Key result
Low-frequency S4 acoustic signals correlate moderately with septal E/e′ in early-stage heart failure.
Why the study?
Although the fourth heart sound marks LV diastolic dysfunction, low-frequency sounds are often audible during the S4 phase in the general population without CHF symptoms or history.
Cross-Sectional (n=60)
Yes
Effect estimate: r = 0.41
p-value: p=0.0012
Specific low-frequency acoustic components observed during the S4 phase by digital phonocardiography are closely associated with echocardiographic markers of left ventricular diastolic function in asymptomatic individuals.
May support acoustic assessment of early diastolic dysfunction; hypothesis-generating and requires prospective validation before clinical use.
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.
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Yagi et al. (2026) conducted a cross-sectional in Stage A or B heart failure (n=60). Low-frequency acoustic signals during the S4 phase was evaluated on Association between S4 phase sound (S4p) and the septal E/e′ ratio (r = 0.41, p=0.0012). Low-frequency acoustic signals during the S4 phase in the 7.81-15.63 Hz band significantly correlated with the septal E/e′ ratio (r = 0.41, p = 0.0012) in asymptomatic men with early-stage heart failure.
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