Segmentation of heart sounds based on dynamic clustering

The heart sound signal is first separated into cycles, where the cycle detection is based on an instantaneous cycle frequency. The heart sound data of one cardiac cycle can be decomposed into a number of atoms characterized by timing delay, frequency, amplitude, time width and phase. To segment heart sounds, we made a hypothesis that the atoms of a heart sound congregate as a cluster in time–frequency domains. We propose an atom density function to indicate clusters. To suppress clusters of murmurs and noise, weighted density function by atom energy is further proposed to improve the segmentation of heart sounds. Therefore, heart sounds are indicated by the hybrid analysis of clustering and medical knowledge. The segmentation scheme is automatic and no reference signal is needed. Twenty-six subjects, including 3 normal and 23 abnormal subjects, were tested for heart sound signals in various clinical cases. Our statistics show that the segmentation was successful for signals collected from normal subjects and patients with moderate murmurs.

► The heart sound signal is separated into cardiac cycles based on the concept of instantaneous cycle frequency.
► The heart sound data of each cardiac cycle is decomposed into time–frequency atoms.
► The atoms of heart sounds behave as clusters in time–frequency plane; but, the atoms of murmurs are dispersed in the plane.
► Heart sounds are indicated by the hybrid analysis of atoms clustering and medical knowledge.