Relationship between accurate auscultation of the fourth heart sound and the level of physician experience.

BACKGROUND: Poor performance by physicians-in-training and interobserver variability between physicians has diminished clinicians' confidence in the value of the fourth heart sound (S4). HYPOTHESIS: We sought to determine if accurate auscultation of an S4 improves with advancing levels of experience. METHODS: We performed a prospective study of 100 patients undergoing left heart catheterization. Patients underwent blinded auscultation by 4 physicians (each from 1 of 4 different levels of experience), computerized acoustic cardiography, measurement of B-type natriuretic peptide (BNP) levels, echocardiography for measurement of left ventricular ejection fraction (LVEF), and cardiac catheterization for measurement of left ventricular end-diastolic pressure (LVEDP). RESULTS: While cardiology fellows', residents', and interns' auscultatory findings demonstrated no significant agreement with acoustic cardiography, an S4 auscultated by cardiology attendings had moderate diagnostic accuracy with acoustic cardiography (odds ratio [OR]: 2.31; receiver-operating-characteristic [ROC] area: 0.60). The sensitivities of the S4 were low (39%-46%) for identifying patients with abnormal measures of left ventricular filling pressure (BNP and LVEDP, respectively), and the specificities were fair (76%-80%) with acoustic cardiography. The S4 was not associated with abnormal LVEF. None of the ausculatory groups performed as well as acoustic cardiography in separating patients based on objective measures of left ventricular filling pressure. Acoustic cardiography had the lowest (superior) negative likelihood ratios compared to any ausculatory group. CONCLUSIONS: The S4 auscultated by cardiology attendings demonstrated superior diagnostic test characteristics compared with internal medicine housestaff and cardiology fellows. Correlations between the S4 and measures of ventricular filling pressure were superior for acoustic cardiography compared to the auscultator groups.

Analysis of PCG signals using quality assessment and homomorphic filters for localization and classification of heart sounds.

BACKGROUND AND OBJECTIVE: Accurate localization of heart beats in phonocardiogram (PCG) signal is very crucial for correct segmentation and classification of heart sounds into S1 and S2. This task becomes challenging due to inclusion of noise in acquisition process owing to number of different factors. In this paper we propose a system for heart sound localization and classification into S1 and S2. The proposed system introduces the concept of quality assessment before localization, feature extraction and classification of heart sounds. METHODS: The signal quality is assessed by predefined criteria based upon number of peaks and zero crossing of PCG signal. Once quality assessment is performed, then heart beats within PCG signal are localized, which is done by envelope extraction using homomorphic envelogram and finding prominent peaks. In order to classify localized peaks into S1 and S2, temporal and time-frequency based statistical features have been used. Support Vector Machine using radial basis function kernel is used for classification of heart beats into S1 and S2 based upon extracted features. The performance of the proposed system is evaluated using Accuracy, Sensitivity, Specificity, F-measure and Total Error. The dataset provided by PASCAL classifying heart sound challenge is used for testing. RESULTS: Performance of system is significantly improved by quality assessment. Results shows that proposed Localization algorithm achieves accuracy up to 97% and generates smallest total average error among top 3 challenge participants. The classification algorithm achieves accuracy up to 91%. CONCLUSION: The system provides firm foundation for the detection of normal and abnormal heart sounds for cardiovascular disease detection.

Non-invasive fetal monitoring using electrocardiography and phonocardiography: A preliminary study.

BACKGROUND: Continuous fetal monitoring is commonly used during pregnancy and labor to assess fetal wellbeing. The most often used technology is cardiotocography (CTG), but this technique has major drawbacks in clinical use. OBJECTIVES: Our aim is to test a non-invasive multimodal technique of fetal monitoring using phonocardiography (PCG) and electrocardiography (ECG) and to evaluate its feasibility in clinical practice, by comparison with CTG. METHODS: This prospective open label study took place in a French university hospital. PCG and ECG signals were recorded using abdominal and thoracic sensors from antepartum women during the second half of pregnancy, simultaneously with CTG recording. Signals were then processed to extract fetal PCG and ECG and estimate fetal heart rate (FHR). RESULTS: A total of 9 sets of recordings were evaluated. Very accurate fetal ECG and fetal PCG signals were recorded, enabling us to obtain FHR for several subjects. The FHR calculated from ECG was highly correlated with the FHR from the CTG reference (from 74% to 84% of correlation). CONCLUSION: This work with preliminary signal processing algorithms proves the feasibility of the approach and constitutes the beginnings of a unique database that is needed to improve and validate the signal processing algorithms.

Time-frequency transforms: a new approach to first heart sound frequency dynamics.

This study employed a new analytical tool, the Binomial joint time-frequency transform, to test the hypothesis that first heart sound frequency rises during the isovolumic contraction period. Cardiac vibrations were recorded from eight open chest dogs using an ultralight accelerometer cemented directly to the epicardium of the anterior left ventricle. The frequency response of the recording system was flat +/- 3 dB from 0.1 to 400 Hz. Three characteristic time-frequency spectral patterns were evident in the animals investigated: 1) A frequency component that rose from approximately 40-140 Hz in a 30-50 ms interval immediately following the ECG R-wave. 2) A slowly varying or static frequency of 60-100 Hz beginning midway through the isovolumic contraction period. 3) Broad-band peaks occurring at the time of the Ia and Ib high frequency components. The presence of rapid frequency dynamics limits the usefulness of stationary analysis techniques for the first heart sound. The Binomial transform provided much better resolution than the spectrograph or spectrogram, the two most common non-stationary signal analysis techniques. By revealing the onset and dynamics of first heart sound frequencies, time-frequency transforms may allow mechanical assessment of individual cardiac structures.

Accelerometer type cardiac transducer for detection of low-level heart sounds.

New applications in phonocardiography require transducers with high sensitivity, low noise, and extended frequency range. This paper compares several different cardiac transducers and describes the development of a low-mass, accelerometer type cardiac transducer which fulfills these objectives. The accelerometer weighs approximately 5 g and has a theoretical sensitivity of 125 mV/g in the frequency range 200-800 Hz. The basic design allows for easy modification of sensitivity and resonant frequency. This transducer has been effective in detecting sounds associated with turbulent blood flow in partially occluded coronary arteries.

[Fetal phonocardiography with a novel approach]. / Magzati fonokardiográfia új megközelítésben.

The long-term recording of the fetal heart rate (FHR) variability is one of the most frequently used tools of routine fetal diagnostics which is usually carried out by the means of ultrasound cardiography. Frequent measurement of FHR is recommendable, however the cost of high quality ultrasound devices is unfortunately so high that this technology is not viable for low-cost devices used in the home-care sector. An alternative approach of FHR recording can be based on the fully non-invasive, passive acoustic recording, called phonocardiography. The evaluation of fetal phonocardiograms is complicated by various internal and external noise factors. The development of accurate and robust fetal phonocardiographs has been studied by biomedical researchers since long. This paper presents a novel two-channel phonocardiographic device and an advanced signal processing method, which provides a performance comparable to that of ultrasound cardiography. The proposed system offers an optimal trade-off between complexity and feasibility and it is viable in low-cost, stand-alone, battery-powered FHR monitoring devices. The developed system provided 83% accuracy compared to the simultaneously recorded reference ultrasound records.

[An analysis of precision and accuracy of the phonocardiogram exercise test].

Phonocardiogram exercise testing (PCGET) is a recently developed method to evaluate cardiac contractility and the cardiac reserve of patients with heart disease and of healthy subjects. In order to test the reliability of PCGET method, the present author conducted a study on its precision and accuracy. Thirty volunteers underwent PCGET. When different examiners measured the S1 amplitude in the same cardiac cycle of the same subject, the data obtained by examiner A were: x +/- s = 5.05 +/- 0.0451; the data obtained by examiner B were: x +/- s = 4.95 +/- 0.0346, F = 1.699, P > 0.05. When different examiners measured the same cardiac cycle of the same subject, the data obtained by examiner A were: x +/- s = 0.789 +/- 0.0018; the data obtained by examiner B were: x +/- s = 0.787 +/- 0.0017, F = 1.167, P > 0.05. The results suggest that PCGET is a nonivasive, convenient, and inexpensive technique to quantitatively evaluate cardiac reserve for abnormal or normal persons.

[Experience in developing devices for medical use exemplified by the electronic stethophonoendoscope]. / Opyt razrabotki priborov meditsinskogo naznacheniia na primere élektronnogo stetofonendoskopa.

The paper describes the use of the expert's error technique to provide evidence and pool medical specifications for an electron amplifying stethophonoendoscope, a medical diagnostic device. It illustrates the impact of variations in amplitude-frequency responses (AFR) on the auscultation properties of the devise. An AFR variation of only 10-12 dB can distort sound perception at auscultation. The results of development of the electron stethophonoendoscope indicate that the correct choice of criteria for expert's estimates allows the device's specifications to be worked out with simultaneous simplification of testing procedures.

Non-invasive monitoring and evaluating cardiac function of pregnant women based on a relative value method.

This paper proposed a relative value method for measuring the indicators of cardiac reserve and investigated the application on monitoring and evaluating cardiac function for pregnant women. A heart sound sensor is placed at the precordial region to detect phonocardiogram. In order to access the cardiac reserve mobilization level during pregnancy, the cardiac reserve indicators of 1,683 normal pregnant women, 96 abnormal cases with different obstetric complications and 624 non-pregnant women were measured, analyzed and compared. The result shows that the differences between the indicators of pregnant and non-pregnant women were significant (p < 0.05). The ratio of diastolic to systolic duration (D/S) was obviously declined with the increase of gestational weeks and the occurrence of obstetric complication. This very encouraging result indicates that the D/S can be used as an indicator for evaluating the cardiac safety of parturition, which provides a reference for cardiac safety assessment of pregnant women.

Characterization of cardiac time intervals in healthy bonnet macaques (Macaca radiata) by using an electronic stethoscope.

Nonhuman primates are used frequently in cardiovascular research. Cardiac time intervals derived by phonocardiography have long been used to assess left ventricular function. Electronic stethoscopes are simple low-cost systems that display heart sound signals. We assessed the use of an electronic stethoscope to measure cardiac time intervals in 48 healthy bonnet macaques (age, 8±5 y) based on recorded heart sounds. Technically adequate recordings were obtained from all animals and required 1.5±1.3 min. The following cardiac time intervals were determined by simultaneously recording acoustic and single-lead electrocardiographic data: electromechanical activation time (QS1), electromechanical systole (QS2), the time interval between the first and second heart sounds (S1S2), and the time interval between the second and first sounds (S2S1). QS2 was correlated with heart rate, mean arterial pressure, diastolic blood pressure, and left ventricular ejection time determined by using echocardiography. S1S2 correlated with heart rate, mean arterial pressure, diastolic blood pressure, left ventricular ejection time, and age. S2S1 correlated with heart rate, mean arterial pressure, diastolic blood pressure, systolic blood pressure, and left ventricular ejection time. QS1 did not correlate with any anthropometric or echocardiographic parameter. The relation S1S2/S2S1 correlated with systolic blood pressure. On multivariate analyses, heart rate was the only independent predictor of QS2, S1S2, and S2S1. In conclusion, determination of cardiac time intervals is feasible and reproducible by using an electrical stethoscope in nonhuman primates. Heart rate is a major determinant of QS2, S1S2, and S2S1 but not QS1; regression equations for reference values for cardiac time intervals in bonnet macaques are provided.

Impedance plethysmography of thoracic region: impedance cardiography.

Impedance plethysmograms were recorded from thoracic region in 254 normal subjects, 183 patients with coronary artery disease, 391 patients with valvular heart disease and 107 patients with congenital septal disorder. The data in 18 normal subjects and 55 patients showed that basal impedance decreases markedly during exercise in patients with ischaemic heart disease. Estimation of cardiac index by this technique in a group of 99 normal subjects has been observed to be more consistent than that of the stroke volume. Estimation of systolic time index from impedance plethysmograms in 34 normal subjects has been shown to be as reliable as that from electrocardiogram, phonocardiogram and carotid pulse tracing. Changes in the shape of plethysmographic waveform produced by valvular and congenital heart diseases are briefly described and the role of this technique in screening cardiac patients has been highlighted.

Application of adaptive FTF/FAEST zero tracking filters to noninvasive characterization of the sound pattern caused by coronary artery stenosis before and after angioplasty.

This article presents a new signal processing application that can be used for acoustical detection of coronary artery disease before and after angioplasty. The adaptive Autoregressive (AR) method based on the FTF/FAEST (Fast transversal filters/Fast a posteriori error sequential techniques) is used to track acoustical behavior associated with coronary occlusions. Using the amplitude trajectory of the second pole pair of this method, 9 out of 10 angioplasty patients were correctly identified using a blind protocol without prior knowledge of whether a given recording was made before and after angioplasty. These results were obtained from signals located between 200 and 300 msec after the end of the second heart sound during the diastolic period.

Doppler measurement of left ventricular isovolumic intervals: a study of feasibility and correlation with conventional techniques.

Pulsed Doppler echocardiography allows simultaneous recording of left ventricular inflow and outflow blood velocities obtained from the apical 5-chamber view. In this study the feasibility and accuracy of pulsed Doppler measurements of left ventricular isovolumic relaxation and contraction times were compared with those derived from two conventional techniques that combined phonocardiograms and M-mode echograms (phono-echo) and M-mode echograms and electrocardiograms (ECG-echo). Thirty-seven subjects--24 healthy volunteers and 13 cardiac patients--were examined. Isovolumic relaxation was consistently longer than isovolumic contraction time. Younger age was associated with shorter isovolumic intervals, while heart rate had a negative correlation with these parameters (r = -0.5). Pulsed Doppler measurements of isovolumic relaxation correlated well with phono-echo, r = 0.89, and ECG-echo, r = 0.75. Isovolumic contraction times measured by Doppler correlated better with those derived by phono-echo, r = 0.75, than those by ECG-echo, r = 0.4. Better correlations were found for both measurements in the normal subgroup than in the whole group. Difficulty was encountered in measuring isovolumic contraction time by Doppler and ECG-echo in the absence of presystolic A-wave, and in subjects with varying cardiac cycle lengths. Thus, pulsed Doppler measurements of left ventricular isovolumic relaxation times were feasible and consistent with the other methods, while isovolumic contraction intervals by Doppler were not.