Ambulatory monitoring of heart sounds via an implanted device is superior to auscultation for prediction of heart failure events.

•S3 identifies patients with 5.7-fold increase in risk of heart failure decompensation.•Deviced-measured S3 (devS3) is superior to auscultation for prognosis.•The superiority of devS3 is sustained for up to 1 year.•Subaudible components of S3 may contribute to its superiority.•DevS3 is objective, continuous and automatic and enables remote monitoring.