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BMC PediatricsBioMed CentralOpen AccessResearch articlePhono-spectrographic analysis of heart murmur in childrenAnna-Leena Noponen*1, Sakari Lukkarinen2, Anna Angerla1 andRaimo Sepponen2Address: 1Pediatric Cardiology, Jorvi Hospital, Department of Pediatric and Adolescent Medicine, Helsinki University Central Hospital, Helsinki,Finland and 2Applied Electronics Laboratory, Department of Electrical and Communication Engineering, Helsinki University of Technology,Espoo, FinlandEmail: Anna-Leena Noponen* - [email protected]; Sakari Lukkarinen - [email protected];Anna Angerla - [email protected]; Raimo Sepponen - [email protected]* Corresponding authorPublished: 11 June 2007BMC Pediatrics 2007, 7:23doi:10.1186/1471-2431-7-23Received: 11 November 2006Accepted: 11 June 2007This article is available from: http://www.biomedcentral.com/1471-2431/7/23 2007 Noponen et al; licensee BioMed Central Ltd.This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0),which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.AbstractBackground: More than 90% of heart murmurs in children are innocent. Frequently the skills ofthe first examiner are not adequate to differentiate between innocent and pathological murmurs.Our goal was to evaluate the value of a simple and low-cost phonocardiographic recording andanalysis system in determining the characteristic features of heart murmurs in children and indistinguishing innocent systolic murmurs from pathological.Methods: The system consisting of an electronic stethoscope and a multimedia laptop computerwas used for the recording, monitoring and analysis of auscultation findings. The recorded soundswere examined graphically and numerically using combined phono-spectrograms. The dataconsisted of heart sound recordings from 807 pediatric patients, including 88 normal cases withoutany murmur, 447 innocent murmurs and 272 pathological murmurs. The phono-spectrographicfeatures of heart murmurs were examined visually and numerically. From this database, 50 innocentvibratory murmurs, 25 innocent ejection murmurs and 50 easily confusable, mildly pathologicalsystolic murmurs were selected to test whether quantitative phono-spectrographic analysis couldbe used as an accurate screening tool for systolic heart murmurs in children.Results: The phono-spectrograms of the most common innocent and pathological murmurs werepresented as examples of the whole data set. Typically, innocent murmurs had lower frequencies(below 200 Hz) and a frequency spectrum with a more harmonic structure than pathological cases.Quantitative analysis revealed no significant differences in the duration of S1 and S2 or loudness ofsystolic murmurs between the pathological and physiological systolic murmurs. However, thepathological murmurs included both lower and higher frequencies than the physiological ones (p 0.001 for both low and high frequency limits). If the systolic murmur contained intensive frequencycomponents of over 200 Hz, or its length accounted for over 80 % of the whole systolic duration,it was considered pathological. Using these criteria, 90 % specificity and 91 % sensitivity in screeningwere achieved.Conclusion: Phono-spectrographic analysis improves the accuracy of primary heart murmurevaluation and educates inexperienced listener. Using simple quantitative criterias a level ofpediatric cardiologist is easily achieved in screening heart murmurs in children.Page 1 of 10(page number not for citation purposes)

BMC Pediatrics 2007, 7:23BackgroundAlthough Dr. Laennec's invention, the stethoscope, hasbeen in clinical use for more than 180 years, and electronic stethoscopes with variable amplification gain havebeen available for over 80 years, it is still difficult tounderstand auscultation findings [1-3]. The phonocardiogram, first developed in 1894, visualizes auscultatory signals [2,4,5]. The spectral phonocardiogram has proven tobe a reliable tool that gives information of whether or notthe murmur is pathological. Based on earlier studies andclinical observations, it has been assumed that pathological murmurs involve sounds of higher frequency [2,5].Phonocardiography and electronic stethoscopy attempt toimprove the diagnostic accuracy of cardiac auscultation.In the most recent studies, digital acoustic analysis hasdemonstrated the validity of these methods [6-11]. Sincethe 1980's, phonocardiographic research activity haddecreased due to the improvements of echocardiography,which yields more visual information. During the pastfew years, however, the improvements of personal computers have made it possible to design new low-cost, highquality phonocardiographic devices [12-17]. Spectralphonocardiography emulates the ear and may be ideal forteaching clinical stethoscopy [4]. The phono-spectrogramcombines traditional phonocardiogram with time-frequency distribution presentation of the signal. The spectrogram was introduced for heart sound analysis as earlyas 1955 by McKusik et al, but was afterwards almost forgotten [4,11].The first evaluation of children's heart murmur is one ofthe basic tasks of welfare clinic practitioners and schoolmedical officers. However, based on their frequently limited auscultation experience, they might not be able to recognize the innocence of a heart murmur. Even theauscultation skills of pediatric residents have been foundto be suboptimal [18-21]. Several healthy children arereferred to pediatric cardiologists or for echocardiography. Parental anxiety may also be a reason to refer thepatient for unnecessary examinations, and it is importantto recognize an innocent murmur as soon as it is found[22-25]. Auscultation training will naturally improvepractitioners' listening skills [26-28].Previous studies have shown that pediatric cardiologists,based on clinical examination, can differentiate innocentfrom pathological murmurs with high sensitivity (82.92%) and specificity (76.99%) [29-33]. Even better resultshave been attained by using advanced signal processingand pattern recognition tools. Artificial neural networkbased screening is reported to have 100% sensitivity andspecificity [13,14].The capability of a doctor or a computerized system to differentiate between pathological and innocent depends on the quality of the pathological murmurs. It iseasy to recognize loud murmurs as pathological by meansof clinical or digital analysis [9]. Serious defects are seldom missed, and the challenge is actually to detect milddefects. Small muscular VSD, mild PS or AS causes nohemodynamic harm, but they may require endocarditisprophylaxis. ASD secundum may also be hard to diagnoseonly by auscultation [34-38].The purpose of this article was to demonstrate the capabilities of a modern digital system for phonocardiographicrecording and analysis and to evaluate its potential for differentiating the characteristic features of heart murmurs inchildren. Another goal was to investigate how the numerical features measured from a phono-spectrogram can beused to distinguish innocent systolic murmurs from pathological murmurs, which are generally hard to identify ina routine clinical examination. This article additionallyconcludes more than ten years' experience of studyingheart sounds.MethodsDataHeart sounds were collected at the outpatient pediatriccardiology clinics of the rural hospitals in the vicinity ofHelsinki from 1995 to 1999. The Ethics Committees ofJorvi (4/95 number 17) and rural hospitals approved thestudy. The study series consisted of 807 children, whoseages ranged from newborn to 16 years. The recordingswere done at random times, i.e. without pre-set dates. Thepatient roster was not available in advance and everypatient with a positive attitude towards the study wereincluded. From each patient, the auscultation finding atthe point of maximal intensity was recorded. The patientswere either children with murmurs referred for a cardiologic evaluation for the first time or patients with a knowndiagnosis. In all cases, the diagnosis was confirmed withechocardiography. The control series consisted of childrenwithout heart murmur, including children with paroxysmal supraventricular tachyarrhythmia, spontaneouslyclosing ventricular septal defect or ductus arteriosus.Healthy child volunteers were also recorded and includedin the control series. Table 1 summarizes the diagnosticfindings.EquipmentA phonocardiographic system developed in Helsinki University of Technology was used to record heart sounds.The system consisted of an electronic stethoscope and amultimedia laptop computer. A parabolic-shaped cupcombined with a high-quality electric microphone andvariable-gain battery-powered amplifier in the electronicstethoscope gave a flat frequency response in the wholefrequency range of usual heart sounds and murmurs(from 75 to 1500 Hz). The laptop computer had standardPage 2 of 10(page number not for citation purposes)

BMC Pediatrics 2007, le 1: Recorded heart soundsDiagnosisNumber%Vibratory murmurEjection murmurVenous humOther innocent musical murmursVentricular septal defect (VSD)Pulmonary stenosis (PS)Aortic stenosis (AS) or coarctation (CoA)Mitral valve defect with (MI) or without leakagePatent ductus arteriosus (PDA)Atrial septal defect (ASD)OtherNo murmur .85.85.33.62.42.13.710.9Total807100multimedia capabilities for audio input and output (16bit resolution in amplitude, variable recording gain andsampling frequencies from 8 kHz up to 44.1 kHz). Soundsignals were recorded digitally using special software forthe monitoring and analysis of auscultation. The softwarewas specifically written for this project, and it had severalend user (general practitioner) friendly capabilities, suchas a database for recordings, basic patient informationinput dialog, real-time graphical monitoring duringrecording, selectable and changeable digital filters, tunable settings for the graphical display and analysis, freezooming and replaying of the interesting parts and toolsfor measuring intensity, duration and frequency range.The software was compatible with standard MicrosoftWindows (NT, 2000, XP) environments.The examiner heard the sounds through earphones andmonitored the signals on the computer screen. Thus, therecording was completed in almost the same time as traditional auscultation. Some additional effort was neededto enter the patient information. The new generationcommercial electronic stethoscopes were also compatiblewith this recording program. During the recording it waspossible to both to listen to the sound and to follow thephonospectrogram from the display screen, the processwas completed often in less than ten minutes.MethodsIn the post-analysis phase, the recorded sounds were replayed, and the fingerprints of innocent and pathologicalheart murmurs were simultaneously examined visually byusing a phono-spectrogram. First the recorded soundswere digitally filtered using pass-band filtering (75–1500Hz) (the 3rd order Butterworth type high-pass and lowpass filters). These filter settings were selected by a longterm subjective trials where the objective was to trim thedisplay to show the details of the murmurs as an experienced practitioner would understand them. For the traditional waveform display the signal was scaled by thesignal's absolute maximum. The resulted waveformshowed the relative intensities of the heart sounds as theear recognizes them and thus absolute intensity scaling isnot needed. Similarly in the spectrogram the intensitieswere scaled by finding the maximum intensity on thetime-frequency distribution and calculating relative intensities in the decibel scale. Thus the value of 0 dB corresponded to the maximum intensity and value of -60 dB,which is almost unbearable to listen to. Short time FastFourier Transform (STFT) with Hanning windowing, 512data samples (46 ms time resolution) and total of 1024FFT points (10.7 Hz frequency resolution) were used forcalculating the spectrogram.The three most common innocent murmurs, i.e. vibratorymurmur, pulmonary ejection murmur and venous hum,and the five most common congenital heart defects, i.e.ventricular septal defect (VSD), aortic valve stenosis (AS),pulmonary valve stenosis (PS), patent ductus arteriosus(PDA) and atrial septal defect (ASD), are presented asexamples of the whole data set.To differentiate between innocent and pathological murmurs, 50 vibratory innocent heart murmurs, 25 innocentpulmonary or aortic ejection murmurs and 50 mild pathological systolic murmurs with intensity equal to or lessthan grade 3/6 were selected from a larger heart sounddatabase for more detailed analysis. 14 of the selectedpathological cases were small VSD, 5 hemodynamicallyloading ASD secundum, 8 PS with a pressure gradient lessthan 30 mmHg, 8 AS with a pressure gradient less than 30mmHg, 3 bicuspid aortic valves with velocity less than 2.0m/s, 1 mild CoA with a measured 15 mmHg RR difference, 1 hypertrophic cardiomyopathy (HOCM) with aseptum thickness of 12 mm but with laminar aortic flow,5 mitral leakage with or without prolapse (MI) and 3 tricuspid valve leakage (TI).ParametersThe timings, the intensities and the frequency contents ofthe sounds were manually extracted from the phono-spectrogram using the software's graphical measurement tools(see any of the Figures from 1, 2, 3, 4, 5, 6, 7, 8). First, thewhole recording is listened to carefully. The locations ofS1 and S2 are recognized from the graphical presentationshowing a moving marker over the phono-spectrogramduring replaying. Then, a shorter interesting area containing three whole heart cycles is selected by zooming the signal. The timings are read from the time-scale (at thebottom) by graphically studying both the phonocardiogram and the spectrogram, deciding the duration of thePage 3 of 10(page number not for citation purposes)

BMC Pediatrics 2007, nd events and dragging the marker over the selectedtime segment. The intensities of S1, S2 and the murmurare read from the scale (on the right) by moving themarker with the mouse over the phonocardiogram. Theloudness of the murmur was estimated from the phonocardiogram by comparing the maximum amplitude of themurmur to the average value of the maximum first andsecond heart sounds Finally, the frequencies in Hertz areread by moving the marker over the spectrogram. The typical intensity for the high and low frequency limits of thesystolic murmurs was around -45–50 dB.StatisticsTo find statistically significant parameters, two-tailed heteroscedastic t-test for independent samples was used tocalculate the p-values. Three sequential beats were manually selected from each recording. The mean value andstandard deviation of the parameters over three beats werecalculated. Based on the statistical results, the relativeduration of the systolic murmur (percentage of murmurduration out of the interval between the end of S1 and thebeginning of S2) and the occurrence of intensive high-frequency components were used as criteria for testing thepathology of the murmur.Figure 2pulmonary ejection murmur in a 7-year-oldInnocentInnocent pulmonary ejection murmur in a 7-year-old.This healthy girl with a normal echocardiographic finding hada soft, midsystolic murmur that was second-degree at themost. The spectrogram shows a frequency of about 100 Hz.Auscultation area: left third intercostal space (LIC3). Duration 52%, peak frequency 111 Hz and volume 18%.ResultsIllustrative examples of most common heart murmursThe system was able to display and reproduce cardiovascular sound events. The musical murmur caused by har-Figure 1vibratory murmur in a 7-year-oldInnocentInnocent vibratory murmur in a 7-year-old. On auscultation, the typical early and midsystolic low-vibrating murmuris best heard at the left fourth intercostal space and the apex(S1 First heart sound, S2 Second heart sound, SM Systolic Murmur). The phonogram shows a rising and fallingearly-to-midsystolic murmur, and the spectrogram shows atypical dense configuration and a descending frequency with amaximum gradient of approx. 150 Hz. The auscultation areawas the left fourth intercostal space (LIC4). Duration 56%,peak frequency 149 Hz and volume 32%.monic movements of the heart or the vasculature, ofwhich vibratory innocent murmur is a good example, wasusually visualized as a well-defined area or line in thespectrogram. Innocent systolic murmur appeared to havea lower peak frequency, below 200 Hz, and shorter duration than pathological murmurs, and it always fadedbefore the second heart sound. The higher the velocity offlow in echogardiography, the more intensive the murmurand the wider the frequency scale. This phenomenon wasclearly visible in the spectrogram.The attached illustrations (Figures from 1, 2, 3, 4, 5, 6, 7,8) show examples of the most typical murmurs in children. The upper part is a traditional phonocardiogramshowing the relative amplitude of the sound. The lowerpart, i.e. the spectrogram, shows the sound intensity ascolors on a frequency scale of 0–1000 Hz. The corresponding intensity scale in decibels is shown on the left.The duration, peak frequency and volume of the murmurwere estimated based on a mean of three sequential beats.Volume was compared to the mean of the amplitudes ofS1 and S2, obtained from the traditional phonocardiogram.Quantitative comparison of innocent and confusingpathological systolic murmursThe mean and standard deviation of the patients' ages forthe three groups are presented in Table 2. The patientswith innocent vibratory murmurs were referred for examination at a younger age than those with ejection murmurs, which seemed confusing to the examiners and werePage 4 of 10(page number not for citation purposes)

BMC Pediatrics 2007, 7:23Figure 3Venoushum in a 1.7-year-oldVenous hum in a 1.7-year-old. Auscultation revealed asystolic-diastolic second-degree murmur that was loudest inearly diastole (DM Diastolic Murmur). Venous hum issometimes a misleadingly loud murmur. It is caused by flowin the jugular veins under the clavicle into the superior venacava. This sound is intensified when the head is turned leftand disappears when lying supine. The hum is heard best atthe right second intercostal space and medially up behind thesternum. The hum is not necessarily heard on every auscultation. The phonogram shows a rather flat contour, and thespectrogram contains 300 Hz and 400 Hz frequencies at thebeginning of diastole, when venous return is fastest. Respiratory sounds are also loud in the area of auscultation, whichsometimes makes the interpretation of the curves difficult.Age 1.7 years. Auscultation area: right second intercostalspace (RIC2). Duration 100 % of systole and diastole, peakfrequency 368 Hz and volume 49 %, at the beginning of diastole.referred closer to school age. The pathological murmurs inthis series included recordings of both new patients andrepeated control recordings of outpatients.There were no significant differences in the duration of S1and S2 between the pathological and physiological systolic murmurs (Table 3). Although S2 was constantly split inASDs, the duration of S2 in these cases did not differ fromthe average in the series. By contrast, the pathologicalmurmurs, measured in either absolute or relative terms,were longer than the innocent vibratory or ejection systolic murmurs (p 0.001).Although the pathological systolic murmurs were somewhat louder than the physiological ones, there were nosignificant differences between the groups (RelativeAmplitude in Table 4). This confirmed that the series fulfilled our aim to select easily confusable cases. However,the pathological murmurs included both lower restenosisAortic4in a 7-month-oldAortic stenosis in a 7-month-old. A third-degree coarse,stenosis-type murmur that does not last until the end of systole is heard in the aortic area. Echocardiography revealedaortic valve stenosis with a 45-mmHg flow gradient. Thephonogram shows a diamond-shaped murmur, and the spectrogram contains early systolic sound waves of approx. 500Hz that coincide with the peak aortic flow. Age 0.6 years.Auscultation area: left third intercostal space (LIC3). Duration 98 %, peak frequency 530 Hz and volume 92 %.higher frequencies than physiological ones (p 0.001 forboth low and high frequency limits).Sensitivity of 76 % and specificity of 84 % were achievedusing a cut-off value of 65 % for the relative duration ofsystolic murmur to differentiate between pathological andphysiological murmurs (Table 5 and Figure 9 – upperleft). Using that cut-off, 12 (24%) pathological and 12 (16%) physiological murmurs were misclassified.When the frequency of 190 Hz for the high frequencylimit was used as a classification criterion, both sensitivityand specificity increased to 88% (Table 6 and Figure 9 –lower left). The number of misclassified cases decreased to6 (12%) in the group of pathological murmurs and to 9(12%) in the group of physiological murmurs.By combining these two criteria, optimal results wereachieved at 80% of the relative duration and with a frequency of 200 Hz as the high frequency limit. Sensitivityapproached 90 % and specificity 91 % (Table 7 and Figure10). There were 5 (10 %) false negative findings and 7 (9%) false positives.DiscussionOver 90 % of heart murmurs in children are physiological. Moreover, 75 % of them are innocent vibratory murmurs (39, 40, 41, 42). The physician needs to quicklyPage 5 of 10(page number not for citation purposes)

BMC Pediatrics 2007, 7:23Figure 5 stenosis in a 9-year-oldPulmonaryPulmonary stenosis in a 9-year-old. Haemodynamicallyinsignificant pulmonary stenosis, with a 17–22 mmHg flowgradient on echocardiography. On auscultation a seconddegree coarse, low-frequency systolic ejection murmur washeard. The phonogram shows the diamond shape compatiblewith stenotic murmur. Flow velocity is highest at the beginning of systole, and the peak frequencies also occur in earlysystole, with a descending frequency contour. The findingsresemble ASD, the main difference being that P2 is quieterthan normal. Because the stenosis is mild, however, P2 canbe heard. Area of auscultation: left second ic space (LIC2).Duration 90%, peak frequency 264 Hz, volume 52 %.confirm the benign nature of the heart murmur and thusto avoid misdiagnosis [25,43]. The combination of a spectrogram and a traditional phonocardiogram can be anadequate method for distinguishing innocent murmursfrom pathological. When quantitative analysis is used systematically, the clinician should know what signals thesystem is processing and how. Visual analysis is the firststep towards understanding automatic analysis, and it is amore reliable way to classify the findings as pathologicalor non-pathological than auscultation alone. Interpretation of the spectrogram helps to understand the hemodynamic events and the origin of heart sounds. Laminar flowwill cause a harmonic wave movement in surrounding tissues, as exemplified by vibratory murmur with a peak frequency of approximately 150 Hz, which has also beenreported in earlier studies [39,44,45]. Rapid flow willcause turbulence. The faster the flow velocity, the higherthe sound frequencies [4,5]. These findings are also illustrated by the analysis of aortic stenosis or ventricular septal defect [6-10].It is not simple to estimate absolute volume of heartsound. The point of maximal intensity of the murmur andthe thickness of the chest vary and affects on the intensities of the sound components. In our study, the gure arteriosusDuctus6in a 2.6-year-oldDuctus arteriosus in a 2.6-year-old. On auscultation, afourth-degree continuous murmur with throbbing pulses.Echocardiography showed a large ductus arteriosus but noother defects. The phonogram shows a consistent (systolicdiastolic) murmur that becomes louder towards endsystoleand is quieter in diastole. The flow is rapid in systole, which iswhen the spectrogram shows the highest frequencies. Areaof auscultation: left second ic space (LIC2). Pansystolic (duration 100 %) and pandiastolic, peak frequency 786 Hz and volume 150%, both in systole.volume of murmur was calculated as a percentage of thevolume of murmur compared to the mean volumes of S1and S2. This may be misleading, as we can see in case 4.The volume of the aortic closure sound is decreasedbecause of valvular stenosis, and the volume of murmur isover estimated compared to auscultation findings.By analyzing the combined phono-spectrogram, it is possible to achieve the level of an experienced pediatric cardiologist in screening heart murmurs. In this study, by usingspecial criteria, sensitivity of 90 % and specificity of 91%were attained. Both sensitivity and specificity were higherthan using phonocradiographic or spectral analysis alone.The results were less good than those obtained in previousstudies using the methods of advanced signal processing,pattern recognition and artificial networks [10,13-15]. Inthese previous studies, however, the series consisted ofpathological cases with distinct and easily recognizablefeatures of heart sounds and murmurs. We agree that it iseasy to distinguish fast turbulent flow with a pressure gradient of over 25 mmHg, and in such cases phono-spectralanalysis is reliable. We here examined the grey area, i.e.typical physiological cases compared to mildly pathological murmurs, and the most common pitfalls.Typically, the screening method is allowed to includesome false positive cases, but false negatives are unaccept-Page 6 of 10(page number not for citation purposes)

BMC Pediatrics 2007, 7:23FigureFairlylarge7 perimembranous VSD in a 7-month-oldFairly large perimembranous VSD in a 7-month-old.A fairly large perimembranous VSD with normal pulmonaryartery pressure (RESP Respiration). On auscultation afourth-degree systolic murmur was heard, and on palpation asmall thrill was felt in the left third intercostal space. Thephonogram shows a pansystolic murmur, but S1 and S2 aredistinguishable. P2 is not enhanced and is split normally. Thisalso suggests that pulmonary resistance is normal. Area ofauscultation: left third ic space (LIC3). Pansystolic (duration100 %), peak frequency 523 Hz and volume 61%.able. In this study, ten (10) small muscular ventricularseptal defects, three (3) cases of mild aortic stenosis, one(1) mild peripheral pulmonary stenosis, one (1) mitralvalve prolapse with leakage and one tricuspid leakage fellbelow the 80 % duration criterion. However, each of thesecases exceeded the 200 Hz frequency limit. Three (3) atrialseptal defects and one (1) slight pulmonary valve stenosisincluded frequencies below 200 Hz, but each of them wassustained for over 80% of the systolic duration. Five (5) ofthe pathological murmurs were not caught with either ofthese two criteria. One (1) of them was a clinically insignificant tricuspid valve leakage, one (1) a very mild mitralvalve leakage, one (1) a bicuspic aortic valve without stenosis and one (1) a bicuspic aortic valve with slight stenosis (pressure gradient 16 mmHg). The last and the worstmissed pathological murmur was recorded from a threeyear-old boy with hypertrophic cardiomyopathy (thickness of ventricular septum 12 mm). Seven out of 75 innocent murmurs exceeded one of the defined screeningcriteria. None of the ejection murmurs exceeded the 80 %duration limit, and 3 cases exceeded the frequency limit.All of these cases were aortic ejection murmurs with aorticvelocity of 1.5–1.8 m/s. Of the vibratory murmurs, one(1) continued for over 80 % of the systolic duration, gureASDin an8 11-year-oldASD in an 11-year-old. On auscultation a quiet systolicejection murmur was heard in the pulmonary area. It resembled the physiological sound but was longer. The secondheart sound was clearly and constantly split. The finding iswell depicted on the phono- and spectrograms. Echocardiography showed a 13 x 8 mm secundum type ASD. Pulmonaryartery flow velocity was 1.7 m/s and aortic flow 0.9 m/s.Because the ASD secundum murmur is caused by increasedpulmonary artery flow, the sound is sometimes difficult todistinguish from the physiological sound. In such cases, attention should be given to the possible splitting of the secondheart sound. Area of auscultation: left second ic space (LIC2).Duration 91 %, peak frequency 126 Hz, volume 19 %.(3) contained frequency components of over 200 Hz, butnone of them exceeded both limits.Slight tricuspid leakage is a harmless finding. Mitral valveleakage and bicuspic aortic valve should be recognizedbecause they require endocarditis prophylaxis. Thepatient with mitral leakage was a fearful retarded boy, andthe recorded signal was weak in amplitude, which is whythe highest frequencies were missed in the analysis, butthe murmur was sustained until the beginning of the second heart sound, implying a pathological finding. Themurmurs due to a bicuspic aortic valve without stenosis orwith slight stenosis did not differ from the hyperkineticaortic ejection murmur. The murmur of the patient withTable 2: Mean and standard deviation of patients' ages in thethree groupsGroupVibratoryEjectionPathologicalAge4.8 3.37.3 5.06.2 4.9Page 7 of 10(page number not for citation purposes)

BMC Pediatrics 2007, le 3: Duration of S1, S2, systolic murmur and relativeduration of systolic le 5: Capability of relative length to distinguish betweenmurmurs: sensitivity is 76

BioMed Central Page 1 of 10 (page number not for citation purposes) BMC Pediatrics . was used for the recording, monitoring and analysis of auscultation findings. The recorded sounds . be used as an accurate screening