Recent research

Ann Biomed Eng. 2009 Feb;37(2):337-53. Epub 2008 Dec 2.

Digital auscultation analysis for heart murmur detection.

Delgado-Trejos E, Quiceno-Manrique AF, Godino-Llorente JI, Blanco-Velasco M, Castellanos-Dominguez G.
Contact: Centro de Investigación, Instituto Tecnológico Metropolitano ITM, Calle 73 No 76A-354 Vía al Volador, Medellín, Colombia.

This work presents a comparison of different approaches for the detection of murmurs from phonocardiographic signals. Taking into account the variability of the phonocardiographic signals induced by valve disorders, three families of features were analyzed: (a) time-varying & time-frequency features; (b) perceptual; and (c) fractal features. With the aim of improving the performance of the system, the accuracy of the system was tested using several combinations of the aforementioned families of parameters. In the second stage, the main components extracted from each family were combined together with the goal of improving the accuracy of the system. The contribution of each family of features extracted was evaluated by means of a simple k-nearest neighbors classifier, showing that fractal features provide the best accuracy (97.17%), followed by time-varying & time-frequency (95.28%), and perceptual features (88.7%). However, an accuracy around 94% can be reached just by using the two main features of the fractal family; therefore, considering the difficulties related to the automatic intrabeat segmentation needed for spectral and perceptual features, this scheme becomes an interesting alternative. The conclusion is that fractal type features were the most robust family of parameters (in the sense of accuracy vs. computational load) for the automatic detection of murmurs. This work was carried out using a database that contains 164 phonocardiographic recordings (81 normal and 83 records with murmurs). The database was segmented to extract 360 representative individual beats (180 per class).

Chest. 2009 Jan;135(1):156-64. Epub 2008 Aug 8.

Mechanism of inspiratory and expiratory crackles.

Vyshedskiy A, Alhashem RM, Paciej R, Ebril M, Rudman I, Fredberg JJ, Murphy R.
Contact: Brigham and Women's, Faulkner Hospitals, Boston University, Harvard School of Public Health, Boston, MA, USA.

OBJECTIVE: Although crackles are frequently heard on auscultation of the chest of patients with common cardiopulmonary disorders, the mechanism of production of these sounds is inadequately understood. The goal of this research was to gain insights into the mechanism of crackle generation by systematic examination of the relationship between inspiratory and expiratory crackle characteristics.
METHODS: Patients with a significant number of both inspiratory and expiratory crackles were examined using a multichannel lung sound analyzer. These patients included 37 with pneumonia, 5 with heart failure, and 13 with interstitial fibrosis. Multiple crackle characteristics were calculated for each crackle, including frequency, amplitude, crackle transmission coefficient, and crackle polarity.
RESULTS: Spectral, temporal, and spatial characteristics of expiratory and inspiratory crackles in these patients were found to be similar, but two characteristics were strikingly different: crackle numbers and crackle polarities. Inspiratory crackles were almost twice as numerous as expiratory crackles (n = 3,308 vs 1,841) and had predominately negative polarity (76% of inspiratory crackles vs 31% of expiratory crackles).
CONCLUSION: These observations are quantitatively consistent with the so-called stress-relaxation quadrupole hypothesis of crackle generation. This hypothesis holds that expiratory crackles are caused by sudden airway closure events that are similar in mechanism but opposite in sign and far less energetic than the explosive opening events that generate inspiratory crackles. We conclude that the most likely mechanism of crackle generation is sudden airway closing during expiration and sudden airway reopening during inspiration.

J Med Eng Technol. 2009;33(1):51-65.

The effectiveness of the wavelet transforms method in the heart sounds analysis.

Debbal SM, Bereksi-Reguig F.
Contact: Genie-Biomedical Laboratory (GBM), Department of Electronics, Faculty of Science Engineering, University Aboubekr Belkaid, Tlemcen, Algeria.

Heart sounds can be used more efficiently by medical doctors when they are displayed visually, rather through a conventional stethoscope. Heart sounds provide clinicians with valuable diagnostic and prognostic information. Although heart sound analysis by auscultation is convenient as a clinical tool, heart sound signals are so complex and non-stationary that they are very difficult to analyse in time or frequency domains. We have studied the extraction of features from heart sounds in the time-frequency domain for recognition of heart sounds through time-frequency analysis. The application of wavelet transform for the heart sounds is thus described. The performance of continuous wavelet transform, discrete wavelet transform and packet wavelet transform is discussed in this paper. After these transformations, we can compare normal and abnormal heart sounds to verify clinical usefulness of our extraction methods for recognition of heart sounds.

Clin Pediatr (Phila). 2008 Nov;47(9):919-25. Epub 2008 Jul 14.

Utility of store-and-forward pediatric telecardiology evaluation in distinguishing normal from pathologic pediatric heart sounds.

Mahnke CB, Mulreany MP, Inafuku J, Abbas M, Feingold B, Paolillo JA.
Contact: Pediatric Department (Cardiology), Tripler Army Medical Center, Honolulu, Hawaii 96859-5000, USA.

Because pediatric cardiologists can accurately diagnose innocent murmurs by physical exam alone, the authors developed a system for remote cardiac auscultation. They hypothesized that their system could accurately classify auscultatory findings as normal/innocent or pathologic. Patients undergoing evaluation underwent examination, echocardiography, and heart sound recording. Pediatric cardiologists evaluated the heart sounds and classified the case as either normal/innocent or pathologic. They reviewed103 heart sound data sets; 85% of the cases were accurately classified as either normal/innocent or pathologic, with a sensitivity of 82% and specificity of 86%. However, when accounting for clinical diagnosis, reviewer uncertainty, and ECG abnormalities, the sensitivity and specificity improved to 91% and 88% (accuracy 89%), respectively. Degree of certainty with the telecardiology diagnosis correlated with correct interpretation (P < .005). Digital heart sound recordings evaluated via telemedicine can distinguish normal/innocent murmurs from pathologic ones. Such a system could improve the use of pediatric cardiology services.

J Cardiovasc Med (Hagerstown). 2008 Nov;9(11):1173-4.

The decline of cardiac auscultation: 'the ball of the match point is poised on the net'.

Dolara A.
Contact: Agenzia Regionale Sanità, Regione Toscana, Italy.

A brief review of the history of cardiac auscultation confirms its decline. The intervention of healthcare institutions may avoid loss of medical culture and increased costs by adequate training of medical staff.

Pediatr Cardiol. 2008 Nov;29(6):1095-100. Epub 2008 Jul 22.

Effectiveness of teaching cardiac auscultation to residents during an elective pediatric cardiology rotation.

Mattioli LF, Belmont JM, Davis AM.
Contact: Division of Cardiology, Department of Pediatrics, University of Kansas Medical Center, Kansas City, 66160, USA.

This study aimed to assess the effectiveness of randomized tracks of prerecorded cardiac sounds as a teaching tool for cardiac auscultation. The study focused on recognizing murmurs when present, distinguishing functional from organic murmurs, and detecting heart disease by auscultation. At both pre- and posttesting, 26 residents listened to 15 randomized tracks of live-recorded cardiac sounds and identified key features. The results indicate that the residents improved at detecting any murmur (66% vs 76%, p = 0.007) and functional murmur (37% vs 54%, p = 0.048), and marginally improved at detecting organic murmur (75% vs 84%, p = 0.129). Detection of absence of murmur declined slightly (69% vs 62%, p = 0.723). The posttest difference in identifying organic versus functional murmurs was striking (84% vs 54%, p < 0.001). Detection of heart disease (sensitivity) improved significantly (76% to 86%, p = 0.016), but there was scant improvement in detecting no disease (specificity) (55% vs 59%, p = 0.601). The residents increased in their ability to detect heart disease when present. However, the false-positive rate for a diagnosis of heart disease remained quite high. To ensure that appropriate referrals will be made, teaching should specifically target the confident recognition of functional murmurs.

J Med Syst. 2008 Oct;32(5):409-21.

Software development for the analysis of heartbeat sounds with LabVIEW in diagnosis of cardiovascular disease.

Topal T, Polat H, Güler I.
Contact: Electronics and Computer Education Department, Faculty of Technical Education, Gazi University, Ankara, Teknikokullar 06500, Turkey.

In this paper, a time-frequency spectral analysis software (Heart Sound Analyzer) for the computer-aided analysis of cardiac sounds has been developed with LabVIEW. Software modules reveal important information for cardiovascular disorders, it can also assist to general physicians to come up with more accurate and reliable diagnosis at early stages. Heart sound analyzer (HSA) software can overcome the deficiency of expert doctors and help them in rural as well as urban clinics and hospitals. HSA has two main blocks: data acquisition and preprocessing, time-frequency spectral analyses. The heart sounds are first acquired using a modified stethoscope which has an electret microphone in it. Then, the signals are analysed using the time-frequency/scale spectral analysis techniques such as STFT, Wigner-Ville distribution and wavelet transforms. HSA modules have been tested with real heart sounds from 35 volunteers and proved to be quite efficient and robust while dealing with a large variety of pathological conditions.

Swiss Med Wkly. 2008 Aug 9;138(31-32):439-52.

Beyond auscultation--acoustic cardiography in the diagnosis and assessment of cardiac disease.

Erne P.
Contact: Head of Cardiology, Kantonsspital Luzern, Luzern, Switzerland.

Auscultation has long been an important part of the evaluation of patients with known and suspected cardiac disease. The subsequent development of phonocardiography provided an analogue visual display that permitted a more detailed analysis of the timing and acoustical characteristics of heart sounds, murmurs, clicks and rubs. In addition, the measurement of systolic time intervals enabled a valuable non-invasive assessment of left ventricular function. Acoustic cardiography, a much more recently developed technology, has enabled the simultaneous acquisition of ECG and cardiac acoustical data. This user-friendly and cost-effective technology permits acquisition of detailed information regarding systolic and diastolic left ventricular function and provides both a computerized interpretation and a visual display of the findings. Its clinical applications include the evaluation of patients with suspected heart failure, ischaemia and cardiac arrhythmias and the optimization of cardiovascular drug and device therapies. It can also be used in a wide variety of ambulatory and inpatient monitoring applications.

Asian Cardiovasc Thorac Ann. 2008 Aug;16(4):288-91.

Esophageal stethoscope in thoracoscopic interruption of patent ductus arteriosus.

Kahrom M, Kahrom H.
Contact: Department of Cardiothoracic Surgery, Qaem Hospital, Mashhad University of Medical Sciences, Mashhad, Iran.

There is a significant rate of residual or recurrent ductal patency after video-assisted thoracoscopic closure of patent ductus arteriosus. Between February 2000 and October 2004, this procedure was carried out on 145 consecutive patients in whom heart sounds were monitored intraoperatively with an esophageal stethoscope. Changes in continuous cardiac murmurs were recorded after placing the 1(st) and 2(nd) vascular clips. There was no ductal flow after clipping twice in 138 (95%) patients; in the other 7, residual flow was abolished at the 3(rd) attempt. All patients left the operating room with no residual ductal patency on echocardiography. After 6 months, there was no incidence of residual patency. Intraoperative esophageal stethoscopy provides remarkably loud and clear heart sounds for direct monitoring and reliable evaluation of the entire course of thoracoscopic patent ductus arteriosus closure, without interrupting the surgical procedure, thus avoiding re-intervention and complications associated with residual ductal flow.

Curr Probl Cardiol. 2008 Jul;33(7):326-408.

Cardiac auscultation: rediscovering the lost art.

Chizner MA.

Cardiac auscultation, long considered the centerpiece of the cardiac clinical examination, is rapidly becoming a lost art. Inadequate emphasis on the essentials of cardiac auscultation has resulted from the widespread availability of more elaborate and expensive "high-tech" diagnostic and therapeutic methods, particularly Doppler echocardiography. However, sophisticated high technology is not a substitute for a solid foundation in clinical cardiology including cardiac auscultation. When used properly, the stethoscope remains a valuable and cost-effective clinical tool that often enables many well-trained and experienced cardiac auscultators to make a rapid and accurate cardiac diagnosis with fewer, if any, additional studies. Not every patient needs every test. Accordingly, this monograph reviews the fundamental principles of the art of cardiac auscultation. Emphasis is placed on the proper use of the stethoscope and the diagnostic and prognostic significance of the myriad heart sounds and murmurs present in patients with and without symptomatic heart disease. A practical clinical overview of the common auscultatory findings encountered in a variety of cardiac disease states and conditions will also be discussed. This monograph will inspire many practitioners to pick up their stethoscope, practice their cardiac examination, perfect their auscultatory skills, and reap the rewards of rediscovering this time-honored method of evaluating the cardiovascular system.


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