Heart Sound Analysis for Blood Pressure Estimation

Heart Sound Analysis for Blood Pressure Estimation

Rui Guedes (Faculdade de Medicina da Universidade do Porto, Portugal), Henrique Cyrne Carvalho (Serviço de Cardiologia, Hospital de Santo António, Centro Hospitalar do Porto, Portugal) and Ana Castro (Universidade do Porto, Portugal)
Copyright: © 2018 |Pages: 11
DOI: 10.4018/978-1-5225-2255-3.ch087

Abstract

This paper aims to give a perspective on how the study of the heart sound relation with blood pressure has evolved. The use of heart sound as a surrogate of the BP has been used with more emphasis on the detection of pulmonary hypertension patients, considering the frequency content, amplitude, and split the second heart sound and its subcomponents, which arise following the closure of the corresponding heart valves. Estimation of BP using the analysis of heart sound is characterized by the simplicity of the equipment used to obtain data, which after analysis allows to achieve promising results that until now were only obtained with techniques far more complex and expensive equipment. The main objective of this article is to understand how heart sound analysis may be used to estimate blood pressure and which methods are employed to detect pulmonary hypertension.
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Background

A noninvasive estimation of the PAP is already in clinical use, the Doppler echocardiography; it uses ultrasound technology to measure PAP by analyzing the speed of blood flowing through the heart. Doppler is widely used by cardiologists, it requires specific equipment, a specialized and trained doctor, and therefore it is difficult to be used for continuous monitoring, or in places without specialized healthcare professionals. Also some patients are not candidates for Doppler due to physiological constraints or poor signal-to-noise ratio: PAP cannot be estimated in 34 to 76% of patients with chronic obstructive pulmonary disease, 10 to 20% of patients with elevated PAP, and the most important in approximately half of patients with normal PAP (Xu, Durand, & Pibarot, 2003); also the Doppler estimations present an average error of 30% compared to right heart catheterization (Smith & Ventura, 2013).

Another method proposed for PAP noninvasive estimation is the heart sound analysis. Phonocardiography is a technique that generates a record of sounds produced by the contracting heart, resulting from valves and associated vessels vibration, the phonocardiogram (PCG), as we can see in Figure 1.

Figure 1.

Phonocardiogram (PCG) representation with first (S1) and second (S2) heart sounds annotated

Key Terms in this Chapter

First Heart Sound (S1): Sound resulting from mitral and tricuspid valves closure.

Pulmonary Arterial Hypertension (PAH): An increase of blood pressure in the pulmonary artery.

Digital Stethoscope: Equipment used to digitally amplify and record sounds from the body.

Electrocardiogram (ECG): A record and representation of the electrical activity of the heart.

Phonocardiogram (PCG): The record and representation of the heart sound.

Blood Pressure (BP): The pressure exerted in the walls of blood vessels by circulating blood.

Second Heart Sound (S2): Sound resulting from aortic and pulmonary valves closure.

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