Remote Teaching of Canine Cardiac Auscultation Using Digital Phonocardiograms.

Veterinary students often struggle to correctly interpret heart sounds. This study sought to evaluate if additional online training using digital phonocardiograms (DPCGs) improves students' ability to identify normal and pathologic heart sounds in dogs. Thirty-six randomly assigned veterinary students listened to and interpreted 10 audio recordings of normal heart sounds (2), heart murmurs (4), and arrhythmias (4) at the start and the end of a 4-week period. Twenty-two students participated in training with DPCGs, including those created from these recordings during this period, via a self-study website (n = 12) or online webinar (n = 10). Their results were compared with those of a control group (n = 14) that did not undergo additional training. Although pre- and post-training test scores did not differ between groups, both training groups showed within-group improvement between the two tests (p = .024, p = .037); the control group did not (p = .49). Although neither training group showed differences in ability to differentiate normal heart sounds from arrhythmias, both showed increased ability to detect and specify heart murmurs and provide refined diagnoses of detected arrhythmias. These results suggest additional training, even without actual patients, improves students' ability to identify heart murmurs and provide specific diagnoses for arrhythmias. Further study with a larger sample size and an additional group without DPCG-based training would help evaluate the effectiveness of DPCGs regarding arrhythmias. Studying a larger sample size would also allow for a training group participating in both training methods, measuring cumulative effectiveness of both methods.

Temporal changes in the presence and intensity of innocent cardiac murmurs in clinically healthy Cairn terrier and Dachshund puppies between 4 and 8 weeks of age.

BACKGROUND: Spontaneous week-to-week variation in the presence and intensity of innocent cardiac murmurs in individual puppies is unknown. METHODS: Sixty privately owned, clinically healthy Cairn terrier and Dachshund puppies between 4 and 8 weeks of age were included. All dogs underwent weekly cardiac auscultation at the breeders' home by a veterinary cardiology specialist using an acoustic stethoscope. On each occasion, a phonocardiogram was recorded with an electronic stethoscope. Furthermore, all dogs were auscultated once at a first opinion veterinary practise and once at the authors' institution, where they also underwent an echocardiographic examination. RESULTS: Two-hundred and eighty-one auscultations were conducted on 32 Cairn terriers and 28 Dachshunds, at the breeders' homes. Innocent murmurs were detected in 19 puppies. Two of these puppies had a detectable murmur on each auscultation. In five of the puppies, the murmur became undetectable during the observation period and in 12 puppies the murmur was intermittently audible. Auscultation at the authors' institution had an unpredictable effect on murmur presence and intensity. Phonocardiography revealed murmurs in 42 puppies. Interpretation of phonocardiograms by two independent observers showed nearly perfect agreement (κ = 0.859). CONCLUSIONS: Remarkable and unpredictable spontaneous week-to-week variation was documented in the presence and intensity of innocent murmurs.

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.

Sound recording and digital phonocardiography of cardiac murmurs in dogs by using a sensor-based electronic stethoscope.

The goals of this study were to present a technique of digitalised sound recordings and phonocardiograms (dPCGs), and to analyse its diagnostic capabilities. Heart sounds of 20 dogs were auscultated in vivo (on-line) and recorded with dPCGs by two authors using a Welch Allyn Meditron Stethoscope System. Sound recordings were auscultated off-line and blindly by four different observers having various auscultatory experiences, then listened to while viewing dPCGs. The results were compared to echocardiographic diagnoses. There was a significant agreement (p < 0.001) between on-line and off-line auscultatory findings regarding the four observers, ranging from 45% to 75% (weighted kappa values: 0.72 to 0.87). The best agreement was achieved by Observer 1 having the highest experience. Significant differences (p < 0.05) were found between Observer 1 and Observer 4 (with the lowest experience) in judging the quality of the murmurs during the off-line and blind auscultation. However, there were only minimal differences (95% to 100% agreements) in dPCG analyses among the four observers regarding intensity and quality of the murmurs while simultaneously listening to and viewing the dPCGs. Significant correlations were found between the traditional '0 to 6 scale' and a new '0 to 3 scale' murmur intensity gradings by all observers (correlation coefficients 0.640 to 0.908; p < 0.01 to p < 0.001). Analysis of dPCGs might be a valuable, additional tool helping with the diagnosis of canine cardiac murmurs, especially for those with less cardiological experience.

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.

Detecting and recording cardiac murmurs in clinically healthy puppies in first opinion veterinary practice at the first health check.

BACKGROUND: The frequency that cardiac murmurs are identified and recorded in first opinion veterinary practices at the first health check in puppies is unknown. The aims of the study were to assess the agreement between first opinion veterinary practitioners, a veterinary student and a veterinary cardiology specialist on detecting murmurs, and to establish whether abnormal auscultation findings had been recorded in the health certificates of clinically healthy puppies. The study included prospective and retrospective investigations, where the prospectively collected auscultation findings from a veterinary cardiology specialist and a trained veterinary student were compared to auscultation findings recorded by first opinion veterinary practitioners. RESULTS: Cardiac auscultation was performed on 331 client-owned, clinically healthy dogs at two time points: at age 34-69 days by a first opinion veterinary practitioner and at age 45-76 days, on average 9 days later, by a veterinary cardiology specialist and a trained veterinary student. Agreement among the three was compared for the presence of a murmur. The degree of inter-observer agreement was evaluated using Cohen's kappa. Auscultation findings, as noted in the pets' passports, from 331 puppies and 43 different first opinion veterinary practices, were retrospectively reviewed and prospectively compared with auscultation findings from a veterinary cardiology specialist. Agreement between the veterinary cardiology specialist and the first opinion veterinary practitioners was poor (Ï° = 0.01) and significantly different (P < 0.001). First opinion veterinary practitioners had recorded a cardiac murmur in only 1 of the 97 puppies in which the veterinary cardiology specialist detected a murmur. Two-hundred-and-fifty-two puppies were auscultated by both the veterinary cardiology specialist and the student. Their agreement was fair (Ï° = 0.40) and significantly different (P = 0.024). The agreement between the student and a first opinion veterinary practitioner on these 252 puppies was poor (Ï° = 0.03) and significantly different (P < 0.001). CONCLUSIONS: This study shows that soft cardiac murmurs are rarely documented during the first veterinary health check in puppies by first opinion veterinary practitioners. Although soft murmurs may not be clinically relevant, finding and recording them is evidence of a carefully performed auscultation. Missing a non-pathological murmur is not of clinical importance; however, missing a pathological murmur could prove detrimental for the individual puppy.

Use of auscultation and Doppler echocardiography in Boxer puppies to predict development of subaortic or pulmonary stenosis.

BACKGROUND: Boxers are predisposed to subaortic and pulmonic stenosis (SAS, PS). Screening of puppies may be useful in estimating the risk of their developing a defect that potentially compromises life expectancy or exercise tolerance. HYPOTHESIS: Presence of SAS or PS in adult Boxers can be predicted by auscultation and Doppler echocardiography at 9-10 weeks of age. ANIMALS: Eighty-five Boxer puppies examined at 9-10 weeks of age and at 12 months of age. METHODS: Prospective, longitudinal observational study. Auscultation by stethoscope and continuous wave-Doppler echocardiography for peak velocities (V(max)) in the aorta (Ao) and pulmonary artery (PA). RESULTS: Intensity of heart murmurs in puppies correlated with V(max)Ao and V(max)PA in adults. V(max)Ao and V(max)PA in puppies correlated with V(max)Ao and V(max)PA in adults, respectively. From puppy to adult, V(max)Ao increased and V(max)PA remained unchanged. The negative predictive value for absent or only a soft (< or =II/VI) murmur in puppies being associated with V(max)Ao and PA < or = 2.4 m/s as an adult was 90% and < or =3.5 m/s 100%. The negative predictive value of a V(max)< or = 2.4 m/s as a puppy still being < or =2.4 m/s as an adult was 94% for Ao and 96% for PA, and of a V(max)< or = 3.5 m/s, 99% for Ao and 100% for PA. CONCLUSIONS AND CLINICAL IMPORTANCE: Even though V(max)Ao increases during growth in Boxer puppies, indicating relative narrowing of the aorta, puppies with V(max)Ao < or = 2.4 m/s do not usually progress to clinically have relevant SAS at 12 months of age.

Cardiac evaluation of clinically healthy captive maned wolves (Chrysocyon brachyurus).

The objective of this project was to determine radiographic vertebral heart sizes and electrocardiographic (ECG) and echocardiographic measurements in healthy anesthetized maned wolves (Chrysocyon brachyurus). The wolves, housed at the White Oak Conservation and Smithsonian National Zoo Conservation and Research Centers, were being anesthetized for annual examinations. Cardiac auscultation, thoracic radiographs, a standard 6-lead ECG, and echocardiography were performed on the wolves while they were under general anesthesia. Thirteen maned wolves were evaluated: five males and eight females. Mean age was 6.4 +/- 4.4 years (range, 2-13 years). Mean weight was 26 +/- 2.95 kg (range, 22-32 kg). Low-grade systolic murmurs were auscultated in three of 13 maned wolves. Evaluation of ECGs revealed a sinus rhythm, with a QRS morphology, and mean electrical axis similar to domestic canines. Radiographic evaluation revealed a mean vertebral heart size of 8.27 +/- 0.48 (range, 7.9-8.6). In addition, the cardiac silhouette was seen to elongate, with an increase in sternal contact in older wolves. Echocardiography showed that mitral valve degenerative changes and insufficiency is likely common in older wolves. Visualization of physiologic regurgitation across the mitral and pulmonary valves was common in wolves of all ages. Left ventricular measurements were similar to those reported for healthy dogs, and several variables correlated well with body weight. Two wolves were found to have one to three heartworms in the right pulmonary artery, and degenerative mitral valve disease was determined in maned wolves older than 6 years of age. All of the wolves in this study were on heartworm preventative and tested negative for heartworm antigen at their annual examinations. The results of this study provide reference information for use in the cardiac evaluation of anesthetized maned wolves.

Age when presumptive innocent cardiac murmurs spontaneously disappear in clinically healthy Cairn terrier puppies.

Innocent cardiac murmurs are common findings in Cairn terrier puppies during their first veterinary health check. The age when these murmurs spontaneously disappear is unreported. The purpose of this study was to establish the age when presumably innocent cardiac murmurs disappear in a population of clinically healthy Cairn terrier puppies. Over a period of 9 months, 227 clinically healthy Cairn terrier puppies (median age, 53 days; range, 45-76 days) underwent auscultation by a veterinary cardiology specialist, who identified 82 puppies with a presumably innocent cardiac murmur. Owners of 20 puppies volunteered to return to the clinic for serial rechecks. Owners of three puppies returned only once, therefore these puppies were censored. Hence this longitudinal observational study followed 17 puppies with monthly cardiac auscultation until the disappearance of their murmurs. The median age of the 20 puppies when the murmur was last audible was 65 days (range 52-285 days). The median age of the 17 puppies when the murmur was no longer audible was 87 days (range 71-347 days; 95% confidence interval 63-111 days). Four of the 17 puppies had a murmur after 3 months of age and two of them had a murmur beyond 6 months of age. The oldest puppy to have an audible murmur was 9.5 months old; this murmur was not audible at 11.5 months of age. In most Cairn terrier puppies in this population, the presumably innocent murmur resolved spontaneously by 3 months of age.

Vertebral heart size in healthy Australian cattle dog.

The vertebral heart score or size (VHS) measurement is routinely used to provide a more objective measurement of cardiomegaly in dogs. However, breed or body conformation can influence the VHS. To assess the specific VHS for the Australian Cattle Dog, left-to-right lateral, right-to-left lateral, dorsoventral and ventrodorsal thoracic radiographs from 20 individuals free from cardiac and pulmonary disease were obtained. The mean VHS was significantly higher in Australian Cattle Dog (10.5 ± 0.4 vertebrae), when compared with the average VHS for 100 normal dogs of different breeds that had been initially published (9.7 ± 0.5 vertebrae). This emphasizes the importance of breed-specific VHS ranges. In our study group of normal Australian Cattle Dogs, the mean VHS was 10.5 ± 0.5 vertebrae (mean ±SD) on right lateral and 10.3 ± 0.5 vertebrae on left lateral radiographs. The VHS on right lateral views was significantly larger than on left lateral views. The VHS was 10.5 ± 0.6 vertebrae on dorsoventral and 11.1 ± 0.6 vertebrae on ventrodorsal radiographs. The VHS on ventrodorsal views was significantly larger than on dorsoventral views.

Heart murmurs and valvular regurgitation in thoroughbred racehorses: epidemiology and associations with athletic performance.

BACKGROUND: Cardiac murmurs associated with valvular regurgitation occur commonly in conditioned performance horses, but their association with athletic performance is unknown. HYPOTHESIS: Cardiac valvular regurgitation has a negative association with race performance. ANIMALS: Five hundred and twenty-six "race fit" Thoroughbred racehorses engaged in either flat (race distance 1,000-2,500 m) or jump racing (race distance 3,200-6,400 m). METHODS: Cardiac auscultation and color flow Doppler (CFD) echocardiography were performed on 777 occasions. The associations between the presence and severity of either an audible cardiac murmur or valvular regurgitation assessed by CFD, and published, objective measures of race performance were determined using a standard regression approach. RESULTS: The prevalence of murmurs and of regurgitation varied significantly between racetypes (P<.02), generally increasing from 2-year olds to chasers. There were no consistent associations between racing performance and either grade of murmur or regurgitation, whether the presence or absence of regurgitation or murmur, or only murmurs > or =3/6 or regurgitation > or =6/9, were considered. CONCLUSIONS AND CLINICAL IMPORTANCE: There were differences in prevalence and severity of murmurs of atrioventricular and aortic valve regurgitation between racehorses in different disciplines. Data also showed that neither regurgitation nor murmurs were negatively associated with Timeform rating, an index of UK racehorse quality, in any of the groups of racehorses studied.

Aortic stenosis in the Dogue de Bordeaux.

OBJECTIVES: To evaluate the occurrence of aortic stenosis and establish echocardiographic reference values in the Dogue de Bordeaux in Denmark. METHODS: Fifty-three dogs were auscultated for evidence of a cardiac murmur and a full echocardiographic examination was performed. The criterion for the diagnosis of aortic stenosis was a peak aortic velocity greater than 2.5 m/s from a subcostal transducer location. RESULTS: A left-basilar ejection murmur was detected in 38 (72 per cent) of the dogs. An aortic ejection velocity greater than 2.5 m/s was identified in 9 (17 per cent) of the dogs from a subcostal view. The aortic annulus in Dogue de Bordeaux was smaller than that considered normal in other breeds with comparable body size. Furthermore, a decreased aortoseptal angle was noticed in dogs with aortic stenosis. CLINICAL SIGNIFICANCE: The Dogue de Bordeaux may be highly predisposed to aortic stenosis. The small aortic annulus noted in healthy and affected Dogue de Bordeaux and a decreased aortoseptal angle noted in affected dogs in this study might reflect key aetiological features in the development of aortic stenosis.

Cardiac evaluation of anesthetized Grevy's zebras (Equus grevyi).

OBJECTIVE: To determine ECG and echocardiographic measurements in healthy anesthetized Grevy's zebras (Equus grevyi). ANIMALS: 20 healthy zebras. PROCEDURES: Auscultation, base-apex ECG, and echocardiography were performed on anesthetized zebras. RESULTS: Low-grade systolic murmurs were detected in the left basilar region in 4 of 20 zebras. Evaluation of ECGs from 19 zebras revealed sinus rhythm with a predominantly negative QRS complex and a mean +/- SD heart rate of 67 +/- 10 beats/min. Echocardiograms of sufficient image quality were obtained for 16 zebras. Interventricular septal thickness in diastole, left ventricular chamber in diastole and systole, left atrial diameter, and left ventricular mass were significantly and moderately correlated with estimated body weight (r values ranged from 0.650 to 0.884). Detectable swirling of blood in the right and sometimes the left ventricles was detected in 9 of 16 zebras, whereas physiologic regurgitation of blood was detected for the aortic valve in 3 zebras, pulmonary valve in 2 zebras, mitral valve in 2 zebras, and tricuspid valve in 1 zebra. CONCLUSIONS AND CLINICAL RELEVANCE: Results of this study provide reference information for use in the cardiac evaluation of anesthetized Grevy's zebras.

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.

N-Terminal Pro-B-Type Natriuretic Peptide and Phonocardiography in Differentiating Innocent Cardiac Murmurs from Congenital Cardiac Anomalies in Asymptomatic Puppies.

BACKGROUND: Differentiating innocent cardiac murmurs from murmurs caused by congenital cardiac anomalies can be challenging with auscultation alone in asymptomatic puppies. HYPOTHESIS: Plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentrations and phonocardiograms recorded by an electronic stethoscope can differentiate innocent from pathologic cardiac murmurs. ANIMALS: A total of 186 client-owned asymptomatic dogs: 135 Cairn Terriers (age: 45-124 days), 20 adult Cairn Terriers (age: 7.5 months to 13.5 years), and 31 puppies of various breeds (age: 29-396 days). METHODS: Study design is a cross-sectional survey. Each dog was auscultated, and when a cardiac murmur was heard, a phonocardiogram was recorded and an echocardiogram was performed. Plasma NT-proBNP concentrations were measured by a single laboratory by an ELISA. RESULTS: No significant (P = .41) difference in plasma NT-proBNP levels was found between puppies without a murmur and puppies with an innocent murmur (median 300 versus 326 pmol/L), and between clinically healthy adult Cairn Terriers and Cairn Terrier puppies. Plasma NT-proBNP levels in puppies with a congenital heart disease were significantly (P < .001) higher than those in puppies with innocent murmurs (median 1,102 versus 326 pmol/L). However, some puppies with severe pulmonic stenosis did not have increased plasma NT-proBNP levels. On phonocardiograms, innocent murmurs had a significantly (P < .001) shorter "murmur-to-systole duration ratio" than the abnormal ones (median 66 versus 100%). The "murmur-to-S1 (first cardiac sound) amplitude ratio" was significantly (P < .001) lower of the innocent murmurs compared with that of the abnormal ones (median 16 versus 58 %). CONCLUSIONS AND CLINICAL IMPORTANCE: Plasma NT-proBNP concentrations within the reference range do not rule out a congenital cardiac anomaly. Murmurs longer than 80% of the systole are most likely abnormal, whereas murmurs shorter than that could be either innocent or pathologic.

Innocent Cardiac Murmur in Puppies: Prevalence, Correlation with Hematocrit, and Auscultation Characteristics.

BACKGROUND: The aims of this study were to establish the prevalence of innocent cardiac murmurs in clinically healthy puppies, to investigate a possible correlation between the presence of an innocent murmur and hematocrit, and to describe the auscultation characteristics of innocent murmurs. HYPOTHESIS: Lower hematocrit contributes to the genesis of innocent murmurs. ANIMALS: Five hundred and eighty-four client-owned clinically healthy puppies, between 20 and 108 days old. METHODS: Two cross-sectional surveys with a 1-year (n = 389 pups) pilot and a half-year (n = 195 pups) principal study periods. Cardiac auscultation was performed by a single, board-certified cardiologist. Hematocrit was measured with an automatized hematology analyzer. Echocardiography was performed only on puppies with a cardiac murmur in the principal study. RESULTS: In the pilot study, 15% of the dogs had a murmur. Innocent murmur was diagnosed in 28% of the 195 dogs in the principal study. Innocent murmurs were systolic, mostly with a musical character and with a maximal intensity of 2 of 6, and mostly with the point of maximal intensity in the left cardiac base. The hematocrit was significantly lower in the group with a murmur compared to the group without (P = .023). CONCLUSIONS AND CLINICAL IMPORTANCE: Innocent murmur was a common finding in puppies at the age when the first veterinary controls usually take place. Physiologic anemia contributes to the genesis of innocent murmurs in puppies. Rising hematocrit in growing puppies can explain the spontaneous disappearance of innocent murmurs with aging. Hematocrit did not differentiate innocent murmurs from abnormal murmurs.

Athletic heart syndrome in dogs competing in a long-distance sled race.

The cardiac effects of endurance training were evaluated by cardiac auscultation and electrocardiographic examination of 48 heavily trained sled dogs (3,000-5,000 km of training), 18 lightly trained sled dogs (300-800 km of training), 19 untrained sled dogs, and 14 mongrel dogs. A grade I-II/VI early- to midsystolic cardiac murmur was auscultated with increasing frequency as training level increased. The QRS duration (66.1 +/- 7.4 ms) and QT interval (236 +/- 20 ms) were significantly (P < 0.05) longer in heavily trained sled dogs than in mongrel dogs (QRS, 60.6 +/- 4.6; QT, 219 +/- 11 ms). A long QT interval (> 250 ms) was observed in 8 (16.7%) heavily trained dogs but not in the other groups. A significant rightward shift in the mean electrical axis of ventricular depolarization in the frontal plane was observed in heavily trained sled dogs. The auscultatory and electrocardiographic findings in heavily trained sled dogs were remarkably similar to those reported in elite human endurance athletes, suggesting that endurance-trained sled dogs provide a naturally occurring model for the athletic heart syndrome.

Atypical hypoplastic left ventricular syndrome in a calf.

An 8-day-old male Angus calf was presented to the University of Illinois, Veterinary Teaching Hospital, Urbana, IL, for lethargy, weakness, and poor suckle reflex. Clinical evaluation revealed a strong left-sided heart murmur and a split S2 sound. The calf died within 48 hours. Necropsy revealed a combination of the following cardiac defects: left ventricular hypoplasia, high ventricular septal defect, left auricular atresia with mitral valve aplasia, patent foramen ovale, patent ductus arteriosus, and pulmonary trunk atresia. Mild suppurative pneumonia with pulmonary edema and congestion were also present. This combination of defects appears to be similar to the hypoplastic left heart syndrome in humans and is reported here for the first time in cattle.

Effect of age and training on murmurs of atrioventricular valvular regurgitation in young thoroughbreds.

Cardiac auscultation was carried out on 111 Thoroughbred horses age 2-5 years to test the hypothesis that athletic training might influence the development of atrioventricular (AV) valve regurgitation in young Thoroughbreds. Murmurs of valvular regurgitation were identified and graded on a 1-6 scale. There were 2 sources of auscultation data: 1) 55 2-year-old horses that were examined by auscultation before training commenced and 9 months later when at race fitness; 2) 56 horses age 2-5 years that were examined on one occasion only (25 2-year-olds, 23 3-year-olds, five 4-year-olds and five 5-year olds). All horses in the second data set were in full training and racing regularly at the time of the examination. To conclude the study, 35 horses were selected randomly from both groups of horses and examined with colour-flow Doppler echocardiography. The aim of the final part of the study was to check specificity and sensitivity of auscultation for detection of AV valve murmurs and therefore validate the auscultation findings. Prior to training, the prevalence in 2-year-old racehorses of murmurs of mitral regurgitation and tricuspid regurgitation was 7.3% (4/55) and 12.7% (7/55), respectively. After training, the prevalence proportions increased to 21.8% (12/55) and 25.5% (14/55). After training, one horse developed a murmur characteristic of aortic regurgitation. The differences in murmur prevalence were statistically significant for mitral and tricuspid regurgitation (paired t test results: mitral regurgitation, P = 0.019; tricuspid regurgitation, P = 0.007), as were the differences in mean murmur grade (P = 0.018 and P = 0.0006, respectively). There were no significant effects of age on the prevalence of valvular regurgitation in 56 horses examined at race fitness. Auscultation was a specific (specificity 100%) and reasonably sensitive method for detection of murmurs of mitral and tricuspid regurgitation (mitral regurgitation: positive predictive value 100%, negative predictive value 84%, tricuspid regurgitation: positive predictive value 100%, negative predictive value 65%). These data suggest that the prevalence and grade of murmurs of mitral and tricuspid valvular regurgitation increase in 2-year-old Thoroughbreds after 9 months of athletic training. Whereas the effects of age and growth on the prevalence of murmurs cannot be ruled out from these data, this study suggests that there is an influence of athletic training on the development of atrioventricular valvular regurgitation in flat-racing Thoroughbreds.

A survey of cardiac auscultatory findings in horses.

Auscultation was used to examine 545 horses for cardiac murmurs and some arrhythmias. The most significant finding was the high prevalence of right-sided holosystolic or pansystolic plateau-type murmurs compatible with a diagnosis of tricuspid regurgitation in National Hunt racing Thoroughbreds of all ages (16.4%). This condition was found in 4.7% of flat-racing Thoroughbreds, 3.7% of non-racing Thoroughbreds and Thoroughbred crosses, and in none of the ponies examined. High prevalences of left-sided early systolic murmurs (53%), left-sided early diastolic murmurs (23%), right-sided early diastolic murmurs (22%) and second degree atrioventricular block (23%) were found in racehorses of both types.