Background and Objectives: The fourth heart sound (S4) is a recognized marker of left ventricular (LV) diastolic dysfunction, suggesting a potential risk of congestive heart failure (CHF). However, low-frequency sounds are often audible during the S4-corresponding phase in the general population without symptoms or a history of CHF. The present retrospective cross-sectional exploratory study examined the acoustic features of the S4 phase sound in patients with stage A or B heart failure in association with echocardiographic markers. Materials and Methods: Sixty asymptomatic male patients underwent simultaneous phonocardiographic and electrocardiographic recordings using Cardio-EGG (AMI Inc.). The amplitude of acoustic signals during the S4 phase was quantified across ten frequency bands using a continuous wavelet transform. Echocardiographic parameters of LV diastolic function were also assessed. Results: Several lower-frequency bands demonstrated significant correlations with LV diastolic indices. After adjustment for age, systolic blood pressure, HbA1c, interventricular septal thickness, and coronary artery disease, strong associations were observed at the fourth left sternal border signals in the [7.81, 15.63) Hz band and septal E/e' (r = 0.41, p = 0.0012). The [15.63, 31.25) Hz band was associated with septal E/e', septal and lateral e' velocities, and the E/A ratio. This frequency range at the apex also correlated with A-wave velocity (p = 0.0011). Conclusions: Specific low-frequency acoustic components observed during the S4 phase are closely associated with echocardiographic markers of left ventricular diastolic function in asymptomatic individuals. These characteristics resemble those of the standard S4, indicating that digital phonocardiography could facilitate the identification of early cardiac dysfunction before the onset of heart failure.

The fourth heart sound (S4) is an auscultatory marker of left ventricular diastolic dysfunction (LVDD). Additionally, S4 correlates with atrial function, which is typically impaired in patients with Type 2 diabetes (T2D) but can improve with sodium-glucose co-transporter-2 inhibitor (SGLT2i) therapy. This case report highlights the dynamic changes in S4 associated with modification of SGLT2i therapy. An 83-year-old male with T2D and LVDD, confirmed via echocardiography, was treated with SGLT2i therapy for 4 years for glycemic control. The therapy was discontinued in December 2023 because of increased nocturnal urination. Two months after discontinuation, the patient developed pronounced S4, accompanied by mild chest discomfort and worsening of evening leg edema. Resumption of SGLT2i therapy led to a marked reduction in S4 along with a remarkable improvement in chest discomfort and edema within 1 month. These findings were confirmed by visual phonocardiography. This case underscores the potential utility of dynamic S4 changes as a noninvasive indicator of SGLT2i therapy adjustment. These findings highlight the novel clinical application of S4 monitoring in mitigating heart failure progression in patients with T2D.

Left atrial mechanical dysfunction is common in horses following the treatment of atrial fibrillation (AF). This study aimed to evaluate the use of an acoustic cardiography monitor (Audicor[®]) in quantifying cardiac mechanical and hemodynamic function in horses with AF before and after treatment and to correlate these findings with echocardiographic measures. Twenty-eight horses with AF and successful transvenous electrical cardioversion were included. Audicor[®] recordings with concomitant echocardiographic examinations were performed one day before, one day after, and two to seven days after cardioversion. Key variables measured by Audicor[®] included electromechanical activating time (EMAT), heart rate-corrected EMATc, left ventricular systolic time (LVST), heart rate-corrected LVSTc, systolic dysfunction index (SDI), and intensity and persistence of the third and fourth heart sound (S3, S4). A repeated-measures ANOVA with Tukey's test was used to compare these variables over time, and linear regression and Bland-Altman analyses were applied to assess associations with echocardiographic findings. Following conversion to sinus rhythm, there was a significant decrease in EMATc and LVSTc (p < 0.0001) and a significant increase in LVST (p = 0.0001), indicating improved ventricular systolic function, with strong agreement between Audicor[®] snapshot and echocardiographic measures. However, S4 quantification did not show clinical value for assessing left atrial function after conversion.

A 54-year-old man presented with a significant fourth heart sound and increased intensity of the second heart sound, despite the absence of heart failure symptoms, in the second week of March 2024. Visualized phonocardiograms confirmed these findings, and further interviews revealed that he had suffered lifestyle changes, such as long commutes and sodium overload, while contributing to the response efforts in the 2024 Noto Peninsula Earthquake. Visualized phonocardiograms were also influential in determining the treatment strategy, persuading the patient to undergo a specific therapy, evaluating the therapeutic effects, and suggesting a new model for clinical practice.

Phonocardiography (PCG) is used as an adjunct to teach cardiac auscultation and is now a function of PCG-capable stethoscopes (PCS). To evaluate the efficacy of PCG and PCS, the authors investigated the impact of providing PCG data and PCSs on how frequently murmurs, rubs, and gallops (MRGs) were correctly identified by third-year medical students. Following their internal medicine rotation, third-year medical students from the Georgetown University School of Medicine completed a standardized auscultation assessment. Sound files of 10 different MRGs with a corresponding clinical vignette and physical exam location were provided with and without PCG (with interchangeable question stems) as 10 paired questions (20 total questions). Some (32) students also received a PCS to use during their rotation. Discrimination/difficulty indexes, comparative chi-squared, and McNemar test p-values were calculated. The addition of phonocardiograms to audio data was associated with more frequent identification of mitral stenosis, S4, and cardiac friction rub, but less frequent identification of ventricular septal defect, S3, and tricuspid regurgitation. Students with a PCS had a higher frequency of identifying a cardiac friction rub. PCG may improve the identification of low-frequency, usually diastolic, heart sounds but appears to worsen or have little effect on the identification of higher-frequency, often systolic, heart sounds. As digital and phonocardiography-capable stethoscopes become more prevalent, insights regarding their strengths and weaknesses may be incorporated into medical school curricula, bedside rounds (to enhance teaching and diagnosis), and telemedicine/tele-auscultation efforts.

Mitral and aortic valve insufficiencies have been commonly reported in horses. The objective of this study was to establish the use of acoustic cardiography (Audicor[®]) in horses with aortic (AI) or mitral valve insufficiency (MI). A total of 17 healthy horses, 18 horses with AI, and 28 horses with MI were prospectively included. None of the horses was in heart failure. Echocardiography and Audicor[®] analyses were conducted. Electromechanical activating time (EMAT), rate-corrected EMATc, left ventricular systolic time (LVST), rate-corrected LVSTc, and intensity and persistence of the third and fourth heart sound (S3, S4) were reported by Audicor[®]. Graphical analysis of the three-dimensional (3D) phonocardiogram served to visually detect murmurs. Audicor[®] snapshot variables were compared between groups using one-way ANOVA followed by Tukey's multiple-comparisons test. The association between Audicor[®] snapshot variables and the corresponding echocardiographic variables was investigated by linear regression and Bland-Altman analyses. Heart murmurs were not displayed on Audicor[®] phonocardiograms. No significant differences were found between Audicor[®] variables obtained in clinically healthy horses and horses with valvular insufficiency. The Audicor[®] device is unable to detect heart murmurs in horses. Audicor[®] variables representing cardiac function are not markedly altered, and their association with corresponding echocardiographic variables is poor in horses with valvular insufficiency that are not in heart failure.

Acoustic cardiography is a completely new technology, it has great advantages in the rapid diagnosis of cardiovascular diseases. The purpose of this study was to investigate the clinical value of the fourth heart sound (S4), cardiac systolic dysfunction index (SDI), and the cardiac cycle time-corrected electromechanical activation time (EMATc) in the prediction of post-percutaneous coronary intervention (PCI) early ventricular remodeling (EVR) in patients with acute myocardial infarction (AMI). We recruited 161 patients with AMI of 72-h post-PCI, including 44 EVR patients with left ventricular ejection fraction (LVEF) < 50% and 117 Non-EVR patients (normal left ventricular systolic function group, LVEF ≥ 50%). EMATc, S4, and SDI were independent risk factors for post-PCI early ventricular remodeling in patients with AMI [S4 (OR 2.860, 95% CI 1.297-6.306, p = 0.009), SDI (OR 4.068, 95% CI 1.800-9.194, p = 0.001), and EMATc (OR 1.928, 95% CI 1.420-2.619, p < 0.001)]. The area under the receiver operating characteristic curve for EMATc was 0.89, with an optimal cutoff point of 12.2, EMATc had a sensitivity of 80% and a specificity of 83%. By contrast, an optimal cutoff point of 100 pg/ml, Serum brain natriuretic peptide had a sensitivity of 46% and a specificity of 83%. Our findings suggest the predictive value of EMATc for the occurrence of EVR in these patients was also identified; EMATc may be a simple, quick, and effective way to diagnose EVR after AMI.

Chronic heart failure (HF) has various phenotypes. It is accompanied by repeated hospitalizations over a long period. Therefore, accumulating long-term observational data of patients with various backgrounds is important to establish a prediction technology for the exacerbation of HF. In a patient with chronic right-sided HF caused by cor pulmonale, heart sounds and electrocardiograms were recorded at home or our hospital twice a week for 7 months including the stable (31 days), pre-exacerbation (2 weeks just before the onset of exacerbation), and hospitalization periods and quantified as cardiac acoustic biomarkers (CABs) using AUDICOR technology (Inovise Medical, Inc., Portland, OR, USA). The relationship between the change in CABs and hospitalization events due to HF were investigated. During the pre-exacerbation period just before the onset of exacerbation of HF leading to hospitalization, inaudible changes in the third heart sound (S3) strength that were probably derived from the right heart were observed. Although the values of the fourth heart sound (S4) strength were high during the stable and pre-exacerbation period, values decreased markedly during hospitalization. These findings suggest that CABs including S3 and S4 are useful for the early detection of signs of HF exacerbation.

Conventional phonocardiography is useful for objective assessment of cardiac auscultation, but its availability is limited. More recently, an ankle-brachial index (ABI) measurement system equipped with simple phonocardiography has become widely used for diagnosing peripheral artery disease, however, whether this simple phonocardiography can be an alternative to conventional phonocardiography remains unclear.This retrospective study consisted of 48 patients with hypertrophic cardiomyopathy (HCM) and 107 controls. The presence of the fourth sound (S4) was assessed by conventional phonocardiography, in addition to apexcardiography and auscultation, in all patients with HCM. S4 was also estimated by the ABI measurement system with the phonocardiographic microphone on the sternum (the standard method) or at the apex (the apex method) in HCM patients and controls.S4 on conventional phonocardiography was detected in 42 of 48 patients (88%) with HCM. Auscultation for the detection of S4 had a sensitivity of 0.78, specificity of 0.57, and accuracy of 0.75. These diagnostic values were generally superior to those of the standard method using the ABI measurement system, whereas the apex method using the ABI measurement system had better diagnostic values, with an excellent specificity of 1.0, sensitivity of 0.77, and accuracy of 0.80. No significant differences were observed in low ABI defined as < 0.9.Simple phonocardiography equipped with the ABI measurement system may be an alternative to conventional phonocardiography for the detection of S4 in patients with HCM when the phonocardiographic microphone is moved from the sternum to the apex.

Pulmonary hypertension (PH) is commonly associated with left heart disease. In this retrospective study, using the database of a clinical study conducted between January 2008 and July 2008, the phenotypes of PH were classified using non-invasive cardiac acoustic biomarkers (CABs) and compared with classification by echocardiography. Records with same-day measurement of acoustic cardiography and right heart catheterization (RHC) parameters were included; cases with congenital heart disease were excluded. Using the RHC measurements, PH was classified as pre-capillary PH (Prec-PH), isolated post-capillary PH (Ipc-PH), and combined pre-capillary and post-capillary PH (Cpc-PH). The first, second, third, and fourth heart sounds (S1, S2, S3, and S4) were quantified as CABs (intensity, complexity, and strength). Forty subjects were selected: 5 had Prec-PH, 5 had Ipc-PH, 8 had Cpc-PH, and 22 had No-PH. CABs were significantly correlated with RHC measurements, with significant differences among phenotypes. Phenotype classification was performed using various CABs, and the diagnostic performance as assessed by the area under the receiver operating characteristic curve was 0.674-0.720 for Prec-PH, 0.657-0.807 for Ipc-PH, and 0.742 for Cpc-PH. High negative and low positive predictive values for phenotype identification were observed. CABs may provide an ambulatory measurement method with home-monitoring friendliness which is more convenient than standard examinations to identify presence of PH and its phenotypes.

Acoustic cardiography can provide simultaneous electrocardiography and acoustic cardiac data to assess the electronic and mechanical heart functions. The aim of this study was to assess whether changes in acoustic cardiographic parameters (ACPs) before and after hemodialysis (HD) are associated with overall and cardiovascular (CV) mortality in HD patients. A total of 162 HD patients was enrolled and ACPs were measured before and after HD, including left ventricular systolic time (LVST), systolic dysfunction index (SDI), third (S3) and fourth (S4) heart sounds, and electromechanical activation time (EMAT). During a follow-up of 2.9 years, 25 deaths occurred with 16 from CV causes. Multivariate analysis showed that high △SDI (per 1; hazard ratio [HR], 2.178; 95% confidence interval [CI], 1.189-3.990), high △EMAT (per 1%; HR, 2.218; 95% CI 1.382-3.559), and low △LVST (per 1 ms; HR, 0.947; 95% CI 0.912-0.984) were independently associated with increased overall mortality. In addition, high △EMAT (per 1%; HR, 2.141; 95% CI 1.117-4.102), and low △LVST (per 1 ms; HR, 0.777; 95% CI 0.637-0.949) were associated with increased CV mortality. In conclusion, the changes in ACPs before and after HD may be a useful clinical marker and stronger prognostic marker of overall and CV mortality than ACPs before HD.