Three-dimensional echocardiography–guided beating-heart surgery without cardiopulmonary bypass: A feasibility study

Varying ultrasound power level to distinguish surgical instruments and tissue

We investigate a new framework of surgical instrument detection based on power-varying ultrasound images with simple and efficient pixel-wise intensity processing. Without using complicated feature extraction methods, we identified the instrument with an estimated optimal power level and by comparing pixel values of varying transducer power level images. The proposed framework exploits the physics of ultrasound imaging system by varying the transducer power level to effectively distinguish metallic surgical instruments from tissue. This power-varying image-guidance is motivated from our observations that ultrasound imaging at different power levels exhibit different contrast enhancement capabilities between tissue and instruments in ultrasound-guided robotic beating-heart surgery. Using lower transducer power levels (ranging from 40 to 75% of the rated lowest ultrasound power levels of the two tested ultrasound scanners) can effectively suppress the strong imaging artifacts from metallic instruments and thus, can be utilized together with the images from normal transducer power levels to enhance the separability between instrument and tissue, improving intraoperative instrument tracking accuracy from the acquired noisy ultrasound volumetric images. We performed experiments in phantoms and ex vivo hearts in water tank environments. The proposed multi-level power-varying ultrasound imaging approach can identify robotic instruments of high acoustic impedance from low-signal-to-noise-ratio ultrasound images by power adjustments.

Phase grouping-based needle segmentation in 3-D trans-rectal ultrasound-guided prostate trans-perineal therapy

A robust and efficient needle segmentation method used to localize and track the needle in 3-D trans-rectal ultrasound (TRUS)-guided prostate therapy is proposed. The algorithmic procedure begins by cropping the 3-D US image containing a needle; then all voxels in the cropped 3-D image are grouped into different line support regions (LSRs) based on the outer product of the adjacent voxels' gradient vector. Two different needle axis extraction methods in the candidate LSR are presented: least-squares fitting and 3-D randomized Hough transform. Subsequent local optimization refines the position of the needle axis. Finally, the needle endpoint is localized by finding an intensity drop along the needle axis. The proposed methods were validated with 3-D TRUS tissue-mimicking agar phantom images, chicken breast phantom images and patient images obtained during prostate cryotherapy. The results of the in vivo test indicate that our method can localize the needle accurately and robustly with a needle endpoint localization accuracy <1.43 mm and detection accuracy >84%, which are favorable for 3-D TRUS-guided prostate trans-perineal therapy.

On mixed reality environments for minimally invasive therapy guidance: systems architecture, successes and challenges in their implementation from laboratory to clinic

Mixed reality environments for medical applications have been explored and developed over the past three decades in an effort to enhance the clinician's view of anatomy and facilitate the performance of minimally invasive procedures. These environments must faithfully represent the real surgical field and require seamless integration of pre- and intra-operative imaging, surgical instrument tracking, and display technology into a common framework centered around and registered to the patient. However, in spite of their reported benefits, few mixed reality environments have been successfully translated into clinical use. Several challenges that contribute to the difficulty in integrating such environments into clinical practice are presented here and discussed in terms of both technical and clinical limitations. This article should raise awareness among both developers and end-users toward facilitating a greater application of such environments in the surgical practice of the future.

Robotics and imaging in congenital heart surgery

The initial success seen in adult cardiac surgery with the application of available robotic systems has not been realized as broadly in pediatric cardiac surgery. The main obstacles include extended set-up time and complexity of the procedures, as well as the large size of the instruments with respect to the size of the child. Moreover, while the main advantage of robotic systems is the ability to minimize incision size, for intracardiac repairs, cardiopulmonary bypass is still required. Catheter-based interventions, on the other hand, have expanded rapidly in both application as well as the complexity of procedures and lesions being treated. However, despite the development of sophisticated devices, robotic systems to aid catheter procedures have not been commonly applied in children. In this article, we describe new catheter-like robotic delivery platforms, which facilitate safe navigation and enable complex repairs, such as tissue approximation and fixation, and tissue removal, inside the beating heart. Additional features including the tracking of rapidly moving tissue targets and novel imaging approaches are described, along with a discussion of future prospects for steerable robotic systems.

Augmented Reality Image Guidance during Off-Pump Mitral Valve Replacement through the Guiraudon Universal Cardiac Introducer

Objective

We report our experience with ultrasound augmented reality (US-AR) guidance for mitral valve prosthesis (MVP) implantation in the pig using off-pump, closed, beating intracardiac access through the Guiraudon Universal Cardiac Introducer attached to the left atrial appendage.

Methods

Before testing US-AR guidance, a feasibility pilot study on nine pigs was performed using US alone. US-AR guidance, tested on a heart phantom, was subsequently used in three pigs (~65 kg) using a tracked transesophageal echocardiography probe, augmented with registration of a 3D computed tomography scan, and virtual representation of the MVP and clip-delivering tool (Clipper); three pigs were used to test feature-based registration.

Results

Navigation of the MVP was facilitated by the 3D anatomic display. AR displayed the MVP and the Clipper within the Atamai Viewer, with excellent accuracy for tool placement. Positioning the Clipper was hampered by the design of the MVP holder and Clipper. These limitations were well displayed by AR, which provided guidance for improved design of tools.

Conclusions

US-AR provided informative image guidance. It documented the flaws of the current implantation technology. This information could not be obtained by any other method of evaluation. These evaluations provided guidance for designing an integrated tool: combining an unobtrusive valve holder that allows the MVP to function properly as soon as positioned, and an anchoring system, with clips that can be released one at a time, and retracted if necessary, for optimal results. The portability of Real-time US-AR may prove to be the ideal practical image guidance system for all closed intracardiac interventions.

Robotic tissue tracking for beating heart mitral valve surgery

The rapid motion of the heart presents a significant challenge to the surgeon during intracardiac beating heart procedures. We present a 3D ultrasound-guided motion compensation system that assists the surgeon by synchronizing instrument motion with the heart. The system utilizes the fact that certain intracardiac structures, like the mitral valve annulus, have trajectories that are largely constrained to translation along one axis. This allows the development of a real-time 3D ultrasound tissue tracker that we integrate with a 1 degree-of-freedom (DOF) actuated surgical instrument and predictive filter to devise a motion tracking system adapted to mitral valve annuloplasty. In vivo experiments demonstrate that the system provides highly accurate tracking (1.0 mm error) with 70% less error than manual tracking attempts.

Clinical value of stereoscopic three-dimensional echocardiography in assessment of atrial septal defects: feasibility and efficiency

Stereoscopic three-dimensional echocardiography(S-3DE) is a novel displaying technology based on real-time 3-dimensional echocardiography (RT-3DE). Our study was to evaluate the feasibility and efficiency of S-3DE in the diagnosis of atrial septal defect (ASD) and its use in the guidance for transcatheter ASD occlusion. Twelve patients with secundum ASD underwent RT-3DE examination and 9 of the 12 were subjected to transcatheter closure of ASD. Stereoscopic vision was generated with a high-performance volume renderer with red-green stereoscopic glasses. S-3DE was compared with standard RT-3D display for the assessment of the shape, size, and the surrounding tissues of ASD and for the guidance of ASD occlusion. The appearance rate of coronary sinus and the mean formation time of the IVC, SVC were compared. Our results showed that S-3DE could measure the diameter of ASD accurately and there was no significant difference in the measurements between S-3DE and standard 3D display (2.89+/-0.73 cm vs 2.85+/-0.72 cm, P>0.05; r=0.96, P<0.05). The appearance of coronary sinus for S-3DE was higher as compared with the standard 3D display (93.3% vs 100%). The mean time of the IVC, SVC for S-3DE monitor was slightly shorter than that of the standard 3D display (11.0+/-3.8 s vs 10.3+/-3.6 s, P>0.05). The mean completion time of interventional procedure was shortened with S-3DE display as compared with standard 3D display (17.3+/-3.1 min vs 23.0+/-3.9 min, P<0.05). Stereoscopic three-dimensional echocardiography could improve the visualization of three-dimensional echocardiography, facilitate the identification of the adjacent structures, decrease the time required for interventional manipulation. It may be a feasible, safe, and efficient tool for guiding transcatheter septal occlusion or the surgical interventions.

Inside the beating heart: an in vivo feasibility study on fusing pre- and intra-operative imaging for minimally invasive therapy

OBJECTIVE

An interventional system for minimally invasive cardiac surgery was developed for therapy delivery inside the beating heart, in absence of direct vision.

METHOD

A system was developed to provide a virtual reality (VR) environment that integrates pre-operative imaging, real-time intra-operative guidance using 2D trans-esophageal ultrasound, and models of the surgical tools tracked using a magnetic tracking system. Detailed 3D dynamic cardiac models were synthesized from high-resolution pre-operative MR data and registered within the intra-operative imaging environment. The feature-based registration technique was employed to fuse pre- and intra-operative data during in vivo intracardiac procedures on porcine subjects.

RESULTS

This method was found to be suitable for in vivo applications as it relies on easily identifiable landmarks, and hence, it ensures satisfactory alignment of pre- and intra-operative anatomy in the region of interest (4.8 mm RMS alignment accuracy) within the VR environment. Our initial experience in translating this work to guide intracardiac interventions, such as mitral valve implantation and atrial septal defect repair demonstrated feasibility of the methods.

CONCLUSION

Surgical guidance in the absence of direct vision and with no exposure to ionizing radiation was achieved, so our virtual environment constitutes a feasible candidate for performing various off-pump intracardiac interventions.

3D echocardiographic visualization for intracardiac beating heart surgery and intervention

Three-dimensional echocardiography has emerged as an essential tool for visualizing cardiac anatomy and for making more accurate measurements of cardiac structure and function. Recently, improvements in 3D beam-forming and transducer technologies have allowed higher resolution imaging from a transesophageal echocardiographic probe. This is creating new avenues for real-time visualization of intracardiac procedures without the need for cardiopulmonary bypass or opening the beating heart. Evolutions in visualization will allow a wider array of reparative procedures to be performed minimally invasively within a beating heart.

Fast block flow tracking of atrial septal defects in 4D echocardiography

We are working to develop beating-heart atrial septal defect (ASD) closure techniques using real-time 3D ultrasound guidance. The major image processing challenges are the low-image quality and the processing of information at high-frame rate. This paper presents comparative results for ASD tracking in time sequences of 3D volumes of cardiac ultrasound. We introduce a block flow technique, which combines the velocity computation from optical flow for an entire block with template matching. Enforcing adapted similarity constraints to both the previous and first frames ensures optimal and unique solutions. We compare the performance of the proposed algorithm with that of block matching and region-based optical flow on eight in vivo 4D datasets acquired from porcine beating-heart procedures. Results show that our technique is more stable and has higher sensitivity than both optical flow and block matching in tracking ASDs. Computing velocity at the block level, our technique tracks ASD motion at 2 frames/s, much faster than optical flow and comparable in computation cost to block matching, and shows promise for real-time (30 frames/s). We report consistent results on clinical intra-operative images and retrieve the cardiac cycle (in ungated images) from error analysis. Quantitative results are evaluated on synthetic data with maximum tracking errors of 1 voxel.

Real-time tracking and shape analysis of atrial septal defects in 3D echocardiography

RATIONALE AND OBJECTIVES

Real-time cardiac ultrasound (US) allows monitoring the heart motion during intracardiac beating heart procedures. Our application assists pediatric atrial septal defect (ASD) closure techniques using real-time 3D US guidance and rigid instruments. ASD tracking is also an important tool for facilitating systematic clinical studies of the dynamic behavior of the intra-atrial communication. One major image processing challenge is associated with the required processing of information at high frame rate, especially given the low image quality.

MATERIALS AND METHODS

We present an optimization scheme for a block flow technique, which combines the probability-based velocity computation for an entire block (a 3D volume centered on the ASD) with cyclic template matching. The adapted similarity imposes constraints both locally (from frame to frame) to conserve energy, and globally (from a reference template) to minimize cumulative errors. The algorithm is optimized for fast and reliable results. For tests, we use three intra-operational 4D ultrasound sequences of clinical infant beating hearts with ASD.

RESULTS

Computing velocity at the block level with an optimized scheme, our technique tracks ASD motion at a frequency of 60 frames/s on clinical 4D datasets. Results are stable and accurate for changes in resolution and block size. In particular, we show robust real-time tracking and preliminary segmentation results of the ASD shape, size and orientation as a function of time.

CONCLUSIONS

We present an optimized block flow technique for real-time tracking of ASD to assist in minimally invasive beating heart surgery. Our method proposes the standard use of references for processing repetitive data. This paper represents, to our knowledge, the first study on the dynamic morphology of ASD that takes into account the angular effect introduced by the slanted position of the intra-atrial communication with respect to the US probe.

Imaging artifacts of medical instruments in ultrasound-guided interventions

OBJECTIVE

Real-time 3-dimensional (3D) ultrasound imaging has the potential to become a dominant imaging technique for minimally invasive surgery. One barrier to its widespread use is that surgical instruments generate imaging artifacts, which can obfuscate their location, orientation, and geometry and obscure nearby tissue. The purpose of this study was to identify and describe the types of artifacts which could be produced by metallic instruments during interventions guided by 3D ultrasound imaging.

METHODS

Three imaging studies were performed. First, imaging artifacts from stainless steel rods were identified in vitro and acoustically characterized. Second, 3 typical minimally invasive instruments were imaged (in vitro and in vivo), and their artifacts were analyzed. The third study compared the intensity of imaging artifacts (in vitro and in vivo) from stainless steel rods with rods composed of 3 different materials and stainless steel rods with roughened and coated surfaces.

RESULTS

For the stainless steel rods, all observed artifacts are described and illustrated, and their physical origins are explained. Artifacts from the 3 minimally invasive instruments are characterized with the use of the artifacts observed with the rods. Finally, it is shown that artifacts can be greatly reduced through the use of alternate materials or by surface modification.

CONCLUSIONS

Instrument artifacts in 3D ultrasound images can be more confusing than those from the same instruments imaged in 2 dimensions. Real-time 3D ultrasound imaging can, however, be used effectively for in vivo imaging of minimally invasive instruments by using artifact mitigation techniques, including careful selection of probe and incision locations, as well as by instrument modification.

GPU based real-time instrument tracking with three-dimensional ultrasound

Real-time three-dimensional ultrasound enables new intracardiac surgical procedures, but the distorted appearance of instruments in ultrasound poses a challenge to surgeons. This paper presents a detection technique that identifies the position of the instrument within the ultrasound volume. The algorithm uses a form of the generalized Radon transform to search for long straight objects in the ultrasound image, a feature characteristic of instruments and not found in cardiac tissue. When combined with passive markers placed on the instrument shaft, the full position and orientation of the instrument is found in 3D space. This detection technique is amenable to rapid execution on the current generation of personal computer graphics processor units (GPU). Our GPU implementation detected a surgical instrument in 31 ms, sufficient for real-time tracking at the 25 volumes per second rate of the ultrasound machine. A water tank experiment found instrument orientation errors of 1.1 degrees and tip position errors of less than 1.8mm. Finally, an in vivo study demonstrated successful instrument tracking inside a beating porcine heart.

Interventional Three-Dimensional Echocardiography: Using Real-time Three-Dimensional Echocardiography to Guide and Evaluate Intracardiac Therapies

Real-time three-dimensional echocardiography (RT3DE) already has demonstrated its utility in guiding intracardiac procedures. This article discusses the advantages RT3DE has over the previous standard of 2D echocardiography.

Live 3-dimensional echocardiography guidance for the insertion of a retrograde cardioplegic catheter through the coronary sinus

OBJECTIVE

We evaluated the feasibility and accuracy of live 3-dimensional (3D) epicardial echocardiography (echo) to guide the insertion of a retrograde cardioplegic catheter into the coronary sinus.

METHODS

A real-time 3D echo system with a x4 matrix transducer was used. Live 3D echo-guided catheter insertion was compared with blind insertion. Completion times and success rates were recorded. During all experiments, the operator was blinded to the target and, in the echo-guided group, the procedure was performed with only ultrasonic guidance.

RESULTS

Live 3D echo provided sufficient spatial resolution and a satisfactory frame rate to provide a "virtual surgeon's view" of the relevant anatomy. Although there was no significant difference in completion time, live 3D echo guidance significantly improved the success rate of catheter insertion as compared to the blind group (90% versus 35%; P <.001).

CONCLUSIONS

Live 3D echo-guided coronary sinus catheter insertion is feasible and safe.

Towards subject-specific models of the dynamic heart for image-guided mitral valve surgery

Surgeons need a robust interventional system capable of providing reliable, real-time information regarding the position and orientation of the surgical targets and tools to compensate for the lack of direct vision and to enhance manipulation of intracardiac targets during minimally-invasive, off-pump cardiac interventions. In this paper, we describe a novel method for creating dynamic, pre-operative, subject-specific cardiac models containing the surgical targets and surrounding anatomy, and how they are used to augment the intra-operative virtual environment for guidance of valvular interventions. The accuracy of these pre-operative models was established by comparing the target registration error between the mitral valve annulus characterized in the pre-operative images and their equivalent structures manually extracted from 3D US data. On average, the mitral valve annulus was extracted with a 3.1 mm error across all cardiac phases. In addition, we also propose a method for registering the pre-operative models into the intra-operative virtual environment.

Three-Dimensional Echocardiography

Over the past 3 decades, echocardiography has become a major diagnostic tool in the arsenal of clinical cardiology for real-time imaging of cardiac dynamics. More and more, cardiologists' decisions are based on images created from ultrasound wave reflections. From the time ultrasound imaging technology provided the first insight into the human heart, our diagnostic capabilities have increased exponentially as a result of our growing knowledge and developing technology. One of the most significant developments of the last decades was the introduction of 3-dimensional (3D) imaging and its evolution from slow and labor-intense off-line reconstruction to real-time volumetric imaging. While continuing its meteoric rise instigated by constant technological refinements and continuing increase in computing power, this tool is guaranteed to be integrated in routine clinical practice. The major proven advantage of this technique is the improvement in the accuracy of the echocardiographic evaluation of cardiac chamber volumes, which is achieved by eliminating the need for geometric modeling and the errors caused by foreshortened views. Another benefit of 3D imaging is the realistic and unique comprehensive views of cardiac valves and congenital abnormalities. In addition, 3D imaging is extremely useful in the intraoperative and postoperative settings because it allows immediate feedback on the effectiveness of surgical interventions. In this article, we review the published reports that have provided the scientific basis for the clinical use of 3D ultrasound imaging of the heart and discuss its potential future applications.

Transesophageal Real-Time Three-Dimensional Echocardiography

OBJECTIVES

The purpose of this study was to develop a transesophageal probe that: 1) enables on-line representation of the spatial structures of the heart, and 2) enables navigation of medical instruments.

BACKGROUND

Whereas transthoracic real-time 3-dimensional (3D) echocardiography could recently be implemented, there is still no corresponding transesophageal system. Transesophageal real-time 3D echocardiography would have great potential for numerous clinical applications, such as navigation of catheters.

METHODS

The newly developed real-time 3D system is based on a transesophageal probe in which multiple transducers are arranged in an interlaced pattern on a rotating cylinder. This enables continuous recording of a large echo volume of 70 mm in length and a sector angle of 120 degrees . The presentation of the volume-reconstructed data is made with a time lag of <100 ms. The frame rate is up to 20 Hz. In addition to conventional imaging, the observer can obtain a stereoscopic image of the structures examined with red/blue goggles.

RESULTS

It was shown in vitro on ventricle- and aorta-form agar models and in vivo that the system enables excellent visualization of the 3D structures. Shape, spatial orientation, and the navigation of various catheters (e.g., EPS-catheter, Swan-Ganz-catheter), stents, or atrial septal defect occluders could be recorded on-line and stereoscopically depicted. The size of the echo sector enables a wide field of view without changing the position of the probe.

CONCLUSIONS

Transesophageal real-time 3D echocardiography can be technically realized with the system presented here. The in vitro and in vivo studies show particularly the potential for navigation in the heart and large vessels on the basis of stereoscopic images.

Proposal for a Novel Concept of a Hybrid, Minimally Invasive Cardiovascular Surgical Practice

Background

Due to the increase in new Interventional cardiovascular technologies, traditional lines of division between the interventional and surgical aspects are expected to blur, with these procedures modified and adopted into cardiovascular surgical practice. This proposal introduces new concepts and visions for such new devices and procedures.

Methods

I-Precision Planning II-Examples of Proposed Devices III-Examples of Proposed Procedures

Results

Over the past few years there has been a growing sense of anxiety about new interventional devices in the cardiovascular surgical community. As physicians, our main task is to formulate simpler, more effective and safer solutions to clinical problems; and as surgeons, we “devise mechanical solutions to clinical problems.”

Conclusions

Nowadays, there is an urgent need for the cardiovascular surgical community to rediscover and reinvent itself. We should see these new innovations as exciting new ideas and tools that we can “modify, simplify and apply” to revitalize our own practice.

Producing diffuse ultrasound reflections from medical instruments using a quadratic residue diffuser

Simultaneous visualization of tissue and surgical instruments is necessary during ultrasound-guided medical procedures. Standard minimally invasive instruments are typically metallic and act as strong specular scatterers. As a result, such instruments saturate the image or disappear according to the angle of incidence, obscuring nearby tissue and making it difficult to determine the instrument's precise location. The objective of this study was to produce diffusive reflections from the surface of surgical instruments for improved visualization in ultrasound. A surface profile based on a 2D quadratic residue diffuser (QRD) was employed, which has been demonstrated to reduce specular reflection in other acoustic applications. The backscattered echo amplitude from the diffusive surface at various angles of insonation was measured and compared to that from unmodified metal surfaces and heart tissue surfaces. The QRD resulted in an 8 dB reduction of the specular signal. Furthermore, the dynamic range for angles up to 75 degrees was less than 20 dB for the QRD and more than 65 dB for a flat surface. The QRD surface produces two beneficial results for the simultaneous imaging of instruments and tissue. First, the conspicuity of diffusive surfaces in ultrasound images is markedly improved in comparison with unmodified metal surfaces. Secondly, the echo amplitude of diffusive metal surfaces differs in mean and standard deviation from that of tissue facilitating image enhancement and segmentation.

Real-Time Three-Dimensional Echocardiography Is Useful in the Evaluation of Patients with Atrioventricular Septal Defects

OBJECTIVE

We sought to determine whether three-dimensional echocardiography (3DE) is useful in the evaluation of patients with atrioventricular septal defect (AVSD).

BACKGROUND

Recent advances in 3DE have enhanced its practicality. We assessed whether 3DE provided new information compared to 2DE among patients with AVSD.

METHODS

We retrospectively reviewed 52 3DE datasets from 51 patients (median age: 4.6 years, range 0-30 years; median BSA: 0.6 m2, range 0.2-1.9 m2) with any type of AVSD during a 1-year period. 3DE findings were compared to 2DE and surgical reports. For each study, AVSD was classified by 2DE as one of the following: unrepaired balanced defect, repaired balanced defect with residual lesions, repaired balanced defect without residual lesions, or unbalanced defect. 3DE was graded as (1) Additive: 3DE resulted in a new finding or changed diagnosis; (2) Useful: While useful, 3DE did not result in new findings or changed diagnosis; or (3) Not useful.

RESULTS

3DE on unrepaired balanced AVSD and repaired AVSD with residual lesions was more often additive/useful (33/36; 92%) than on repaired AVSD without residual lesions or unbalanced AVSD (9/16 (56%), P=0.009). 3DE was additive or useful in all three patients with unbalanced AVSD being considered for biventricular repair. Useful information obtained by 3DE included: precise characterization of mitral regurgitation and cleft leaflet, substrate for subaortic stenosis, valve anatomy, and presence and location of additional septal defects.

CONCLUSION

3DE provides useful and additive information in unrepaired balanced AVSD, repaired AVSD with residual lesions, and unbalanced AVSD under consideration for biventricular repair.

Three-dimensional echo-guided beating heart surgery without cardiopulmonary bypass: atrial septal defect closure in a swine model

OBJECTIVE

In this study, we tested 3 techniques of atrial septal defect closure under real-time 3-dimensional echocardiography guidance in a swine model.

METHODS

The operations were conducted under the sole guidance of a modified real-time 3-dimensional echocardiography guidance system with a x4 matrix transducer (Sonos 7500, Philips Medical Systems, Andover, Mass). Eighteen swine were anesthetized, and after median sternotomy, the echo probe was applied directly to the surface of the right atrium. To create an atrial septal defect, balloon atrial septostomy and atrial septal defect enlargement were performed. Subsequently, 3 different techniques of atrial septal defect closure were attempted: group I, direct suture closure; group II, closure of the atrial septal defect using the Amplatzer device (AGA Medical Corp, Golden Valley, Minn); and group III, patch closure of the atrial septal defect (n = 6 each).

RESULTS

Real-time 3-dimensional echocardiography guidance provided sufficient spatial resolution and a satisfactory frame rate to provide a "virtual surgeon's view" of the relevant anatomy during the entire procedure. All atrial septal defects were enlarged, and the mean final size was 8.5 +/- 1.8 mm. Atrial septal defect closure was successfully accomplished with all the 3 surgical techniques examined. In groups I and III, the needles (1-3 sutures) and staples (6-12 staples) penetrated the tissue and patch material consistently, whereas in group III, the Amplatzer atrial septal defect device was easily deployed. There was no incident device/staple embolization or air introduction. Neither intraoperative 2-dimensional color Doppler echocardiography nor postmortem macro-evaluation revealed any residual shunts.

CONCLUSIONS

Beating heart atrial septal defect closure under real-time 3-dimensional echocardiographic guidance is feasible and, unlike catheter-based devices, applicable for any type of secundum atrial septal defect.

Robotic pediatric cardiac surgery: Present and future perspectives

Advances in robotic technology and imaging systems have enabled the broad application of minimally invasive techniques in cardiac surgery, including coronary artery bypass grafting and mitral valve repair in adults. In pediatric cardiac surgery, however, current robotic systems have been used primarily to facilitate thoracoscopic pediatric procedures on extracardiac lesions, such as ligation of patent ductus and division of vascular rings. The use of smaller instruments with sophisticated robotic wrists may make it possible to perform more complex extracardiac procedures even in young infants. Additionally, future technological improvements, including incorporation of tactile feedback, instrument tracking, and intracardiac imaging (such as real-time 3-dimensional echocardiography), may enable intracardiac robotic surgery to be performed in children. This article reviews the current and potential future applications of pediatric robotic surgery and the developmental work required to enable performance of these procedures, along with an overview of the problems associated with the use of current robotic surgical systems in children.