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

University of California, Davis, California USA (D.N.S.); University of Washington, Seattle, Washington USA (M.O.); GE Global Research, Schenectady, New York USA (K.T., A.D., D.W.); Irvine Biomedical Inc/St Jude Medical, Irvine, California USA (P.C.); University of Southern California, Los Angeles, California USA (K.K.S., J.C.); Stanford University, Palo Alto, California USA (P.K.-Y., O.O.); University of California, Los Angeles, California USA (A.M., K.S.); and Oregon Health & Science University, Portland, Oregon USA (D.J.S.).

Address correspondence to David J. Sahn, MD, Department of Pediatric Cardiology, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd, L608, Portland, OR 97239-3098 USA., E-mail: sahnd{at}ohsu.edu

Objective. The purpose of this study was to develop a high-resolution, near-field-optimized 14-MHz, 24-element broad-bandwidth forward-looking array for integration on a steerable 9F electrophysiology (EP) catheter. Methods. Several generations of prototype imaging catheters with bidirectional steering, termed microlinear (ML), were built and tested as integrated catheter designs with EP sensing electrodes near the tip. The wide-bandwidth ultrasound array was mounted on the very tip, equipped with an aperture of only 1.2 by 1.58 mm. The array pulse echo performance was fully simulated, and its construction offered shielding from ablation noise. Both ex vivo and in vivo imaging with a porcine animal model were performed. Results. The array pulse echo performance was concordant with Krimholtz-Leedom-Matthaei model simulation. Three generations of prototype devices were tested in the right atrium and ventricle in 4 acute pig studies for the following characteristics: (1) image quality, (2) anatomic identification, (3) visualization of other catheter devices, and (4) 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 2 cm, 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.

Key Words: ablation • electrophysiology • interventional guidance • intracardiac ultrasound array • miniaturized

Abbreviations: cMUT, capacitive micromachined ultrasound transducer • EP, electrophysiology • FBW, fractional bandwidth • ML, microlinear • PZT, lead zirconate titanate • RF, radio frequency • RFA, radio frequency ablation • 3D, 3-dimensional • 2D, 2-dimensional