Girish Narayan

Single-Breathhold, Four-Dimensional, Quantitative Assessment of LV and RV Function Using Triggered, Real-Time, Steady-State Free Precession MRI in Heart Failure Patients

To validate a novel, real‐time, steady‐state free precession (SSFP), single‐breathhold technique for the assessment of left ventricular (LV) and right ventricular (RV) function in heart failure patients.

Peri-Infarct Ischemia Determined by Cardiovascular Magnetic Resonance Evaluation of Myocardial Viability and Stress Perfusion Predicts Future Cardiovascular Events in Patients with Severe Ischemic Cardiomyopathy

BACKGROUND We assessed whether cardiovascular magnetic resonance imaging (CMR) of peri-infarct ischemia provides prognostic information in severe ischemic cardiomyopathy (ICM) patients referred for revascularization. METHODS Twenty-one patients with severe ICM were recruited prospectively for combined stress adenosine perfusion, late gadolinium enhancement, and rest perfusion studies. The patients were followed for in-hospital and post-discharge cardiovascular events. RESULTS During 12+/- 9.8 months follow-up, 67% of the patients with peri-infarct ischemia and 13% of the patients without peri-infarct ischemia had cardiovascular events (p = 0.03). CONCLUSION. In severe ICM patients, the presence of peri-infarct ischemia was associated with a higher incidence of cardiovascular events.

An evaluation of using real-time volumetric display of 3D ultrasound data for intracardiac catheter manipulation tasks

The enthusiasm for novel, minimally invasive, catheter based intracardiac procedures has highlighted the need to provide accurate, realtime, anatomically based image guidance to decrease complications, improve precision, and decrease fluoroscopy time. The recent development of realtime 3D echocardiography creates the opportunity to greatly improve our ability to guide minimally invasive procedures (Ahmad, 2003). However, the need to present 3D data on a 2D display decreases the utility of 3D echocardiography because echocardiographers cannot readily appreciate 3D perspective on a 2D display without ongoing image manipulation. We evaluated the use of a novel strategy of presenting the data in a true 3D volumetric display, Perspecta Spatial 3D System (Actuality Systems, Inc., Burlington, MA). Two experienced echocardiographers performed the task of identifying the targeted location of a catheter within 6 different phantoms using four display methods. Echocardiographic images were obtained with a SONOS 7500 (Philips Medical Systems, Inc., Andover, MA). Completion of the task was significantly faster with the Perspecta display with no loss in accuracy. Echocardiography in 3D significantly improves the ability of echocardiography for guidance of catheter based procedures. Further improvement is achieved by using a true 3D volumetric display, which allows for more intuitive assessment of the spatial relationships of catheters in three-dimensional space compared with conventional 2D visualization modalities.

Feasibility of noncontact intracardiac ultrasound ablation and imaging catheter for treatment of atrial fibrillation

Atrial fibrillation (AF) affects 1% of the population and results in a cost of

Feasibility of intravascular ultrasound ablation and imaging catheter for treatment of atrial fibrillation

2.8 billion from hospitalizations alone. Treatments that electrically isolate portions of the atria are clinically effective in curing AF. However, such minimally invasive catheter treatments face difficulties in mechanically positioning the catheter tip and visualizing the anatomy of the region. We propose a noncontact, intracardiac transducer that can ablate tissue and provide rudimentary imaging to guide therapy. Our design consists of a high-power, 20 mm by 2 mm, 128-element, transducer array placed on the side of 7-French catheter. The transducer will be used in imaging mode to locate the atrial wall; then, by focusing at that location, a lesion can be formed. Imaging of previously formed lesions could potentially guide placement of subsequent lesions. Successive rotations of the catheter will potentially enable a contiguous circular lesion to be created around the pulmonary vein. The challenge of intracardiac-sized transducers is achieving high intensities (300-5000 W/cm2) needed to raise the temperature of the tissue above 43degC. In this paper, we demonstrate the feasibility of an intracardiac-sized transducer for treatment of atrial fibrillation. In simulations and proof-of-concept experiments, we show a 37degC temperature rise in the lesion location and demonstrate the possibility of lesion imaging

Intravascular ultrasound ablation and imaging catheter for treatment of atrial fibrillation

Atrial fibrillation (AF) affects 1% of the population and is responsible for 15-20% of all strokes (1); this results in more than 460,000 hospitalizations and a cost of more than

High intensity focused ultrasound for imaging and treatment of arrhythmias

2.8 billion per year. Clinical studies show that circumferential pulmonary vein ablation, a surgical procedure that creates contiguous patterns of lesions that electrically isolate regions of the atria, have been effective in curing AF (2). However, current minimally invasive catheter procedures that use radiofrequency (RF) electrodes under fluoroscopic guidance are often unable to create these contiguous patterns. Difficulties arise in visualizing the anatomy and location of previous lesions and moving the catheter tip to those locations, particularly in the dynamic environment of the heart. Not only can intravascular ultrasound arrays deliver dy- namically, steerable therapy, they can also image the region of interest with good tissue contrast to correctly position the lesion. We propose the use of an intracardiac linear ultrasound array placed at the end of a 7 French catheter. Previously, we showed an intracardiac-sized transducer (20 mm by 2 mm) can create temperature rises of 45 degrees necessary for ablation. In this work, we illustrate the possibility of visualizing such a high intensity focused ultrasound (HIFU) lesion with conventional ultrasound imaging. I. INTRODUCTION An intracardiac ultrasound transducer addresses the issues of precisely positioning lesions and visualizing these lesions and anatomy during the AF procedure. Ultrasound therapy can be dynamically and electronically steered to precise locations as the transducer is roughly anchored in particular position; this dynamic steering can compensate for cardiac motion and variable anatomy. Unlike fluoroscopy, ultrasound imaging also provides real-time images of tissue and lesions with good tissue contrast. This can offer significant improvement in the ability to treat arrhythmias (4), (5), (6). Separate ultrasound imaging probes have been used to guide high intensity focused ultrasound (HIFU) transducers by displaying the anatomy and also detecting past lesions as bright echogenic regions (7), (8), (9). Though these echogenic regions fade 1-2 min after HIFU application, they persist for long enough periods to guide the placement of adjacent lesions for formation of contiguous patterns.

Apparatus and method for self-guided ablation

Atrial fibrillation (AF) affects 1% of the population and is associated with stroke and death. AF is often triggered by foci and reentrant pathways located near the pulmonary vein. Clinical studies show that circumferential pulmonary vein ablation destroys these electrical pathways, thereby eliminating AF (Pappone, C. et al., 2003). Currently, radiofrequency (RF) electrodes are used for such treatment. However, these procedures take over 7 hours and have <80% long term success. RF burn patterns often have discontinuities, which means that electrical pathways are still intact to trigger AF. Balloon and lasso catheters have been suggested to create a continuous circumferential burn, but are not successful because it can be difficult for the catheters to form good contacts with the tissue. Intravascular ultrasound arrays can be precisely electronically steered, making it easier to produce continuous burn patterns. The same array could also image the region of interest to position the burn correctly. While large external ultrasound transducers have been used ex vivo to ablate cardiac tissue (Strickberger, A.S. et al., 1999), external ultrasound for heart procedures is difficult because air in the lungs deflects much of the ultrasound. We propose the use of an intravascular linear ultrasound array placed at the end of a catheter. We present calculations, designs, and a proof of concept experiment demonstrating the feasibility of such an intravascular ablation system.