Time–Frequency Analysis of the Second Heart Sound to Assess Pulmonary Artery Pressure

A method is proposed for noninvasive assessment of the pulmonary artery pressure based on separation of the aortic and pulmonary components of the second heart sound S 2 and determining the delay time between them. The algorithm for separating the aortic and pulmonary components is based on the Wigner–Ville transform. Analysis of the phonocardiograms of 96 patients with pulmonary hypertension (PH) recorded by doctors of the Scientific Research Center of Cardiology using an original set of equipment was carried out. In 53 patients with PH, it was possible to separate S 2 signals into components and determine the delays between them. We construct the dependence of delays between the components on pulmonary artery pressure (PAP), measured by right heart catheterization (RHC). For seven patients with PH, the obtained dependences were used to predict the PAP value from the measured time delay. For five patients, the determination coefficient for the predicted PAP values was 0.83, which indicates a fairly good correlation with measurements by the RHC method.