Experimental Studies With a 9F Forward-Looking Intracardiac Imaging and Ablation Catheter

Abstract

Objective To develop a high resolution, near field optimized 14 MHz 24-element broad bandwidth forward-looking array for integration on a steerable 9 French (Fr) electrophysiology (EP) catheter. Methods Several generations of prototype imaging catheters with bi-directional steering, termed the Micro-Linear (ML), have been built and tested as an integrated catheter design with EP sensing electrodes near the tip. The wide bandwidth ultrasound array is mounted on the very tip, equipped with an aperture of only 1.2 mm by 1.58 mm. The array pulse echo performance has been fully simulated and its construction offers shielding from ablation noise. Both ex-vivo and in-vivo imaging with a porcine animal model were performed. Results The array pulse-echo performance is concordant with KLM simulation. Three generations of prototype devices were tested in four acute pig studies in the right atrium and ventricle for a) image quality, b) anatomic identification, c) visualization of other catheter devices, and d) for a mechanism for stabilization when imaging ablation. The ML catheter is capable of both low artifact ablation imaging on a standard clinical imaging system and high frame rate myocardial wall strain rate imaging for detecting changes in cardiac mechanics associated with ablation. Conclusions The imaging resolution performance of this very small array device, together with its penetration beyond 2cm, is excellent considering its very small array aperture. The forward looking intracardiac catheter has been adapted to work easily on an existing commercial imaging platform with very minor software modifications.

Thermal strain imaging: a review

“…A specially designed US compatible RFA system was integrated into a prototype 9F forward-looking microlinear (ML) intracardiac echocardiography catheter array to simultaneously image and ablate the right atrial wall [75]. Additionally, a thermocouple normally residing inside the electrode was pulled out to touch the tissue for thermal strain validation.…”

Thermal expansion imaging for monitoring lesion depth using M-mode ultrasound during cardiac RF ablation: in vitro study

“…In comparison with the large Depth visual variations observed in Fig. 5, given a controlled CF = 0.4 N the Depth visual values for the same ablation times (20,40. .…”

“…The contact surface of the US probe and the electrode opening is on the same plane, which removes the need of a coupling medium between tissue and US transducer. This is an advantage with respect to more complex US array/catheter designs, which typically require US gel [34] or irrigated water [40] as coupling media. The US transducer is a conventional 20 MHz piezoelectric element and is driven by negative square pulses with an amplitude of 50 V and 25 ns duration generated by an USBox ultrasound pulser/receiver (LeCoeur Electronique, Chuelles, France).…”

Ultrasound compatible RF ablation electrode design for catheter based guidance of RF ablation — In vivo results with thermal strain imaging

“…The smallest array device is known as the "MicroLinear" (ML) which currently exists as a 9F (3 mm) forward imaging catheter with bidirectional steering and at least two tip region electrodes, one for EP mapping and the other for distal tip ablation capability ( Figure 2). The catheter and array general construction have been described before [7,8] and have proven to be useful in imaging a specific intracardiac site when coupled with electroanatomical guidance.…”