Evaluation of a new smartphone-based digital stethoscope featuring phonocardiography and electrocardiography in dogs and cats

This study assessed a new smartphone-based digital stethoscope (DS) featuring simultaneous phonocardiographic and one-lead electrocardiogram (ECG) recording in dogs and cats. The audio files and ECG traces obtained by the device were compared with conventional auscultation and standard ECG. A total of 99 dogs and nine cats were prospectively included. All cases underwent conventional auscultation using an acoustic stethoscope, standard six-lead ECG, standard echocardiography and recordings with the DS. All the audio recordings, phonocardiographic files and ECG traces were then blind reviewed by an expert operator. The agreement between methods was assessed using Cohen's kappa and the Bland-Altman test. Audio recordings were considered interpretable in 90% animals. Substantial agreement was found in the diagnosis of heart murmur (κ = 0.691) and gallop sound (k = 0.740). In nine animals with an echocardiographic diagnosis of heart disease, only the DS detected a heart murmur or gallop sound. ECG traces recorded with the new device were deemed interpretable in 88 % animals. Diagnosis of heart rhythm showed moderate agreement in the identification of atrial fibrillation (k = 0.596). The detection of ventricular premature complexes and bundle branch blocks revealed an almost perfect agreement (k = 1). Overall, the DS showed a good diagnostic accuracy in detecting heart murmurs, gallop sounds, ventricular premature complexes and bundle branch blocks. A clinically relevant overdiagnosis of atrial fibrillation was found but without evidence of false negatives. The DS could represent a useful screening tool for heart sound abnormalities and cardiac arrhythmias..

Comparison of conventional and sensor-based electronic stethoscopes in detecting cardiac murmurs of dogs

BACKGROUND AND OBJECTIVE

Cardiac auscultation is one of the most important parts of the cardiological examination traditionally performed with acoustic stethoscopes. The aim of this study was to compare the sensitivities and the diagnostic capabilities of traditional and electronic stethoscopes in detecting canine heart murmurs.

MATERIALS AND METHODS

The study was performed on 21 dogs referred for cardiologic examination with suspected heart murmurs. Six out of these dogs had cardiac murmurs bilaterally. Cardiac auscultation was performed independently by a final-year veterinary student (AB=I1) and by an experienced clinician (KV=I2), both using a traditional and a Welch Allyn Meditron electronic sensor-based stethoscope. Final diagnoses were established by echocardiography and by digital phonocardiography.

RESULTS

Correct detection of a murmur was made by I1 with a traditional stethoscope in 20/27 (74.0%) of the suspected murmurs (p=0.30, kappa[κ] =0.2) and with the electronic stethoscope in 26/27 (96.3%), respectively (p=0.0013, κ=0.75). I2 correctly detected the murmurs with the traditional stethoscope in 25/27 (92.6%) cases (p=0.0013, κ=0.75) and with the electronic stethoscope in all 27/27 (100%) cases (p=0.00012, κ=1). Agreements of murmur intensity gradings between traditional and electronic stethoscopes were highly significant (I1: p=6.9´10⁻⁸; κ=0.79), (I2: p=5.2´10⁻¹¹; κ=0.92). When grading the murmurs with the traditional stethoscope, there was a significant agreement between I1 and I2 (p=2.9´10⁻⁷; κ=0.79), being even higher with the electronic stethoscope (p=1.1´10⁻¹¹; κ=0.92).

CONCLUSION

The electronic stethoscope was more sensitive than the traditional one in detecting and grading cardiac murmurs being especially useful for I1 with less experience. However, it can be suggested to use a traditional and an electronic stethoscopes simultaneously to optimally utilize their advantages.

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.

Supplemental embolization coil implantation for closure of patent ductus arteriosus in a beagle dog

Embolization coil for the occlusion of patent ductus arteriosus (PDA) was inserted in a beagle dog diagnosed as PDA with systolic murmur. Residual shunt was observed three months postoperatively and then supplemental coil was inserted. In the past only one coil was required for the closure of PDA in our cases with good post-operative results. In this case, however, the largest coil presently available (8 mm in diameter with 5 loops) was inadequate to make sufficient closure within 3 months postoperatively and supplemental coil insertion was necessary to produce a successful occlusion.

Application of phonocardiography for detecting hypoxia-induced cardiovascular adaptation in the chicken

Phonocardiography was evaluated as a noninvasive technique for diagnosis of cardiovascular adaptation and disease in broiler chickens. Heart sounds (HSs) were compared in a fast-growing (FG) commercial broiler line that is highly susceptible to chronic right heart failure resulting from pulmonary hypertension syndrome (PHS) and in a non-selected slow-growing (SG) broiler line that is resistant to PHS. HSs were analyzed in broilers reared in hypobaric hypoxia (HYP) and normobaric (CON) conditions. PHS was induced by a combination of embryonic hypoxia and HYP exposure. HSs were recorded with a microphone placed at the thoracic inlet of each chicken. Electrocardiograms were used to mark the sampling interval for the first, second, and total HS. Digitized HS signals were analyzed for peak frequency, mean peak frequency, and band width. Birds were examined for PHS lesions when 6 wk of age, at the end of each experiment. HSs were compared by line and treatment (Experiment 1) or by treatment and week (Experiment 2). In addition, HS frequencies were analyzed within the HYP treatment group for differences between birds with severe or no gross PHS lesions. HS frequencies generally decreased with age and were also lower in the FG than the SG line. Hypobaric exposure decreased all HS frequencies in the SG line and components of the first HSs in the FG line. The SG line did not develop gross lesions of PHS. In the FG line, significant differences in HS frequencies were observed between HYP and CON groups but not between PHS- and PHS+ broilers. Frequency changes described in humans with PHS were not observed. Further development to maximize the resolution of the HS waveforms and improved matching of the sampling interval to the electrical or hemodynamic output of the chicken heart may allow its use as a diagnostic tool for differentiating broilers with normal cardiac function or physiologic adaptation from those with cardiovascular disease.

Auscultation in mild mitral regurgitation in dogs: observer variation, effects of physical maneuvers, and agreement with color Doppler echocardiography and phonocardiography

Observer variation in diagnosing mild mitral regurgitation in dogs by cardiac auscultation was assessed by having 6 veterinarians with different levels of experience examine 57 Cavalier King Charles Spaniels. Comparisons with color Doppler echocardiography and phonocardiography were made, and the effects of 2 physical maneuvers on the auscultatory findings were evaluated. Using mildly diseased dogs, interobserver agreement in diagnosing the presence or absence of left-sided murmurs ranged from 63% to 88%. The agreement with phonocardiography (range, 53-91%) increased with the amount of observer experience. The 2 most experienced observers could discern soft ejection murmurs from regurgitant murmurs and were able to diagnose 89% of the dogs with regurgitant jets larger than 30% of the left atrial area. In general, less experienced observers diagnosed most jets larger than 50%. In many dogs with small jets, no murmur was found by auscultation and phonocardiography. The audibility of mild regurgitation was significantly reduced in dogs that were difficult to auscultate. Early systolic murmurs were typical of mild regurgitation, whereas holosystolic murmurs typified severe regurgitation. In a few dogs, late systolic murmurs alternated with holosystolic murmurs. Systolic clicks were found phonocardiographically in 18 dogs with mild to moderate regurgitation, but the audibility apparently was low. In many mildly affected dogs, physical maneuvers increased murmur intensity. Thus, some form of dynamic auscultation might facilitate the diagnosis of mild regurgitation. Auscultatory findings in mild regurgitation appear to depend on observer experience, circulatory status, and how difficult the dog is to auscultate.

Analysis of murmur intensity, duration and frequency components in dogs with aortic stenosis

A study was undertaken to investigate the relationship between murmur intensity, murmur duration, duration to peak intensity and frequency components with degree of aortic stenosis in boxers. Measurements were made from phonocardiograms obtained from 35 boxers with ejection-type murmurs, and values were compared with those obtained for aortic flow velocity measured by Doppler echocardiography. Murmur intensity graded by auscultation was significantly correlated with aortic flow velocity (P < 0.001), and murmur duration, expressed as a percentage of systole was significantly correlated with aortic flow velocity (P < 0.001), independent of heart rate. Dogs with early systolic murmurs not exceeding 50 per cent of systole had aortic flow velocities of less than 1.5 m/second and no echocardiographic abnormalities, in contrast with dogs with murmurs of longer duration. Dogs with only high frequency components had lower aortic velocities than those that also had components in the medium frequency range (P < 0.01).

[Clinical findings in a lamb with congenital multiple abnormalities]

A case of multiple, congenital malformations, with special emphasis on cardiac malformations (atrial- and ventricle septum defect, Ductus Botalli persistens, bilateral ventricle and atrial dilatation) in a lamb are described. Clinical findings, X-ray, ultrasound examination, electrocardio- and phonocardiogram, as well as pathology are discussed.

Ancillary tests of the cardiovascular and lymphatic system

Clinical signs of cardiovascular or lymphatic disease may not be specific. Even such signs as edema, cardiac murmur, or cyanosis require further investigation to make a final diagnosis, determine prognosis, or assess treatment response. This article describes indications, description, and interpretation of the electrocardiogram, echocardiogram, phonocardiogram, arterial blood gases, pericardiocentesis, cardiac catheterization, lymph node aspirate or biopsy, indirect blood pressure determination, and other tests associated with the investigation of cardiovascular or lymphatic disease of food animals.

Ventricular septal defects in bovine twins

Ventricular septal defects were diagnosed in twin cows. One of the cows was slaughtered, and the other died of complications associated with the defect. This and other reports may provide evidence to determine the basis of ventricular septal defects in cattle.

The Wolff-Parkinson-White syndrome in a Holstein-Friesian cow

A case of Wolff-Parkinson-White (WPW) syndrome in a Holstein-Freisian cow aged 10-year-old was examined in detail. In electrocardiogram (ECG), the P-wave was the same configuration in both the normal and abnormal ECG. The PR-interval shortened from 0.2 to 0.1 second and the duration of the QRS-complex prolonged from 0.1 to 0.12 second compared with normal ECG. The delta wave, characterized in WPW syndrome, could not be recognized. In echocardiogram, notches were recognized at the early stage of ventricular contraction in the interventricular septum. This cow was, therefore, diagnosed as type B WPW syndrome. The abnormal ECG disappeared by the administration of procainamide. It was strongly indicated that the ventricular contraction showing abnormal ECG was generated only by the stimulation through an accessory pathway in this cow.

An investigation of the second heart sound in the normal horse

The second heart sound was evaluated in conscious, normal horses using intracardiac and external sound detection devices and echocardiography. The second heart sound (S2) in the normal horse is single or split by a narrow interval, not usually detected by external phonocardiographic evaluation. Splitting of S2 was classified as normal (aortic [A2] preceding pulmonic [P2] components) in 66.7 per cent and reversed (P2 preceding A2) in 33.3 per cent of the horses studied. Normal splitting appears to result from lower impedance of the pulmonary vasculature delaying the onset of P2. Reverse splitting appears to result from a delay in A2 resulting from prolongation of PEP and LVET. There does not appear to be variation in splitting of S2 due to respiration based on the cases in which this was measured.

Acquired cardiovascular disease

This article reviews the etiology, clinical findings, and significance of diseases of the heart valves, myocardium, pericardium, and great vessels of the horse. Each valve is considered separately from the point of view of murmur production. In addition, the role of the cardiovascular system in the etiology of sudden and unexpected death is considered.

Spontaneous mitral valve prolapse in a breeding colony of rhesus monkeys

Mitral valve prolapse was observed in 26 of 92 animals in a harem breeding colony of rhesus monkeys (Macaca mulatta). The affected animals had a systolic murmur best auscultated over the mitral region with the animal in a sitting position. Mid-to-late systolic clicks were also heard. Phonocardiographic examination also demonstrated systolic murmurs and clicks in six of 16 animals. Twenty-three of the animals were studied by M mode and/or two-dimensional echocardiography. The diagnosis was confirmed in 12 animals that had a murmur during the examination. Electrocardiograms revealed T wave abnormalities in five animals and left or right ventricular hypertrophy in five. Four adult animals that died during the course of the study were confirmed at necropsy as having prolapse of the posterior and/or anterior mitral valve leaflets into the atrium. Analysis of the breeding records suggested that mitral valve prolapse was a dominant genetic trait with an approximate birth incidence of 16% to 20% in the colony. The existence of mitral valve prolapse in a nonhuman primate species provides a unique opportunity to study the disease in an experimental animal.

Echocardiography in foals from birth to three months old

Simultaneous echocardiograms, phonocardiograms and electrocardiograms were performed on 16 foals at the following times after birth: 15 mins, 60 mins, 2, 4, 12, 24, 48 h, four, seven, 14 days and four, eight and 12 weeks. Positive correlations were found between both age and body weight and the following measurements: left ventricular end-diastolic dimension, right ventricular end-diastolic dimension, left atrial dimension and aortic root dimension, posterior left ventricular wall thickness and interventricular septal thickness. Heart rate was negatively correlated with left ventricular electromechanical systole, ejection time and isovolumic contraction time. Means and standard deviations are presented for 29 echocardiographic parameters and the results are discussed against the background of the transitional neonatal circulation.

Blood pressure, electrocardiogram and echocardiogram measurements in the growing pony foal

Twelve newborn pony foals underwent cardiovascular examinations (auscultation, arterial blood pressure measurements, electrocardiograms and M-mode echocardiograms) on their first day of life and then on Days 7, 14, 21, 30, 60 and 90. An age dependent, statistically significant, rapid increase of the arterial blood pressure in the first month was documented together with a slower decrease of the resting heart rate after two and three months of life. Innocent soft systolic murmurs were audible over the left heart base in a large number of the foals. The electrocardiograms showed age dependent increases of the PR-, QRS- and QT- intervals and a trend of the mean electrical axis in the frontal plane to rotate towards the left side. The ventricular dimensions, measured by M-mode echocardiography, increased with the growth of the pony foals. Linear regression equations were calculated for the right and left ventricular internal dimensions in relation to body weight (bwt). The other echocardiographic parameter had low correlations with bwt.

Three cases of ruptured mitral valve chordae in the horse

The paper describes clinical observations in three horses with ruptured mitral valve chordae. Horses with ruptured mitral valve chordae may have a history of sudden onset of acute distress with predominantly respiratory symptoms. On auscultation there will be a widespread pansystolic murmur with an extension of the area of cardiac auscultation. The third heart sound may be very pronounced and unduly prolonged, associated with high volume flow during early ventricular filling in diastole. However, these sounds are not specific for chordal rupture--they are typical of severe mitral regurgitation. The electrocardiogram may show predominantly backward spatial vectors during ventricular depolarisation. The condition gives rise to left ventricular volume overload and pulmonary hypertension would be expected in horses showing signs of cardiovascular disturbance or those recently affected. Care is necessary during post mortem examination to avoid cutting through the mitral valve before a proper assessment has been made of the chordal insertions.

A study of the first heart sound spectra in normal anesthetized cats: possible origins and chest wall influences

Heart sound recordings were taken from cats. The heart sounds were recorded directly from the chest wall and through an esophageal tube. The phono transducer and the esophageal tube were both placed over the base of the heart. Ultrasound M-mode, or motion-mode, recordings were taken to study the mitral valve dynamics. After analogue to digital conversion, electrocardiogram gated first heart sounds of each phono record were analyzed by the fast Fourier transform to obtain a frequency spectrum. Relative energies in 15 Hz bandwidths up to 150 Hz were correlated with the mitral valve closing velocity of the anterior mitral leaflet, obtained from the M-mode echocardiograms. The closing velocity correlated best with the energy in the 30-45 Hz bandwidth and 60-75 Hz bandwidth for the externally and internally monitored phonocardiogram respectively. The chest wall acted as a low pass filter, that is, the wall favoured the transmission of low frequencies and the energy transmitted decreased as wall thickness increased.

Ventricular septal defects in three familially-related female Saanen goats

Ventricular septal defects were diagnosed in 3 familially-related Saanen goats, a 4-year-old doe and 2 female kids aged 18 weeks, by clinical examination, electrocardiography, phonocardiography and thoracic radiography. Findings were contrasted with those from 3 clinically normal goats. Cardiac catheterisation was attempted on the 2 affected kids before euthanasia. Blood pressure tracings and selective contrast cardioangiography successfully demonstrated the defect in one case, but the other died shortly after anaesthetic induction. The adult goat, suspected paternal grand-dam of the affected twins, died without premonitory signs at 4.5 years of age. Necropsy confirmed the diagnosis in all 3 cases.

Phonocardiography in the horse: 2. The relationship of the external phonocardiogram to intracardiac pressure and sound

The paper describes observations during individual cardiac cycles on the changing pressures and sounds recorded from the various chambers of the heart and aorta, related to phonocardiograms from an external microphone hand-held over the cardiac area. The majority of the first sound appears to arise from the left side of the heart after the AV valves have closed and the second sound is a consequence of sudden deceleration of blood against already closed semilunar valves. Systolic murmurs at the aortic root may be benign from increased flow and turbulence at the peak of ejection but these may not be recorded externally.

Phonocardiography in the horse: 1. The intracardiac phonocardiogram

Using microtransducers, the intracardiac phonocardiogram was recorded in 8 horses from the right heart and in 6 of them also on the left side. All 4 heart sounds were recorded but not in all sites. Their timing was related to pressure events. Systolic ejection murmurs were recorded in both the pulmonary artery and the aorta. Diastolic murmurs were recorded in 2 horses with aortic regurgitation, with maximum amplitude in the left ventricle. The findings were similar to those reported in man and agree with some of the recent concepts on heart sound production.

A phonocardiographic study of equine heart sounds

The occurrence and timing of heart sounds were examined from phonocardiograms taken from the mitral, aortic and tricupsid recording areas in each of 18 horses. 10 sound events could be identified with each cardiac cycle. Atrial contraction produced up to 3 sound events. The first heart sound consisted of 4 components whereas the second sound was single. Two sound events were associated with the 3rd heart sound in early diastole. The occurrence of third and fourth heart sound components varied between horses and between recording areas. The mitral recording area was considered most satisfactory for routine phonocardiographic studies in horses.

Systolic time intervals in domestic ponies: alterations in a case of coarctation of the aorta

This report describes the measurement of systolic time intervals in a nine year old female domestic pony which was found at necropsy to show coarctation of the aorta and bilateral ventricular hypertrophy. Electrocardiogram, phonocardiogram and direct arterial blood pressure were recorded from the pony in a standing unmedicated state and systolic time intervals were measured from the resulting tracings. A prolongation of left ventricular ejection time and shortening of the pre-ejection period were observed in comparison to a group of normal ponies similarly examined. Such changes are consistent with outflow tract obstruction. The pony was also hypotensive and this condition was interpreted as a long-term compensation for the obstructive lesion. It is likely that the changes in systolic time intervals were at this stage predominantly affected by the hypotension. The report notes that the existence of such a case of spontaneous cardiovascular disease in the pony population might suggest the utility of the animal as a resource in comparative cardiovascular physiology and medicine.