American College of Cardiology

Quinones ET AL., ACC/AHA CLINICAL COMPETENCE STATEMENT ON ECHOCARDIOGRAPHY
J Am Coll Cardiol 2003;41:687-708

ACC/AHA Clinical Competence Statement on Echocardiography

A Report of the American College of Cardiology/American Heart
Association/American College of Physicians–American Society of Internal Medicine Task Force on Clinical Competence

Developed in Collaboration with the American Society of Echocardiography, the Society of Cardiovascular Anesthesiologists, and the Society of Pediatric Echocardiography

IX. Emerging New Technologies

Over the past few years several new technologies or applications for echocardiography have emerged that continue to improve our ability to care for cardiac patients. Because they are new, there has not been sufficient experience with all of them for specialty societies to provide written recommendations regarding training requirements, documentation, and maintenance of competence. However, it is the consensus of this writing group that, because these new technologies are in current use, this document should provide, in as much as it is possible, a set of recommendations for training requirements and establishment of competence.

1. Hand-Carried Ultrasound Devices.
Overview and Indications for the Procedure. The era of an "ultrasound-assisted" physical examination has arrived, having been brought about by improvements on an old concept of a "hand-carried ultrasound (HCU) scanner." A HCU device is defined as a small ultrasound machine (typically less than six pounds), with limited diagnostic capabilities designed for evaluating gross structural or functional abnormalities of the cardiovascular system, which does not fulfill the criteria for a current state-oftheart limited or comprehensive echocardiographic examination (Table 24).

The ASE has defined the principal use of HCU as a method of extending the accuracy of bedside physical examination ⁽²⁰⁾. The instrument is designed primarily for a "focused" user-specific ultrasound examination. The intent is to appropriately reduce under- and over-utilization of more expensive technology. This definition implies that a state-of-the-art instrument is not always necessary to answer specific pertinent user questions. However, the words, "targeted" and "focused" are often equated with incomplete, inadequate, or inaccurate information, which may lead to inappropriate over- or under-utilization of this and other diagnostic methods or technology. It is the consensus opinion of this writing committee that "extension of the physical examination" should not be interpreted as a license for untrained individuals to use poor imaging techniques that will result in inaccurate diagnosis. The user of an HCU determines which image or information is important to the specific clinical question asked and must take personal responsibility for the quality and use of the obtained information. Consequently, the user should be held accountable for appropriate training, application, documentation, and interpretation of HCU data.

Minimum Knowledge Required for Performance and Interpretation. Competence in performing and/or interpreting echocardiography using an HCU requires all of the basic knowledge of ultrasound physics, instrumentation, cardiac anatomy, physiology, and pathology described in the sections on General Principles and Adult Transthoracic Examination.

Training Requirements. Training and credentialing recommendations for physicians performing and interpreting adult TTE have been discussed in detail in Section C. We endorse the ASE recommendations that individuals employing an HCU specifically for cardiovascular education or self-instruction should have at least a basic Level 1 of training, as outlined on Table 5. However, Level 1 training may not be adequate for the independent performance and interpretation of a clinical HCU examination. In this setting, we recommend Level 2 training as defined in Table 5. Individuals with less training must consult directly with an echocardiographer with Level 2 or 3 training. This will safeguard the patients' interests and ensure accurate diagnoses, optimal management, and appropriate use of more expensive comprehensive examinations when necessary.

Proof of Competence. Depending on its use (i.e., adult transthoracic, pediatrics, or adult congenital) the user of an HCU is expected to meet the full competence requirements of that specific application.

Maintenance of Competence. Recommendations for maintenance of competence are identical to those outlined under the specific application, such as transthoracic, pediatric, or adult congenital. Physicians with competence in each of these areas automatically have competence in using an HCU for these applications.

2. Contrast Echocardiography.
Overview and Indications for the Procedure. Intravenous contrast agents are available for enhancing endocardial border delineation and improving the Doppler signal. The use of contrast with harmonic imaging provides opacification of the left ventricular cavity and improved endocardial border detection. The technique is especially useful in obese patients and those with lung disease. Stress echocardiography examinations can be challenging, and a short acquisition time is essential in delineating regional wall motion abnormalities induced by peak exercise. The use of contrast can improve the ability to obtain diagnostic information and/or increase diagnostic accuracy. The ASE Task Force on Contrast Echocardiography states that "Intravenous contrast agents demonstrate substantial value in the difficult-to-image patient with comorbid conditions that limit an ultrasound evaluation of the heart" (21). Future applications may include the evaluation of myocardial perfusion at rest or during exercise or pharmacologic stress.

Minimum Knowledge Required for Performance and Interpretation. Competence in the performance and interpretation of contrast echocardiography requires all of the basic knowledge of ultrasound physics, instrumentation, cardiac anatomy, physiology, and pathology described in the preceding sections. Unique to contrast echocardiography is the need to understand microbubble characteristics and their interactions with cardiac ultrasound, along with the indications and contraindications for various contrast agents.

Training Requirements. The basic prerequisites for independent competence in echocardiography (Level 2 training) must be met before or during the training experience with contrast. The operator performing contrast echocardiography in conjunction with other special cardiovascular ultrasound examinations, such as stress, perioperative, and TEE, must be in the process of completing or must have completed, the additional subspecialty training credentials recommended in this document.

Proof and Maintenance of Competence. Contrast echocardiography technology is currently evolving, and proof-of-competence and maintenance of competence recommendations have not been established. For now, it is accepted that physicians with Level 2 competence in echocardiography who have learned how to apply contrast agents and interpret contrast-enhanced studies are competent.

3. Intracoronary and Intracardiac Ultrasound.
Overview and Indications for the Procedure. Intracoronary ultrasound is performed with a miniaturized flexible ultrasound catheter that provides detailed information of the vessel wall (22). The high frequency transducers (e.g., 20 to 40 MHz) enable the acquisition of high-resolution images with limited depth of penetration. Today, this technology is not considered as an alternative to angiography but, rather, a complementary diagnostic technique. The clinical advantages associated with the use of intracoronary ultrasound have not yet been fully established in randomized trials. However, there is increasing evidence from large prospective studies that ultrasound guidance improves the results of catheter-based intracoronary interventions in terms of immediate lumen enlargement, reduced procedure-related complications, and long-term prevention of restenosis (23-25). Although intracoronary ultrasound has become a routinely applied diagnostic technique in interventional cardiology, few attempts have been made to standardize the examination procedure, the definitions, and the format of reporting qualitative and quantitative data. Indications for intracoronary ultrasound in association with coronary interventions include: 1) lesion assessment and selection of treatment; 2) detection and characterization of vascular/plaque calcium; 3) delineation of plaque eccentricity; 4) identification of type of vessel remodeling; and 5) intracoronary guidance during balloon angioplasty, directional atherectomy, and stent placement.

Intracardiac ultrasound catheters are of larger caliber and are suitable for entering larger vessels and fluid-filled cavities (26). This technology has been used to define cardiovascular anatomy, to guide procedures, and to assess the results of interventions. There are currently two cathetertipped ultrasound transducer technologies: 1) radially arranged piezoelectric elements or rotating element transducers, which generate a two-dimensional radial image; and 2) linear or phased array transducers, which generate a longitudinal two-dimensional image. The intracardiac transducers are of lower frequency (5 to 10 MHz) to enable a greater depth of image penetration into blood or fluid containing cavities and contiguous structures. The phased-array technology also incorporates a full complement of imaging, Doppler, and articulation features.

The use of intracardiac ultrasound has not been fully tested in randomized trials. However, it is reported that this technology can be used to: 1) guide and access the result of an interventional procedure and better visualize cardiovascular anatomy and physiology; 2) reduce radiation exposure; 3) substitute for TEE during interventional procedures; 4) aid in positioning interventional devices; 5) provide echo and Doppler anatomic and hemodynamic information; and 6) direct an atrial septostomy.

Minimum Knowledge Required for Performance and Interpretation. There are no currently published standards defining the minimum requirements for performance and interpretation of intracoronary or intracardiac ultrasound. However, similar to other emerging new technologies, competence in performing and/or interpreting the ultrasound examination requires all of the basic knowledge of ultrasound physics, instrumentation, cardiovascular anatomy, physiology, and pathology described in the sections on General Principals and TTE. Physicians performing the examination must also have skills in inserting and manipulating the catheter to obtain the required views and knowledge of normal anatomy and pathology of the structures seen with the ultrasound catheter.

Training and Competence Requirements. Training and competence requirements have not been defined. However, competence will assuredly require a minimum training comparable to Level 2 and a repetitive exposure to the technique consistent with the recommendations for other emerging technologies.

4. Echo-Directed Pericardiocentesis.
Overview and Indications for the Procedure. Cardiac tamponade is a serious, potentially life threatening, condition that can be clinically challenging from both diagnostic and therapeutic perspectives. Presenting symptoms can be diverse and nonspecific (i.e., tachycardia, hypotension, increased jugular venous pressure, pulsus paradoxus) and may therefore be misinterpreted. Two-dimensional and Doppler echocardiography can readily confirm the presence of an effusion and provide accurate assessment of its hemodynamic significance.

Historically the percutaneous pericardiocentesis procedure was essentially "blind," and serious complications were common. The introduction of echo-guided pericardiocentesis has substantially decreased both the major (1.2%) and minor complications (3.5%) of this procedure (27). Echoguided pericardiocentesis is much less expensive and traumatic than a surgical pericardiocentesis. In addition, the echo-guided approach has resulted in the common use of a pericardial catheter for intermittent drainage, which has further reduced recurrence rates and the need for surgical management of the effusion. Echo-guided pericardiocentesis is considered to be the primary therapy for patients with clinically significant effusions, and it is often the definitive therapy. Success in the relief of tamponade is reported to be 97%, single needle passage provides access to the effusion in 89% of patients.

Minimum Knowledge Required for Performance and Interpretation. Competence in performing an echo-directed pericardiocentesis requires a basic knowledge of ultrasound physics, instrumentation, cardiac anatomy, physiology, and pathology as described in the sections on General Principals and TTE. In addition, physicians performing the procedure must have procedural skills in localizing the optimal entry site (i.e., where the fluid is closest to the skin surface), introducing the needle into the pericardial space, passing the guiding wire, and introducing a draining catheter when required.

Training Requirements. Physicians performing an echo-guided pericardiocentesis must meet established training and credentialing recommendations for performing a state-of-the-art limited or complete echocardiographic examination. Although training requirements have not been formally published, we recommend that trainees have at least a Level 2 echocardiography training and be personally tutored by an experienced Level 2 or 3 echocardiographer in the performance of at least 5 to 10 echo-guided pericardiocenteses.

Maintenance of Competence. There are no established competence criteria beyond those for adult TTE. However, it is essential to maintain a high level of echocardiographic skill and review the essentials of the echo-guided pericardiocentesis technique frequently.