Three-dimensional echocardiography–guided atrial septectomy: An experimental study

Three-dimensional echocardiography in congenital heart disease

Complex intracardiac anatomy and spatial relationships are inherent to congenital heart defects (CHDs). Recognition of the limitations of two-dimensional echocardiography has stimulated clinical interest in three-dimensional imaging. The current review examines contemporary studies in the following areas where three-dimensional echocardiography has provided additive value in CHD: (1) visualization of morphology, (2) quantitation of chamber sizes and ventricular function, and (3) image-guided interventions.

Design of a Surgical Port for Minimally Invasive Beating-Heart Intracardial Procedures

Direct-access, minimally invasive, beating-heart intracardial procedures have the potential to replace many traditional surgical procedures requiring cardio-pulmonary bypass as long as micro-emboli are prevented from entering the cardiovascular system. A new surgical port was developed to introduce surgical instruments into chambers of the beating heart during minimally invasive, intracardial surgical procedures without allowing the introduction of micro-emboli 0.1 mm or larger in size. The design consists of an outer port body that is secured to the heart wall using a purse string suture and a series of inner tubular sleeves that form the interface between the port and the transecting instrument. The design enables rapid tool changes and accommodates a wide variety of instruments. The port uses a fluid purging system to dislodge and remove emboli from a surgical instrument. Laboratory and clinical tests show that the port adequately seals around a surgical instrument and prevents the introduction of emboli with diameters greater than 0.1 mm into the heart while minimizing hemorrhage.

A novel cardioport for beating-heart, image-guided intracardiac surgery

OBJECTIVE

Intracardiac beating-heart procedures require the introduction and exchange of complex instruments and devices. To prevent potential complications such as air embolism and bleeding, a universal cardioport was designed and tested.

METHODS

The design consists of a port body and a series of interchangeable sleeves. The port uses a fluid purging system to remove air from the instrument before insertion into the heart, and a valve system minimizes blood loss during instrument changes.

RESULTS

The cardioport was tested ex vivo and in vivo in pigs (n = 5). Beating-heart procedures, such as septal defect closure and mitral valve repair, were modeled. Ex vivo trials (n = 150) were performed, and no air emboli were introduced using the port. In comparison, air emboli were detected in 40% to 85% of the cases without the use of the port-based purging system. Port operation revealed excellent ergonomics and minimal blood loss.

CONCLUSIONS

A novel cardioport system designed to prevent air entry and blood loss from transcardiac instrument introduction was shown to be an enabling platform for intracardiac beating-heart surgery. The port system improves safety and facilitates further development of complex instruments and devices for transcardiac beating-heart surgery.

Off-Pump Atrial Septal Defect Closure Using the Universal Cardiac Introducer®

Objective

Optimal atrial septal defect (ASD) closure should combine off-pump techniques with the effectiveness and versatility of open-heart techniques. We report our experience with off-pump ASD closure using the Universal Cardiac Introducer (UCI) in a porcine model. The goal was to create an ASD over the fossa ovale (FO) and position a patch over the ASD under ultrasound (US) imaging and augmented virtual reality guidance.

Methods

An US probe (tracked with a magnetic tracking system) was positioned into the esophagus (transesophageal echocardiographic probe) for real-time image-guidance. The right atrium (RA) of six pigs was exposed via a right lateral thoracotomy or medial sternotomy. The UCI was attached to the RA wall. A punching tool was introduced via the UCI, navigated and positioned, under US guidance, to create an ASD into the FO. A patch with its holder and a stapling device were introduced into the RA via the UCI. The patch was positioned on the ASD. Occlusion of the ASD was determined using US and Doppler imaging.

Results

The FO membrane was excised successfully in all animals. US image-guidance provided excellent visualization. The patch was positioned in all cases with complete occlusion of the ASD. The stapling device proved too bulky, impeding circumferential positioning.

Conclusions

Using the UCI, ASD closure was safe and feasible. US imaging, combined with virtual and augmented reality provided accurate navigating and positioning. This study also provided valuable information on the future design of anchoring devices for intracardiac procedures.

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.

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.

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.

Characterization of Atrial Septal Defect Assessed by Real-time 3-Dimensional Echocardiography

OBJECTIVE

The aim of this study was to describe a quantitative evaluation by real-time 3-dimensional (3D) echocardiography (RT-3DE) of atrial septal defect (ASD) and atrial septum that is important for patient selection for transcatheter closure, and to assess the reliability of RT-3DE findings compared with operation.

METHODS

Forty-five patients, who were scheduled for surgical or transcatheter closure of an ASD, were included in the study.

RESULTS

In 43 patients (96%), 3D reconstructions allowed optimal imaging of the ASD. The correlations between the ASD maximal diameter by RT-3DE and operation or balloon sizing were excellent (r > 0.95). All surrounding rims of the atrial septum could be assessed on 3D reconstruction; except for the aortic rim, a cross-sectional reconstruction was created mimicking the transesophageal echocardiographic cross section (r > 0.92).

CONCLUSION

RT-3DE allows accurate determination of ASD location, ASD size, and surrounding tissue of the atrial septum, and might replace transesophageal echocardiography for patient selection for surgical or transcatheter closure.

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.

3D ultrasound in robotic surgery: performance evaluation with stereo displays

BACKGROUND

The recent advent of real-time 3D ultrasound (3DUS) imaging enables a variety of new surgical procedures. These procedures are hampered by the difficulty of manipulating tissue guided by the distorted, low-resolution 3DUS images. To lessen the effects of these limitations, we investigated stereo displays and surgical robots for 3DUS-guided procedures.

METHODS

By integrating real-time stereo rendering of 3DUS with the binocular display of a surgical robot, we compared stereo-displayed 3DUS with normally displayed 3DUS. To test the efficacy of stereo-displayed 3DUS, eight surgeons and eight non-surgeons performed in vitro tasks with the surgical robot.

RESULTS

Error rates dropped by 50% with a stereo display. In addition, subjects completed tasks faster with the stereo-displayed 3DUS as compared to normal-displayed 3DUS. A 28% decrease in task time was seen across all subjects.

CONCLUSIONS

The results highlight the importance of using a stereo display. By reducing errors and increasing speed, it is an important enhancement to 3DUS-guided robotics procedures.