Abstract
This study introduced entropy measures to analyze the heart sound signals of people with and without pulmonary hypertension (PH). The lead II Electrocardiography (ECG) signal and heart sound signal were simultaneously collected from 104 subjects aged between 22 and 89. Fifty of them were PH patients and 54 were healthy. Eleven heart sound features were extracted and three entropy measures, namely sample entropy (SampEn), fuzzy entropy (FuzzyEn) and fuzzy measure entropy (FuzzyMEn) of the feature sequences were calculated. The Mann–Whitney U test was used to study the feature significance between the patient and health group. To reduce the age confounding factor, nine entropy measures were selected based on correlation analysis. Further, the probability density function (pdf) of a single selected entropy measure of both groups was constructed by kernel density estimation, as well as the joint pdf of any two and multiple selected entropy measures. Therefore, a patient or a healthy subject can be classified using his/her entropy measure probability based on Bayes’ decision rule. The results showed that the best identification performance by a single selected measure had sensitivity of 0.720 and specificity of 0.648. The identification performance was improved to 0.680, 0.796 by the joint pdf of two measures and 0.740, 0.870 by the joint pdf of multiple measures. This study showed that entropy measures could be a powerful tool for early screening of PH patients.
Highlights
Pulmonary hypertension (PH) is a hemodynamic and pathophysiological condition in which pulmonary artery pressure rises above a certain threshold
In the early stage of PH, the symptoms are not apparent to be perceived by physicians but the mechanical activity of the heart has quietly changed and it can be reflected to some degree in the heart sound signals [2,3]
The p values of entropy measures related to Int_s1 (No 31–33) were much greater than others, which meant that these measures were not significant between PH and healthy group
Summary
Pulmonary hypertension (PH) is a hemodynamic and pathophysiological condition in which pulmonary artery pressure rises above a certain threshold. PH is a potentially fatal disease that can cause right heart failure [1]. If the PH is not diagnosed in a timely manner and no pretreatments are done actively, it will have serious consequences. In the early stage of PH, the symptoms are not apparent to be perceived by physicians but the mechanical activity of the heart has quietly changed and it can be reflected to some degree in the heart sound signals [2,3]. Previous studies have shown that the time interval between the aortic component (A2) and the pulmonary component (P2) of the second heart sound (S2), as well as the dominant frequency of P2, increases in PH patients and they bring potential values to noninvasive diagnosis of PH [4,5].
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