial Tissue RF “Ground” 130 Ω → 80 Ω *Unpublished Data

Simplified Bipolar Setup Using Abbott Precision/NavX System

Sauer PJ, Tzou WS, et al. Heart Rhythm Case Reports 2018

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130 Ω → 80 Ω Sauer WH, et al. Heart Rhythm 2015 100W delivered through 3.5 mm tip RFA catheter To deliver higher power (up to 100W) to a catheter normally limited to 50 W:

• 1. Set up bipolar ablation with 8 mm “active”

and 3.5 mm cooled tipped catheter as “return”

• 2. Set generator to 50W and then titrate to

highest power (70 W or 100 W)

• 3. Watch impedance and ICE images for steam

pop warning RF Ablation Catheter

Altering Surrounding Ionic Content

Ablation Lesion Normal Saline Half-Normal Saline

• Electricity (RF current) will follow the path
• f least resistance
• Saline has a very low impedance (~90 Ω)

compared to blood and tissue

• There is a saline “cloud” that results in an

effective increased distribution of RF

• Increasing the impedance of this “cloud”

may force RF current to targeted tissue

Can we Influence the Flow of RF Energy Delivery with Impedance Modulation

• Epicardium
• Usually fills with saline (low impedance ~90 Ω)
• Removal of saline results in larger lesions1
• Addition of half normal saline (higher impedance) results in

even larger lesions2

• Externally Irrigated Catheters
• Allows for a saline “cloud” that reduces the impedance of

surrounding environment

• Can use higher impedance HNS (~180 Ω)
• 1. Aryana, d’Avila, et al. Heart Rhythm 2016;
• 2. Nguyen, Sauer, et al. JACC CEP 2017

180 Ω Radiofrequency Generator/Irrigation 30cc/min via Cool flow Solutions: Normal ½ Normal D5W Indifferent electrode Tissue Cath tip Guide Catheter Body

RF Loss Measurement Set up

Create seal

multimeter

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RF Loss Results

• Relative Current Distribution

into Tissue and Blood

Surrounding Blood Tissue

10 20 30 40 50 60 70 80 90 Tissue Blood

Tissue (HNS) Tissue (NS) Pericardium

Elements of RF Energy Delivery to Epicardium

Myocardial Tissue RF “Ground” Environment Surrounding the Catheter Saline 90 Ω Tissue 130 Ω Pericardium

Elements of RF Energy Delivery to Epicardium

Myocardial Tissue RF “Ground” Epicardial Space Evacuated Tissue 130 Ω

Removal of saline leads to larger lesions. Aryana…d’Avila. Heart Rhythm 2016

Pericardium

Elements of RF Energy Delivery to Epicardium

Myocardial Tissue RF “Ground” Environment Surrounding the Catheter HNS 180 Ω Tissue 130 Ω Relative insulation surrounding catheter to enhance RF delivery in Epicardium

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2015 2016 2017 2018 Site and Approach for HNS RFA

5 10 15 20 25 30 35 Pap Other Septum LVS Endocardial Epicardial Epi Vein Bipolar

94 Patients with failed VT RFA attempt in the same ablation session

Acute Success 0% → 83% with HNS Acute Success 0% → 83% with HNS

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0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Low Flow High Flow SP No SP

10 11 12 13 14 15 Average Max Depth (mm)

Bipolar 1/2 NS Bipolar NS

500 550 600 650 700 750 Average Lesion Volume (µL)

* *

* p < 0.05

What About Bipolar Half Normal Saline?

Futyma, et al., Circulation Journal 2017 Valderrabano, et al. Circulation EP 2016

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Briceño, Garcia, et al. JACC CEP 2019 Briceño, Garcia, et al. JACC CEP 2019

RAO LAO

Case Courtesy of Roderick Tung, MD

Nguyen/Sauer, et al. JCE 2014

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Enhancing RF Ablation – Metallic Antennae

1 2 3 4 5 6 7 8 Sham Copper Iron Titanium

Lesion Depth

Nguyen DT, Sauer WH, et al. Heart Rhythm 2015 Romero, Shivkumar, et al. Heart Rhythm Case Reports 2018

Summary

• We can modify the system impedance to increase RF current to

targeted myocardial tissue

• Bipolar ablation will result in deeper lesions and may allow for

increased power/RF current delivery

• Half normal saline can result in a deeper lesion, especially if used in

the epicardium

• Coronary arteriole and venous wires can be used to map and ablate

intramyocardial substrate

Thank You

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