Feasibility of Off-Pump ASD Closure Using Real-Time 3-D Echocardiography

(#2001-7025 ... June 27, 2001)

Stephen W. Downing, MD,¹ William R. Herzog, Jr., MD,¹ Michael C. McElroy, RDCS,² Timothy B. Gilbert, MD¹

¹University of Maryland School of Medicine, Baltimore, MD
²Volumetrics Corporation, Durham, NC

ABSTRACT

Background: If surgeons could "see" through blood and cardiac chamber walls, it would ultimately be unnecessary to open the heart or use cardiopulmonary bypass to perform procedures such as atrial septal defect (ASD) closure or mitral valve repair. Conventional echocardiography generates crosssectional images that are not satisfactory as the only visualization for surgical procedures, and current 3-Dimensional (3-D) CT and echo systems take several minutes to compose and process a single still frame. Recently, however, the
first system for real-time 3-D echocardiography has been developed. This study examines whether real-time 3-D echocardiography can provide images of sufficient anatomic definition, depth perception, and image resolution to substitute for optical visualization in performing ASD closures.

Methods: A prototype Volumetrics 3-D echocardiographic system was evaluated in a water bath on a complex-surfaced standard reference model to determine the image resolution and define the ideal imaging parameters. A static image and views of sutures being placed with an endoscopic needle driver and two commercial suture placement devices were evaluated at multiple angles and distances from the target. The resulting images were graded by a blinded reviewer. Once the best imaging parameters were determined,
five porcine ASDs were closed with interrupted sutures, running sutures, or a pursestring suture using only echo visualization.

Results: The highest quality images were obtained with the probe at a distance of 4-6 cm and at angles perpendicular or 45 degrees forward to the target. Spatial and temporal resolutions were adequate to suture all ASDs closed under only echo guidance.

Conclusions: The evaluated real-time 3-D echo system provided adequate spatial and temporal information to act as a guide for surgical procedures.