CAM 20227

Acoustic Cardiography

Category:Medicine   Last Reviewed:July 2019
Department(s):Medical Affairs   Next Review:July 2999
Original Date:July 2012    

Description:
Acoustic cardiography is a technique that simultaneously records the electrical and acoustical aspects of the heart. By integrating the acoustic and electric properties, acoustic cardiography is intended to enhance the diagnostic ability of simple auscultation. The information from acoustic cardiography has also been used to optimize hemodynamic parameters for device placement, particularly with cardiac resynchronization therapy (CRT).

Background
Acoustic cardiography utilizes three inputs: a singe electrocardiogram (EKG) lead from two standard electrodes and two audio sensors placed at the usual V3 and V4 positions of the chest. These three channels synchronously record electrical and audio information. The audio information is processed using wavelet signal processing techniques and a diagnostic algorithm that filters out extraneous noise and uses time-frequency analysis to objectively define the heart sounds and the intervals between sounds. An analogue visual display of the audio data is then displayed and paired with the electrical data from the EKG recording.

Output from acoustic cardiography can generate numerous parameters, some of which may have clinical applicability. Three of these measures are: 1)  S3 strength - a quantitative measure of the intensity of the S3 heart sound, which is an abnormal sound that is associated with systolic dysfunction; 2)  electromechanical activation time (EMAT), defined as the interval between the onset of the QRS complex and the closure of the mitral valve. EMAT is the main parameter that is used to optimize CRT therapy by choosing the interval that optimizes cardiac output; 3) left ventricular systolic time (LVST), defined as the interval between mitral valve closure and aortic valve closure. This length of the LVST has been correlated with changes in ejection fraction.

Auscultation for an S3 is part of the physical exam when evaluating for presence of heart failure. The presence of an S3 indicates systolic dysfunction and is a specific physical exam finding supporting systolic heart failure. The S3 is an indistinct sound that can be difficult to hear and is not present in all patients with systolic dysfunction. Other components of the diagnostic evaluation for heart failure include a variety of clinic symptoms and physical exam findings such as dyspnea, orthopnea, pulmonary rales, increased jugular venous pressure and peripheral edema. Routine diagnostic evaluation for heart failure also includes measurement of brain natriuretic peptide (BNP) and other common laboratory measures, and a chest X-ray. A direct measure of ejection fraction by echocardiography, nuclear medicine imaging or other imaging modalities is a crucial component of clinical evaluation for heart failure. Systolic dysfunction can be confirmed by echocardiography and/or other imaging modalities.

Optimization of CRT therapy is usually done using Doppler echocardiography. Optimization involves manipulation of the atrioventricular (AV) and interventricular (VV) pacer settings in order to maximize left ventricular (LV) filling and stroke volume. Some evidence has reported that optimization improves overall clinical benefit, but these data are not uniform. Also, the question of whether re-optimization should be performed following initial optimization is controversial, as is the timing of re-optimization if it is performed.

Regulatory Status
The AudicorTM system and electrodes received 510(k) marketing clearances from the U.S. Food and Drug Administration (FDA) for "use in acquiring, analyzing and reporting EGG and heart sounds (phonocardiograph) data and to provide interpretation of the data for consideration by physicians."

Related Policies
20210 Biventricular Pacemakers (Cardiac Resynchronization Therapy) for the Treatment of Heart Failure

Policy:
Acoustic cardiography is considered INVESTIGATIONAL for the diagnosis of heart failure and for the optimization of CRT hemodynamic parameters.

Benefit Application
Blue Card®/National Account Issues
State or federal mandates (e.g., FEP) may dictate that all FDA-approved devices, drugs or biologics may not be considered investigational, and, thus, these devices may be assessed only on the basis of their medical necessity.

Rationale
Most studies of acoustic cardiography identified in the literature evaluate the technology in two general areas. First, it has been used as an aid for the diagnosis of systolic dysfunction, primarily using S3 detection, or S3 strength, compared with auscultation alone. Other studies have used acoustic cardiography for optimization of cardiac resynchronization therapy (CRT), utilizing the parameter of electromechanic activation time (EMAT) and comparing this method of optimization with Doppler echocardiography. These two categories of evidence are examined separately as follows.

In patients with suspected heart failure, does acoustic cardiography improve the ability to diagnose systolic dysfunction?

Michaels et al.(3) evaluated whether acoustic cardiography improved detection of S3 and S4 in 90 patients referred for angiography. A total of 35 subjects at various levels of clinical experience, from medical student to attending, listened to recordings of each patient’s heart sounds using auscultation alone, and then using both auscultation and acoustic cardiography. The criterion standard for the presence or absence of heart sounds was the consensus of two experienced readers who were blinded to other aspects of the study.

There was improvement in the ability to detect S3 in each cohort of clinical training, with overall accuracy improving by between 2 percent to 18 percent. The improvement in accuracy was statistically significant for more experienced trainees but not for medical students. For example, using auscultation alone, residents detected an S3 correctly in 68 percent of patients. This improved to 85 percent when auscultation was combined with acoustic cardiography. For attending physicians, the accuracy of S3 detection was 72 percent with auscultation alone, and this was improved to 80 percent (p<0.01) with the addition of acoustic cardiography.

Maisel et al.(4) evaluated the predictive ability of acoustic cardiography for acute heart failure in 995 patients older than 40 years who presented to the emergency department with dyspnea. The main parameter used was the strength of the S3 sound graded on a 0 to 10 scale. The criterion standard for the diagnosis of acute heart failure (AHF) was consensus by two cardiologists who were blinded to the results of acoustic cardiography. For the entire population, the S3 strength was predictive of AHF in univariate analysis but was not an independent predictor in multivariate analysis. For the subpopulation of patients who were labeled as “gray zone” patients based on an intermediate level of brain natriuretic peptide (BNP; 100-499 pg/mL), the information from acoustic cardiography improved the diagnostic accuracy of AHF from 47 percent to 69 percent. Another potentially problematic subgroup examined was obese patients (body mass index >30), in whom auscultation is often more difficult. In this population, the sensitivity of S3 detection improved from 14 percent to 28 percent with the addition of acoustic cardiography, but the specificity decreased from 99 percent to 88 percent.

A second study compared the diagnostic accuracy of acoustic cardiography with BNP in 433 patients who had results from acoustic cardiography, BNP and echocardiography.(5) Echocardiography was used as the criterion standard to diagnose of systolic dysfunction. When compared with BNP alone, acoustic cardiography was more accurate in diagnosing systolic dysfunction (area under the curve [AUC], 0.88 vs. 0.67, respectively; p<0.001). When confined to patients with BNP levels in the indeterminate range, acoustic cardiography also outperformed BNP in diagnosing systolic dysfunction (AUC, 0.89 vs. 0.64, respectively; p<0.001).

Wang et al.(6) evaluated the ability of acoustic cardiography to distinguish between patients who had heart failure with systolic dysfunction (n=89), heart failure with normal systolic function (n=94) and hypertension without clinical heart failure (n=109). All patients underwent acoustic cardiography and echocardiography, and the diagnostic accuracy of acoustic cardiography was compared with echocardiography. For distinguishing patients with hypertension from patients with heart failure and normal systolic function, the sensitivity of acoustic cardiography was 55 percent, the specificity was 90 percent and AUC was 0.83. For distinguishing heart failure and normal systolic function from heart failure with systolic dysfunction, the sensitivity of acoustic cardiography was 53 percent, the specificity was 91 percent and AUC was 0.81. These values were not significantly different from echocardiography for any of the measures reported.

In a subsequent study, Wang et al. evaluated the ability of acoustic cardiography to identify severe systolic dysfunction (left ventricular ejection fraction [LVEF], ≤ 35 percent) and/or severe diastolic dysfunction (presence of a restrictive LV filling pattern) in patients with heart failure with reduced ejection fraction.(7) The study included 127 adult inpatients with heart failure with reduced ejection fraction. All patients underwent acoustic cardiography and echocardiography, and the diagnostic accuracy of acoustic cardiography was compared with echocardiography. The authors used a Systolic Dysfunction Index (SDI) to quantify systolic dysfunction on acoustic cardiography. The SDI was based on S3 score, QRS duration, QR interval and percent EMAT and was mapped onto a scale of 0 to 10, where an SDI greater than 5 indicates an LVEF less than 50 percent, and an SDI greater than 7.5 indicates an LVEF less than 35 percent and elevated LV filling pressure. An SDI greater than 5 was the best predictor to discriminate patients with LVEF less than or equal to 35 percent from those with moderate systolic dysfunction (LVEF between 35 percent and 50 percent), associated with an AUC of 0.79 (95 percent confidence interval [CI], 0.71 to 0.87), with sensitivity of 87 percent and specificity of 60 percent. For the subgroup of 122 patients with diastolic dysfunction, an S3 score greater than 4 best predicted a restrictive filling pattern, associated with an AUC of 0.76 (95 percent CI, 0.67 to 0.84), with sensitivity of 81 percent and specificity of 55 percent.

Section Summary
Acoustic cardiography may improve the accuracy of detection of an S3 heart sound, although this finding has not been consistent in all subgroups examined. Acoustic cardiography has not been demonstrated to be an independent predictor of the diagnosis of acute heart failure when combined with other relevant clinical information. To demonstrate an incremental benefit in the diagnosis of heart failure, the improvement in diagnostic accuracy with and without acoustic cardiography must be in the context of the entire spectrum of clinical information collected routinely in the workup of a patient with suspected heart failure. For example, two studies report that acoustic cardiography improves the accuracy of heart failure diagnosis for patients with a “gray zone” BNP. However, a gray zone BNP does not necessarily mean the diagnosis of heart failure is uncertain when all clinical information is considered. Therefore, this type of evidence is not sufficient to conclude that acoustic cardiography improves the diagnosis of heart failure. Acoustic cardiography measurements correlated with echocardiographic findings in patients with heart failure in several studies. However, whether a strategy of patient management using acoustic cardiography leads to improved clinical outcomes has not been demonstrated.

In patients treated with a CRT device, does optimization of hemodynamic parameters by acoustic cardiography improve outcomes, compared with optimization by Doppler echocardiography?

Toggweiler et al.(8) reported that optimization of CRT settings by EMAT resulted in improved measures of clinical and hemodynamic factors such as work capacity, maximum oxygen uptake, ejection fraction and end systolic volume. However, this study did not compare EMAT with Doppler echocardiography and, thus, does not offer relevant data on this question.

Zuber et al.(9) reported the correlation of optimal atrioventricular (AV) and interventricular (VV) intervals, as determined by echocardiography and acoustic cardiography in 43 patients with a CRT device. There was a high correlation for the optimal AV delay intervals (r=0.86, p<0.001) and a moderate correlation for the VV delay intervals (r=0.58, p<0.05). These authors also reported that the test-retest reproducibility was higher for the EMAT method (r=0.91) than for echocardiography (r=0.35) and that the intraobserver variability was similar for EMAT versus echocardiography (9.9 percent vs. 8.5 percent, respectively).

In a similar study, Hasan et al.(10) reported the correlation of acoustic cardiography and echocardiography for optimization of CRT in 22 subjects. The correlation between the overall values as determined by each method was high (r=0.90, p<0.001). In most patients (77.3 percent), the values obtained from echocardiography and acoustic cardiography were within 20 ms of each other. The authors also reported that acoustic cardiography took less time to perform and was easier to interpret.

Taha et al.(11) also evaluated the correlation of acoustic cardiography with echocardiography for optimization of CRT settings, using the parameter of S3 signal strength rather than EMAT. There was a high correlation between the two parameters for optimization of AV delay (r=0.86, p<0.001) and a somewhat lower correlation for optimization of VV delay (r=0.64, p<0.001). For VV delay, the optimal intervals were identical in 56 percent of patients, and for VV delay, the optimal intervals were identical in 75 percent of patients.

Zuber et al.(12) evaluated the agreement in optimal AV and VV values using a number of different optimization methods in 20 patients treated with a CRT device. The different methods included various sequencing of Doppler echocardiography and EMAT parameters. There was poor agreement between the different methods of optimization, and there was not one method that was clearly preferable to the others.

Section Summary
There is a high correlation between optimization of CRT settings by Doppler echocardiography and acoustic cardiography using EMAT values. EMAT may be simpler and easier to perform compared with Doppler echocardiography. However, it is extremely unlikely that clinical centers performing CRT optimization would not have expertise in performing echocardiography for this purpose. There is no evidence that health outcomes are improved when using acoustic cardiography for optimization compared to echocardiography.

Other Applications of Acoustic Cardiography
Acoustic cardiography has been evaluated in small studies in settings other than CRT optimization and the diagnosis of heart failure.

Toggweiler et al. reported results of a prospective cohort study to evaluate the role of acoustic cardiography in follow-up for left ventricular function among patients who had undergone an anthracycline-containing chemotherapy regimen.(13) The study included 187 patients who had undergone anthracycline treatment for a variety of cancers at a single institution. At baseline, at completion of anthracycline-containing chemotherapy and at long-term follow-up, patients underwent evaluation with echocardiography and acoustic cardiography. Left ventricular function was evaluated with acoustic cardiography using EMAT values. Over a mean follow-up of 3.8 years, the mean LVEF, measured by echocardiography, decreased from 64 percent at baseline to 61 percent postchemotherapy (p<0.001) and remained at 61 percent at late follow up (p<0.01 vs. baseline). Mean EMAT increased from 80 ms at baseline to 84 postchemotherapy (p<0.01), and increased to 89 at late follow-up (p<0.01 vs. baseline). The relative percent change in EMAT correlated with relative changes in the LVEF (r=-0.33, p<0.01). Eight patients (4 percent) developed systolic dysfunction. A percent change in EMAT of greater than 12.4 percent after chemotherapy had a sensitivity and specificity of 88 percent and 85 percent, respectively, for identifying patients with systolic dysfunction. The authors recommend the use of acoustic cardiography for monitoring patients based on the high sensitivity and specificity for identifying systolic dysfunction. However, this study is limited by relatively small size, single-center design and a limited number of cancer diagnoses that were included, which makes generalizing the results to wider patient care difficult.

Chan et al. evaluated the role of acoustic cardiography in the evaluation of the severity of pulmonary arterial hypertension (PAH) in a prospective case-control study of 40 cases with PAH and 130 controls without clinical or hemodynamic evidence of PAH.(14) The intensity (measured by peak-to-peak amplitude and expressed in mV) and complexity (measured as a dimensionless index based on spectral analysis) of S1 and S2 were evaluated. Patients with PAH were found to have significantly greater S2 complexity compared with controls (p<0.001 for both lead V3 and V4 position); S2 complexity was associated with mean pulmonary artery pressure among patients with PAH (r=0.55, p<0.001). The clinical implications of these findings are not well-defined.

Summary
Acoustic cardiography is a technique that integrates electric and acoustic information to enhance the ability to detect and characterize heart sounds. Published literature has evaluated the use of acoustic cardiography primarily in two areas: (1) as an aid in the diagnosis of heart failure and (2) for optimization of hemodynamic parameters in patients with a cardiac resynchronization therapy (CRT) device.

A number of published articles support that acoustic cardiography improves the detection of an S3 compared with auscultation alone. In addition, heart failure-related findings on acoustic cardiography correlate with echocardiographic findings. However, there is no evidence that acoustic cardiography contributes independent predictive information when added to a standard clinical workup for heart failure that includes physical exam findings, laboratory testing and routine imaging studies.

When used to optimize CRT settings, several studies report that acoustic cardiography has a high correlation with Doppler echocardiography. No studies have demonstrated that acoustic cardiography is superior to echocardiography for this purpose, and, therefore, there is no evidence that acoustic cardiography improves outcomes when used for optimization of CRT.

Clinical Practice Guidelines and Position Statements
The American College of Cardiology Foundation and the American Heart Association published updated guidelines on the management of heart failure in 2013.(15) The guidelines discuss the use of acoustic cardiography in the diagnostic evaluation of patients with suspected acutely decompensated heart failure and state that acoustic cardiography is one of several diagnostic options that are not yet validated.

References:

  1. Erne P. Beyond auscultation--acoustic cardiography in the diagnosis and assessment of cardiac disease. Swiss Med Wkly 2008; 138(31-32):439-52.
  2. Bertini M, Delgado V, Bax JJ et al. Why, how and when do we need to optimize the setting of cardiac resynchronization therapy? Europace 2009; 11 Suppl 5:v46-57.
  3. Michaels AD, Khan FU, Moyers B. Experienced clinicians improve detection of third and fourth heart sounds by viewing acoustic cardiography. Clin. Cardiol. 2010; 33(3):E36-42.
  4. Maisel AS, Peacock WF, Shah KS et al. Acoustic cardiography S3 detection use in problematic subgroups and B-type natriuretic peptide "gray zone": secondary results from the Heart failure and Audicor technology for Rapid Diagnosis and Initial Treatment Multinational Investigation. Am J Emerg. Med 2011; 29(8):924-31.
  5. Kosmicki DL, Collins SP, Kontos MC et al. Noninvasive prediction of left ventricular systolic dysfunction in patients with clinically suspected heart failure using acoustic cardiography. Congest Heart Fail 2010; 16(6):249-53.
  6. Wang S, Lam YY, Liu M et al. Acoustic cardiography helps to identify heart failure and its phenotypes. Int J Cardiol 2012.
  7. Wang S, Fang F, Liu M et al. Rapid bedside identification of high-risk population in heart failure with reduced ejection fraction by acoustic cardiography. Int J Cardiol 2013; 168(3):1881-6.
  8. Toggweiler S, Zuber M, Kobza R et al. Improved response to cardiac resynchronization therapy through optimization of atrioventricular and interventricular delays using acoustic cardiography: a pilot study. J Card Fail 2007; 13(8):637-42.
  9. Zuber M, Toggweiler S, Quinn-Tate L et al. A comparison of acoustic cardiography and echocardiography for optimizing pacemaker settings in cardiac resynchronization therapy. Pacing Clin Electrophysiol 2008; 31(7):802-11.
  10. Hasan A, Abraham WT, Quinn-Tate L et al. Optimization of cardiac resynchronization devices using acoustic cardiography: a comparison to echocardiography. Congest Heart Fail 2006; 12 Suppl 1:25-31.
  11. Taha N, Zhang J, Ranjan R et al. Biventricular pacemaker optimization guided by comprehensive echocardiography-preliminary observations regarding the effects on systolic and diastolic ventricular function and third heart sound. J Am Soc Echocardiogr 2010; 23(8):857-66.
  12. Zuber M, Toggweiler S, Roos M et al. Comparison of different approaches for optimization of atrioventricular and interventricular delay in biventricular pacing. Europace 2008; 10(3):367-73.
  13. Toggweiler S, Odermatt Y, Brauchlin A et al. The clinical value of echocardiography and acoustic cardiography to monitor patients undergoing anthracycline chemotherapy. Clin Cardiol 2013; 36(4):201-6.
  14. Chan W, Woldeyohannes M, Colman R et al. Haemodynamic and structural correlates of the first and second heart sounds in pulmonary arterial hypertension: an acoustic cardiography cohort study. BMJ Open 2013; 3(4).
  15. Yancy CW, Jessup M, Bozkurt B et al. 2013 ACCF/AHA Guideline for the Management of Heart Failure: A Report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. Circulation 2013; 128(16):e240-e327.

Coding Section

Codes Number Description
CPT  

See Policy Guidelines

ICD-9-CM Diagnosis   Diagnosis Investigational for all diagnoses
ICD-10-CM (effective 10/01/15)   Investigational for all diagnoses
  I11.0 Hypertensive heart disease with heart failure
  I50.1-I50.9 Heart failure code range
  Z45.018 Encounter for adjustment and management of other part of cardiac pacemaker
  Z45.09 Encounter for adjustment and management of other cardiac device
ICD-10-PCS (effective 10/01/15)   ICD-10-PCS codes are only used for inpatient services.
  4A02X4Z Measurement, cardiac, external, electrical activity
  4A02XHZ Measurement, cardiac, external, sound

Procedure and diagnosis codes on Medical Policy documents are included only as a general reference tool for each policy. They may not be all-inclusive. 

This medical policy was developed through consideration of peer-reviewed medical literature generally recognized by the relevant medical community, U.S. FDA approval status, nationally accepted standards of medical practice and accepted standards of medical practice in this community, Blue Cross and Blue Shield Association technology assessment program (TEC) and other non-affiliated technology evaluation centers, reference to federal regulations, other plan medical policies and accredited national guidelines.

"Current Procedural Terminology© American Medical Association.  All Rights Reserved" 

History From 2014 Forward     

07/09/2019 

Annual review, no change to policy intent. 

07/30/2018 

Annual review, no change to policy intent. 

07/31/2017 

Annual review, no change to policy intent 

07/13/2016

Annual review, no change to policy intent. 

07/06/2015 

Annual review, no change to policy intent. Added coding. 

07/29/2014

Annual review. Added related policy. Updated rationale and references. No change to policy intent.


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