Color-Flow Doppler Echocardiography in Adults

Number: 0008

Policy

1. Aetna considers color-flow Doppler echocardiography in adults medically necessary for the following indications:

   1. Evaluation of aortic diseases
   2. Evaluation of aortocoronary bypass grafts
   3. Evaluation of hypertrophic cardiomyopathy (formerly known as idiopathic hypertrophic subaortic stenosis)
   4. Evaluation of prosthetic valves
   5. Evaluation of septal defects
   6. Evaluation of site of left-to-right or right-to-left shunts
   7. Evaluation of the severity of valve stenosis and regurgitation

2. Aetna considers color-flow Doppler echocardiography in adults experimental and investigational for all other indications (e.g., to guide catheter ablation in ventricular tachycardia) because its effectiveness for these indications has not been established.

Background

This policy is based on guidelines on diagnostic echocardiography in adults from the American College of Cardiology (Cheitlin et al, 2003).

Echocardiography is an ultrasound technique for diagnosing cardiovascular disorders.  It is subdivided into M-mode, two-dimensional (2-D), spectral Doppler, color Doppler, contrast, and stress echocardiography (Beers and Berkow, 1999).

Echocardiography is usually performed by placing a transducer over the chest.  In transesophageal echocardiography, however, the transducer is placed at the tip of an endoscope that is inserted into the esophagus (Beers and Berkow, 1999).  Even smaller transducers can be placed on intravascular catheters, permitting intravascular recordings of vessel anatomy and blood flow.

Two-dimensional (or cross-sectional) echocardiography is the dominant echocardiographic technique (Beers and Berkow, 1999; Gottdiener et al, 2004).  It uses pulsed, reflected ultrasound to provide spatially correct real time tomographic images of the heart, which are recorded on videotape and resemble cineangiograms.  Two-dimensional echocardiography provides information about the cardiac chamber size, wall thickness, global and regional systolic function, and valvular and vascular structures.  B-mode imaging refers to cross-sectional 2-D images displayed without motion, and provides detail of static structures.

M-mode (or motion-mode) echocardiography creates a continuous 1-D graphic display, and is useful for measuring single dimensions of walls and chambers of the heart, which can be used to estimate chamber volumes and left ventricular mass (Beers and Berkow, 1999; Gottdiener et al, 2004).  M-mode echocardiography is performed by directing a stationary pulsed ultrasound beam at some portion of the heart. 

The Doppler technique uses reflections from moving red blood cells to characterize blood flow (Beers and Berkow, 1999; Gottdiener et al, 2004).  Spectral Doppler echocardiography uses ultrasound to record the velocity, direction, and type of blood flow in the cardiovascular system.  The spectral Doppler signal is displayed on a strip chart recorder or videotape. 

Stress echocardiography uses any combination of the above echocardiography modalities, before and during (or shortly after) a physical or pharmacological stress intervention (Beers and Berkow, 1999; Gottdiener et al, 2004).  Most commonly, a treadmill or exercise bicycle is used for stress echocardiography.  In patients who are unable to exercise, stress testing can be performed with pharmacological agents, such as dobutamine, that increased myocardial oxygen demand, or vasodilators that produce coronary steal.  These tests have utility primarily in the detection of myocardial ischemia and viability. 

Contrast echocardiography is an M-mode or 2-D echocardiographic examination during which contrast agents are administered via venous injection (Beers and Berkow, 1999; Gottdiener et al, 2004).  Venous contrast injections are used to enhance left ventricular endocardial borders and Doppler signals and to assess myocardial perfusion.

Color Doppler echocardiography is essentially 2-D Doppler echocardiography with flow encoded in color to show its direction (red is toward and blue is away from the transducer) (Beers and Berkow, 1999; Gottdiener et al, 2004).  In color flow mapping, blood flow velocity is measured along each sector line of a 2-D echocardiographic image and is displayed as color coded pixels.  Color flow Doppler is most useful for assessing valves for regurgitation and stenosis, detecting the presence of intracardiac shunts, and imaging blood flow in the heart.

Evidence-based guidelines from the American College of Cardiology, American Heart Association, and American Society of Echocardiography (Antman et al, 2003) outlined the accepted capabilities for Doppler echocardiography in the adult patient.  Specific indications were classified as relating to "anatomy-pathology" or to "function", and each potential indication was rated from "most helpful" to "not useful."  

Among indications related to anatomy-pathology, color Doppler was rated as most helpful for evaluating septal defects (Antman et al, 2003).  Color Doppler was considered not useful for all other indications related to anatomy-pathology: evaluation of chamber size, thickness of walls, relation of chambers, early closure of mitral valve, systolic anterior motion of mitral valve, left ventricular mass, left ventricular masses (tumor, clot, vegetation), masses in atria and right ventricle, anatomic valvular pathology, and pericardial effusion. 

Among functional indications, color Doppler was considered most useful for evaluating the site of right-to-left and left-to-right shunts (Antman et al, 2003).  Color Doppler was also considered useful for evaluating severity of valve stenosis and valve regurgitation and evaluation of prosthetic valves.  Color Doppler was also considered to be of some use in evaluating aortic diseases.  Color Doppler was considered not useful for assessment of global left ventricular systolic function (ejection fraction), evaluation of regional wall motion, measurement of right ventricular and pulmonary artery systolic pressures, measurement of left ventricular filling pressure, measurement of stroke volume and cardiac output, assessment of left ventricular diastolic function, and identifying ischemia and viable myocardium with exercise or pharmacological stress.

Nishimura et al (2011) examined the significance of measurement of stenosis by aliasing coronary flow (the MOSAIC method) for the detection of proximal left coronary stenosis in patients with unstable angina (UA) by means of transthoracic Doppler echocardiography.  Patients (n = 107) with UA were evaluated.  Proximal left coronary flow was sought in the short axis at the aortic root level using color Doppler guidance.  When detected coronary flow showed color aliasing, the color velocity range was gradually increased until color aliasing nearly disappeared.  Then, the color baseline was shifted until the color flow showed "isovelocity".  Proximal coronary flow was detected in 86 (80.4 %) of 107 patients.  In these 86 patients, an optimal cut-off value of isovelocity greater than or equal to 47.5 cm/second predicted significant coronary stenosis (percent diameter stenosis greater than or equal to 70 %) of the proximal left anterior descending (American Heart Association segment 6) or left main coronary artery with a sensitivity of 88 %, specificity of 97 %, positive predictive value of 98 %, and negative predictive value of 86 %.  In all 107 patients, the same cut-off value predicted significant coronary stenosis with a sensitivity of 78 %, specificity of 98 %, positive predictive value of 98 %, and negative predictive value of 81 %.  The authors concluded that the MOSAIC method may play a complementary role in expeditious risk stratification and decision making in patients with UA.

The American College of Radiology's Expert Panel on Cardiovascular Imaging (Ho et al, 2011) states that echocardiography using color flow Doppler is essential for evaluating blood flow as seen across an atrial defect or a ventricular septal defect or across a valve.  Assessment of the valves (sclerosis, fusion, estimation of valve gradients) and determination of right ventricular systolic pressure can usually be achieved.

An UpToDate review on "Catheter ablation for ventricular arrhythmias" (Ganz, 2012) states that "[i]ntracardiac echocardiography (ICE) with 2D and Doppler color flow imaging may be useful to guide mapping and ablation catheters and monitor morphologic changes after ablation".  The reference cited was the study by Ren et al (2002) that comprised only 4 patients with ventricular tachycardia.  Thus, there is currently insufficient evidence to support the use of color-flow Doppler echocardiography during ventricular tachycardia ablation.

An UpToDate review on “Principles of Doppler echocardiography” (Manning, 2013) states that “Color flow imaging is typically used in the screening and assessment of regurgitant flows.  It is also useful in the assessment of intracardiac shunts (e.g., atrial and ventricular septal defects) and pulmonary vein flow, and to assist in continuous wave Doppler alignment for tricuspid regurgitation velocities”.

Appendix

Note on documentation requirements:

Physicians are reminded to bill the findings of the diagnostic test as the primary indication rather than the referring physician’s diagnosis, as indicated by Medicare’s Diagnostic Imaging Billing guidelines.  These guidelines are available in the Medicare Claims Processing Manual, Chapter 13 - Radiology Services and Other Diagnostic Procedures (revised November 2016).  This is also indicated in the ICD-9-CM Coding Guidelines, Section IV, Paragraph L. 

The above policy is based on the following references: