Diseño, elaboración y validación de un simulador realista y de bajo costo para exploración cardiaca / Design, assembly and validation of a low-cost, high-fidelity simulator for heart exploration

Resumen Introducción: La exploración cardiaca es una competencia clínica fundamental que requiere exposición o entrenamiento continuo. La baja disponibilidad y accesibilidad de pacientes con patología cardiaca constituye una barrera para adquirir esta competencia. Se han documentado inadecuadas habilidades de auscultación cardiaca en estudiantes de medicina, residentes y médicos graduados. Objetivo: Elaborar y validar un simulador de alta fidelidad y bajo costo para exploración cardiaca. Métodos: Se diseñó y elaboró un simulador para exploración cardiaca, realista y de bajo costo capaz de reproducir ruidos cardiacos normales. Posteriormente se realizó la validación del simulador por un grupo de expertos que emitieron su opinión de acuerdo con una escala tipo Likert. Resultados: El 94 % afirmó que el simulador motiva el aprendizaje de la exploración cardiaca y 92 % lo consideró un modelo realista; 91 % consideró que el simulador es una herramienta atractiva para fortalecer el aprendizaje y 98 % recomendó seguir utilizándolo. Conclusiones: El uso del simulador facilita la adquisición de competencias y estimula el aprendizaje en el estudiante, lo cual puede ser atribuido a la práctica deliberada, a un mayor tiempo de exposición y a la interacción cognitiva.

Abstract Introduction: Heart exploration is an essential clinical competence that requires continuous training and exposure. Low availability and accessibility to patients with heart disease constitutes a barrier to acquiring this competence. Inadequate cardiac auscultation skills in medical students, residents, and graduate physicians have been documented. Objective: To develop and validate a low-cost, high-fidelity simulator for heart exploration. Methods: A low-cost, high-fidelity heart examination simulator capable of reproducing normal cardiac sounds was designed and developed. Subsequently, the simulator was validated by a group of experts who gave their opinion according to a Likert scale. Results: Ninety-four percent agreed that the simulator motivates the learning of heart exploration, and 92 % considered it to be a realistic model; 91 % considered that the simulator is an attractive tool to reinforce learning and 98 % recommended its further use. Conclusions: The use of the simulator facilitates the acquisition of skills and stimulates learning in the student, which can be attributed to repeated practice, longer exposure time and cognitive interaction.

Analyzing approaches to mathematic modeling of heart sounds

The article introduces the findings of the analysis of the existing approaches to the development of mathematical models of acoustic heart phenomena. The analysis of mathematical methods that can be used to model heart sounds has been performed with the use of reference signals from the 3M Open Library (Littmann Library) and a set of signals obtained by the authors during their previous scientific efforts. The analysis findings have allowed revealing the approaches and methods that are most suitable for developing the mathematical models of human phonocardiograms (normal and pathological) for further research efforts meant to develop methods to single out heart beats against the high level of interference and creating intervalograms to characterize the heart rate at the current moments of time. In addition to the generation of model phonocardiograms, the article reviews the methods to analyze model and real-life phonocardiograms with the assessment of an input from random and deterministic components.

Changes of some biochemical markers and cardiac function in New Zealand rabbits with chronic heart failure / 中国应用生理学杂志

OBJECTIVE@#This article investigated the changes of some biochemical markers and cardiac function in chronic heart failure (CHF), and provided the basis for the diagnosis of CHF.@*METHODS@#New Zealand rabbit CHF model was established using adriamycin (ADR). Twenty New Zealand rabbits were randomly divided into model group (=15) and control group (=5), injected with ADR and saline solution the ear vein respectively, 2 times a week, lasting for 8 weeks. After that, myocardial enzymes, carotid artery pressure, echocardiogram (ECG) and phonocardiogram (PCG) of all New Zealand rabbits were detected and recorded.@*RESULTS@#Compared with control group, all parameters of the model group were changed significantly (<0.05).@*CONCLUSIONS@#CHF leads to myocardial damage in New Zealand rabbits, decreased systolic and diastolic function, cardiac reserve index can be used to assess cardiac function.

Usefulness of the second heart sound for predicting pulmonary hypertension in patients with interstitial lung disease / Utilidade da segunda bulha cardíaca na predição de hipertensão pulmonar em portadores de doenças intersticiais pulmonares

CONTEXT AND OBJECTIVE: P2 hyperphonesis is considered to be a valuable finding in semiological diagnoses of pulmonary hypertension (PH). The aim here was to evaluate the accuracy of the pulmonary component of second heart sounds for predicting PH in patients with interstitial lung disease. DESIGN AND SETTING: Cross-sectional study at the University of Brasilia and Hospital de Base do Distrito Federal. METHODS: Heart sounds were acquired using an electronic stethoscope and were analyzed using phonocardiography. Clinical signs suggestive of PH, such as second heart sound (S2) in pulmonary area louder than in aortic area; P2 > A2 in pulmonary area and P2 present in mitral area, were compared with Doppler echocardiographic parameters suggestive of PH. Sensitivity (S), specificity (Sp) and positive (LR+) and negative (LR-) likelihood ratios were evaluated. RESULTS: There was no significant correlation between S2 or P2 amplitude and PASP (pulmonary artery systolic pressure) (P = 0.185 and 0.115; P= 0.13 and 0.34, respectively). Higher S2 in pulmonary area than in aortic area, compared with all the criteria suggestive of PH, showed S = 60%, Sp= 22%; LR+ = 0.7; LR- = 1.7; while P2> A2 showed S= 57%, Sp = 39%; LR+ = 0.9; LR- = 1.1; and P2 in mitral area showed: S= 68%, Sp = 41%; LR+ = 1.1; LR- = 0.7. All these signals together showed: S= 50%, Sp = 56%. CONCLUSIONS: The semiological signs indicative of PH presented low sensitivity and specificity levels for clinically diagnosing this comorbidity.

RESUMO CONTEXTO E OBJETIVO: Hiperfonese de P2 tem sido considerada como achado valoroso no diagnóstico semiológico de hipertensão pulmonar (HP). O objetivo foi de avaliar a acurácia do componente pulmonar da segunda bulha cardíaca em predizer HP nos pacientes portadores de doenças intersticiais pulmonares. TIPO DE ESTUDO E LOCAL: Estudo transversal na Universidade de Brasília e Hospital de Base do Distrito Federal. MÉTODOS: Os sons cardíacos foram adquiridos com estetoscópio eletrônico e analisados por fonocardiografia. Os sinais clínicos sugestivos de HP, como B2 mais intensamente audível em área pulmonar que aórtica, P2 > A2 na área pulmonar e P2 presente em área mitral foram confrontados com parâmetros cardiográficos no exame de Doppler sugestivos de HP. Sensibilidade (S), especificidade (E), razões de verossimilhança positiva (RV+) e negativa (RV-) foram avaliados. RESULTADOS: Não houve correlação significativa entre amplitude de B2 e P2 e a PSAP (pressão sistólica arterial pulmonar) (P = 0,185 e 0,115; P = 0,13 e 0,34; respectivamente). A análise da presença de B2 mais intensa na área pulmonar que aórtica, quando comparada a todos os critérios sugestivos de HP, mostrou S = 60%; E = 22%; RV+ = 0,7; RV- = 1,7; enquanto P2 > A2 mostrou: S = 57%; E = 39%; RV+ = 0,9; RV- = 1,1; e P2 no foco mitral mostrou: S = 68%; E = 41%; RV+ = 1,1; RV- = 0,7. Todos os sinais juntos mostraram S = 50%; E = 56%. CONCLUSÃO: Os sinais semiológicos indicativos de HP apresentam baixos valores de especificidade e sensibilidade para diagnóstico clínico dessa comorbidade.

Segmentação automática para classificação digital de sinais de fonocardiograma / Automatic segmentation for signal classification of digital phonocardiogram

Com o avanço tecnológico surgem novas ferramentas que auxiliam os médicos no diagnóstico de diversas doenças. Na área cardiovascular, após permanecer por um longo período em segundo plano, a ausculta cardíaca voltou a ser muito utilizada devido ao surgimento, no mercado, de estetoscópios digitais. Tais aparelhos contam com novos recursos tecnológicos que permitem a captação e a análise de dados de forma automática, oferecendo mais informações ao profissional da área. Levando em conta essa nova ascensão da área de Fonocardiografia,o presente trabalho se dedicou à separação das bulhas S1 e S2 por meio de ferramentas computacionais, com o propósito de auxiliar médicos não especialistas em Cardiologia a verificar a existência de possíveis anormalidades no som cardíaco. Acreditando na possibilidade de este procedimento vir a ser utilizado posteriormente para auxiliar no reconhecimento de padrões dos sons cardíacos, este trabalho se propôs a criar um algoritmo para detecção automática de anormalidades que afetam as bulhas S1 e S2. Assim, aplicou-se a técnica de Wavelet sobre uma base de dados de sons cardíacos constituída de 1209 bulhas...

An Improved Empirical Mode Decomposition Algorithm for Phonocardiogram Signal De-noising and Its Application in S1/S2 Extraction / 生物医学工程学杂志

In this paper, an improved empirical mode decomposition (EMD) algorithm for phonocardiogram (PCG) signal de-noising is proposed. Based on PCG signal processing theory, the S1/S2 components can be extracted by combining the improved EMD-Wavelet algorithm and Shannon energy envelope algorithm. Firstly, by applying EMD-Wavelet algorithm for pre-processing, the PCG signal was well filtered. Then, the filtered PCG signal was saved and applied in the following processing steps. Secondly, time domain features, frequency domain features and energy envelope of the each intrinsic mode function's (IMF) were computed. Based on the time frequency domain features of PCG's IMF components which were extracted from the EMD algorithm and energy envelope of the PCG, the S1/S2 components were pinpointed accurately. Meanwhile, a detecting fixed method, which was based on the time domain processing, was proposed to amend the detection results. Finally, to test the performance of the algorithm proposed in this paper, a series of experiments was contrived. The experiments with thirty samples were tested for validating the effectiveness of the new method. Results of test experiments revealed that the accuracy for recognizing S1/S2 components was as high as 99.75%. Comparing the results of the method proposed in this paper with those of traditional algorithm, the detection accuracy was increased by 5.56%. The detection results showed that the algorithm described in this paper was effective and accurate. The work described in this paper will be utilized in the further studying on identity recognition.

Research on biometric method of heart sound signal based on GMM / 中国医疗器械杂志

<p><b>OBJECTIVE</b>Extraction of cepstral coefficients combined with Gaussian Mixture Model (GMM) is used to propose a biometric method based on heart sound signal.</p><p><b>METHODS</b>Firstly, the original heart sounds signal was preprocessed by wavelet denoising. Then, Linear Prediction Cepstral Coefficients (LPCC) and Mel Frequency Cepstral Coefficients (MFCC) are compared to extract representative features and develops hidden Markov model (HMM) for signal classification. At last, the experiment collects 100 heart sounds from 50 people to test the proposed algorithm.</p><p><b>RESULTS</b>The comparative experiments prove that LPCC is more suitable than MFCC for heart sound biometric, and by wavelet denoising in each piece of heart sound signal, the system achieves higher recognition rate than traditional GMM.</p><p><b>CONCLUSION</b>Those results show that this method can effectively improve the recognition performance of the system and achieve a satisfactory effect.</p>

Analysis of the heart sound with arrhythmia based on nonlinear chaos theory / 生物医学工程学杂志

In this paper, a new method based on the nonlinear chaos theory was proposed to study the arrhythmia with the combination of the correlation dimension and largest Lyapunov exponent, through computing and analyzing these two parameters of 30 cases normal heart sound and 30 cases with arrhythmia. The results showed that the two parameters of the heart sounds with arrhythmia were higher than those with the normal, and there was significant difference between these two kinds of heart sounds. That is probably due to the irregularity of the arrhythmia which causes the decrease of predictability, and it's more complex than the normal heart sound. Therefore, the correlation dimension and the largest Lyapunov exponent can be used to analyze the arrhythmia and for its feature extraction.

The acquisition and analysis of heart sound signals based on DSP / 生物医学工程学杂志

Heart sound signals acquisition is the primary basis for achieving non-invasive diagnosis of coronary heart disease. In this paper, a digital signal processor (DSP)-based on miniaturized circuit of heart sound signals acquisition and analysis platform was designed to achieve the functions of filtering, collecting, processing, displaying and the communicating with PC. With the self-developed experimental platform, we collected 228 cases of heart sounds of clinical data, and processed the signals using de-noising method with wavelet transform. These experimental results indicated that the db6 wavelet has the most obvious de-noising effect among the four most commonly used wavelets, i.e., haar, db6, sym8, and coif5. One wavelet at different levels possessed different de-noising effects, with level-5 db6 decomposition obtaining the most desirable result.

Change of cardiac reserve during abnormal pregnancy and its evaluation / 中国医学科学院学报

<p><b>OBJECTIVE</b>To investigate the change of cardiac reserve during abnormal pregnancy and explore its evaluation methods.</p><p><b>METHODS</b>Totally 96 women with abnormal pregnancies (AP group), 356 women with normal pregnancies (NP group), and 100 women of childbearing age (CBA group) were monitored by the exercise cardiac contractility monitor (ECCM). Phonocardiogram of participants at resting status was recorded by ECCM. The amplitude of first heart sound (S1), the amplitude of second heart sound (S2), cardiac cycle, diastolic duration (D), and systolic duration (S) were detected and then the S1/S2 ratio,the D/S ratio, and heart rate (HR) were calculated.</p><p><b>RESULTS</b>Compared with the CBA group, S1/S2 ratio and HR were significantly higher and D/S was significantly lower in both AP group and NP group (all P<0.001). Compared with the NP group, S1/S2 ratio and HR were significantly higher in AP group and D/S was significnatly lower (all P<0.001). A D/S ratio less than 1.1 or S1/S2 ratio higher than 1.8 was associated with higher risk of poor pregnancy outcomes. Among four common pregnancy-associated abnormalities, the level of cardiac reserve was lowest in eclampsia, followed by twins, gestational diabetes mellitus, and gestational hypertension.</p><p><b>CONCLUSIONS</b>Cardiac reserve is mobilized during pregnancy, and is especially during the abnormal pregnancies due to the heavy cardiac burden. S1/S2 ratio, D/S ratio, and HR are useful in evaluating the cardiac reserve during abnormal pregnancy.</p>

Spectral analysis and LDB based classification of heart sounds with mechanical prosthetic heart valves / 生物医学工程学杂志

Auscultation, the act of listening for heart sounds to aid in the diagnosis of various heart diseases, is a widely used efficient technique by cardiologists. Since the mechanical prosthetic heart valves are widely used today, it is important to develop a simple and efficient method to detect abnormal mechanical valves. The study on five different mechanical valves showed that only the case of perivalvular leakage could be detected by spectral estimation. Though it is possible to classify different mechanical valves by using time-frequency components of the signal directly, the recognition rate is merely 84%. However, with the improved local discriminant bases (LDB) algorithm to extract features from heart sounds, the recognition rate is 97.3%. Experimental results demonstrated that the improved LDB algorithm could improve classification rate and reduce computational complexity in comparison with original LDB algorithm.

A relative value method for measuring and evaluating neonatal cardiac reserve.

Objective. To devise some indicators for measuring and evaluating the neonatal cardiac reserve by using phonocardiogram test (PCGT). Methods. Two hundred and thirty one (231) full term and one hundred and fifty four (154) preterm infants participated in this study. The amplitude ratio of the first heart sound to the second heart sound (S1/S2), the ratio of diastolic to systolic duration (D/S) and the cardiac contractility change trend after stimulation (CCCTS) of the neonates were measured, calculated and analyzed. Results. The S1/S2, D/S and CCCTS of full preterm infants were higher than that of preterm infants. The differences of D/S and CCCTS between them were significant (P<0.05). According to the full term neonatal cardiac reserve data, a normal reference range of full term neonatal cardiac reserve was primarily known. Conclusions. The indicators S1/S2, D/S and CCCTS may be beneficial for evaluating the neonatal cardiac reserve. We can screen out neonates with reduced cardiac reserve by using the phonocardiogram test.

A clinical study of cardiac reserve mobilizing condition for pregnant women / 生物医学工程学杂志

This study was conducted on the basis of informed consent of subjects and was approved by the ethical review committee concerned. 527 pregnant women voluntarily participated in this project for the investigation of cardiac reserve mobilizing condition. Using the digital technique of heart sound signal processing, we measured the heart rate (HR), the ratio of the first heart sound to the second heart sound (S1/S2)and the ratio of diastolic to systolic duration (D/S) during pregnancy. There was significant difference of HR and S1/S2 between the group of non-pregnant (G1), the group of 28-36 pregnant weeks (G2), and the group of 37-42 pregnant weeks (G3) (HR, S1/S2: G1 vs G2, G1 vs G3: P < 0.01). HR of the pregnant women increased with the increase of pregnant weeks. D/S decreased with the increase of pregnant weeks. There was significant difference of D/S between G1, G2, and G3 (G1 vs. G2: P < 0.01; G1 vs. G3: P < 0.01). There was also significant difference of D/S between G2 and G3 (G2 vs. G3: P < 0.05). Everybody in the non-pregnant women group was found to have D/S > or = 1.30; 64.33% of pregnant women were found to have 1.00 < D/S < 1.30, whereas 3.05% of pregnant women were found to have D/S < 1.00. These data revealed that the heart burden of the pregnant woman increased with the increase of pregnant weeks and the mobilization of cardiac reserve.

A new method for heart sound analysis in time domain / 生物医学工程学杂志

In order to discriminate normal and abnormal heart sounds accurately and effectively, a new method is proposed to analyze heart sounds, namely heart sound characteristic waveform (HSCW) method. Digital stethoscope is used to collect heart sound signals. The recorded data are transmitted to a computer by USB interface for analysis based on HSCW, which is extracted from an analytical model of single degree-of-freedom (SDOF). Furthermore, a case study on the normal and abnormal cardiac sounds is demonstrated to validate the usefulness and efficiency of the proposed HSCW method. Besides, in order to test the accuracy of discriminating normal and abnormal heart sounds, 40 normal and 20 abnormal heart sounds are collected and analyzed, the accuracy performances are achieved by 92.5% and 95.0%, respectively.

A basis for application of cardiac contractility variability in the Evaluation and assessment of exercise and fitness / 生物医学工程学杂志

Cardiac contractility variability (CCV) is a new concept which is introduced in the research field of cardiac contractility in recent years, that is to say, there are some disparities between cardiac contractilities when heart contracts. The changing signals of cardiac contractility contain a plenty of information on the cardiovascular function and disorder. In order to collect and analyze the message, we could quantitatively evaluate the tonicity and equilibrium of cardiac sympathetic nerve and parasympathetic nerve, and the effects of bio-molecular mechanism on the cardiovascular activities. By analyzing CCV, we could further understand the background of human being's heritage characteristics, nerve types, the adjusting mechanism, the molecular biology, and the adjustment of cardiac automatic nerve. With the development of the computing techniques, the digital signal processing method and its application in medical field, this analysis has been progressing greatly. By now, the assessment of CCV, just like the analysis of heart rate variability, is mainly via time domain and frequency domain analysis. CCV is one of the latest research fields in human cardiac signals being scarcely reported in the field of sports medicine; however, its research progresses are of important value for cardiac physiology and pathology in sports medicine and rehabilitation medicine.

A study on the four modes for transmitting heart sound signal / 生物医学工程学杂志

As an important human body sound signal, heart sound is of great value in the researches on diagnostics of heart diseases. This study sought to explore the methods of transmitting heart sound through the telephone correspondence system for simultaneous telemetering cardiac contractility and heart rate. Heart sounds were transmitted from a phone to another phone with 4 modes, the wirelessly transmitted distance between the two phones being 5 m, 10 km, and 1000 km, respectively. The results of experiments show that telemetering cardiac contractility and heart rate can be realized by the telephone correspondence system. Such methods have the advantages of being noninvasive, inexpensive, rapid and convenient; moreover, they can be used repeatedly and be available for in-home use.

Development of heart sound signal detection system based on USB interface / 生物医学工程学杂志

This paper introduces a type of heart sound recording, analysis and processing system based on USB interface. The system consists of high performance sensor sampling heart sounds, the preprocessing circuit, the A/D conversion module and the USB based high-speed computer communications interface. The experiments show that it is noninvasive, convenient, inexpensive and rapid in detecting the cardiac contractility of patients with heart disease as well as of healthy subjects. This system has provided a reliable technical platform for evaluating the cardiac contractility reserve.

Synchronous playing and acquiring of heart sounds and electrocardiogram based on labVIEW / 生物医学工程学杂志

In this paper is described a comprehensive system, which can acquire heart sounds and electrocardiogram (ECG) in parallel, synchronize the display; and play of heart sound and make auscultation and check phonocardiogram to tie in. The hardware system with C8051F340 as the core acquires the heart sound and ECG synchronously, and then sends them to indicators, respectively. Heart sounds are displayed and played simultaneously by controlling the moment of writing to indicator and sound output device. In clinical testing, heart sounds can be successfully located with ECG and real-time played.

Application and comparison of continuous wavelet transform and matching pursuit method in analyzing phonocardiographic signals / 生物医学工程学杂志

Heart sounds are highly valuable to the clinical diagnoses of most cardiovascular diseases, so the analysis of phonocardiographic signals is helpful to diagnosing cardiovascular diseases clinically. Phonocardiographic signals are non-stable, so it is necessary to choose appropriate method in time-frequency analysis. The traditional method such as Fourier Transform is dissatisfactory. Continuous Wavelet Transform (CWT) and Matching (MPM) Pursuit Method are both effective methods. They can be used to extract and cluster the characteristics of the signals. By analysis and comparison, the two methods showed the advantages over traditional methods. Additionally, their respective merits and demerits are indicated.

Application of independent component analysis for separating phonocardiogram signals / 生物医学工程学杂志

Independent component analysis (ICA) is a novel method developed in recent years for Blind Source Separation. In this paper, the phonocardiogram (PCG) was separated into three components by applying ICA. The basic principle of ICA was introduced in this paper. A fast and robust fixed-point algorithm for ICA was used to analyze PCG signals in this study. The experiments showed that ICA could separate the components of heart sounds from PCG signals successfully.