Musical Murmur Research Articles

The Music Within: A Doppler Harmonic Pattern Report in Non-Subarachnoid Hemorrhage Related Cerebral Vasospasm

A 40-year-old male presented an episode of severe thunderclap headache with right hemiparesis. Imaging revealed severe stenosis in the left middle cerebral artery, associated with increased mean velocities detected by Transcranial Doppler Ultrasound (TCD). Notably, a distinctive "tin whistle" sound, known as a doppler harmonic effect, near the highest velocity point was observed during the examination. Extensive workup was performed, including CSF analysis and laboratory investigations, and the diagnosis of Reversible Cerebral Vasoconstriction Syndrome (RCVS) was established. Treatment involving medication and daily monitoring led to a decline in the left MCA's velocity, enabling the patient's discharge with no recurrent headaches or neurological deficits. Notably, a follow-up MRI exhibited the disappearance of the left MCA stenosis. This report discusses the rare occurrence of "musical murmurs" in cerebrovascular diseases, underscoring the potential for early diagnosis using techniques like TCD in emergency settings, particularly in conditions like RCVs.

Understanding intracranial aneurysm sounds via high-fidelity fluid-structure-interaction modelling

BackgroundSince the 1960s, the origins of intracranial aneurysm bruits and musical murmurs have been debated, with proposed mechanisms ranging from self-excitation (i.e., resonance) by stable pulsatile flow, to vibration caused by unstable (laminar vortex shedding or turbulent) flow. This knowledge gap has impeded the use of intracranial sounds a marker of aneurysm remodelling or rupture risk. New computational techniques now allow us to model these phenomena.MethodsWe performed high-fidelity fluid-structure interaction simulations capable of understanding the magnitude and mechanisms of such flow-induced vibrations, under pulsatile flow conditions. Six cases from a previous cohort were used.ResultsIn five cases, underlying flow instabilities present as broad-band, random vibrations, consistent with previously-described bruits, while the sac also exhibits resonance, rocking back and forth in different planes of motion, consistent with previously described musical murmurs. Both types of vibration have amplitudes in the range of 0.1 to 1 μm. The murmurs extend into diastole, after the underlying flow instability has dissipated, and do not exhibit the characteristic repeating frequency harmonics of previously hypothesized vortex-shedding mechanisms. The remaining case with stable pulsatile flow does not vibrate. Spectrograms of the simulated vibrations are consistent with previously reported microphone and Doppler ultrasound recordings.ConclusionsOur results provide a plausible explanation for distinct intracranial aneurysm sounds and characterize the mechanical environment of a vibrating aneurysm wall. Future work should aim to quantify the deleterious effects of these overlooked stimuli on the vascular wall, to determine which changes to the wall makeup are associated with vibration.

Spectral Bandedness in High-Fidelity Computational Fluid Dynamics Predicts Rupture Status in Intracranial Aneurysms.

Recent studies using high-fidelity computational fluid dynamics (CFD) have revealed high-frequency flow instabilities consistent with clinical reports of bruits and "musical murmurs", which have been speculated to contribute to aneurysm growth and rupture. We hypothesized that harmonic flow instabilities ("spectral bandedness") in aneurysm CFD data may be associated with rupture status. Before testing this hypothesis, we first present a novel method for quantifying and visualizing spectral bandedness in cardiovascular CFD datasets based on musical audio-processing tools. Motivated by previous studies of aneurysm hemodynamics, we also computed a selection of existing metrics that have demonstrated association with rupture in large studies. In a dataset of 50 bifurcation aneurysm geometries modeled using high-fidelity CFD, our spectral bandedness index (SBI) was the only metric significantly associated with rupture status (AUC = 0.76, p = 0.002), with a specificity of 79% (correctly predicting 19/24 unruptured cases) and sensitivity of 65% (correctly predicting 17/26 ruptured cases). Three-dimensional flow visualizations revealed coherent regions of high SBI to be associated with strong near-wall inflow jets and vortex-shedding/flutter phenomena in the aneurysm sac. We speculate that these intracycle, coherent flow instabilities may preferentially contribute to the progressive degradation of the aneurysm wall through flow-induced vibrational mechanisms, and that their absence in high-fidelity CFD may be useful for identifying intracranial aneurysms at lower risk of rupture.

The Divine Feminine Presence in Ibn ‘Arabi and Moses de Leon

This paper is an investigation of the divine feminine power as depicted in the texts of Hispanic mystics from Sufi, Hebrew, and Christian traditions. This work is intended to investigate the origin and subsequent development of a transcendent reconciliation of polarity, its diverse manifestations, and the attainment of a common goal, the quintessential of the Perfect Human Being. The architect of the encounter that leads to Union is “Sophia”. She is the Secret. Only those who are able to discern Her own immeasurable dimension may contemplate the Lady who dwells in the sacred geometry of the abyss. Sophia is linked to the hermetic Word, She is allusive, clandestine, poetic, and pregnant with symbols, gnostic resonances, and musical murmurs that conduct the “traveler” through dwellings and stations towards an ancient Sophianic knowledge that leads to the “germinal vesicle”, the “inner wine cellar”, to the Initium, to the Motherland. She is the Mater filius sapientae, who through an alchemical transmutation becomes a song to the absent Sophia whose Presence can only be intuited. Present throughout the Creation, Sophia is the axis around which the poetics of the Taryuman al-ashwaq rotates and the kabbalistic Tree of Life is structured.

Musical murmur in a dog with acute chordae tendineae rupture

Abstract : A 6 year-old, spayed female, Maltese dog was presented with precordial thrill and mild coughing. Thoracicauscultation revealed a grade V/VI systolic murmur with maximal intensity over the left apex characterized by musicalmurmur. Echocardiography revealed mild myxomatous degeneration of mitral valve and ruptured chordae tendineae.Musical murmur was produced due to the vibration of ruptured piece of chordae tendineae along with regurgitant flow.After treatment with furosemide and ramipril, clinical signs resolved and precordial thrill reduced. This case reportdescribes typical clinical signs and phonocardiogram of musical murmur in a dog with acute chordae tendineae rupture.Keywords : chordae tendineae rupture, mitral valve disease, musical murmur Mitral valve disease (MVD) is the most common acquiredheart disease in small breed-dogs and characterized by myx-omatous valvular degeneration [3, 5, 6, 7, 8]. It results inmitral valve insufficiency creating systolic mitral regurgita-tion, which in turn leads to a left apical systolic murmur [7].Usually with MVD, systolic murmur intensity is related to dis-ease severity. However, occasionally with mild stage of MVD,the murmur has a musical quality and striking intensity [9].This case describes sudden onset of precordial thrill char-acterized as musical murmur resulted from acutely rupturedchordae tendineae with midly degenerated mitral valve.A 6 year-old, spayed female, Maltese dog was presentedwith sudden onset of precordial thrill and mild nocturnalcoughing. Thoracic auscultation revealed a grade V/VI sys-tolic murmur with maximal intensity over the left apex. Lab-oratory data including a complete blood count, serumbiochemical analysis were within normal ranges. Evaluationof the electrocardiogram showed mildly prolonged P wave.Thoracic radiography revealed bronchointerstitial pattern inbilateral caudal lung lobes. 2D-echocardiography demon-strated slightly thickened mitral valve and pieces of rupturedchordae tendineae attached to the tip of mitral valve leaflet(Fig. 1). Doppler echocardiography revealed mild systolicturbulent flow in the left atrium running around atrial wallwith peak velocity 2.07 m/sec and pressure gradient 17.2mmHg (Fig. 1). There was no marked evidence of cardiacremodeling. Phonocardiography was performed, and showedmid-systolic diamond shape murmur with variable ampli-tudes (Fig. 2). Recorded sound files of phonocardiogramrevealed sharp, pitched ‘wheeping’ sound, characterized asmusical murmur. The blood sample collected aseptically wassubmitted for aerobic and anaerobic blood culture, and theresult was negative. Based on the physical and clinical exam-ination, the dog was diagnosed as mitral valve degeneration(MVD) with chordae tendineae rupture (CTR). Furosemide(Lasix, 0.5 mg/kg, oral, twice daily; Handok phrmaceuticals,Korea) and ramipril (Vasotop, 0.125 mg/kg, oral, once adaily; Intervet, Korea) were administered. After 1 month ofmedical treatment, nocturnal coughing was improved andprecordial thrill was reduced.Generally, musical murmur is characterized by a strikingmusical quality and is frequently so loud that it can be heardover the entire thorax. The murmur has been described inhuman literature using following terms: “cooing of a dove,”,“buzzing of a saw”, “like a cuckoo clock,” “like the spinningof a top” [1]. Musical murmur would occur owing to the res-onance of vibrating structure projecting into the regurgitantblood flow. In human medicine, musical murmur is most fre-quently occurred in aortic stenosis [4]. In the present case, itwas ruptured piece of chordae tendineae flailed with mitralvalve during systole vibrating with turbulent blood flow thatmade loud, pinched sound. The size of turbulent jet flow wasrelatively small and ran around the atrial wall. The directionof jet flow indicated that the degeneration of anterior leafletwas worse than posterior leaflet.Historically, CTR is commonly described as a devastatingcomplication of MVD, because it is responsible for acute leftheart failure leading to pulmonary edema and death [2, 8].However, one study suggested that 24.6% of the dogs withCTR were asymptomatic and therefore assigned to Interna-tional Small Animal Health Council (ISACHC) classes Iaand Ib at the time of diagnosis [8]. In this case, 2-D echocar-

Musical murmurs on transcranial ultrasound in childhood migraine with aura

A 12-year-old girl presented with headache, nausea, decreased level of consciousness, and diplopia. Brain MRI, arteriography (figure e-1 on the Neurology® Web site at www.neurology.org), vasculitic markers, and CSF were normal, as were EEGs and ECGs. Transcranial color-coded ultrasonography of the basilar artery revealed typical musical murmurs ("seagull cry") indicative of a hemodynamically significant stenosis (video).(1) Sumatriptan provided symptomatic relief; basilar flow normalized on ultrasonography (figure e-2). The clinical presentation suggested childhood migraine with aura; the ultrasound and normal arteriography suggested focal, transient vasospasm during a migraine attack. Topiramate was effective long-term. The high prevalence of childhood migraine (up to >20%)(2) suggests that ultrasound may be a useful diagnostic tool.

The “seagull cry” in a patient with a cerebral arteriovenous malformation

IntroductionThe “seagull cry” is an acoustic phenomenon heard during duplex ultrasound. It is caused by harmonic covibrations of a vessel wall in the presence of high-velocity blood flow. It has been reported in a few cases of cerebrovascular disease, such as severe intracranial stenosis, vasospasm or carotid-cavernous fistula. Material and methodsA 35-year-old man underwent transcranial color-coded sonography (TCCS) for work-up of a severe new-onset headache. ResultsDoppler spectral analysis of the right intracranial carotid bifurcation revealed multiple pairs of mirror-image parallel strings, and a high-frequency seagull cry was heard. Computed tomography-angiography and magnetic resonance imaging of the brain showed an arteriovenous malformation in the right temporal lobe. DiscussionThe seagull cry is a “musical murmur” with single or multiple frequency that sounds like a musical tone. This is the first report of this phenomenon in a cerebral arteriovenous malformation.

Musical murmurs on internal carotid artery: sonological herald of vessel dissection?

Musical murmurs on internal carotid artery: sonological herald of vessel dissection?

Intelligent Identification of Childhood Musical Murmurs

Heart murmurs are often the first signs of heart valvular disorders. However, most heart murmurs detected in children are innocent musical murmurs (also called Still′s murmurs), which should be distinguished from other murmur types that are mostly pathological, such as regurgitant, obstructive, and flow murmurs. In order to reduce both unnecessary healthcare expenditures and parental anxiety, this study aims to develop algorithms for intelligently identifying musical murmurs in children. Discrete wavelet transform was applied to phonocardiographic signals to extract features. Singular value decomposition was applied on the matrix derived from continuous wavelet transform to extract extra features. The sequential forward feature selection algorithm was then utilized to select significant features. Musical murmurs were subsequently differentiated via a classification procedure consisting of three classification techniques: discriminant analysis, support vector machine, and artificial neural network. The results of 89.02% sensitivity, 84.76% specificity and 87.36% classification accuracy were achieved.

Matrix decomposition based feature extraction for murmur classification

Heart murmurs often indicate heart valvular disorders. However, not all heart murmurs are organic. For example, musical murmurs detected in children are mostly innocent. Because of the challenges of mastering auscultation skills and reducing healthcare expenses, this study aims to discover new features for distinguishing innocent murmurs from organic murmurs, with the ultimate objective of designing an intelligent diagnostic system that could be used at home. Phonocardiographic signals that were recorded in an auscultation training CD were used for analysis. Instead of the discrete wavelet transform that has been used often in previous work, a continuous wavelet transform was applied on the heart sound data. The matrix that was derived from the continuous wavelet transform was then processed via singular value decomposition and QR decomposition, for feature extraction. Shannon entropy and the Gini index were adopted to generate features. To reduce the number of features that were extracted, the feature selection algorithm of sequential forward floating selection (SFFS) was utilized to select the most significant features, with the selection criterion being the maximization of the average accuracy from a 10-fold cross-validation of a classification algorithm called classification and regression trees (CART). An average sensitivity of 94%, a specificity of 83%, and a classification accuracy of 90% were achieved. These favorable results substantiate the effectiveness of the feature extraction methods based on the proposed matrix decomposition method.

Clinical relevance of musical murmurs in color-coded duplex sonography of peripheral and visceral vessels

Musical murmurs (MMs) are Doppler phenomena which sound like high-frequency musical sounds. They reflect high and turbulent flow within relevant stenoses and were first described in degenerated bioprosthetic valves and later in intracranial vessels and were associated either with high-grade arterial stenosis, small collateral arteries or carotid cavernous fistulas. Objective of this article is to illustrate the spectrum of imaging of MMs observed in renal, intestinal and peripheral vessels. Four experienced vascular ultrasound laboratories had been asked to report their cases with documented musical tones in color coded duplex sonography (CCDS) within a two year observational period (2008 and 2009). Documented Doppler findings and corresponding clinical data were analyzed. MMs were found in 18 patients with an incidence of 0.05 % and were observed in high grade stenosis in hemodialysis access (n = 5), in post-biopsy arteriovenous fistulas after renal transplantation (n = 3), in renal transplant artery (n = 1) and vein (n = 3), stenoses in peripheral (n = 2) and intestinal arterial disease (n = 2), and in peripheral veins (n = 2). The so called musical murmurs are a rare but potentially relevant finding in CCDS. They are caused by a variety of underlying pathologies with different clinical implications, however correct interpretation is mandatory since urgent therapy might be necessary.

Pilot Study of New Diagnostic Criteria for Middle Cerebral Artery Stenosis by Transcranial Doppler

Current criteria for middle cerebral artery (MCA) stenosis by transcranial Doppler were mainly based on the flow velocity acceleration, ignoring other useful parameters. We tested the accuracy of new criteria using magnetic resonance angiography (MRA) as the confirmative method. A compositive score for each MCA was calculated according to following parameters: Velocity Scale (score 0-6 for peak systolic velocity <140 to > or = 300 cm/second), Hemodynamic Scale (score 0-5 for diffuse or focal velocity increase; score 0-6 for differences between bilateral MCA; score 17 for damping velocity), and Spectrum Scale (score 0-2 for normal spectrum, turbulence, and musical murmurs). The median scores in normal-mild, moderate, and severe groups on MRA differed significantly (P < .001). The optimal cutoff score for <50% and > or = 50% stenosis was 3 with the PPV of 72.3% (95% confidence interval [CI]: 65.3% to 78.5%) and negative predictive value (NPV) of 89.5% (95% CI: 85.9% to 92.3%), for moderate and severe stenosis was 6 with the PPV of 85.9% (95% CI: 76.7% to 92.0%) and NPV of 61.9% (95% CI: 50.6% to 72.1%). Both scores performed better than peak systolic or mean velocity. This new method was feasible and reliable and showed some advantages over the velocity-only method. Further studies using digital subtraction angiography as the gold standard are needed to ameliorate the new criteria.

“The Seagull Cry”

Duplex ultrasound is widely used to detect vascular dysfunction after kidney transplantation. We describe musical murmurs found in renal allografts. A 29-year-old man with an increase in serum creatinine 1 month after cadaveric kidney transplantation was referred for duplex ultrasound to exclude perfusion dysfunction. Renal arterial and venous circulation was normal. However, during Doppler spectral recording, a loud “seagull cry” was audible (audio file in the online-only Data Supplement). Spectral analysis displayed mirror-image parallel strings and bands of low to moderate frequency (Figure 1A and B). A small arteriovenous fistula, presumably after previous biopsy, was detected as cause of the turbulent flow. Inasmuch as no bleeding complication or pseudoaneurysm formation occurred, a conservative strategy was chosen, and follow-up with duplex ultrasound was recommended. Figure 1. A and B, Renal transplant with …

Transcranial Doppler ultrasonography in intensive care

Transcranial Doppler is an innovative, flexible, accessible tool for the bedside monitoring of static and dynamic cerebral flow and treatment response. Introduced by Rune Aaslid in 1982, it has become indispensable in clinical practice. The main obstacle to ultrasound penetration of the skull is bone. Low frequencies, 1-2 MHz, reduce the attenuation of the ultrasound wave caused by bone. Transcranial Doppler also provides the advantage of acoustic windows representing specific points of the skull where the bone is thin enough to allow ultrasounds to penetrate. There are four acoustic windows: transtemporal, transorbital, suboccipital and retromandibular. The identification of each intracranial vessel is based on the following elements: (a) velocity and direction; (b) depth of signal capture; (c) possibility of following the vessel its whole length; (d) spatial relationship with other vessels; and (e) response to homolateral and contralateral carotid compression. The main fields of clinical application of transcranial Doppler are assessment of vasospasm, detection of stenosis of the intracranial arteries, evaluation of cerebrovascular autoregulation, non-invasive estimation of intracranial pressure, measure of effective downstream pressure and assessment of brain death. Mean flow velocity is directly proportional to flow and inversely proportional to the section of the vessel. Any circumstance that leads to a variation of one of these factors can thus affect mean velocity. The main pathological condition affecting flow velocity is the vasospasm. Vasospasm is a frequent complication of subarachnoid haemorrhage, it often remains clinically silent and the factors that make it symptomatic are largely unknown. Threshold velocities above which vasospasm comes into place are well defined as regards the median cerebral artery, while there is no consensus for the other vessels. Nevertheless, an increase in velocity alone is not sufficient to arrive at a diagnosis of vasospasm; a condition of hyperaemia also presents with an increase in flow velocity. The Lindegaard Index has therefore been introduced, which is defined by the ratio between the mean flow velocity in the median cerebral artery and the mean flow velocity in the internal carotid artery. Criteria for diagnosis of a stenosis >50% of an intracranial vessel with transcranial Doppler include: (a) segmentary acceleration of flow velocity; (b) drop in velocity below the stenotic segment; (c) asymmetry; and (d) circumscribed flow disturbances (turbulence and musical murmur). The transcranial Doppler enables us to assess both components of self-regulation. The static component is measured by observing changes in flow velocity caused by pharmacologically induced episodes of hypertension and hypotension. The dynamic component of autoregulation can be measured using a method devised by Aaslid known as the 'cuff test'. A very effective and safe device for measuring cerebral autoregulation is the transient hyperaemic response test. This test is based on the compensatory vasodilatation of the arterioles, which occurs after brief compression of the common carotid. Csonyka proposed the following formula based on clinical observation for the calculation of cerebral perfusion pressure: CPP = MAP x FVd/FVm + 14. Brain death is defined as the irreversible cessation of all functions of the whole brain. The clinical criteria are usually considered sufficient to establish a diagnosis of brain death; however, they might not be sufficient in patients who have been on sedatives or when there are ethical or legal controversies. Many authors have demonstrated the existence of a transcranial Doppler pattern, which is typical of brain death.

Pulsed Doppler echocardiographic detection of the origin of musical murmurs in a case of pacemaker implantation

We report a case of systolic and diastolic musical murmurs that developed 4 years after DDD pacemaker implantation. Echocardiographic examination disclosed no evidence of serious pacemaker-related complications. Pulsed Doppler examination with a sample volume at the right ventricular portion of a pacemaker lead showed prominent harmonic signals. The timing of the signals was consistent with that of musical murmurs. We considered vibration of the pacemaker lead as a possible origin of the musical murmurs. Systolic and diastolic musical murmurs can develop without serious cause in a patient with a transvenous pacemaker. Pulsed Doppler examination was useful in detecting the origin of musical murmurs.

An assessment of the terminology used by diplomates and students to describe the character of equine mitral and aortic valve regurgitant murmurs: correlations with the physical properties of the sounds.

Twenty students and 16 diplomates listened to 7 recordings made from 7 horses with either aortic (n = 3) or mitral valve (n = 4) regurgitant murmurs. A total of 30 different terms were used to describe the character of these murmurs. However, only 4 terms were used in a repeatable and consistent manner. Most people described the character of a given mitral or aortic valve murmur with 1 or 2 terms. Diplomates drew from a pool of terms that was about half the size of that used by students--8.1 +/- 2.0 terms for diplomats (mean +/- 1 SD) versus 13.1 +/- 1.8 terms for students (P > .001). Only blowing, honking, buzzing, and musical were markedly associated with the recording played. Frequency analysis of the murmurs allowed them to be classified as containing harmonics (n = 4) or not containing harmonics (n = 3). Blowing was used to describe murmurs without harmonics on 39 of 48 occasions and corresponds to the term noisy used in some older descriptions of equine murmurs. Honking, musical, and buzzing were markedly associated with murmurs that contained harmonics; these terms were used 23, 13, and 12 of a possible 64 times, respectively. The frequency of buzzing and honking murmurs (72.7 +/- 9.3 and 88.4 +/- 46.3 Hz, respectively) was markedly lower than that of musical murmurs (156.8 +/- 81.1 Hz) (all P values < .01). Honking murmurs (0.392 +/- 0.092 seconds) were shorter than those described as buzzing or musical (0.496 +/- 0.205 and 0.504 +/- 0.116 seconds, respectively). The data suggest that the terminology for the character of aortic and mitral regurgitant murmurs should be restricted to 4 terms: blowing, honking, buzzing, and musical. Honking, buzzing, and musical describe murmurs with a peak dominant frequency and harmonics; blowing describes murmurs without a peak frequency. Effective communication could be enhanced by playing examples of reference sounds when these terms are taught so that nomenclature is used more uniformly.

The Venturi Effect and Cerebrovascular Ultrasound

Background: One of the most frequent diagnostic pitfalls in cerebrovascular ultrasound is the evaluation of the vertebrobasilar system in the case of vertebral artery (VA) hypoplasia because the diagnostic findings are sometimes suggestive of significant pathologies, but may be completely normal as well. The Venturi effect is a phenomenon of hydrodynamics which describes a drop in hydrostatic pressure along areas of high flow velocities. Method: We review the physical background of the Venturi effect and describe how it can explain both physiological and pathological flow phenomena encountered during cerebrovascular ultrasound investigations. We focused on flow phenomena at the vertebrobasilar junction by theoretically calculating conditions with different influx angles and flow velocities on two-dimensional digital subtraction angiography images. In the discussion, we also address other areas of cerebrovascular ultrasound, where the Venturi effect is of particular interest. Results and Conclusions: The blood flow velocity within the VAs and the angle between a hypoplastic VA and the basilar artery (BA) are important determinants of the intraluminal pressures of these arteries and thus their resistances. In the case of angles below 90° between the distal VA and the BA, abnormal extracranial flow profiles may suggest downstream VA stenosis or occlusion, whereas in the case of angles above 90°, a diagnosis of an AV fistula downstream to the V4 segment may be assumed. Furthermore, various hemodynamic effects at the site of a stenosis of the brain supplying arteries can also be explained by a transstenotic pressure drop created by the Venturi effect, particularly the generation of musical murmurs. The systolic dip (‘systolic deceleration’) at the origin of the VA due to subclavian artery stenosis is also a consequence of the Venturi effect.

Cerebral blood flow velocities in an infant with moyamoya disease

Moyamoya disease is a progressive cerebrovascular disorder with bilateral occlusion of the basal circulation and development of collateral blood supply. In a 6-month-old female with multifocal ischemic infarctions, transcranial pulsed Doppler sonography revealed extremely high and low cerebral blood flow velocities, dampened waveforms, reversed flow, and musical murmurs. Magnetic resonance angiography revealed different degrees of vascular stenosis and an abnormal collateral network. Moyamoya disease was confirmed by conventional angiography at the age of 10.5 months. Pulsed-wave transcranial Doppler sonography is a noninvasive screening method in infants at risk of moyamoya disease.

Time-frequency analysis of heart murmurs. Part I: Parametric modelling and numerical simulations.

The object of this study is to compare the performance of two new bilinear time-frequency representation techniques with the spectrogram to characterise the behaviour of heart murmurs produced by bioprosthetic heart valves implanted in the mitral or aortic position. The murmurs are those of mitral stenosis, mitral regurgitation, aortic stenosis, aortic regurgitation, a diastolic musical murmur and a systolic musical murmur. In the first part of the study, the general characteristics of the amplitude and the spectral content of these murmurs are determined by visual observation of the spectrogram of phonocardiograms obtained from several patients with known valvular pathology complemented with a literature review. A parametric model is then generated for each murmur signal. Stenotic and regurgitant murmurs are modelled as the sequential output of a bank of low-pass filters excited by a white noise input signal. The basic parameters of each filter are selected to simulate, as a function of time, the basic characteristics of random heart murmurs. Musical murmurs are modelled as a frequency-modulated deterministic sinusoid of constant amplitude. Numerical simulations of these random and musical heart murmurs are then generated and will be used in Part II to determine the best of three time-frequency representation techniques for analysing heart murmur signals.

Time-frequency analysis of heart murmurs. Part II: Optimisation of time-frequency representations and performance evaluation.

The basic parameters of the spectrogram, the Choi-Williams, and the Bessel distributions are adjusted to provide the best time-frequency representations (TFRs) of the simulated murmur signals of mitral stenosis, mitral regurgitation, aortic stenosis, aortic regurgitation, and of two musical murmurs. The initial adjustment of the parameters of each TFR technique is performed by computing and minimising the relative averaged absolute error between the frequency contours at -3 dB and -10 dB of each TFR of the simulated murmurs and those of the theoretical distribution of the same signals. The results show that the spectrogram generally provides very good to excellent performance in representing the TFRs of stenotic and regurgitant murmurs. Improvements provided by the Choi-Williams and the Bessel distributions are minor but not systematic for the two signal-to-noise ratios tested (0 and 30 dB) and for the two frequency contours estimated. The Bessel and the Choi-Williams distributions provide the best performance for the musical murmurs. The study shows that although a single technique cannot be optimal for all six murmurs, the spectrogram using a Hamming window of 30 ms is an acceptable compromise to detect the six simulated heart murmurs.