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Laboratory Structure
The laboratory structure can be divided into a minimum of four components: the physical laboratory, the equipment, the sonographer, and the physician. The ASE has previously addressed the issue of quality of the laboratory, sonographers, and physicians in its proposed local coverage determination ( http://www.asefiles.org/LCD.pdf ).
Physical Laboratory
Existing echocardiography laboratories should be accredited by the Intersocietal Commission for the Accreditation of Echocardiography Laboratories. New laboratories should have processes for moving the laboratories toward laboratory accreditation by submitting applications within 2 years of the onset of operation. The ASE recognizes that the process of lab accreditation is resource intensive and may require the commitment of additional personnel.
Laboratory accreditation alone, however, is not sufficient, as there are facets of laboratory operation and needs for laboratory policies that are not currently addressed by the laboratory accreditation process of the Intersocietal Commission for the Accreditation of Echocardiography Laboratories. For example, in addition to the typical methods for requesting an echocardiographic study, a mechanism should be in place for ordering urgent echocardiographic studies and for communicating the urgency of studies to the laboratory staff members and interpreting physicians. This mechanism should be understood by all ordering physicians. Sufficient support staff members should be available to assist with scheduling and reporting of studies and to ensure the timely relay of results to ordering clinicians. Sufficient laboratory staff members must be able to recognize and respond to common medical emergencies and have competency in basic life support skills.
The laboratory space must have the necessary sanitizing equipment, ranging from a designated room to perform high-level disinfection of transesophageal echocardiographic (TEE) probes to necessary cleansing products for the transthoracic echocardiographic (TTE) transducers, ultrasound machines, and beds. Sinks and approved hand cleaners must be readily available in each area in which echocardiography is performed.
Equipment
The equipment available for the performance of echocardiographic procedures must be capable of performing two-dimensional, M-mode, and color and spectral (both flow and tissue) Doppler imaging. The display must be able to identify the institution, patient name, and date and time of study. The electrocardiogram and depth or flow velocity calibrations must be present on all displays. The machines should have the capability to display other physiologic signals, such as phases of respiration. If the laboratory performs stress echocardiography, a sufficient number of machines must have software that allows split-screen and quad-screen display for simultaneous image comparison. Transducers that can provide high-frequency and low-frequency imaging, as well as a dedicated nonimaging continuous-wave Doppler transducer, must be available for transthoracic imaging. Pediatric laboratories must have transducers that cover the proper frequency range for high-resolution imaging of patients of the variety of sizes present in the pediatric population. Transesophageal imaging probes should be multiplane. All machines should have harmonic imaging capabilities and other instrument settings to enable the optimization of both standard and contrast-enhanced ultrasound exams.
Each machine must also have a digital image storage method that should be compatible with Digital Imaging and Communications in Medicine standards. Study images must be maintained for the time period mandated for medical record retention in individual states.
Contrast agents and intravenous supplies should be available for staff members to use for patients who are difficult to image. Echocardiographic imaging beds, which include a drop-down portion of the mattress to facilitate apical imaging, are recommended. Equipment required to treat medical emergencies, including oxygen, suction, and “code” carts, must be available.
The accuracy of all laboratory imaging equipment should be tested, and laboratories should adhere to manufacturers’ recommendations regarding preventive maintenance. The results of this testing and all service records for all equipment must be maintained in the laboratory.
Sonographer
Each sonographer should achieve and maintain minimum standards in education and credentialing within 2 years of the start of employment. This includes the initial education required to be eligible for credentialing exams and the continuing education required to ensure competency, maintain credentials, and become familiar with the latest technologies. Credentialing can be as a registered diagnostic cardiac sonographer through the American Registry of Diagnostic Medical Sonographers or as a registered cardiac sonographer through Cardiovascular Credentialing International. For sonographers who perform pediatric or fetal echocardiography, the minimum standard includes more specialized credentials. Some sonographers may be required to have a work experience component prior to eligibility for credentialing exams, and so it is recognized that laboratories may employ some sonographers who may not yet have credentials. However, in such circumstances, a credentialed sonographer should be immediately available to provide supervision. A majority of the echocardiographic studies in a laboratory should be performed by a credentialed sonographer, and a majority of the sonographers should have appropriate cardiac sonographer credentials. The laboratory should demonstrate a process aimed at having all sonographers credentialed. Local or state requirements, including licensure, may also exist for sonographers and must be fulfilled.
Physician
All physicians independently interpreting echocardiograms must have a minimum of level II training in TTE imaging as defined by the American College of Cardiology/American Heart Association/American College of Physicians-American Society of Internal Medicine Task Force on Clinical Competence in Echocardiography or its equivalent and must meet annual criteria to maintain that competence. Those who trained prior to the incorporation of this level of training in fellowship programs must have achieved adequate training through an experience-based pathway and must meet annual criteria for maintaining competence. Demonstration of special competency and board certification through passing a National Board of Echocardiography examination is desirable. Each laboratory should have a physician director who has completed level III training in echocardiography. If this is not feasible, a combination of level II training and current certification from the National Board of Echocardiography is acceptable, though less desirable.
The different types of echocardiographic studies will require different levels of physician supervision. For diagnostic tests billed to the Centers for Medicare and Medicaid Services, specific levels of physician supervision are mandated. Currently there are three categories determined by the Centers for Medicare and Medicaid Services: those requiring “general supervision” (a physician provides general oversight and need not be on site), those requiring “direct supervision” (a physician must be in the office suite and immediately available), and those requiring “personal supervision” (a physician must be in the room). The physician lab director must ensure that the various types of echocardiographic studies are appropriately supervised. At a minimum, the Centers for Medicare and Medicaid Services regulations should be followed. However, some laboratories may impose more stringent requirements.
Laboratory Structure
The laboratory structure can be divided into a minimum of four components: the physical laboratory, the equipment, the sonographer, and the physician. The ASE has previously addressed the issue of quality of the laboratory, sonographers, and physicians in its proposed local coverage determination ( http://www.asefiles.org/LCD.pdf ).
Physical Laboratory
Existing echocardiography laboratories should be accredited by the Intersocietal Commission for the Accreditation of Echocardiography Laboratories. New laboratories should have processes for moving the laboratories toward laboratory accreditation by submitting applications within 2 years of the onset of operation. The ASE recognizes that the process of lab accreditation is resource intensive and may require the commitment of additional personnel.
Laboratory accreditation alone, however, is not sufficient, as there are facets of laboratory operation and needs for laboratory policies that are not currently addressed by the laboratory accreditation process of the Intersocietal Commission for the Accreditation of Echocardiography Laboratories. For example, in addition to the typical methods for requesting an echocardiographic study, a mechanism should be in place for ordering urgent echocardiographic studies and for communicating the urgency of studies to the laboratory staff members and interpreting physicians. This mechanism should be understood by all ordering physicians. Sufficient support staff members should be available to assist with scheduling and reporting of studies and to ensure the timely relay of results to ordering clinicians. Sufficient laboratory staff members must be able to recognize and respond to common medical emergencies and have competency in basic life support skills.
The laboratory space must have the necessary sanitizing equipment, ranging from a designated room to perform high-level disinfection of transesophageal echocardiographic (TEE) probes to necessary cleansing products for the transthoracic echocardiographic (TTE) transducers, ultrasound machines, and beds. Sinks and approved hand cleaners must be readily available in each area in which echocardiography is performed.
Equipment
The equipment available for the performance of echocardiographic procedures must be capable of performing two-dimensional, M-mode, and color and spectral (both flow and tissue) Doppler imaging. The display must be able to identify the institution, patient name, and date and time of study. The electrocardiogram and depth or flow velocity calibrations must be present on all displays. The machines should have the capability to display other physiologic signals, such as phases of respiration. If the laboratory performs stress echocardiography, a sufficient number of machines must have software that allows split-screen and quad-screen display for simultaneous image comparison. Transducers that can provide high-frequency and low-frequency imaging, as well as a dedicated nonimaging continuous-wave Doppler transducer, must be available for transthoracic imaging. Pediatric laboratories must have transducers that cover the proper frequency range for high-resolution imaging of patients of the variety of sizes present in the pediatric population. Transesophageal imaging probes should be multiplane. All machines should have harmonic imaging capabilities and other instrument settings to enable the optimization of both standard and contrast-enhanced ultrasound exams.
Each machine must also have a digital image storage method that should be compatible with Digital Imaging and Communications in Medicine standards. Study images must be maintained for the time period mandated for medical record retention in individual states.
Contrast agents and intravenous supplies should be available for staff members to use for patients who are difficult to image. Echocardiographic imaging beds, which include a drop-down portion of the mattress to facilitate apical imaging, are recommended. Equipment required to treat medical emergencies, including oxygen, suction, and “code” carts, must be available.
The accuracy of all laboratory imaging equipment should be tested, and laboratories should adhere to manufacturers’ recommendations regarding preventive maintenance. The results of this testing and all service records for all equipment must be maintained in the laboratory.
Sonographer
Each sonographer should achieve and maintain minimum standards in education and credentialing within 2 years of the start of employment. This includes the initial education required to be eligible for credentialing exams and the continuing education required to ensure competency, maintain credentials, and become familiar with the latest technologies. Credentialing can be as a registered diagnostic cardiac sonographer through the American Registry of Diagnostic Medical Sonographers or as a registered cardiac sonographer through Cardiovascular Credentialing International. For sonographers who perform pediatric or fetal echocardiography, the minimum standard includes more specialized credentials. Some sonographers may be required to have a work experience component prior to eligibility for credentialing exams, and so it is recognized that laboratories may employ some sonographers who may not yet have credentials. However, in such circumstances, a credentialed sonographer should be immediately available to provide supervision. A majority of the echocardiographic studies in a laboratory should be performed by a credentialed sonographer, and a majority of the sonographers should have appropriate cardiac sonographer credentials. The laboratory should demonstrate a process aimed at having all sonographers credentialed. Local or state requirements, including licensure, may also exist for sonographers and must be fulfilled.
Physician
All physicians independently interpreting echocardiograms must have a minimum of level II training in TTE imaging as defined by the American College of Cardiology/American Heart Association/American College of Physicians-American Society of Internal Medicine Task Force on Clinical Competence in Echocardiography or its equivalent and must meet annual criteria to maintain that competence. Those who trained prior to the incorporation of this level of training in fellowship programs must have achieved adequate training through an experience-based pathway and must meet annual criteria for maintaining competence. Demonstration of special competency and board certification through passing a National Board of Echocardiography examination is desirable. Each laboratory should have a physician director who has completed level III training in echocardiography. If this is not feasible, a combination of level II training and current certification from the National Board of Echocardiography is acceptable, though less desirable.
The different types of echocardiographic studies will require different levels of physician supervision. For diagnostic tests billed to the Centers for Medicare and Medicaid Services, specific levels of physician supervision are mandated. Currently there are three categories determined by the Centers for Medicare and Medicaid Services: those requiring “general supervision” (a physician provides general oversight and need not be on site), those requiring “direct supervision” (a physician must be in the office suite and immediately available), and those requiring “personal supervision” (a physician must be in the room). The physician lab director must ensure that the various types of echocardiographic studies are appropriately supervised. At a minimum, the Centers for Medicare and Medicaid Services regulations should be followed. However, some laboratories may impose more stringent requirements.
Imaging Process
Patient Selection
The appropriate selection of patients for echocardiography is essential to the delivery of effective and cost-conscious care to avoid overuse, underuse, or misuse of echocardiography. Only when the prior probability of patient benefit is sufficiently high and exceeds the risks of the test should echocardiography be performed. The goal of processes to improve patient selection for echocardiography is to minimize inappropriate studies. However, it is recognized that criteria alone cannot be used to judge appropriateness, as individual patient considerations and physician judgment should take precedence over rigid adherence to published appropriate use criteria.
To the extent possible, laboratories should track rates of appropriate and inappropriate requests for echocardiography by tracking the reasons for ordered studies and other patient information required to ascertain appropriateness. However, it is recognized that in current practice, echocardiography laboratories may not have sufficient clinical information or the resources available to determine the appropriateness of all studies. Nonetheless, it is reasonable that echocardiography laboratories should (1) ensure that all staff members understand the appropriate use criteria; (2) develop processes to reduce the number of inappropriate referrals, including the education of referring physicians; and (3) actively apply appropriate use criteria to selected procedures. On the basis of this understanding, the following recommendations regarding echocardiography utilization are made:
- 1.
At a minimum, the American College of Cardiology Foundation and ASE appropriate use criteria documents pertaining to echocardiography should be available for review in every echocardiography laboratory. As part of its quality improvement program, each laboratory should formally review these criteria annually with all sonographers and interpreting physicians. Appropriate use criteria cover the common circumstances for which echocardiographic exams may be used, but they are not intended to be all inclusive. Laboratories should also regularly review published performance measures related to imaging and national quality measures pertaining to cardiovascular ultrasound. In addition, laboratories should aim to develop and implement strategies to educate their referring providers about the appropriate use criteria, clinical scenarios in which echocardiography is commonly overused and underused, and other national standards pertaining to the optimal utilization of cardiovascular ultrasound. Multiple approaches will probably be necessary to influence physician practice behavior. Possible strategies include, but are not limited to, (1) the integration of these standards into the test ordering process, aligning the choices for procedural indication with the appropriate use criteria (see below); (2) direct mailings, faxes, or e-mails of the appropriate use criteria or summaries to referring physicians; and (3) explicit discussion of the appropriate use criteria and other optimal use standards at local continuing medical education conferences. Not all of these options will be achievable by all laboratories.
- 2.
Because TEE imaging is an invasive procedure requiring performance by a specially trained physician and involves small immediate risks for serious adverse events, all echocardiography laboratories should carefully track appropriateness of referrals for this procedure. The primary operator should be knowledgeable about the patient’s medical history and present state of health and the indication for the procedure. This level of involvement places the primary operator in a position to assess the appropriateness of the procedure he or she is being asked to perform, which should be systematically assessed for all TEE studies prior to their performance. Audits on a periodic basis of random samples of TEE reports and patient records for procedural appropriateness should be considered.
- 3.
Similarly, for stress echocardiography, all echocardiography laboratories should monitor the appropriateness of referrals. The physician or the specially trained person who directly supervises the stress test should be knowledgeable about the patient’s medical history and symptomatic status and the reason for the test so that he or she can confirm that the stress echocardiographic study is indicated and that the best mode of stress is used. Audits on a periodic basis of random samples of stress echocardiographic reports and patient records for test appropriateness should be considered.
- 4.
In the future, for best practice, a level that may not be achievable by all, laboratories should develop processes that enable them to determine if each echocardiographic study is ordered appropriately or not. This would eventually allow for systematic review of the mix of appropriate and inappropriate indications, comparison with national norms, and feedback to ordering physicians.
- 5.
With regard to other considerations, at this time, the benefits of systematic approaches to enhance the proportion of appropriate echocardiographic exams and the optimal strategies for achieving this goal have not been established. However, these recommendations provide quality metrics and a framework for internal practice assessment and improvement.
Other issues related to test utilization and patient selection should also be part of a quality echocardiography laboratory. These include the following:
- 1.
Access: A mechanism should be in place that allows tracking of the wait times for both inpatient and outpatient echocardiographic studies, and each laboratory should have standards regarding the timeliness of test performance.
- 2.
Test selection: A mechanism should be in place for the determination of the proper or best test components to be performed for each test request. This is to ensure that the correct components of a TTE or TEE study (i.e., rest, stress, limited, Doppler, three-dimensional, M-mode, shunt assessment) or the optimum stress modality (pharmacologic or exercise) is performed on the basis of the reason for the test and the characteristics of the patient.
Image Acquisition
Adequate image acquisition in echocardiography relies on a variety of components, including the patient’s condition and body habitus, satisfactory ultrasound equipment, competent technical manipulation, and consistent methods of acquisition. Sonographer credentialing helps ensure quality by verifying knowledge of technology, image acquisition, and manifestations of disease. Laboratory accreditation verifies institutional practices relating to image acquisition, by mandating consistent and complete imaging protocols. The standard integration of two-dimensional, color, and spectral Doppler modalities is required to provide a comprehensive evaluation by TTE and TEE imaging. Assessment of the number of complete studies with all components (two-dimensional, color, and Doppler) reported provides a method to estimate compliance with current imaging standards. This should be measured for each sonographer annually.
Advances in technology have led to improvements in the visualization of cardiac structures with echocardiography. All laboratories must have quality assurance policies to minimize uninterpretable or nondiagnostic studies. Such policies might include the use of contrast or other imaging modalities. In patients with technically difficult images, left-heart contrast agents provide a tool to decrease the number of nondiagnostic procedures by enhancing endocardial border definition. Laboratories should have written policies for the use of contrast agents. This should include the requirements for, and the content of, written orders for contrast administration, which may vary by site. Quantifying and monitoring the number of nondiagnostic exams determines the effective integration of contrast in the echocardiography laboratory. A complete TTE or TEE study is one that images all cardiac chambers, valves, and great vessels from a series of multiple views and performs Doppler assessment of antegrade and retrograde flow across all cardiac valves, as well as the atrial and ventricular septa.
Sufficient time must be allotted for each study according to the procedure type. Forty-five to 60 minutes should be allotted for the acquisition of the images for a complete TTE study. An additional 15 to 30 minutes may be required for complicated cases.
All studies should document the patient’s height and weight so that measurements can be indexed, when appropriate, to parameters of body size. Blood pressure and heart rate at the time of the examination should also be recorded.
Digital acquisition should include as many cardiac cycles as needed to accurately assess the cardiac structures. This may be one to two beats for image planes of normal structures, two or more beats for image planes that include abnormalities, and more extended captures for patients with arrhythmias, complex congenital heart disease, agitated saline contrast images or when diagnoses are being considered in which cardiac physiology or structure can be affected by the respiratory cycle.
The recommended images for a complete or comprehensive two-dimensional TTE study including spectral and color Doppler are listed in Table 1 . For all imaging protocols, if any view or Doppler signal that is recommended cannot be adequately obtained, it still should be recorded to demonstrate that it was attempted.
| Parasternal long axis |
| 2D image |
| M mode of left ventricle and left atrium/aorta (if lab standard) |
| Color flow Doppler of valves |
| RV inflow view |
| Color and spectral Doppler |
| Parasternal short axis |
| Short-axis view at the aortic valve level and RVOT |
| Color flow Doppler should be used to evaluate pulmonic, aortic and tricuspid valves |
| Spectral Doppler of RVOT and pulmonic valve |
| Left ventricle at MV level |
| Left ventricle at mid level |
| M mode if lab standard |
| Left ventricle at apex |
| Apical four chamber |
| 2D imaging of the four chambers (maximizing length of left ventricle) |
| Color flow Doppler of valvular inflow and regurgitation should be assessed at the valves |
| Pulsed-wave Doppler of all valves should be assessed |
| Pulsed-wave Doppler of pulmonary veins (for diastolic function) |
| Doppler tissue imaging (for diastolic function) |
| Strain and strain rate are optional |
| CW Doppler to evaluate valves |
| Multiple views should be used to get highest velocity of abnormal flows. |
| Transmitral color M mode is optional |
| Color Doppler of interatrial septum |
| Apical five chamber |
| 2D imaging |
| Color flow Doppler of LVOT |
| Pulsed-wave Doppler of LVOT if aortic stenosis or insufficiency is present or suspected or for calculation of stroke volume/cardiac output |
| CW Doppler of aortic valve if aortic stenosis is present or suspected |
| Apical two chamber |
| 2D imaging |
| Color flow Doppler of MV |
| Apical long axis |
| 2D imaging |
| Color flow Doppler to visualize aortic and mitral forward and regurgitant flow |
| Pulsed-wave Doppler of LVOT if aortic stenosis or insufficiency is present or suspected or for calculation of stroke volume/cardiac output |
| CW Doppler of aortic valve if aortic stenosis is present or suspected |
| Subcostal views |
| Four chamber |
| 2D imaging, including assessment of interatrial septum |
| Color flow at interatrial septum to assess for shunt |
| Short axis |
| Complementary to parasternal views |
| IVC assessment |
| IVC images to evaluate size and dynamics |
| Doppler of hepatic veins, when appropriate |
| Suprasternal notch |
| Long-axis view of the aortic arch |
| Pulsed-wave Doppler in descending aorta in cases of aortic regurgitation |
| Other views as indicated for further clarification or assessment of specific pathologies |
| Right parasternal view |
| Long-axis view to evaluate the ascending aorta |
| Agitated saline contrast |
| At rest and with release of Valsalva maneuver for intra-cardiac or intra-pulmonary shunting |
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