High-power bipolar ablation for incessant ventricular tachycardia utilizing a deep midmyocardial septal circuit

At a Glance

Metadata	Details
Publication Date	2015-11-01
Journal	HeartRhythm Case Reports
Authors	William H. Sauer, David Steckman, Mathew M. Zipse, Wendy S. Tzou, Ryan G. Aleong
Institutions	University of Colorado Anschutz Medical Campus
Citations	21
Analysis	Full AI Review Included

Technical Analysis of High-Power Bipolar RF Ablation for Cardiac Arrhythmia Refractory Cases

Documentation based on: Sauer et al., “High-power bipolar ablation for incessant ventricular tachycardia utilizing a deep midmyocardial septal circuit” (Heart Rhythm Case Reports 2015;1:397-400).

Executive Summary

This paper details a successful, non-standard high-power radiofrequency (RF) ablation approach used to treat incessant ventricular tachycardia (VT) originating from a deep, refractory midmyocardial septal circuit. The findings directly support the demand for ultra-high performance, thermally managed materials in advanced electrophysiology tools.

Refractory Target: The VT originated from the basal to mid interventricular septum, previously refractory to standard sequential unipolar and lower-power bipolar ablation configurations.
Methodology: A novel high-power bipolar setup was utilized, switching the conventional ‘active’ (3.5-mm irrigated) and ‘ground’ (8-mm non-irrigated) catheter roles via a custom-designed cable to maximize current density.
Peak Performance: RF power was aggressively titrated up to 70 W (significantly higher than the standard 50 W limit for the 3.5-mm irrigated catheter).
Achieved Result: The high-power 70 W bipolar ablation successfully terminated the incessant VT in 69 seconds, creating a transmural lesion capable of affecting the deep midmyocardial circuit.
Thermal Challenge: The limiting factor was acute thermal stress, evidenced by rapid impedance drops (10-15 Ω) and the risk of steam pop, highlighting the critical need for materials with superior thermal dissipation properties.
Relevance to 6CCVD: The extreme power density required for this technique necessitates materials (like MPCVD diamond) capable of managing high current loads and rapidly dissipating heat to maintain safety margins and prevent steam formation in next-generation high-power ablation tips.

Technical Specifications

Hard data extracted from the reported case study regarding the custom high-power ablation procedure.

Parameter	Value	Unit	Context
Maximum RF Power (Bipolar)	70	W	Delivered through the 8-mm catheter (Active)
Maximum Ablation Duration (Per Spot)	5	minutes	Applied to allow for maximum conductive heating
Successful VT Termination Time	69	seconds	Total time of 70 W bipolar ablation required
Active Catheter Tip Size	8	mm	Non-irrigated (custom setup for 70 W delivery)
Ground Catheter Tip Size	3.5	mm	Open-irrigated (custom setup as ground)
Clinical VT Cycle Length	500	ms	Measured before the final successful ablation
Septal Myocardial Thickness (ICE)	1.6	cm	Interventricular septum region of interest
Baseline Bipolar Impedance (Range)	140-160	Ω	Reflects increased current density vs. unipolar
Impedance Drop During Ablation	10-15	Ω	Slow drop noted during successful 70 W lesioning
Required Lesion Depth	> 1.5	cm	Necessary to achieve transmurality in thick septum
Standard Unipolar Power Limit	50	W	Limit for the 3.5-mm irrigated catheter (prior attempt)

Key Methodologies

The success of the procedure relied on modifying standard RF equipment to achieve unprecedented power delivery across the ventricular septum.

Initial Attempt (Unsuccessful): Sequential unipolar ablation was attempted from both the RV and LV sides of the septum using a 3.5-mm open-irrigated catheter at 50 W for up to 5 minutes.
Circuit Modification for Bipolar Ablation:
- The standard grounding patch was disconnected.
- A custom cable was used to plug an 8-mm Celsius catheter (non-irrigated) into the RF generator’s grounding port.
- A 3.5-mm ThermoCool SF catheter (irrigated) remained plugged into the generator as the standard active component.
Active/Ground Assignment Switch:
- The initial bipolar setup (3.5-mm active, 8-mm ground) proved unsuccessful.
- The assignments were switched: the 8-mm non-irrigated catheter became the “Active” component, and the 3.5-mm irrigated catheter became the “Ground.”
- This switch allowed the generator to deliver power up to 70 W, monitored through the 8-mm active catheter.
Targeted Ablation: Catheters were aligned directly across the mid to basal interventricular septum, confirmed via ICE imaging and biplane fluoroscopy, to maximize current density.
Thermal Monitoring: Temperature and power regulation were only available for the 8-mm active catheter. The thermal status of the 3.5-mm ground catheter was monitored solely by observing echogenicity and bubble formation via Intracardiac Echocardiography (ICE).

6CCVD Solutions & Capabilities

The need for high-power density delivery, safe thermal management, and robust custom fabrication in advanced RF ablation tools aligns perfectly with 6CCVD’s expertise in MPCVD diamond engineering. Diamond offers the highest thermal conductivity available (up to 2000 W/m·K), making it the ideal component for next-generation ablation tips and thermal sinks where power is drastically increased.

Applicable Materials for Advanced RF Ablation Tools

To replicate or extend this high-power ablation technique safely and predictably, high-performance diamond components are essential, providing superior thermal dissipation and customizable electrical properties.

6CCVD Material Grade	Core Benefit	Application in RF Ablation
Optical Grade SCD	Extreme Thermal Conductivity (Insulating)	Used as a high-efficiency thermal sink or substrate underneath metal electrodes to rapidly transfer heat away from the electrode-tissue interface, mitigating steam pop risk at 70 W+.
Heavy Boron-Doped PCD (BDD)	Highly Conductive (Metallic) and Chemically Inert	Ideal for use as the active electrode tip itself, providing high conductivity, extreme wear resistance, and the ability to integrate temperature sensors directly into the conductive diamond structure.
High Purity SCD (Insulating)	Perfect Dielectric Strength	Used as a passivation layer or insulating boundary layer in complex multi-electrode sensing arrays or bipolar setups to ensure current is directed precisely.

Customization Potential for Ablation Tool Engineering

6CCVD offers the specialized manufacturing required to transition experimental setups, like the custom 70 W configuration in the research paper, into standardized, predictable clinical tools.

Precision Geometric Shaping: Ablation electrodes require millimeter and sub-millimeter precision. 6CCVD provides custom dimensions for PCD plates/wafers up to 125mm and complex micro-machining to create unique tip geometries required for directional or bipolar RF delivery.
Integrated Metalization and Bonding: The success of bipolar RF relies on stable, low-impedance electrical contacts. 6CCVD offers internal, high-reliability metalization services, including Au, Pt, Pd, Ti, W, and Cu, crucial for robust integration onto existing catheter shafts or for creating stable contact pads for sensing elements.
Ultra-Low Roughness Polishing: For applications requiring precise mechanical engagement or fluid dynamics (such as irrigated tips), 6CCVD guarantees surfaces with extremely low roughness: Ra < 1nm for SCD and Ra < 5nm for inch-size PCD.
Custom Thickness Capabilities: We provide SCD and PCD components from 0.1µm up to 500µm thickness, allowing engineers to optimize the diamond layer for specific thermal conductance or structural support required for high-force catheter tips.

Engineering Support

The modifications made in this paper (custom cabling, monitoring non-standard components via ICE) demonstrate the need for highly reliable, thermally integrated materials. 6CCVD’s in-house PhD team specializes in the thermal, electrical, and mechanical properties of MPCVD diamond and can assist engineers in designing material solutions for similar Cardiac Electrophysiology and High-Power RF Ablation projects.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. We ship globally (DDU default, DDP available).

Tech Support

Original Source

DOI: https://doi.org/10.1016/j.hrcr.2015.01.018

References

2011 - Endocardial unipolar voltage mapping to detect epicardial ventricular tachycardia substrate in patients with nonischemic left ventricular cardiomyopathy [Crossref]
2008 - Irrigated radiofrequency catheter ablation guided by electroanatomic mapping for recurrent ventricular tachycardia after myocardial infarction: the Multicenter ThermoCool Ventricular Tachycardia Ablation Trial [Crossref]
2006 - Large radiofrequency ablation lesions can be created with a retractable infusion-needle catheter [Crossref]
2010 - Bipolar ablation of the interventricular septum is more efficient at creating a transmural line than sequential unipolar ablation [Crossref]
2014 - Successful simultaneous unipolar radiofrequency ablation of septal ventricular tachycardia using 2 ablation catheters [Crossref]
2012 - Bipolar irrigated radiofrequency ablation: a therapeutic option for refractory intramural atrial and ventricular tachycardia circuits [Crossref]
2014 - Radiofrequency cardiac ablation with catheters placed on opposing sides of the ventricular wall: computer modelling comparing bipolar and unipolar modes [Crossref]