9/14/2019 Disclosures • I have disclosed relationships with the following commercial Tips and Tricks for Mapping and interests: Ablation of LV Summit and Biosense-Webster, Grant/Research Support Intramural Substrate Boston Scientific, Consultant Abbott, Consultant William H. Sauer, MD Chief, Cardiac Arrhythmia Service Brigham and Women’s Hospital Harvard Medical School 94 Patients with failed VT RFA attempt in the same ablation session Audience Response LVS When faced with inaccessible LV summit or intramyocardial substrate refractory to high power RF: Septum A. Give Up and Try Meds Other B. Refer to Cardiac Surgeon C. Refer to Radiation Oncology for SBRT D. Keep Giving High Power Lesions Pap E. Increase RF Current Delivery to Targeted Tissue 0 5 10 15 20 25 30 35 Endocardial Epicardial Epi Vein Bipolar Nguyen, Tzou, Sauer, et al. JACC CEP 2018 1
9/14/2019 Road Map - Innovations to Improve Lesions Back to Basics ▪ 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 • Impedance Modification located on the patient’s surface. • Patch Location and Surface Area • Bipolar Ablation • Adjacent Metal Heating and RF Current • Irrigant Ionic Content ▪ 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 2
9/14/2019 Myocardial Tissue 130 Ω → 80 Ω RF “Ground” *Unpublished Data Simplified Bipolar Setup Using Abbott Precision/NavX System Sauer PJ, Tzou WS, et al. Heart Rhythm Case Reports 2018 3
9/14/2019 Altering Surrounding Ionic Content • Electricity (RF current) will follow the path RF Ablation Catheter of least resistance 100W delivered through Normal Saline Half-Normal 3.5 mm tip RFA catheter Saline • Saline has a very low impedance (~90 Ω ) To deliver higher power (up to 100W) to a compared to blood and tissue catheter normally limited to 50 W: 1. Set up bipolar ablation with 8 mm “active” • There is a saline “cloud” that results in an and 3.5 mm cooled tipped catheter as “return” effective increased distribution of RF 2. Set generator to 50W and then titrate to highest power (70 W or 100 W) 130 Ω → 80 Ω • Increasing the impedance of this “cloud” 3. Watch impedance and ICE images for steam may force RF current to targeted tissue pop warning Ablation Lesion Sauer WH, et al. Heart Rhythm 2015 RF Loss Measurement Can we Influence the Flow of RF Energy Set up Delivery with Impedance Modulation Catheter Body multimeter • Epicardium Radiofrequency Generator/Irrigation • Usually fills with saline (low impedance ~90 Ω ) Guide 30cc/min via Cool flow • Removal of saline results in larger lesions 1 Solutions: • Addition of half normal saline (higher impedance) results in Normal ½ Normal even larger lesions 2 D5W • Externally Irrigated Catheters • Allows for a saline “cloud” that reduces the impedance of Create seal surrounding environment Tissue Cath tip • Can use higher impedance HNS (~180 Ω ) Indifferent electrode 180 Ω 1. Aryana, d’Avila , et al. Heart Rhythm 2016; 2. Nguyen, Sauer, et al. JACC CEP 2017 4
9/14/2019 Elements of RF Energy Delivery to Epicardium RF Loss Results • Relative Current Distribution Pericardium into Tissue and Blood Saline 90 Ω Tissue (HNS) Myocardial Environment Tissue Surrounding the Tissue (NS) Catheter Surrounding Blood Tissue 130 Ω Tissue RF “Ground” 0 10 20 30 40 50 60 70 80 90 Tissue Blood Elements of RF Energy Delivery to Epicardium Elements of RF Energy Delivery to Epicardium Relative insulation surrounding catheter to enhance RF delivery in Pericardium Pericardium Epicardium Epicardial Space Evacuated HNS 180 Ω Myocardial Myocardial Environment Tissue Tissue Surrounding the Catheter Tissue 130 Ω Tissue RF “Ground” RF “Ground” 130 Ω Removal of saline leads to larger lesions. Aryana …d’Avila . Heart Rhythm 2016 5
9/14/2019 2015 2016 2017 2018 94 Patients with failed VT RFA attempt in the same ablation session Acute Success 0% → 83% with HNS LVS Septum Other Pap 0 5 10 15 20 25 30 35 Acute Success 0% → 83% with HNS Endocardial Epicardial Epi Vein Bipolar Site and Approach for HNS RFA 6
9/14/2019 100% What About Bipolar Half Normal Saline? 90% 80% 15 750 70% Average Max Depth (mm) Average Lesion Volume (µL) 14 700 60% * * 50% 13 650 40% 12 600 30% 11 550 20% 10% 10 500 Bipolar 1/2 NS 0% * p < 0.05 Low Flow High Flow Bipolar NS SP No SP Valderrabano, et al. Circulation EP 2016 Futyma, et al., Circulation Journal 2017 7
9/14/2019 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 8
9/14/2019 Enhancing RF Ablation – Metallic Antennae Lesion Depth 8 7 6 5 4 3 2 1 0 Sham Copper Iron Titanium Nguyen DT, Sauer WH, et al. Heart Rhythm 2015 Romero, Shivkumar, et al. Heart Rhythm Case Reports 2018 Summary Thank You • 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 9
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