Journal of the Practice of Cardiovascular Sciences

: 2017  |  Volume : 3  |  Issue : 2  |  Page : 70--73

Novel electro-acoustic technology for the screening and management of heart failure

A Vijayasimha 
 Director, Audicor Cardiometrics Private Limited, Bangalore, India

Correspondence Address:
A Vijayasimha
Audicor Cardiometrics Private Limited, Bangalore

How to cite this article:
Vijayasimha A. Novel electro-acoustic technology for the screening and management of heart failure.J Pract Cardiovasc Sci 2017;3:70-73

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Vijayasimha A. Novel electro-acoustic technology for the screening and management of heart failure. J Pract Cardiovasc Sci [serial online] 2017 [cited 2022 May 22 ];3:70-73
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Electro-Acoustic Cardiography is a novel synthesis of two well-established diagnostic modalities electrocardiography (ECG) and phonocardiography. Conventionally, these modalities are conducted separately; however, subjecting these two orthogonal biosignals to simultaneous and concurrent analysis reveals a much greater degree of specificity in pointing to the causative factors of hemodynamic insufficiency within the heart detailing information regarding the systolic and diastolic left ventricular function. While some observational clinical studies have been carried out within the hospital, the technology holds the greatest potential as a screening tool for cardiovascular disease (CVD) prevention and management. The experiences using this user-friendly and cost-effective electro-acoustic cardiography are discussed.

 History of Electro-Acoustic Cardiography

The synthesis of the simultaneous analysis of ECG and digitally acquired heart sounds was first examined by Warner et al.[1] in 2003, in the enhanced detection of the left ventricular enlargement using a combination of ECG and phonocardiography. Classically, S3 and S4 heart sounds have strongly indicated pathologies of the left ventricle, but due to their low frequency, timing, and low intensity, the sensitivity using a stethoscope was poor. The adaptation of the enhanced Wigger's Diagram into a comprehensive bedside tool was later developed into a tightly integrated device for ambulatory use.

Shah and Michaels [2] using the Audicor system and the timing parameters that come from the combined ECG and heart sounds [Figure 1] sought to test the characteristics and physiology of the phonocardiographic S3 and systolic time intervals (STI) in two separate cohorts of 90 and 81 patients undergoing cardiac catheterization.{Figure 1}

All patients underwent the computerized phonocardiographic heart sound analysis with the Audicor system, B-type natriuretic peptide (BNP) testing, echocardiography, and invasive LV pressure measurement within a 4-h period. Mean LV end-diastolic pressure and BNP were higher, and LV ejection fraction (LVEF) was lower, in those with an S3. The sensitivities of the S3 to detect abnormalities in the LV function were only 30%–50%. However, specificity for detecting elevated LV end-diastolic pressure, elevated BNP, and decreased LVEF were high, at 92%, 87%, and 92%, respectively. Therefore, although it has limited sensitivity, the S3 detected by the Audicor system is closely related to the elevated filling pressure and also highly specific in detecting LV dysfunction. The combination of S3 and STI provided a greater sensitivity and specificity for LV dysfunction.

Efstratiadisand Michaels [3] in a study of 25 patients with heart failure concluded that an abnormal percentage electromechanical activation time (%EMAT) was strongly correlated with an impaired LV contractility and hence a lower LVEF (50.9% ± 18.6% with normal EMAT vs. 32.0% ± 10.9% with abnormal EMAT, P = 0.015), end-systolic elastance (3.07 ± 1.56 mmHg/mL vs. 1.43 ± 0.83 mmHg/mL, P = 0.018), and peak isovolumetric LV pressure at the end-diastolic volume (317 ± 90 mmHg vs. 222 ± 67 mmHg, P = 0.015). An abnormal %EMAT was also associated with a higher end-systolic volume index (33.6 ± 29.3 mL/m 2 vs. 71.0 ± 35.8 mL/m 2, P = 0.011), end-diastolic volume index (61.2 ± 29.8 mL/m 2 vs. 100.3 ± 40.8 mL/m 2, P =.012), and dyssynchrony (26.1% ± 6.0% vs. 31.5% ± 3.5%, P = 0.028). There was no difference in end-diastolic pressure (20.3 ± 7.9 mmHg vs. 21.4 ± 12.3 mmHg, P = 0.78).

Rogers et al.[4] achieved a greater diagnostic accuracy for LV hypertrophy by combining BNP with electro-acoustic cardiography. This is an example of how these distinctly orthogonal signals combine to provide a higher degree of sensitivity and specificity.

Zuber and Erne [5],[6] study confirmed the limited sensitivity (28%–33%) [Figure 2] of using standard ST depression criteria during a 12-lead ECG exercise tolerance testing (ETT), even with an intermediate pretest probability for CAD since a majority of their patients had ≥2 multiple risk factors. At similar specificity, the Audicor electro-acoustic cardiographic S4 provided improved sensitivity (52%–56%) for the detection of angiographically proven CAD. The disjunctive combination of ECG or the S4 resulted in modest improvement sensitivity (68%) at the expense of reduced specificity (84%) over just the presence of S4 alone [Table 1].{Figure 2}{Table 1}

The utility of the Audicor electro-acoustic cardiography technology encompassed the whole of the cardiac care cycle from early stage triaging to predicting the discharge outcomes, Chao et al.[7] It was recognized by heart failure specialists across the world as a competent technology for the diagnosis and monitoring of heart failure that is not only low cost and easy to use but also a modality which can perform a satisfactory examination in <3 min, something that is very desirable in a population screening program. A wearable version of the technology called the ApoPatch Dx was designed keeping in mind the point of care use and the emerging practice of telecardiology in monitoring.

 Use and Interpretation of the Significance of Audicor Biomarkers

The Audicor biomarkers, EMAT, and SDI [Figure 3] and [Figure 4] are used in conjunction with the strength and frequency of the digitally acquired S3 and S4 heart sounds, patient history, and symptoms to lead to a confirmatory diagnosis of heart failure. A 10 s report provides both an overall summary call out to the heart's function for the purpose of triage by the frontline caregiver and a detailed parametric report for the attending Cardiologist, either at the site or remotely through a telemedicine network.{Figure 3}{Figure 4}

 Case Studies

OPD examination and monitoring patient response to therapy

Presentation of patients at the Out Patient Department (OPD) accompanied with symptoms of fatigue, dyspnea, and edema in the lungs and in the lower limbs require recognizing LV hypertrophy, LV systolic dysfunction, arrhythmias, and MI as the first level of triage in heart failure, as in the patient expressing symptoms with uncontrolled hypertension (s210/d110) despite compliance to the medication of ACE inhibitors, beta-blockers, and calcium channel blocker prescribed exhibiting elevated markers in the compromised heart performance, namely, EMAT, S4, and SDI.

Screening of populations and triaging heart disease

Electro-acoustic cardiography's utility in the public health screening and triaging are characterized by the ability of the technology to quickly identify with a high degree of specificity the prevalence of cardiovascular abnormalities. Totally 135 patients with known diabetes and above the age of 40 were invited to the screening camp in a middle-income community in Mumbai. History and symptoms were recorded by a paramedic and physical examination using the Audicor ApoPatch, and an Omron 100 BP apparatus was conducted by volunteer physicians with a postgraduate degree in internal medicine. Patients with abnormal EMAT and SDI with uncontrolled hypertension were referred back to their specialist for review. The average turnaround time for recording a simultaneous measurement of blood pressure and electro-acoustic cardiography was 1.2 min per patient. Totally 51 of the 135 patients recorded had uncontrolled hypertension with systolic over 150 mmHg.

Clinical efficacy through monitoring patient response to therapy

Patients undergoing HF management need to be closely observed and monitored for the efficacy of the HF treatment. Toggweiler et al.[8] used acoustic cardiography to optimize arterioventicular (AV) and interventricular (VV) delays in cardiac resynchronization therapy and achieved significant improvement in cardiac performance with objective clinical and hemodynamic parameters (EMAT) in comparison to the typical “out of the box” settings. Hasan et al.[9] reported that in the clinical setting for the optimization of CRT/CRM device the use of acoustic cardiographic technique outweighed ECG in time, ease of use, and relative cost of the procedure.

Economic benefit and impact of the technology in primary care

Peacock et al.[9],[10] using the highly specific and rapid examination of patients presenting at the ED with symptoms indicating acute decompensated heart failure, the Audicor acoustic cardiograph was able to reduce the misdiagnosis rate by 32% which would have cost over $ 2500 in additional costs due to misdiagnosis.


The management of CVD as a part of the Noncommunicable Disease Prevention and Control Programs has been severely limited by the specificity and sensitivity of the frontline diagnostic tools currently available. The needs for the proper management of CVD and its associated comorbidities necessitates meeting the following requirements:

Availability of reliable data.....A quick screening device that requires minimal preparation and provides immediate interpretable resultsLow operating costCan be used by a minimally skilled technicianMust be adaptable to use in teleconsultation situation where adequate information of hemodynamic performance is indicatedShould be suitable for ambulatory and long-term monitoring for “dynamic” cardiology.

The Audicor electro-acoustic cardiography device presents a well-developed, simple, low cost, and quick examination tool providing a high degree of sensitivity and specificity for heart failure. Its ambulatory feature provides for long-term monitoring of paroxysmal events as well as easy accessibility in the management of CHF.


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