The Sonographer Attachment Programme At USA Report : Mayo Clinic: Advanced Echo =Sonographer And Contrast Agent=

Sonographer And Contrast Agent

The impact of contrast agents (transpulmonary and agitated saline) on the clinical applications of echocardiography has been dramatic over the last decade.Currently, the Food and Drug Administration approved indications for transpulmonary agents include the enhancement of left ventricular endocardial border definition.The augmentation of Doppler signals and intracardiac shunt detection can also be enhanced with the administration of contrast agents. The use of contrast agents in each of these clinical situations is well established and has become standard practice in many echocardiography laboratories.  The development of newer agents promises to bring additional advances in the utility of contrast echocardiography, including the real-time assessment of myocardial perfusion coronary flow detection and flow reserve measurements the delivery of pharmacologic or genetic therapy and in combination with continuous ultrasonography, as a therapy for discriminatingly dissolving life-threatening blood clots. As these applications continue to expand, so must the role and responsibilities of the cardiac sonographer.

Contrast echocardiography requires a high level of competence and expertise, in addition to the skills frequently required in standard cardiac sonography practice, such as assisting with transesophageal echocardiography and performing stress echocardiography, interventional and/or interoperative procedures, and fetal echocardiography. The American Society of Echocardiography (ASE) highly recommends that cardiac sonographers take the appropriate steps to become trained in the administration of the contrast agents used in echocardiography.The sonographer is often the first person to recognize the need for contrast, but the physician is ultimately responsible for ordering its use, which ideally should be done on a case-by-case basis. However, we recognize that there are situations in which the physician is not immediately available, and in such instances, another option might be the use of standing orders,with explicit indications listed as to when to use a contrast agent.This alternative would require active involvement of the laboratory medical director for the development of standing orders and specific protocols.

The cardiac sonographer’s role in performing contrast echocardiography consists of 4 components:

1. A thorough understanding of microbubble physics, instrumentation, and the application of cardiac ultrasonographic scanning techniques for the acquisition of high-quality images during contrast administration.

2. Recognition of the indications for use of a contrast agent for left heart-chamber border delineation, enhancement of Doppler signals, and intracardiac/intrapulmonary shunt detection.

3. Obtainment of intravenous (IV) access or evaluation of an existing IV line for administration of a contrast agent by a sonographer.

4. Performance of the IV injection or the infusion of the contrast agent.

It is recognized that, given the variety of practice situations, some of these components (ie, [3] and [4]), may not necessarily be a part of the sonographer’s responsibilities. However, in the interest of providing a timely patient diagnosis especially in situations in which the test results will affect the patient’s clinical management, a qualified cardiac sonographer can determine the need for a contrast agent and, if necessary, establish IV access and even potentially administer a contrast agent.This may be the case if the physician or a registered nurse is not present but is available in the immediate area and can provide direct supervision for the insertion of an IV line or for the administration of the contrast agent. It is preferable that a physician and/or a nurse have direct involvement with a contrast study because the sonographer cannot administer a contrast agent (ie, bolus injections) and simultaneously perform a quality echocardiographic examination without additional support.

All persons involved in contrast echocardiography must be well trained and demonstrate competency. Cardiac sonographers need to be credentialed in their respective discipline (adult and/or pediatric). Importantly, when direct supervision by a physician or registered nurse is available and established, and when written laboratory protocols are in place, a credentialed sonographer can initiate the process, obtain IV access, and have a registered nurse or physician administer the appropriate agent. In rare situations, another qualified sonographer could administer the appropriate contrast agent if the registered nurse or physician is not available at the time of the study.

When To Perform Contrast Echocardiography

The cardiac sonographer has the responsibility to carry out the physician’s order for the performance of the examination and therefore initially determines the overall technical quality of the echocardiogram. Thus this person is often in the primary position to identify the need for contrast enhancement. It is well established that in up to 20% of resting studies, the endocardial border definition of the left ventricle is suboptimal. This has been defined as the inability to visualize at least 2 myocardial segments of the left ventricle. Suboptimal visualization of certain segments, such as the anterior or lateral walls, may be even worse during stress echocardiography. The enhancement of left ventricular endocardial border definition can be facilitated by using transpulmonary contrast agents.

Other clinical situations that may require the use of contrast are the Doppler signal enhancement of tricuspid regurgitation jet velocity for estimating pulmonary artery pressure, and the improvement of aortic, pulmonic, and mitral valve spectral signals for further analysis of valvular disease severity. In addition, if 2-dimensional echocardiography identifies previously unsuspected findings suggestive of intracardiac or intrapulmonary shunt, this may necessitate the performance of a right-heart contrast study to determine the presence or absence of shunt flow. The cardiac sonographer often can identify the need for a contrast agent in these clinical situations and can improve the efficiency and accuracy of the echocardiographic examination.

To address these clinical issues, the sonographer must have a physician’s order for the contrast agent and a preapproved and written procedure plan, established by the medical director, for initiation of the appropriate contrast agent indicated in the particular situation. The supervising or interpreting physician’s approval for the study should be obtained whenever possible on a case-by-case basis. However, in the consideration of procedure time, patient satisfaction, or unnecessary delay, a standing order or laboratory policy directive can be considered an alternative means to accomplish timely completion of the echocardiographic examination. In some instances, the echocardiography laboratory medical director could provide standing orders, with the approval of the hospital administration and medical staff and in accordance with state laws regarding administration of pharmaceutical agents.

It is recommended that only credentialed sonographers who practice in accredited  or, at least, Level II  laboratories be granted the authority to determine the need for contrast agent usage when the supervising physician is not immediately available. The ASE’s view is that these persons have achieved a standard of competency, are well experienced, and can apply independent judgment with sufficient problem-solving skills to assume the responsibility of determining when to incorporate contrast agents.

Intravenous Access For Contrast Injection

The third component of the cardiac sonographer’s role in performing contrast echocardiography involves obtaining proper IV access for injections of the agent. This represents an opportunity for the sonographer to learn new skills, gain an enhanced role in the laboratory, and provide higher-quality patient care. Echocardiography laboratories that have registered nurses, physicians, or IV teams readily available to assist in contrast studies are at an advantage and represent the ideal situation, but they may reflect a minority of laboratory settings. The task of obtaining IV access should not be considered a role reserved only for nurses and physicians. Many allied health professionals are trained to perform venipuncture, including phlebotomists, emergency medical technicians, and radiologic and nuclear medicine technologists. Respiratory therapists perform direct radial artery cannulization to obtain blood samples for blood gases. As with any health care professional who performs IV insertion techniques, the sonographer must complete the appropriate training and certification process before assuming this skill.

The difficulty in obtaining IV training is recognized; however, it may be facilitated by the active involvement of the echocardiography laboratory medical director, or through consultation with nursing administration or perhaps with the clinical laboratory director. The hospital system might offer a program, and courses might be offered in a community college or by independent clinical laboratories. In addition, professional organizations and ultrasound contrast companies are investigating avenues for IV training. When available, local resources are the best approach for the sonographer seeking certification.

It is recommended that IV training encompass knowledge of venous anatomy and appropriate sites of access, risks to patients and the health care professional, use of sterile technique, infection control, and safety precautions. Additional components of training are the confirmation of venous access and the knowledge of proper supplies, including the selection and inspection of the various angiocatheters and needles to be used. A checklist that outlines the procedure and process may be useful. Sonographers should obtain appropriate patient consent and provide an explanation of the procedure. Other elements that must be in place are documentation of the training provided, certification, periodic skill assessment, and close supervision.

An additional consideration for cardiac sonographers is those patients with existing IV lines, whether in the arm or other sites. It is recommended that sonographers who use these sites have thorough knowledge of the catheter type, IV patency, and medications being infused and have direct contact with the patient’s nurse for consultation and assistance. This will ensure proper use of the existing IV line and prevent complications.

The ASE recommends that only credentialed sonographers who have had proper IV training, with verified competency, be allowed to perform this procedure, and these persons must be fully aware of the risks and benefits of IV insertion. It is strongly recommended that contrast studies be done only in settings where direct supervision by a physician or nurse is available. Patient safety remains the most important component.

Injection Or Infusion Of Contrast Agent

After IV access is secured, the injection or infusion of the contrast agent is the remaining component of the contrast echocardiography examination. The recommended approach is that a registered nurse or physician performs the actual injection or infusion of the agent while the cardiac sonographer focuses on acquisition of the images. However, in situations in which the nurse or physician is not readily available and a written policy is in place, a sonographer might perform this function. Other allied health professionals perform injections or administer drugs on standing, preapproved written orders or after obtaining verbal orders from a physician.

Any person who administers the contrast agent must have knowledge of the proper technique for injection or infusion, the approved indications, the agent’s safety profile (ie, contraindications), the possible allergic reactions, and the potential risk to the patient. This requires carefully explaining the procedure to the patient, answering questions and addressing concerns, and obtaining consent (written, when necessary). The current contrast agents have an excellent safety profile, and complications are extremely rare. However, of particular concern are patients with intracardiac or intrapulmonary right-to-left shunts, in whom the potential for adverse events are greater. Importantly, a nurse or physician should be available for immediate response, and the necessary emergency equipment and medications should be available in case of allergic reaction.

It is the official position of the ASE that cardiac sonographers who administer contrast agents must have demonstrable training and skills with thorough product knowledge, and laboratories must have clearly defined written policies and procedures in place, including standing orders from the laboratory medical director. Only credentialed cardiac sonographers should be given this responsibility, and the use of contrast agents should be carried out in accredited or, at least, Level II echocardiography laboratories.

The Sonographer Attachment Programme At USA Report : Mayo Clinic: Advanced Echo =3D Echo=

Three Dimensional Echocardiogram

Attempts to record and display ultrasound images in 3D format were first reported in the 1960s. One of the earliest studies described the acquisition of a series of parallel scans of a human orbit to reconstruct 3D anatomy. Despite the limited technology of the day, these initial studies demonstrated that complex anatomic structures were ideally displayed using 3D techniques. Concerns about image quality and the computational power needed for storage and reconstruction greatly limited the early application of this methodology.

More than a decade later, investigators began to obtain 3D ultrasound images of the heart. Through the careful tracking of a transducer, a sequence of 2-dimensional (2D) echocardiograms could be recorded, aligned, and reconstructed into a 3D data set. This methodology was limited by the need for offline data processing to create and display the 3D images. In the early 1990s, von Ramm and colleagues developed the first real-time 3D (RT3D) echocardiographic scanner, capable of acquiring volumetric data at frame rates sufficient to depict cardiac motion. More recently, further improvements in design and engineering have led to the commercialization of RT3D echocardiography. This methodology has evolved quickly, and different versions of RT3D imaging are currently available on several platforms.

Reconstruction Techniques

Early approaches to 3D echocardiography were based on the principle that a 3D data set could be reconstructed from a series of 2D images. In this method, serial 2D images are obtained using either freehand scanning or a mechanically driven transducer that sequentially recorded images at predefined intervals. With freehand scanning, a series of images is obtained by manually tilting the transducer along a fixed plane, and a spatial locator attached to the transducer translates the 3D spatial location onto a Cartesian coordinate system. This approach has several practical limitations, including the relative bulk of the acoustic spatial locators, which makes transducer manipulation difficult, and the need for a clear and direct path between the acoustic locators and the transmitter. For electromagnetic spatial locator systems, an additional problem is the potential for interference of the electromagnetic field by ferromagnetic material in close proximity to the transducer (eg, material in hospital beds and medical equipment).

An alternative to freehand scanning is the use of a mechanized transducer to obtain serial images at set intervals in a parallel fashion or by pivoting around a fixed axis in a rotational, fanlike manner. Because the intervals and angles between the 2D images are defined, a 3D coordinate system can be derived from the 2D images in which the volume is more uniformly sampled than with the freehand scanning approach.

More recently, the use of a transesophageal or transthoracic multiplane probe has emerged as a readily available method to obtain rotational images at defined interval angles around a fixed axis. Typically, images are collected over a 180-degree rotation at set intervals. To minimize reconstruction artifacts, sequential images are gated to both electrocardiography (ECG) and respiration. Acquisition of a complete data set typically takes 1 to 5 minutes, depending on respiratory and heart rates and the predefined spatial intervals. During cardiac surgery, respiration can be suspended during acquisition to minimize the effects of respiratory motion.

The quality of 3D reconstructions from 2D images depends on a number of factors, including the intrinsic quality of the ultrasound images, the number (or density) of the 2D images used to reconstruct the 3D image, the ability to limit motion artifact, and adequate ECG and respiratory gating. In general, the greater the number of images obtained (ie, the smaller the space intervals between images), the better the 3D reconstruction. However, increasing the number of images also lengthens the acquisition time, which can potentially introduce motion artifact. Consequently, the optimal number of images necessary for 3D reconstruction depends on the cardiac structure being examined and the resolution required. For example, 4 to 6 serial images are usually adequate for volume reconstructions of the left ventricle (LV), whereas more images are often needed to visualize more complex, rapidly moving structures, such as mitral and aortic valves. Once the 2D images have been obtained, they are processed offline with customized or commercially available software. The cardiac structures are manually or semiautomatically traced to the 3D spatial coordinates to reconstruct a 3D image.

Protocols

A complete 3D echocardiographic study includes an assessment of ventricular function, valvular morphology, and hemodynamic status. Unlike 2D echocardiography, in which standard views are described based on the plane through which they pass, 3D echocardiography is inherently volumetric. As such, it permits both an external view of the heart and multiple internal perspectives (through cropping).

As an alternative to a complete 3D study, 3D echocardiography can be performed selectively as a complement to a 2D study. Instead of a complete 3D echocardiogram, a more focused 3D imaging study may be appropriate in some cases. For example, in a patient with mitral stenosis, the 3D portion of the study may be limited to visualization and quantification of the mitral orifice. Focused 3D imaging for LV volume calculation, typically performed with an apical 4 chamber wide-angle acquisition, also can be used to complement standard 2D imaging.

The ability to extract hemodynamic information derived from 3D color Doppler ultrasonography is currently being investigated. To capture and analyze color flow imaging in 3 dimensions, the area of interest should be obtained within the 3D data set, with the angle of the ultrasound beam aligned as parallel as possible to the direction of blood flow. Depth and sector settings should be optimized for color Doppler resolution. Extraneous flows can be cropped so that only the area of interest is displayed. The color Doppler flow patterns can be analyzed in multiple views to provide a complete assessment of the color Doppler data.

Clinical Application: Chamber Quantification

Left Ventricle

LV chamber and mass quantification have been studied extensively using 3D echocardiography. Initial 3D methods to measure LV volumes used reconstruction techniques that, although more accurate and reproducible than 2D methods, required long acquisition and post processing times. Moreover, the accuracy of the volume calculations was highly dependent on image quality. The introduction of real-time imaging systems that use matrix phased-array transducers with more processing elements has significantly improved image quality. In addition, LV quantification algorithms that can interface with 3D data sets obtained with matrix phased-array transducers are now widely available and are increasingly robust.

The wideangle acquisition mode is often used to acquire the entire LV volume, from which a detailed analysis of global and regional wall motion can be done. Images may be displayed with either orthogonal long-axis views or multiple short-axis views. Currently, data analysis is performed offline on a personal computer with dedicated 3D software. Data also can be analyzed online with software intrinsic to the ultrasound machine. Because a data set comprises the entire LV volume, multiple slices from different orientations can be obtained from base to apex to evaluate wall motion. If image quality is limited, then acquisition can be combined with infusion of contrast to improve the delineation of the endocardial border. An advantage of a 3D data set over 2D is the ability to manipulate the plane to align the true long axis and minor axis of the LV, hence avoiding foreshortening and oblique imaging planes. Once the LV axes are appropriately aligned, LV volumes can be calculated with a centroid-based algorithm that typically uses 2 or 3 planes, thereby shortening processing time. In addition, the LV volumes can be segmented, which allows for regional LV function assessment.

LV volume assessment by RT3D has been demonstrated to be rapid, accurate, reproducible, and superior to conventional 2D methods. The superiority of the RT3D approach has been demonstrated in various clinical situations, but its use is limited in patients with a poor acoustic window. An alternative method of calculating ventricular volumes from an RT3D cardiac volume data set uses the disc summation method. This technique may be advantageous in patients with asymmetrical ventricles. LV volume and mass obtained by RT3D echocardiography compare favorably with those obtained with cardiac magnetic resonance imaging (MRI) or radionuclide volumes. In addition, RT3D echocardiography has demonstrated efficacy and accuracy in assessing LV volumes in remodeled ventricles after myocardial infarction and in assessing global LV dyssynchrony.

Preliminary clinical studies on the use of RT3D in stress echocardiography confirm the feasibility of this technique and report sensitivity and specificity comparable to 2D stress imaging. An advantage of RT3D stress imaging is the decreased imaging time; standard views can be obtained with only 1 or 2 image acquisitions. In preliminary clinical studies, average acquisition times decreased from 65 to 28 seconds with RT3D imaging.

Right Ventricle

 Assessment of right ventricle (RV) function by 2D echocardiography is limited because of the asymmetrical, pyramidal shape of the RV, which does not conform to simple geometric assumptions. In theory, direct visualization of the entire chamber should be possible with 3D techniques, thereby overcoming the inherent limitations of tomographic methods. To date, most studies that have applied 3D echocardiographic techniques to the RV have involved primarily rotational or freehand scanning methods,  most of these series demonstrated improved accuracy of RV function assessment. The recent development and availability of RT3D echocardiography has the potential to further improve the ability to assess RV chamber size, volume, and function.

Left Atrium

In a limited number of studies, left atrial volume has been accurately quantified by 3D echocardiography using both reconstructive and realtime techniques. The 3D echocardiographic methods correlate well with MRI and appear to have accuracy comparable to 2D left atrial volume methods.

Clinical Application : Valvular Heart Disease

The recent widespread availability of RT3D echocardiography obviates many of the practical limitations of reconstructive 3D techniques and offers the potential for greater clinical application for valvular heart disease both in standard diagnostic evaluation and in real-time guidance during surgical valve repair. This technique is ideally suited for assessing valve function given the nonplanar anatomy of the cardiac valves and the associated anatomic and spatial alterations associated with valvular heart disease.

Mitral Valve

The 3D echocardiography technique has contributed significantly to our understanding of mitral valve function and anatomy. The mitral valve is particularly suited to 3D assessment because of the complex interrelationships among the valve, chordae, papillary muscles, and myocardial walls. This technique can provide important insight into mitral valve structure, demonstrating the saddle shape of the mitral annulus, with high points located anteriorly and low points oriented in a mediolateral direction. This has helped clarify the appropriate diagnostic imaging planes from which mitral valve prolapse should be diagnosed, thereby avoiding false positive interpretations.

In addition, 3D echocardiography has provided important mechanistic insights into functional and ischemic mitral regurgitation resulting from derangements of the normal spatial relationships of the mitral valve leaflets to its chordal attachments, papillary muscles, and the LV. Distortion of the normal spatial relationship between the LV and mitral valve apparatus results in papillary muscle displacement and tethering of the mitral leaflets, leading to incomplete closure of the leaflets and mitral regurgitation . The 3D echocardiography technique has identified changes in annular shape occurring with functional mitral regurgitation. These mechanistic and anatomic insights based on 3D analysis have provided the basis for the development of new approaches to treating ischemic mitral regurgitation.

Three-dimensional echocardiography has been used to define and localize mitral leaflet lesions in mitral valve prolapse, endocarditis, and congenital mitral abnormalities.  This application has been particularly important in guiding surgical repair.

The RT3D approach has also demonstrated efficacy in quantifying mitral regurgitation by using 3D guidance to directly measure the proximal flow convergence region. It has provided insight into how premitral orifice geometry affects the calculation of mitral valve area in mitral stenosis. Calculation of mitral valve area by 3D echocardiography has been demonstrated to be accurate, reproducible, and less variable than conventional 2D methods and thus has been recommended as the first line method. In addition, 3D echocardiography has been used for guidance during percutaneous mitral valvuloplasty.

Aortic Valve

Three-dimensional echocardiography has been applied for anatomic assessment of the aortic valve and root morphology and to calculate the valve area in aortic stenosis. The technique has been used to delineate aortic flow patterns and has demonstrated feasibility and accuracy in quantifying aortic regurgitation. Other applications have included the detection and localization of aortic valve vegetations, assessment of congenital outflow obstruction abnormalities, and demonstration of morphological changes in the valve after balloon dilation.

Tricuspid and Pulmonary Valves

Compared with the aortic and mitral valves, the tricuspid and pulmonary valves have been less widely studied with 3D echocardiography. This technique has demonstrated anatomic changes with rheumatic and degenerative tricuspid valve disease and has accurately reconstructed congenital tricuspid valve abnormalities, such as atrioventricular canal defects. For the pulmonary valve, 3D assessment has been limited to descriptive case reports defining anatomic abnormalities associated with pulmonary valve stenosis and endocarditis.

Clinical Application : Congenital Heart Disease

Clinical investigations examining the role of 3D echocardiography in patients with congenital heart disease have emphasized the unique perspective provided by 3D imaging and the versatility of the technique in patients with simple defects or complex conditions and in the postoperative state. Three-dimensional echocardiography, using both reconstruction methods and RT3D, has been used to detect several forms of congenital heart disease. The ability to record and analyze the entire cardiac structure and the ability to display complex spatial relationships are potential advantages of 3D imaging over 2D echocardiography. In addition, the decreased examination time afforded by RT3D echocardiography may reduce the need for sedation in some children.

In patients with atrial septal defects, 3D echocardiography can record the size and shape of the defect. It also can show the precise location of the defect and the extent of residual surrounding tissue. In patients with secundum atrial septal defects, the extent of the retroaortic rim often determines the feasibility of repair with percutaneous closure devices. Three-dimensional echocardiography also has been used after atrial septal defect closure to evaluate the success of the procedure and identify the origin of residual shunting. In patients with ventricular septal defects, the ability to interrogate the entire septum is frequently cited as an advantage of the 3D technique. A novel application of 3D imaging in patients with ventricular septal defects involves using offline reconstruction to measure the shape and size of the color flow jet, which allows for accurate measurement of the magnitude of shunting in patients with isolated ventricular septal defects.

Various 3D echocardiographic techniques have been used to evaluate RV and LV size and function in patients with congenital heart disease. The approach to the LV is similar to that described previously and permits quantification of dimension, volume, mass, and ejection fraction. Owing to the ellipsoidal shape of the LV, the advantages of 3D over 2D echocardiographic techniques are limited, because simple geometric assumptions can be used to calculate LV volumes; however, the RV’s asymmetrical shape invalidates the simple geometric assumptions used for LV volume calculations. In this case, the ability to record and analyze the entire chamber rather than relying on simplifying assumptions has proven superior. In patients with congenital heart diseases that involve RV pathology, 3D echocardiography correlates well with MRI for the measurement of RV volume. Three-dimensional echocardiography has been successfully applied to the detection and assessment of several anatomic defects. For example, the circumferential extent and severity of discrete subaortic membranes have been successfully visualized with 3D echocardiography. With the apical view, a unique en face image of the membrane can be recorded, which permits analysis of the effective orifice area and the dynamic nature of the defect. Congenital malformations of the mitral valve also have been assessed with 3D echocardiography. The complex nature of these defects can make a thorough anatomic evaluation difficult. In such cases, the perspective provided by 3D echocardiography can provide a complete preoperative assessment of the extent and severity of the valvular abnormality.

Clinical Application : Intraoperative Applications

The accuracy, feasibility, and value of 3D echocardiography also have been demonstrated in the intraoperative environment. Intraoperative 3D echocardiography provides accurate and often additional anatomic information compared with 2D transesophageal (TEE) imaging. In limited studies examining 2D and 3D TEE intraoperative evaluation of mitral valve prolapse anatomy, 3D TEE evaluation provided complementary and additional information compared with 2D TEE for localization of prolapsed scallops. Intraoperative 3D TEE also has been used to identify distortion and folding of the mitral annulus as a cause of functional mitral stenosis or worsening mitral regurgitation during beating heart surgery. Finally, intraoperative 3D TEE has proven valuable in patients undergoing surgery for congenital heart lesions. For example, the superiority of intraoperative 3D TEE compared with 2D has been demonstrated by its ability to provide en face and oblique views of left atrioventricular valve malformations in patients undergoing reoperation for persistent regurgitant lesions after previous repair of atrioventricular septal defects.

Intraoperative epicardial RT3D echocardiography has been used to improve spatial orientation and assess the extent of septal thickening, mitral valve systolic anterior motion, and postsurgical LV outflow tract patency in a patient with hypertrophic cardiomyopathy undergoing septal myectomy. It also has been used to guide and monitor off-pump atrial septal defect closure in a beatingheart animal model. Finally, intraoperative epicardial and postoperative transthoracic RT3D echocardiography has been used to evaluate changes in LV volume and function during cardiac surgery in patients undergoing infarct exclusion surgery for ischemic cardiomyopathy. In contrast to 3D echocardiographic imaging, conventional 2D methods may not accurately quantify LV volumes in patients with severe ischemic cardiomyopathy, especially in the presence of significant geometric changes due to LV aneurysm.

Clinical Application : Contrast Echocardiography

The use of contrast with 3D echocardiography to improve quantification of LV volumes offers several advantages. The RT3D technique (single or full volume) provides the most practical approach. Triggering, although not essential, increases the signal-to-noise ratio and thus is superior to non triggered imaging. Preliminary clinical studies have shown promise with regard to improved LV surface identification and volume and ejection fraction measurement. Another evolving application of contrast 3D echocardiography is in the evaluation of myocardial perfusion. The ability to record the entire LV and to quantify the full extent of hypoperfused myocardium is a potential advantage of this approach. However, the problem of microbubble destruction, even with triggered imaging, remains a challenge. This is especially true when matrix array transducers are used, which results in suboptimal myocardial opacification due to high acoustic power. Further technological developments should lead to improvements in all of these areas and will contribute to more practical applications of contrast 3D echocardiography. 

Future Direction

Ongoing developments in 3D echocardiography include technological innovations and expanding clinical applications. Automated surface extraction and quantification, single-heartbeat full-volume acquisition, transesophageal RT3D imaging, the ability to navigate within the 3D volume, and stereoscopic visualization of 3D images are some of the technological advances that can be expected over the next several years. These will further enhance the quality and clinical applications of 3D echocardiography. In addition, standardized and focused 3D protocols will be developed and refined to optimize clinical application of this technique. Tagging and/or tracking the LV surface in real time may provide new approaches to quantifying myocardial mechanics, such as regional shape and strain. This approach has great potential and will complement and likely compare favorably with the quantitative ability of cardiac MRI. The superior temporal resolution of echocardiography should offer unique advantages for this purpose. In the future, combining the greater temporal resolution of 3D echocardiography with the excellent spatial resolution of MRI (or computed tomography) may yield an imaging data set with unsurpassed anatomic and physiological infrmation, an approach called “fusion imaging”.