Douglas N. Stephens, Aman Mahajan, Seshadri Balaji, Aaron Mark Dentinger, Robert I. Lowe, Xiao Kui Li, Raymond Chia, K. Kirk Shung, David J. Sahn, James Pemberton, Kai Erik Thomenius, Kalyanam Shivkumar, Matthew O'Donnell, and Muhammad Ashraf
Catheter-based electrophysiology (EP) testing and transcatheter radio frequency (RF) ablation are well-established modalities for the diagnosis and treatment of many types of arrhythmias.1–6 Catheter ablation can be performed in any chamber of the heart and in patients with diverse structural cardiac abnormalities,7 including infants and children.8,9 Catheter ablation requires precise localization of structures within the heart, real-time intracardiac hemodynamics, and accurate identification of important anatomic landmarks and the catheter position. Currently available approaches to spatial guidance and anatomic localization of the ablation are electroanatomic (EA) mapping,10,11 fluoroscopy,11,12 and echocardiography. Preliminary reports have shown the use of intracardiac imaging during catheter ablation to assist in identifying endocardial contact and lesion formation.13,14 Intracardiac echocardiography (ICE) has allowed imaging from the right side of the heart for imaging both right- and left-sided cardiac chambers and structures.15–23 Although the earlier devices were lower-frequency versions of intracoronary intravascular ultrasound devices (often mechanically driven), later devices also provided color and spectral Doppler imaging. In 1995, a 10F steerable (±25°–30°) side-looking AcuNav catheter device (Acuson; Siemens Medical Solutions, Mountain View, CA) was approved for intracardiac imaging from the right side of the heart in patients. It functions as a vector array with a 5.5- to 10-MHz frequency. Although animal studies have suggested very high-quality imaging and ease of use, human studies have identified problems related to near-field resolution and color Doppler quality as well as difficulty in imaging larger abnormal structures at a distance of greater than 8 cm from the probe.24 In addition, the cost of these devices as single-use products has spurred the formation of a network of secondary vendors that provide resterilization of AcuNav catheters with varying levels of performance verification. With our 2001 National Institutes of Health Bioengineering Research Partnership grant, funded for 5 years by the National Heart, Lung, and Blood Institute, we proposed to build an advanced imaging device that combines the advantages of electrical mapping and ablation with 2-dimensional (2D) echocardiography, tissue velocity imaging (TVI), and strain rate imaging (SRI). The ICE device was designed to provide ultrasound imaging and procedural guidance for EP-based rhythm analysis, ablation, and resynchronization. This report details the development and initial experimental animal studies of the applicability of our 9F side-looking ultrasound array catheter, which, because of its substantial flexibility of steering, we have dubbed the hockey stick (HS). It is electrode equipped for EP recording and 3-dimensional (3D) NavX guidance integration (St Jude Medical Corp, Minneapolis, MN), and its development was supported by the National Institutes of Health Bioengineering Research Partnership cited above. The study tested the hypothesis that this new device could be built to run on a Vivid 7 scanner (GE Healthcare, Milwaukee, WI) and could image cardiac anatomy to locate landmarks, visualize ablation performed with other devices, and, using online strain and tissue Doppler methods, show the changes in regional mechanics or the propagation of contraction occurring after ablation- or pacing-induced changes in regional synchrony. We also evaluated the integration of 3D electrofield fusion mapping and display of our devices with the NavX system.