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

Identification and Clinical Significance of Heart Murmurs in Puppies Involved in Puppy Trade

The detection of a congenital heart defect at purchase is an important step in early detection from a clinical and legal standpoint. Indeed, some cardiac abnormalities may be corrected with surgery, and very often, treatment needs to be performed early before congestive heart failure or irreversible heart damage can occur. From a legal viewpoint, if the defect is revealed in a newly purchased puppy, the buyer may be required to return it and receive compensation. Puppies affected with congenital heart defects are likely to die prematurely, causing emotional suffering to the owner. Furthermore, by considering breed predisposition, early recognition allows breeders to avoid breeding from particular dogs with genetic defects and prevent the continuation of genetic defects in breeding lines. Given gaps in the literature about the recognition of murmurs in the puppy trade, the present article describes how to identify a heart murmur in a puppy during a pre-purchase examination and its significance from a clinical and legal viewpoint. In the canine population, the prevalence of cardiac defects ranges between 0.13 and 1.6%. Pulmonic stenosis is the most common defect found in puppies, followed by patent ductus arteriosus, subaortic stenosis, and ventricular septal defect. On the basis of the above considerations, the veterinarian should recognize and identify the murmur following a protocol for routine examination of puppies involved in trade.

Cardiac auscultation skills in final year veterinary students and recent veterinary graduates, referral hospital veterinary surgeons and veterinary cardiologists or cardiology residents

BACKGROUND

Cardiac auscultation is an important part of the physical examination. This study evaluated cardiac auscultation skills in veterinary students and compared their abilities to recent veterinary graduates, referral hospital veterinary surgeons and veterinary cardiologists or cardiology residents. In addition it compared their self-predicted quiz scores to their actual scores, evaluating if they could accurately predict their own performance level.

METHODS

A digital recording device was used to record auscultation sounds from 12 different patients with a diagnosis confirmed by a board-certified veterinary cardiologist. The sound files and associated phonocardiograms were uploaded to a video sharing website. A cloud-based online multiple-choice quiz was generated and shared with final year veterinary students, recent veterinary graduates, referral hospital veterinary surgeons and veterinary cardiologists or cardiology residents.

RESULTS

There were 128 participants: 51 final year veterinary students, 62 recent veterinary graduates, and 10 referral hospital veterinary surgeons and five veterinary cardiologists or cardiology residents. No difference was found between the cardiac auscultation skills of recent veterinary graduates and final year veterinary students. Veterinary students' self-predicted scores were lower than actual scores.

CONCLUSIONS

Recent veterinary graduates did not perform better than final year veterinary students in this study, suggesting that auscultation skills do not continue to improve in the first few years after graduation. Efforts should be made to maximise students' learning in cardiac auscultation skills. Veterinary students show a lack of confidence in cardiac auscultation skills.

Detection of innocent systolic murmurs by auscultation and their relation to hematologic and echocardiographic findings in clinically normal Whippets

OBJECTIVE

To determine murmur prevalence by auscultation of 105 apparently healthy Whippets without signs of cardiac disease, to determine the origin of these murmurs, and to evaluate the influence of sex, type of pedigree (ie, bred for showing or racing), and training on these murmurs.

DESIGN

Cross-sectional study.

ANIMALS

105 client-owned Whippets.

PROCEDURES

All dogs were auscultated by the first author and underwent a complete physical and cardiological examination, together with a hematologic assessment. Several RBC variables and echocardiographic variables were compared between dogs with or without a murmur at the level of the aortic valve.

RESULTS

44 of 105 (41.9%) dogs had no murmur. A soft systolic murmur was present with point of maximal intensity at the level of the aortic valve in 50 (47.6%) dogs, at the level of the pulmonic valve in 8 (7.6%) dogs, and at the level of the mitral valve in 3 (2.9%) dogs. No significant differences were found in heart rate, rhythm, murmur presence, point of maximal intensity, and murmur grade between males and females, between dogs with race- and show-type pedigrees, or between dogs in training and not in training. Dogs with a murmur at the level of the aortic valve had a significantly higher aortic and pulmonic blood flow velocity and cardiac output, compared with dogs without a murmur.

CONCLUSIONS AND CLINICAL RELEVANCE

Whippets have a high prevalence of soft systolic murmurs in the absence of any structural abnormalities, which fit the description of innocent murmurs. No influence of sex, pedigree type, or training was found on the occurrence of these murmurs in Whippets.

Time-frequency and complexity analyses for differentiation of physiologic murmurs from heart murmurs caused by aortic stenosis in Boxers

OBJECTIVE

To investigate whether time-frequency and complexity analyses of heart murmurs can be used to differentiate physiologic murmurs from murmurs caused by aortic stenosis (AS) in Boxers.

ANIMALS

27 Boxers with murmurs.

PROCEDURES

Dogs were evaluated via auscultation and echocardiography. Analyses of time-frequency properties (TFPs; ie, maximal murmur frequency and duration of murmur frequency > 200 Hz) and correlation dimension (T(2)) of murmurs were performed on phonocardiographic sound data. Time-frequency property and T(2) analyses of low-intensity murmurs in 16 dogs without AS were performed at 7 weeks and 12 months of age. Additionally, TFP and T(2) analyses were performed on data obtained from 11 adult AS-affected dogs with murmurs.

RESULTS

In dogs with low-intensity murmurs, TFP or T(2) values at 7 weeks and 12 months did not differ significantly. For differentiation of physiologic murmurs from murmurs caused by mild AS, duration of murmur frequency > 200 Hz was useful and the combination assessment of duration of frequency > 200 Hz and T(2) of the murmur had a sensitivity of 94% and a specificity of 82%. Maximal murmur frequency did not differentiate dogs with AS from those without AS.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that assessment of the duration of murmur frequency > 200 Hz can be used to distinguish physiologic heart murmurs from murmurs caused by mild AS in Boxers. Combination of this analysis with T(2) analysis may be a useful complementary method for diagnostic assessment of cardiovascular function in dogs.

Heart energy signature spectrogram for cardiovascular diagnosis

A new method and application is proposed to characterize intensity and pitch of human heart sounds and murmurs. Using recorded heart sounds from the library of one of the authors, a visual map of heart sound energy was established. Both normal and abnormal heart sound recordings were studied. Representation is based on Wigner-Ville joint time-frequency transformations. The proposed methodology separates acoustic contributions of cardiac events simultaneously in pitch, time and energy. The resolution accuracy is superior to any other existing spectrogram method. The characteristic energy signature of the innocent heart murmur in a child with the S3 sound is presented. It allows clear detection of S1, S2 and S3 sounds, S2 split, systolic murmur, and intensity of these components. The original signal, heart sound power change with time, time-averaged frequency, energy density spectra and instantaneous variations of power and frequency/pitch with time, are presented. These data allow full quantitative characterization of heart sounds and murmurs. High accuracy in both time and pitch resolution is demonstrated. Resulting visual images have self-referencing quality, whereby individual features and their changes become immediately obvious.

Screening for aortic stenosis in the Boxer: Auscultatory, ECG, blood pressure and Doppler echocardiographic findings

OBJECTIVES

This study was conducted to estimate the incidence of aortic stenosis (AS) in a group of Boxers evaluated by auscultation, ECG, blood pressure measurement and Doppler-echocardiography.

BACKGROUND

The Boxer is a breed at significantly increased risk of AS. The prevalence of murmurs and Doppler-echocardiographic findings consistent with AS in this breed is reportedly high.

ANIMALS, MATERIALS AND METHODS

Eighty-nine Boxers were evaluated by auscultation, and final murmur grade recorded after stress testing. Doppler echocardiography was performed in fifty-five adult Boxers. Electrocardiograms (ECG, n=53), non-invasive blood pressure measurement (n=32), and Holter monitoring (n=24) were performed in selected dogs. Degree of AS was based on the aortic peak flow velocity (Ao PFV). Final Ao PFV was recorded as the highest value obtained after stress testing. AS was defined as an Ao PFV>2m/s on continuous wave Doppler, using the subcostal window. Pressure gradients (Deltap) were calculated using the modified Bernoulli equation (Deltap=4V(2)). Mild AS was defined as Deltap=16-40mmHg, moderate AS Deltap=40-75mmHg, and severe AS Deltap>75mmHg.

RESULTS

62% of adult Boxers evaluated by echocardiography had an Ao PFV>2m/s suggestive of AS. Systolic basilar ejection murmurs were diagnosed in 73%. Murmur intensity showed a statistically significant correlation with Ao PFV (p<0.05). ECG abnormalities were only detected in dogs with severe AS.

CONCLUSION

The study reports on systolic murmurs and Doppler-echocardiographic findings consistent with AS, as well as ECG and blood pressure measurements in a sample of pure-breed Boxers.

Congenital Heart Diseases in the Boxer Dog: A Retrospective Study of 105 Cases (1998–2005)

Subaortic stenosis (SAS) is one of the most common congenital heart diseases (CHD) in dogs with Boxers being predominantly affected. However, the increasing availability of modern diagnostic imaging systems now allows a better assessment of cardiac morphology and function, thereby facilitating early detection of CHD in awake animals. In this context, the case records of Boxer dogs diagnosed with CHD using echocardiography combined with Doppler mode, were retrospectively reviewed (1998-2005). One hundred and five Boxers exhibiting either a single CHD (53/105, 50.5%) or association of several CHD (52/105, 49.5%) were included. The most common CHD was atrial septal defect (ASD) observed in 56.2% of these animals (59/105), followed by mitral dysplasia (58/105, 55.2%), and SAS (49/105, 46.7%). SAS was associated with one or two CHD in 29.5% of cases (31/105). Most of the dogs with a low intensity left heart base systolic murmur had an isolated ASD whereas most of the dogs with a similar but high intensity murmur had SAS, either isolated or associated with a concurrent CHD. The incidence of ASD and mitral dysplasia in Boxer dogs is higher than previously assumed, and ASD is a common cause of left heart base systolic murmur in this breed of dog. This confirms that the detection of such a murmur should not be used as the unique criterion for diagnostic confirmation of SAS.

Clinical, echocardiographic, and electrocardiographic abnormalities in Boxers with cardiomyopathy and left ventricular systolic dysfunction: 48 cases (1985-2003)

OBJECTIVE

To identify clinical, echocardiographic, and electrocardiographic abnormalities in Boxers with cardiomyopathy and echocardiographic evidence of left ventricular systolic dysfunction.

DESIGN

Retrospective study.

ANIMALS

48 mature Boxers.

PROCEDURE

Medical records were reviewed for information on age; sex; physical examination findings; and results of electrocardiography, 24-hour ambulatory electrocardiography, thoracic radiography, and echocardiography.

RESULTS

Mean age of the dogs was 6 years (range, 1 to 11 years). Twenty (42%) dogs had a systolic murmur, and 9 (19%) had ascites. Congestive heart failure was diagnosed in 24 (50%) dogs. Seventeen (35%) dogs had a history of syncope. Mean fractional shortening was 14.4% (range, 1% to 23%). Mean left ventricular systolic and diastolic diameters were 4.5 cm (range, 3 to 6.3 cm) and 5.3 cm (range, 3.9 to 7.4 cm), respectively. Twenty-eight (58%) dogs had a sinus rhythm with ventricular premature complexes (VPCs), and 20 had supraventricular arrhythmias (15 with atrial fibrillation and 5 with sinus rhythm and atrial premature complexes). Sixteen of the dogs with supraventricular arrhythmias also had occasional VPCs. Morphology of the VPCs seen on lead II ECGs was consistent with left bundle branch block in 25 dogs, right bundle branch block in 8, and both in 11.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that Boxers with cardiomyopathy and left ventricular dysfunction frequently have arrhythmias of supraventricular or ventricular origin. Whether ventricular dysfunction was preceded by electrical disturbances could not be determined from these data, and the natural history of myocardial disease in Boxers requires further study.

Boxer dog cardiomyopathy: an update

Boxer dog cardiomyopathy is an inheritable form of myocardial disease characterized most commonly by ventricular tachycardias, syncope, and, sometimes, systolic dysfunction and heart failure. Careful evaluation of boxer dog cardiomyopathy by several investigators has demonstrated that the disease may be best classified as arrhythmogenic right ventricular cardiomyopathy. Affected dogs have a variable prognosis; although some succumb to sudden cardiac death, many can remain asymptomatic or be successfully managed on antiarrhythmics for years.

Low intensity heart murmurs in boxer dogs: inter-observer variation and effects of stress testing

Inter-observer variation in the detection and grading of low intensity heart murmurs in boxer dogs was investigated. Six veterinarians with different levels of experience examined 27 boxers by cardiac auscultation. The dogs were auscultated before and after exercise, and the results were compared with phonocardiographic and echocardiographic examinations performed at rest and during two different stress tests. A subvalvular aortic ridge was identified in six dogs on two-dimensional echocardiography. Using dogs with low intensity murmurs or dogs free of heart murmurs, inter-observer agreement was positively correlated to the level of experience at rest (weighted kappa [kappa] 0.14 to 0.75), while the agreement was poor after exercise (weighted kappa 0.01 to 0.36). The presence of a subvalvular aortic ridge was associated with higher aortic flow velocities (P<0.002) and higher auscultatory murmur grading (P<0.001). There was an increase in murmur duration during one kind of stress test (P<0.001) and in aortic flow velocity during the other (P=0.001).

Aortic ejection velocity in healthy Boxers with soft cardiac murmurs and Boxers without cardiac murmurs: 201 cases (1997-2001)

OBJECTIVE

To determine aortic ejection velocity in healthy adult Boxers with soft ejection murmurs without overt structural evidence of left ventricular outflow tract obstruction and in healthy Boxers without cardiac murmurs.

DESIGN

Retrospective study.

ANIMALS

201 Boxers.

PROCEDURE

Dogs were examined independently by 2 individuals for evidence of a cardiac murmur, and a murmur grade was assigned. Maximal instantaneous (peak) aortic ejection velocity was measured by means of continuous-wave Doppler echocardiography from a subcostal location. Forty-eight dogs were reexamined approximately 1 year later.

RESULTS

A soft (grade 1, 2, or 3) left-basilar ejection murmur was detected in 113 (56%) dogs. Overall median aortic ejection velocity was 1.91 m/s (range, 1.31 to 4.02 m/s). Dogs with murmurs had significantly higher aortic ejection velocities than did those without murmurs (median, 2.11 and 1.72 m/s, respectively). Auscultation of a murmur was 87% sensitive and 66% specific for the identification of aortic ejection velocity > 2.0 m/s. An ejection murmur and aortic ejection velocity > 2.0 m/s were identified in 73 (36%) dogs. For most dogs, observed changes in murmur grade and aortic ejection velocity during a follow-up examination 1 year later were not clinically important.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that ejection murmurs were common among healthy adult Boxers and that Boxers with murmurs were likely to have high (> 2.0 m/s) aortic ejection velocities. The cause of the murmurs in these dogs is unknown.

Progression of aortic stenosis in the boxer

Thirty-five boxers that had been referred to the Royal (Dick) School of Veterinary Studies between 1989 and 1994 with left heart base murmurs and aortic velocities greater than 1.5 m/second on Doppler echocardiography were recalled for clinical examination and Doppler echocardiography between 1995 and 1996. Five dogs (14 per cent) showed an increase in murmur grade on repeat visit. Six dogs (17 per cent) showed an increase in aortic velocity of greater than 20 per cent. Eight dogs (23 per cent) had developed aortic valvular or subvalvular two-dimensional echocardiographic changes that had not been present at the initial visit. Seven dogs (20 per cent) had developed aortic regurgitation, and three dogs (8 per cent) mitral regurgitation.

Prevalence of murmurs consistent with aortic stenosis among boxer dogs in Norway and Sweden

The prevalence and severity of cardiac murmurs consistent with subclinical or clinically detectable aortic stenosis among purebred boxer dogs in Norway and Sweden were evaluated. Two hundred and thirty-one boxers, randomly selected or investigated at dog shows, were examined by phonocardiography by two veterinarians and classified on the basis of the characteristics of their murmurs into categories 0 to 4. No murmur was detected in 23 per cent of the dogs, murmurs classified as category 1 were diagnosed in 25 per cent of the dogs, as category 2 in 46 per cent, as category 3 in 7 per cent cent, and two dogs had category 4 murmurs. In 55 per cent of the dogs, primarily those with very soft murmurs, there was some variation in the intensity of the murmur from beat to beat. The prevalence of cardiac murmurs among Norwegian and Swedish boxers was high and similar to the prevalence reported in Great Britain.