Could a smartphone app become a remote stethoscope?

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Will we soon be able to use an app as a stethoscope at home? Image credit: Sergey Narevskih/Stocksy.
  • Researchers assessed the feasibility of using a smartphone’s built-in microphone to record heart sounds by studying the quality of heart sounds recorded on smartphones and the factors influencing the quality of the recordings.
  • Overall, three out of four recordings were of good quality, meaning they could be further processed to obtain medically relevant data.
  • The results indicate that the quality of heart sound is not influenced by the version of the phone or the biological sex of the user, but users over the age of 60 seem to have lower quality recordings.
  • This study paves the way for a future where individuals, especially those with heart conditions, can easily record their own heart sounds at home, improving the diagnostic process.

Everyone knows the “lub-dub… lub-dub” sounds that the heart makes. The reason why the heart makes these sounds has to do with its function of circulating blood throughout the body.

The heart muscle pumps blood by continually contracting and relaxing. During heart contraction, we hear the “lub” sound, known as the first heart sound, S1, and during heart relaxation, we hear the “dub” sound, the second heart sound, S2.

The traditional tool used by physicians to listen to heart sounds is the stethoscope.

Heart sounds can be a useful marker of heart failure, but currently they are only assessed in a clinical setting. It would be helpful if patients could record their own heart sounds while at home.

Using a smartphone with a high quality built-in microphone is one of the ways in which heart sounds can be easily captured by individuals from the comfort of their homes. To date, several prototype mobile applications for recording heart sounds have been developed and made available to the public, including iStethoscope and CPstethoscope.

Now researchers from King’s College London in the UK and Maastricht University in the Netherlands have conducted a study to investigate the feasibility of using a smartphone as a stethoscope and to assess potential factors that influence the quality of cardiac sound recordings.

“This research proves that mobile technologies are a viable way to record heart sounds and that in the future heart patients and physicians could use home recordings to verify [the] existence or progression of heart disease,” explains Dr. Pablo Lamataco-author of the study and professor of biomedical engineering at King’s College London.

The results of this study were published in the European Heart Journal – Digital Health.

In collaboration with heart patients across the British Heart Foundation (BHF) and Evelina’s Children’s Heart Organization (ECHO), and with experts from Cell Design Studioresearchers have developed a smartphone application that measures heart sounds.

To use the Echoes app, the user only has to place his smartphone on his chest and press “record”. The app has a signal processing algorithm that filters heart sound recordings to remove any background noise.

The Echoes app asks users to voluntarily provide anonymous basic demographic data, including age, gender, height, weight, and if applicable, any heart conditions.

Between May 21 and October 4, 2021, 1,148 people downloaded the Echoes app and contributed 7,597 heart sound recordings, which were uploaded to a Google Firebase database.

Researchers found that eight out of 10 users (80%) were able to make a good quality heart sound recording. A “good quality” recording is one that can be interpreted for analysis.

Overall, three out of four records (75%) could be further processed to obtain medically relevant data.

The researchers then looked at factors affecting the quality of heart sound recordings in these users. They found that the following factors did not affect the quality of recordings:

  • phone version
  • biological sex of the user.

However, researchers observed that users over the age of 60 had lower quality recordings.

During his doctoral dissertation defense, Dr Hongxing LuoStudy co-author and postdoctoral researcher at Maastricht University argued that the problem of poor quality heart sound recordings by older users can be solved.

One of the easiest solutions, he said, is to have users use an earphone to listen to their heart sounds while they search for the position with the loudest heart sounds.

As hospitals already have several tools to assess patients’ heart conditions, such as a echocardiogram (ECG) and Magnetic resonance imaging (MRI), Dr. Luo thinks the most promising direction for a technology like Echoes is in remote cardiac monitoring, especially for the following patient categories:

  • heart failure patients
  • post-operative follow-up of patients with valvular heart disease
  • post-operative follow-up of patients with arrhythmia.

Dr Lamata described the Echoes app as “a tool to empower patients[s] to manage their own conditions.

Dr. James LeiperProfessor of Molecular Medicine at the University of Glasgow and Associate Medical Director at the British Heart Foundation, notes:

“As we enter the era of digital medicine, technology like Echoes could revolutionize the diagnosis and monitoring of heart disease at home. Further research is needed to test how the app can be used in tandem with existing heart monitoring techniques. However, if successful, this development could mark an important step towards the availability of cardiac monitoring tools.

Dr. Dominik Linzprofessor of circulatory, kidney and lung physiology at the University of Copenhagen, stressed that it is important for researchers to identify “specific thresholds for [heart sound measurements] which should result in action” by the cardiologist evaluating patient data via the Echoes app.

One limitation of the study is that the Echoes app was only available to iPhone users, thus excluding Android users – who make up more than half of smartphone users – from the study. .

When asked if the Echoes app will become available to the general public, Dr. Pablo Lamata said Medical News Today“We are now planning our next release, to also include an Android version, hopefully by May next year.”

The Echoes app currently only detects S1 and S2 heart sounds, and the researchers said “the usefulness of recognizing pathological heart sounds, including S3, S4, and murmurs, should be investigated in a future study involving patients”.

The researchers also noted that the study population may not reflect a truly general population “because smartphone users are likely younger and more educated.” Further research is needed to assess the reproducibility of these results.


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