Steffen Pauws, Tilburg University, Netherlands
These authors have contributed equally to this work and share first authorship
This is an open-access article distributed under the terms of the
Acute heart failure (AHF) is a life-threatening condition and a common cause of hospitalization. The defining clinical feature of AHF is volume overload, leading to pulmonary and peripheral edema and consequently to weight gain. Vocal biomarkers have the potential to facilitate the early detection of worsening HF and the prevention of AHF episodes by offering a non-invasive, low-barrier monitoring tool. The AHF-Voice study is a prospective monocentric cohort study designed to investigate the trajectories of voice alterations during and after episodes of AHF, identify potential vocal biomarkers, and enhance the understanding of the pathophysiological mechanisms underlying these voice changes. It will examine the characteristics and determinants of vocal biomarkers, analyzing their correlations with patients' clinical status and comparing them to alternative clinical parameters in HF. Further, it aims to determine whether specific vocal biomarkers can accurately map different HF phenotypes and assess their association with patient trajectories
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Heart failure (HF) affects over 64 million individuals globally, with symptoms like breathlessness, fatigue, and edema (
Patients with worsening HF usually experience a gradually increasing volume overload, accompanied by body weight gain and symptoms like dyspnea, peripheral edema and fatigue. Without adequate treatment, the patient will eventually require hospitalization due to further deterioration. The international HF guidelines recommend that patients assess their body weight daily as a primary non-invasive self-monitoring measure (
In recent years, advancements in digital technologies including artificial intelligence have facilitated the utilization of the human voice as a vocal biomarker for the diagnosis and management of diseases (
Furthermore, the underlying pathophysiological mechanisms of voice alterations in patients with HF remain poorly understood. Several hypotheses are being discussed. (1) Murton et al. suggested that AHF-related volume overload leads to vocal fold edema that may cause changes in phonation, such as a hoarse voice with a limited vocal range, and leads to a changed fundamental and more irregular frequency (higher jitter) (
The AHF-Voice study aims to improve the understanding of vocal biomarkers in HF by exploring the characteristics of voice alteration in patients with AHF via daily voice recordings throughout their in-hospital period of decompensation-recompensation and the post-discharge period thereafter. Additionally, it will assess the self-perceived measurements of voice alteration and anatomically visual differences in the state of decompensation and recompensation.
The “Acute Heart Failure Voice Analysis Prospective Cohort Study” (AHF-Voice study) aims to explore the relationship between congestion and voice alterations in patients with AHF, with a view to reflecting their clinical condition. The study will address the following key questions: (1) What are the characteristics and determinants of vocal alterations in patients with AHF? (2) To what extent do these vocal alterations correlate with the patient's clinical status during an AHF episode? (3) To what extent are vocal biomarkers sensitive to changes over time, and how do they compare to established clinical parameters in HF such as quality of life or NT-proBNP levels? (4) Can specific vocal biomarkers or combinations thereof be mapped to different HF phenotypes? (5) Are vocal biomarkers associated with patient prognosis? (6) Are voice alterations in patients with AHF associated with pathophysiological changes, such as vocal fold edema, that affect vocal fold oscillation?
The AHF-Voice study is designed as a prospective monocentric observational cohort study. The study is being conducted at the University Hospital Würzburg as part of the UNISONO project, which is funded by the German Federal Ministry of Education and Research (Grant #16SV8877). The study was approved by the local Ethics Committee (245/22-me), complies with the Declaration of Helsinki and adheres to the STROBE reporting guidelines (
All patients hospitalized at the Department Internal Medicine I of the University Hospital Würzburg are screened for study participation. The study period will be 6 months after index hospitalization, including structured follow-up visits after 6 weeks and 6 months.
Design of the AHF-Voice main study and its two sub-studies. The figure shows the data collection over time. In the main study, daily voice recordings are performed during index hospitalization (blue smartphone), and voice recordings are continued at home on the patients’ own smartphones, if available (orange smartphone). In addition, body composition analyses and patient-related outcome measurements are carried out during admission, discharge, and follow-up visits. In the Strobo sub-study, a video-laryngostroboscopy and a voice field measurement will be performed on admission, discharge, and follow-up time points. As part of the In-ear sub-study, the in-ear sensor is used daily during index hospitalization, and at the 6-week and 6-month follow-up visits. BCM, body composition monitor; GAD-2, generalized anxiety disorder-2, KCCQ, Kansas City cardiomyopathy questionnaire; PHQ-2, patient health questionnaire-2.
Inclusion criteria are: hospitalization with AHF (diagnosis compatible with international guidelines including edema, dyspnea, fatigue, and/or signs of congestion in chest x-ray and elevated NT-proBNP levels) (
During the index hospitalization, detailed phenotyping of each patient will be conducted, including medical history, clinical data (e.g., transthoracic echocardiogram, electrocardiogram), and routine blood tests. At index hospitalization, patients will complete quality of life self-report questionnaires regarding health-related quality of life (23-item Kansas City Cardiomyopathy Questionnaire) (
User interface of the specifically designed smartphone application in the AHF-Voice study. The application facilitates the recording of three distinct voice tasks: (1) spontaneous speech, (2) sustained vowel, and (3) reading of a text passage, one after the other. Additionally, the application allows the patient to maintain a weight diary. Screenshots from
In addition to the daily voice recordings, patients contributing to the
All patients are asked to continue with the use of the mobile application for daily voice recordings after discharge on their own smartphone, if available. Six weeks and 6 months after the index hospitalization, patients are invited to the outpatient clinic of the Comprehensive Heart Failure Center at the University Hospital Würzburg (
AHF-Voice utilizes a number of surrogate markers to assess the level of congestion. Daily weight recordings are taken during hospitalization and follow-up visits. Patients with their own smartphone can log their daily weight through app-based entries. Routine laboratory parameters, including NT-proBNP levels, are measured at admission and discharge. Additionally, body composition assessments will be performed at admission, discharge, and during follow-up visits, providing insights into fluid overload.
The smartphone application has been developed specifically for voice recording in the study. The app is available for iOS and Android systems and was developed through an iterative process that actively involved patients with HF in dedicated focus groups. Their feedback was incorporated into the design of the user interface to create a user-friendly and easy-to-use application (see
During index hospitalization, all patients are asked to perform daily voice recordings with a study smartphone (iPhone SE 2023, Apple Inc., Cupertino, USA) under the supervision of the study staff. Patients are then prompted through a voice dialogue interface on the smartphone app to perform the following set of speech tasks:
Sustained vowel phonation (vowel/a:/) Spontaneous speech Reading standardized passage (“Northwind and Sun”)
During index hospitalization, study staff ensures that the same time of day is chosen for the daily voice recordings (e.g., 30 min–1 h after waking up). After discharge, patients will be asked to continue using the smartphone app on their own smartphone, if available. These patients will be instructed to install the smartphone app on their device prior to discharge, and will then be prompted to perform the speech tasks once a day. In addition, the daily weight measurements can be entered into the app. During the follow-up period, patients who do not own a smartphone will not collect voice recordings after discharge, but will contribute to the data set when attending the outpatient visits after 6 weeks and 6 months.
The in-ear sensor called
Application principle of the c-med° alpha in-ear sensor. The illustration shows the functionality of the in-ear sensor and illustrates its position within the ear canal. The data, which includes the pulse rate, oxygen saturation, and body temperature, is transmitted to a smartphone via bluetooth. Reproduced with permission from “
Withdrawal of consent will trigger premature termination of follow-up. Reason for withdrawal will be documented, and efforts will be made to complete the clinical information for this last patient contact. In case a patient misses a follow-up visit, study staff contact the patient directly in order to motivate him/her to attend the clinical follow-up visit at the Comprehensive Heart Failure Center (CHFC). If a visit at the CHFC isn't possible, telephone follow-up assessments and/or completion of background information via the general practitioner or other care providers will be attempted.
In general, there is no consensus about how to determine the sample size for clinical prediction models when applying AI methods (
The sample size calculation was performed using GPower software and based on the study of Amir et al. (
Data are summarized using descriptive statistics. For continuous variables, normally distributed data are presented as mean and standard deviation, while non-normally distributed data are expressed as median and quartiles. Categorical variables are reported as absolute numbers and percentages.
Data will be described using conventional methods according to the nature of the data. Repetitively sampled data will be investigated using generalized estimating equations (GEE) for repeated measures analysis (vocal feature) or repeated measures analysis of (co)variance (rANCOVA; e.g., for clinical data). To investigate the prognostic utility, Kaplan–Meier plots for graphical inspection and uni- and multivariable Cox proportional hazards regression analyses will be used. Subgroup analyses will include age, sex,
AI-based methods, including machine learning and deep learning will be performed for the derivation of clinically meaningful vocal biomarker in patients with AHF applying primarily a binary approach (“decompensated” vs. “recompensated”).
All patients of the AHF-Voice study will be included, possibly with censored observation times. All efforts will be taken to prevent missing values in subjects who are alive. Whenever there is the possibility of significant bias due to missing data, additional analyses using imputation techniques will be employed and used for supportive sensitivity analysis.
Between April 2023 and November 2024, 131 patients were recruited for the AHF-Voice Study. 50 (38%) of the patients participated in the
Baseline characteristics of the AHF-Voice study cohort (
Characteristic | Value |
---|---|
Sociodemographic | |
Age (years) | 75 ± 10 |
Women | 40 (31) |
Heart failure characteristics | |
NYHA functional class (III/IV) | 112 (86) |
Ischemic heart failure etiology | 55 (42) |
50 (38) | |
Left ventricle ejection fraction ( |
|
≤40% | 48 (37) |
41–49% | 17 (13) |
≥50% | 62 (47) |
Comorbidities | |
Atrial fibrillation | 49 (37) |
Peripheral artery disease | 22 (17) |
Diabetes mellitus | 50 (38) |
Arterial hypertension | 117 (89) |
Chronic obstructive pulmonary disease | 23 (18) |
Malignoma | 14 (11) |
Current smoker | 13 (10) |
Former smoker | 65 (50) |
Medical history | |
Percutaneous coronary intervention/bypass | 46 (35) |
Valvular replacement (interventional/surgical) | 19 (15) |
Pacemaker or defibrillator | 33 (25) |
Measurements | |
Body mass index (kg/m2) | 30 ± 7 |
Systolic blood pressure (mmHg) | 133 ± 26 |
NT-proBNP (pg/ml) | 5,215 [2,650; 13,558] |
eGFR—CKD-EPI (ml/min/1.73 m2) | 44 [35; 70] |
C-reactive protein (mg/dl) | 1.0 [0.4; 2.5] |
Patient-reported outcome | |
Visual analog scale ( |
40 [25; 50] |
KCCQ-overall summary score ( |
38 [27; 53] |
PHQ-2 (score 0–6) ( |
1 [0; 2] |
GAD-2 (score 0–6) ( |
0 [0; 1] |
Patient characteristics | |
Own smartphone | 77 (59) |
Length of hospital stay (days) | 10 [7; 15] |
Voice recordings obtained during hospitalization | 21 [15; 30] |
Data are
eGFR- CKD-EPI, estimated glomerular filtration rate—chronic kidney disease epidemiology collaboration equation, GAD-2, generalized anxiety disorder—2; KCCQ, Kansas City cardiomyopathy questionnaire; NT-proBNP, N-terminal pro B-natriuretic peptide; NYHA, New York Heart Association Functional Class, PHQ-2, patient health questionnaire-2.
Overall, 3,072 voice recordings (1,024 per voice task) were collected during the hospitalization period of all 131 patients, corresponding to a median of 21 [15; 30] voice recordings (7 [5; 10] per voice tasks) per patient.
The AHF-Voice study has been designed to provide new insights into the etiology, characteristics, determinants, progression, and prognostic utility of vocal biomarkers in patients experiencing an episode of AHF. Smartphone-based daily voice recordings are used as a substrate to detect subtle vocal changes, which are then associated with conventional markers of congestion.
The AHF-Voice study cohort represents a well-phenotyped population of patients with AHF. It comprises a high proportion of patients with NYHA functional class III and IV at admission, indicating a substantial number of patients with significant congestion. The cohort includes a significant proportion of patients with
Changes of vocal biomarkers over time and their determinants remain under-researched. Previous studies only suggested the existence of distinct vocal biomarker patterns in individuals exhibiting either congested or decongested states (
According to the European Laryngological Society (ELS) and the American Speech-Language-Hearing Association, a comprehensive voice assessment for general voice impairments in the field of phoniatrics is suggested (
As previously stated, the pathophysiological reasons for voice alterations in patients with HF remain unclear. The considerable number of patients participating in the
The importance of digital health technology in clinical trials is increasing (
The study has several limitations. First, selection bias may affect the generalizability of the findings, as only German-speaking participants were included, which limits the applicability of the results to non-German speakers. Further studies should be conducted in additional languages in order to gain a more comprehensive understanding of the impact of language. Alterations in voice quality resulting from upper respiratory infections during the study period could confound the analysis of vocal biomarkers. For this purpose, a longitudinal data collection approach was chosen, and clinical (e.g., fever) and laboratory parameters (e.g., C-reactive protein) of inflammation assessed at each study visit. Finally, it is possible that participants' increased awareness of potential voice disorders, due to their involvement in the study, may influence their self-assessments of their voice.
The AHF-Voice study provides a comprehensive framework deriving vocal biomarkers from voice recordings, covering all four dimensions of voice diagnostics: self-reported outcomes, physician-reported assessments, visual evaluation of the vocal cords, and acoustic voice analyses. The longitudinal design of the study permits the continuous monitoring of the voice over time, thereby offering valuable insights into the trajectories of voice alterations and their association with disease progression and prognosis in patients with HF experiencing an AHF episode. Moreover, the investigation aims to explore the potential of vocal biomarkers as a future tool for telemonitoring, with the objective to enable the early detection of decompensation in HF patients. In addition, the AHF-Voice study will inform on the utility of vocal biomarkers as digital endpoints for future HF trials.
The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding author.
The studies involving humans were approved by medical ethics committee, University Würzburg. The studies were conducted in accordance with the local legislation and institutional requirements. The participants provided their written informed consent to participate in this study.
FKerw: Writing – original draft, Writing – review & editing. MBaus: Writing – original draft, Writing – review & editing. MBaur: Writing – review & editing. FKrau: Writing – review & editing. CM: Writing – review & editing. RP: Writing – review & editing. KR: Writing – review & editing. SF: Writing – review & editing. MW: Writing – review & editing. JH: Writing – review & editing. SSt: Writing – review & editing, Writing – original draft.
The author(s) declare that financial support was received for the research and/or publication of this article. The authors declare that this study received funding from Federal Ministry of Education and Research (BMBF, #16SV8877) and was conducted within the UNISONO project. The funder was not involved in the study design, collection, analysis, interpretation of data, the writing of this article, or the decision to submit it for publication.
FKerw is supported through the clinician scientist-program UNION-CVD of the German Research Council (DFG, #413657723); he reports travel support from Novartis and Lilly, and research support from Novartis and Bayer, all unrelated to the study. MBaus reports travel support from Lilly, unrelated to the study. MBaur reports no funding and disclosures in relation to the study. FKrau reports no funding and disclosures in relation to the study. CM reports research cooperation with the University of Würzburg and Tomtec Imaging Systems funded by a research grant from the Bavarian Ministry of Economic Affairs, Regional Development and Energy, German Germany (MED-1811-0011 and LSM-2104-0002); she is supported by the German Research Foundation (DFG) within the Comprehensive Research Center 1525 “Cardio-immune interfaces” (453989101, project C5) and receives financial support from the Interdisciplinary Center for Clinical Research - IZKF Würzburg (advanced clinician-scientist program; AdvCSP 3). She further received advisory and speakers honoraria as well as travel grants from Tomtec, Edwards, Alnylam, Pfizer, Boehringer Ingelheim, Eli Lilly, SOBI, AstraZeneca, NovoNordisk, Alexion, Janssen, Bayer, Intellia, and EBR Systems; she serves as principal investigator in trials sponsored by Alnylam, Bayer, NovoNordisk, Intellia and AstraZeneca, all unrelated to the study. RP is a partner in Lenox UG, which has set itself the goal of translating scientific findings into digital health applications. Lenox UG holds shares in HealthStudyClub GmbH; he received consulting fees, reimbursements for congress attendance and travel expenses as well as payments for lectures in the context of diabetes topics and in connection with mobile health and e-mental health topics, all unrelated to the study. KR is supported by the German Research Council (DFG) and the Interdisciplinary Centre for Clinical Research (IZFK) Würzburg. He receives travel grants from MED-EL, Advance Bionics and Cochlear, all unrelated to the study. SF is supported by the German Research Council (DFG). He has received consultancy and lecture fees as well as support/ travel grants for meetings from Abbot, Abiomed, Amarin, Amgen, AstraZeneca, Bayer, Berlin-Chemie, Biotronik, Boehringer, Bristol-Myers Squibb, Boehringer, Daiichi Sankyo, Edwards, Lilly, Novartis, Novo Nordisk, Pfizer, Sanofi-Aventis, Siemens, Vifor, Zoll, all unrelated to the study. MW is an employee of Cosinuss GmbH. JH is CEO and cofounder of ZANA Technologies GmbH. She reports research funded by the German Federal Ministry of Education and Research (BMBF); she reports research supported from AstraZeneca and Boehringer Ingelheim, all unrelated to the study. SSt is supported by the German Federal Ministry of Education and Research (BMBF); he received honoraria as speaker or member of advisory boards by AstraZeneca, Bayer, Boehringer Ingelheim, Novartis, NovoNordisk, Pfizer, Servier, Vifor, all unrelated to the study; he reports research support from Alnylam, Akcea, Amgen, AstraZeneca, Bayer, Boehringer Ingelheim, Cytokinetics, Lilly, MSD, Novartis, NovoNordisk, Pfizer, all unrelated to the study.
The author(s) declare that no Generative AI was used in the creation of this manuscript.
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AHF, acute heart failure; ELS, European laryngological society; GAD-2, generalized anxiety disorder—2; KCCQ, Kansas City cardiomyopathy questionnaire; LVEF, left ventricular ejection fraction; NT-proBNP, N-terminal prohormone of brain natriuretic peptide; NYHA, New York Heart Association; PHQ-2, patient health questionnaire-2; RBH, roughness, breathiness, hoarseness; RPM, remote patient management.