{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T12:47:19Z","timestamp":1785415639054,"version":"3.56.0"},"reference-count":30,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2026,7,6]],"date-time":"2026-07-06T00:00:00Z","timestamp":1783296000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001691","name":"Japan Society for the Promotion of Science","doi-asserted-by":"crossref","award":["JP21K10300"],"award-info":[{"award-number":["JP21K10300"]}],"id":[{"id":"10.13039\/501100001691","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/501100001691","name":"Japan Society for the Promotion of Science","doi-asserted-by":"crossref","award":["JP24K02714"],"award-info":[{"award-number":["JP24K02714"]}],"id":[{"id":"10.13039\/501100001691","id-type":"DOI","asserted-by":"crossref"}]},{"award":["JP21K10300"],"award-info":[{"award-number":["JP21K10300"]}],"id":[{"id":"https:\/\/ror.org\/00hhkn466","id-type":"ROR","asserted-by":"publisher"}]},{"award":["JP24K02714"],"award-info":[{"award-number":["JP24K02714"]}],"id":[{"id":"https:\/\/ror.org\/00hhkn466","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Medicina"],"abstract":"<jats:p>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\u2032 (r = 0.41, p = 0.0012). The [15.63, 31.25) Hz band was associated with septal E\/e\u2032, septal and lateral e\u2032 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.<\/jats:p>","DOI":"10.3390\/medicina62071300","type":"journal-article","created":{"date-parts":[[2026,7,6]],"date-time":"2026-07-06T08:05:38Z","timestamp":1783325138000},"page":"1300","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Low-Frequency Components of the Heart Sound Corresponding to the Fourth Heart Sound Phase, Assessed by Phonocardiography, Correlate with Early Variations in Echocardiographic Indices Related to Diastolic Function"],"prefix":"10.3390","volume":"62","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6805-6428","authenticated-orcid":false,"given":"Kunimasa","family":"Yagi","sequence":"first","affiliation":[{"name":"Department of Internal Medicine, Kanazawa Medical University Hospital, 1-1 Daigaku, Uchinada, Kahoku 920-0293, Ishikawa, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuhei","family":"Yasui","sequence":"additional","affiliation":[{"name":"AMI Inc., 2-13 302 Higashisengokucho, Kagoshima 892-0842, Kagoshima, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5718-438X","authenticated-orcid":false,"given":"Shumpei","family":"Saito","sequence":"additional","affiliation":[{"name":"AMI Inc., 2-13 302 Higashisengokucho, Kagoshima 892-0842, Kagoshima, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Makoto","family":"Iwazawa","sequence":"additional","affiliation":[{"name":"AMI Inc., 2-13 302 Higashisengokucho, Kagoshima 892-0842, Kagoshima, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shimpei","family":"Ogawa","sequence":"additional","affiliation":[{"name":"AMI Inc., 2-13 302 Higashisengokucho, Kagoshima 892-0842, Kagoshima, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Taketsugu","family":"Tsuchiya","sequence":"additional","affiliation":[{"name":"Department of Cardiology, Kanazawa Medical University Hospital, Kahoku 920-0293, Ishikawa, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0008-7629-5008","authenticated-orcid":false,"given":"Tomoya","family":"Kaneda","sequence":"additional","affiliation":[{"name":"Department of Internal Medicine, Keiju Medical Center, 94 Tomioka-cho, Nanao 926-8605, Ishikawa, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Masaji","family":"Miyamoto","sequence":"additional","affiliation":[{"name":"Department of Internal Medicine, Keiju Medical Center, 94 Tomioka-cho, Nanao 926-8605, Ishikawa, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fuminori","family":"Yamagishi","sequence":"additional","affiliation":[{"name":"Department of Internal Medicine, Itoigawa General Hospital, 457-1 Takegahana, Itoigawa 941-8502, Niigata, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-4191-8398","authenticated-orcid":false,"given":"Junji","family":"Kobayashi","sequence":"additional","affiliation":[{"name":"Department of Medicine, Division of Diabetes, Metabolism and Endocrinology, Chiba University Hospital, Chiba 260-8677, Chiba, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hideki","family":"Origasa","sequence":"additional","affiliation":[{"name":"Data Science and AI Innovation Research Promotion Center, Institute of Statistical Mathematics, Shiga University, Hikone 525-8522, Shiga, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tatsuya","family":"Kawasaki","sequence":"additional","affiliation":[{"name":"Department of Cardiology, Matsushita Memorial Hospital, Moriguchi 570-8540, Osaka, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Naohito","family":"Yamasaki","sequence":"additional","affiliation":[{"name":"Department of Cardiology and Geriatrics, Kochi Medical School, Nankoku 783-8505, Kochi, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Takashi","family":"Muro","sequence":"additional","affiliation":[{"name":"Heart Valve Center, Midori Hospital, 1-16 Sumiyoshi, Nishi-ku, Kobe 651-2133, Hyogo, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nobuo","family":"Fukuda","sequence":"additional","affiliation":[{"name":"Department of Internal Medicine, National Hospital Organization, Shikoku Medical Center for Children and Adults (SMCCA), Zentsuji 765-8507, Kagawa, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,7,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2238","DOI":"10.1001\/jama.293.18.2238","article-title":"Association between phonocardiographic third and fourth heart sounds and objective measures of left ventricular function","volume":"293","author":"Marcus","year":"2005","journal-title":"JAMA"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"431","DOI":"10.1016\/j.cardfail.2008.01.010","article-title":"Association of the fourth heart sound with increased left ventricular end-diastolic stiffness","volume":"14","author":"Shah","year":"2008","journal-title":"J. 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