Retrospective study of congenital heart defects in 151 dogs

An Intrapericardial Technique for PDA Ligation: Surgical Description and Clinical Outcome in 35 Dogs

A number of surgical techniques have been reported for dissection and ligation of patent ductus arteriosi (PDAs) in dogs. The objectives of this study were to provide a detailed description of an intrapericardial technique for PDA dissection and ligation and to report the clinical outcome of that technique in dogs. Medical records of 35 dogs were retrospectively reviewed for signalment, clinical signs, echocardiographic findings, surgical time, intra- and postoperative complications, and completeness of ductal closure. Median surgery time was 60 min (range, 35–125 min). Neither intraoperative nor postoperative complications occurred. Within 48 hr of surgery, the continuous left basilar heart murmur was absent in all dogs, and complete echocardiographic closure was confirmed in 29 of 32 dogs. Residual flow was identified echocardiographically in three dogs within 48 hr of surgery. Residual flow was decreased in one dog at 1 mo, which resolved within 33 mo. One dog had mild residual flow postoperatively but did not return for follow-up. The intrapericardial technique was successful for PDA dissection and ligation and had a lower rate (6%) of echocardiographic residual flow compared with previously reported techniques.

Congenital Pulmonic Stenosis a Retrospective study of 24 cases seen between 1990-1999

BACKGROUND

PBV is the treatment of choice for humans with pulmonic stenosis and whilst this procedure has been used in dogs the longer term benefits remain to be evaluated.

OBJECTIVES

The purpose of this study was to evaluate the long term effects of pulmonary balloon valvuloplasty (PBV) in dogs with congenital pulmonic stenosis, with respect to clinical signs, echocardiographic parameters and survival time. Methods - Pulmonic stenosis was diagnosed in 24 dogs between 1990-1999. Eighteen cases were treated with PBV, six were not treated.

RESULTS

Twelve of the treated cases were alive and asymptomatic at the time of writing. Follow up periods ranged from six months to nine years post PBV. Prior to treatment the mean Doppler pressure gradient across the pulmonic valve was 98mmHg, 24 hours post treatment the mean was 65mmHg and in the long term this was maintained at 64mmHg. Three of the dogs (17 per cent) treated with PBV restenosed during the follow up period. Four of the six untreated dogs were alive at the time of writing, two to four and a half years after presentation. The mean Doppler gradient for this group was 89 mm Hg on presentation.

CONCLUSION

At this stage in the follow up period there is no significant difference in survival times between the treated and untreated groups. However, symptomatic dogs with pulmonic stenosis treated with PBV have experienced a reduction in clinical signs and therefore an improved quality of life.

Familial subvalvular aortic stenosis in golden retrievers: inheritance and echocardiographic findings

OBJECTIVES

To describe the echocardiographic findings and pedigree analysis of golden retrievers with subvalvular aortic stenosis.

METHODS

Seventy-three golden retrievers were evaluated by auscultation and echocardiography. A subcostal continuous-wave Doppler aortic velocity ê2·5 m/s and presence of a left basilar systolic ejection murmur were required for diagnosis of subvalvular aortic stenosis. Three echocardiographic characteristics were recorded: evidence of aortic insufficiency, subvalvular ridge or left ventricular hypertrophy. A disease status score was calculated by totalling the number of echocardiographic -characteristics per subject.

RESULTS

Thirty-two of 73 dogs were affected and their aortic velocities were as follows: range 2·5 to 6·8 m/s, median 3·4 m/s and standard deviation 1·2 m/s. Echocardiographic characteristics of 32 affected dogs were distributed as follows: left ventricular hypertrophy 12 of 32, aortic insufficiency 20 of 32 and subvalvular ridge 20 of 32. Disease status score ranged from 0 to 3 with a median of 2. There was a statistically significant correlation between aortic velocity and disease status score (r=0·644, P<0·0001). Subvalvular aortic stenosis was observed in multiple generations of several families and appears familial.

CLINICAL SIGNIFICANCE

Subvalvular aortic stenosis in the golden retriever is familial. Severity of stenosis correlates well with cumulative presence of echocardiographic characteristics (left ventricular hypertrophy, subvalvular ridge and aortic insufficiency).

Ventricular septal defect with aortic valve insufficiency in a New Zealand White rabbit

A heart murmur was detected in a 10 mo old, female New Zealand White rabbit. Auscultation revealed cardiac murmurs both at the left and right hemithorax. Phonocardiography confirmed the systolic-diastolic nature of the left-sided and the systolic character of the right-sided murmur. Electrocardiography showed normal sinus rhythm; tall R waves and large T waves in lead II; and deep S waves in leads II, III, and aVF. Thoracic radiography demonstrated generalized cardiomegaly with prominent pulmonary vasculature. Echocardiography revealed a perimembraneous ventricular septal defect with aortic insufficiency. Signs of biventricular volume overload, relative pulmonic stenosis, and pulmonary valve insufficiency were also seen as consequences of the defect. Necropsy demonstrated a ventricular septal defect just below the aortic valve, a dilated pulmonary trunk, dilated and hypertrophied ventricles, dilated atria, and rightward displacement of the aortic root. Cardiac histopathology showed ventricular cardiomyocyte degeneration (swelling and hypereosinophilia of the cytoplasm with a loss of cross striation, and nuclear hyperchromasia), cartilaginous metaplasia of the aorta, and subendocardial fibrosis of the right ventricular flow tract.

Retrospective review of congenital heart disease in 976 dogs

BACKGROUND

Knowledge of epidemiology is important for recognition of cardiovascular malformations.

OBJECTIVE

Review the incidence of congenital heart defects in dogs in Italy and assess breed and sex predispositions.

ANIMALS

Nine hundred and seventy-six dogs diagnosed with congenital heart disease (CHD) of 4,480 dogs presented to Clinica Veterinaria Gran Sasso for cardiovascular examination from 1997 to 2010.

METHODS

A retrospective analysis of medical records regarding signalment, history, clinical examination, radiography, electrocardiography, echocardiography, angiography, and postmortem examination was performed. Breed and sex predisposition were assessed with the odds ratio test.

RESULTS

CHD was observed in 21.7% of cases. A total of 1,132 defects were observed with single defects in 832 cases (85%), 2 concurrent defects in 132 cases (14%), and 3 concurrent defects in 12 cases (1%). The most common defects were pulmonic stenosis (PS; 32.1%), subaortic stenosis (SAS; 21.3%), and patent ductus arteriosus (20.9%), followed by ventricular septal defect (VSD; 7.5%), valvular aortic stenosis (AS; 5.7%), and tricuspid dysplasia (3.1%). SAS, PS, and VSD frequently were associated with other defects. Several breed and sex predispositions were identified.

CONCLUSIONS AND CLINICAL RELEVANCE

The results of this study are in accordance with previous studies, with slight differences. The breed and sex predilections identified may be of value for the diagnosis and screening of CHD in dogs. Additionally, the relatively high percentage of concurrent heart defects emphasizes the importance of accurate and complete examinations for identification. Because these data are from a cardiology referral center, a bias may exist.

Therapeutic changes of plasma N-terminal pro-brain natriuretic peptide concentrations in 9 dogs with patent ductus arteriosus

The plasma N-terminal proBNP (NT-proBNP) concentration is measured for determining the diagnosis and severity of heart failure in dogs. However, it is still unclear whether measurements of circulating NT-proBNP levels provide clinical utility as an indicator of therapeutic efficacy. Thus, we investigated the surgical correction-related changes of plasma NT-proBNP concentrations in 9 dogs with patent ductus arteriosus (PDA). Physical examination, thoracic radiography and echocardiography were conducted both before and after surgery. Similarly, the plasma NT-proBNP concentrations were determined using an enzyme immunoassay for canine pro-BNP. The International Small Animal Cardiac Health Council (ISACHC) class and murmur grade were significantly improved after surgery compared with before surgery. Vertebral heart size (VHS) and cardiothoracic ratio (CTR) were significantly decreased after surgery. Fractional shortening was significantly decreased and relative wall thickness (RWT) was significantly increased after surgery. Furthermore, the plasma NT-proBNP concentrations were significantly decreased by surgical correction. The plasma NT-proBNP concentration showed significant positive correlation with the ISACHC class, murmur grade, VHS and CTR and significant negative correlation with the RWT. Therefore, measurement of plasma NT-proBNP levels can be used to monitor the effectiveness of therapies such as surgical correction of PDA.

Balloon valvuloplasty for treatment of pulmonic stenosis in English Bulldogs with an aberrant coronary artery

BACKGROUND

English Bulldogs (EB) with pulmonic stenosis (PS) sometimes have an aberrant coronary artery (CA) type R2A encircling the pulmonary artery (PA). Balloon valvuloplasty (BV) is treatment of choice for severe PS, but is considered to be contraindicated in dogs with aberrant CA.

HYPOTHESIS

Conservative BV in EB with aberrant CA is safe and improves clinical signs and quality of life.

ANIMALS

Four client-owned EB with severe PS were retrospectively reviewed/analysed.

METHODS

Retrospective study: Case records, echocardiography, BV, and follow-up investigations of EB diagnosed with severe PS and treated with BV were reviewed. The ratios of PA to aortic (Ao) velocity time integral (VTI) were calculated to assess progression/improvement of PS.

RESULTS

An aberrant CA was confirmed on angiography in all EB. Conservative BV was performed, using a balloon of the size of the PA annulus or smaller (0.6-1 x PA annulus size). All dogs survived the procedure, but only a mild reduction in pressure gradient was achieved. There was an improvement in PA to Ao VTI in 3 of 4 dogs (P < or = .017), which were free of evidence of congestive heart failure (CHF) 5, 10, and 15 months after BV. One dog that had right-sided CHF when BV was performed died due to progressive right-sided CHF within 3 months.

CONCLUSIONS

Conservative BV in EB might be safe and might improve quality and quantity of life.

Welfare epidemiology as a tool to assess the welfare impact of inherited defects on the pedigree dog population

The effect that breed standards and selective breeding practices have on the welfare of pedigree dogs has recently come under scrutiny from both the general public and scientific community. Recent research has suggested that breeding for particular aesthetic traits, such as tightly curled tails, highly domed skulls and short muzzles predisposes dogs with these traits to certain inherited defects, such as spina bifida, syringomyelia and brachycephalic airway obstruction syndrome, respectively. Further to this, there is a very large number of inherited diseases that are not related to breed standards, which are thought to be prevalent, partly as a consequence of inbreeding and restricted breeding pools. Inherited diseases, whether linked to conformation or not, have varying impact on the individuals affected by them, and affect varying proportions of the pedigree dog population. Some diseases affect few breeds but are highly prevalent in predisposed breeds. Other diseases affect many breeds, but have low prevalence within each breed. In this paper, we discuss the use of risk analysis and severity diagrams as means of mapping the overall problem of inherited disorders in pedigree dogs and, more specifically, the welfare impact of specific diseases in particular breeds.

Cardiac conotruncal malformations in a family of beagle dogs

OBJECTIVES

To study forms of congenital heart disease present in a family of beagle dogs with a strong prevalence of ventricular septal defect and to document the pathological findings associated with the ventricular septal defects and investigate the mode of transmission.

METHODS

The animals were investigated by physical examination, radiography, electrocardiography and ultrasonography to diagnose the presence of congenital heart disease. Some animals were diagnosed at post-mortem examination and the dead animals underwent post-mortem examination to verify the presence of ventricular septal defect. An analysis of pedigree was undertaken and two of the affected animals were mated to investigate the mode of transmission.

RESULTS

Among the 28 dogs evaluated clinically or by post-mortem examination, 14 cases of ventricular septal defect were identified. The post-mortem examination showed some abnormalities of the ventricular outflow region associated with malformation of conotruncal septum development. When two affected dogs were bred, congenital heart disease was present in all of the offspring.

CLINICAL SIGNIFICANCE

The congenital heart disease identified in this beagle family can be classified as conotruncal malformation, and an autosomal recessive mode of inheritance was suggested by pedigree analysis.

Cardiac troponin I as a marker for severity and prognosis of cardiac disease in dogs

The use of cardiac troponin I (cTnI) to assess the severity of disease and prognosis in 120 dogs presented for cardiac evaluation was analysed. cTnI concentrations were measured using a commercially available assay. Dogs were placed into three groups: group 1, cTnI0.15ng/mL; group 2, cTnI 0.151-1.0ng/mL; group 3, cTnI>1.01ng/mL. Dogs in group 1 were significantly younger (P<0.0001) and had no or stable cardiac diseases and longest survival times, whereas those in groups 2 and 3 had severe cardiac diseases and significantly reduced survival times (P<0.0001). Thirty dogs with initially increased cTnI concentrations had a repeat assay less than 2months later with significant reductions in cTnI concentrations (P=0.005). Initial cTnI concentrations could not differentiate dogs that survived in group 3 from those that did not. However, dogs that survived showed significant cTnI reductions (P=0.015) in the repeated assay in contrast to the dogs that died (P=0.22). It was concluded that cTnI is useful in assessing the prognosis and severity of cardiac diseases in dogs, and progression and response to treatment can be assessed by repeat sampling. cTnI concentrations >1.0ng/mL and persistent increases in cTnI concentrations are indicators of a poor prognosis in dogs with cardiac disease.

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.

Aortic endocarditis associated with a perforated septal membranous aneurysm in a boxer dog

Perimembranous ventricular septal defect is a common congenital heart disease in the dog. It can partially or completely close with age by development of a membranous ventricular septal aneurysm. Aortic endocarditis is a reported complication of ventricular septal defect and membranous ventricular septal aneurysm in human beings. This report describes a case of aortic endocarditis associated with a membranous ventricular septal aneurysm perforated by a small ventricular septal defect in a boxer dog.

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.

Tricuspid valve dysplasia and Ebstein's anomaly in dogs: case report

Two cases of tricuspid valve dysplasia are reported. Dogs were presented for evaluation of weakness and ascites. In both cases, echocardiography disclosed tricuspid insufficiency and, in one of them, tricuspid leaflets also were displaced down into the right ventricle, substantiating Ebstein's anomaly. Medical therapy for congestive heart failure was initiated. One of the dogs suddenly died shortly after diagnosis was established. Although the other dog recovered much better initially, sudden death also occurred. Post-mortem examinations showed right atrioventricular enlargement, and thickened tricuspid leaflets. Clinical features, diagnostic methods and medical therapy are discussed in this paper.

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.

Retrospective Study of 156 Atrial Septal Defects in Dogs and Cats (2001-2005)

Atrial septal defect (ASD) is a common congenital heart disease (CHD) in humans, but considered relatively rare in veterinary medicine. However, modern echocardiographic and Doppler techniques currently offer a good view of the morphology of the interatrial septum, thus facilitating earlier detection of ASD in awake animals. In this context, we carried out a retrospective study of cases of recently diagnosed ASD in dogs and cats at the Cardiology Unit of Alfort (2001-2005) using echocardiography combined with colour Doppler mode. ASD was diagnosed in 156 animals and represented 37.7% of all canine and feline CHDs (n = 414). ASD was the most common CHD after mitral dysplasia in both species. Boxer and Domestic shorthair were the most common canine and feline breeds affected. Most defects (98.7%) were secundum-type ASD, without clinical signs in 73.7% of cases. The most common clinical signs included systolic murmur heard over the left heart base (20.2%), exercise intolerance (7.0%), syncope (5.3%), dyspnoea (2.6%) and cough (2.6%). Animals that presented a systolic heart murmur over the left base had a significantly larger ASD than others (P < 0.05). These data suggest that the incidence of ASD is higher than previously assumed. ASD should be suspected, for example, in instances of left basal systolic heart murmur, although its clinical and haemodynamic consequences are usually minor.

Evaluation of survival rate and prognostic indicators for surgical treatment of left-to-right patent ductus arteriosus in dogs: 52 cases (1995-2003)

OBJECTIVE

To determine factors associated with long-term survival in dogs treated surgically for patent ductus arteriosus (PDA).

DESIGN

Retrospective case series. Animals-52 dogs treated surgically for left-to-right shunting PDA.

PROCEDURE

Data pertaining to age, breed, sex, body weight, clinical examination findings, type and duration of medical treatment, results of thoracic radiography and echocardiography, and surgical and postoperative complications were collected from records. Follow-up information was obtained from medical records or telephone interviews with owners or referring veterinarians.

RESULTS

22 dogs had mitral valve regurgitation. Mean weight and age were not significantly different between dogs with or without mitral valve regurgitation. Twenty-four (46.2%) dogs had clinical signs related to cardiac insufficiency. Left atrial dilatation was observed in 56.3% of dogs that were radiographed. Sonographic imaging was used to diagnose left atrial dilatation in 23 dogs and left ventricular dilatation in 25 dogs. The 1- and 2-year survival rates were 92% and 87%, respectively. Diagnosis of mitral valve regurgitation before surgery was not associated with the probability of survival. Age, weight, lethargy, preoperative treatment with angiotensin-converting enzyme inhibitors, and right atrial dilatation on radiographs at the time of surgery were negatively associated with probability of survival.

CONCLUSIONS AND CLINICAL RELEVANCE

Surgical treatment of PDA was curative in young dogs without clinical signs of heart failure. Surgical correction of PDA should be recommended as early as possible after diagnosis, and mitral valve regurgitation is not a contraindication for surgery.

Echocardiographic Diagnosis of Congenital Membranous Ventricular Septal Aneurysm in the Dog and Cat

Membranous ventricular septal aneurysm was diagnosed by echocardiography in 17 dogs and three cats. The aneurysm appeared as a thin membrane protruding into the right ventricle from the margins of a congenital ventricular septal defect (VSD). The aneurysm was intact in nine dogs and two cats and perforated by a small VSD in eight dogs and one cat. Other congenital heart defects were present in seven dogs. In all animals, the aneurysm was an incidental finding observed during echocardiographic examination, and it did not appear to directly cause any cardiac dysfunction.

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).

Tissue Doppler Imaging and Echo-Doppler Findings Associated with a Mitral Valve Stenosis with an Immobile Posterior Valve Leaflet in a Bull Terrier

A mitral valve stenosis was diagnosed in a 2-year-old female Bull Terrier by use of two-dimensional (2-D) and M-mode echocardiography, colour-flow imaging and spectral Doppler examinations. Tissue Doppler Imaging was also performed to assess the segmental radial myocardial motion. The mitral valve stenosis was characterized by a decreased mitral orifice area/left ventricle area ratio (0.14), an increased early diastolic flow velocity (E wave = 1.9 m/s), a prolonged pressure half-time (106 ms) and a decreased E-F slope (4.5 cm/s) on pulsed-wave Doppler examination. This mitral stenosis was associated with an immobile posterior leaflet, as seen on 2-D and M-mode echocardiography. Immobility of the posterior mitral leaflet is considered to be a rare finding in humans and, to our knowledge, has not been precisely documented in dogs with mitral valve stenosis.

Pulmonic stenosis in two cats

The clinical, radiographic and echocardiographic features of two cases of pulmonic stenosis in cats are presented. A rarely reported combination of pulmonic stenosis and tricuspid valve dysplasia is described.

Long-term follow-up of dogs with patent ductus arteriosus

Postocclusion survival data from dogs with left-to-right shunting patent ductus arteriosus (PDA) was available from 80 dogs, diagnosed from 1990 to 2000. Of these, 37 had undergone a procedure to close the ductus and were re-evaluated at the time of this study; clinical data from the follow-up examination was compared with that from the original examination. Radiographically, the right ventricle remained apparently enlarged, and the aortic bulge associated with dilation of the descending aorta did not disappear after closure. On M-mode echocardiography, left ventricular chamber diameter in diastole and systole and left ventricular posterior wall in systole decreased significantly. Mitral endocardiosis was a common feature. Residual flow was evident in 46 per cent of the animals. Late closure occurred in 8 per cent of the dogs, and trivial recanalisation in 19 per cent. The maximum survival time postclosure was 168 months and, after non-occlusion, 114 months, suggesting that dogs with PDA follow an unpredictable course. However, there was a significant difference in survival times between the corrected and non-corrected group.

Canine tricuspid valve malformation, a model of human Ebstein anomaly, maps to dog chromosome 9

BACKGROUND

Ebstein anomaly of the tricuspid valve is a congenital cardiac malformation characterised by downward displacement of the attachment of the septal and posterior leaflets of the tricuspid valve. Canine tricuspid valve malformation (CTVM) is morphologically similar to Ebstein anomaly; familial occurrence of CTVM has been described. Several observations suggest a genetic cause but most cases appear to be sporadic.

METHODS

Three purebred Labrador Retriever kindreds enriched for CTVM underwent clinical examination and echocardiography. DNA was extracted from whole blood. Genotyping was carried out using polymorphic repeat markers with an average spacing of 15 cM and polymorphic information content of 0.74.

RESULTS

Pedigree analysis identified CTVM segregating as an autosomal dominant trait with reduced penetrance. Genome wide linkage analysis in one kindred identified a CTVM susceptibility locus on dog chromosome 9 (CFA9) with a maximum multipoint lod score of 3.33. The two additional kindreds showed a conserved disease haplotype.

CONCLUSIONS

This study identifies a CTVM susceptibility locus on CFA9 and a founder effect in apparently unrelated Labrador Retriever kindreds. These results provide the basis for a positional candidate cloning effort to identify the CTVM disease gene. Identification of the CTVM gene will permit mutation screening of patients with Ebstein anomaly, which should provide additional insights into the genetic programmes of valve development.

Comparison of the incidence of residual shunting between two surgical techniques used for ligation of patent ductus arteriosus in the dog

OBJECTIVE

To compare the incidence of residual patent ductus arteriosus (PDA) flow after ligation using 2 different dissection techniques: a standard dissection and a method described by Jackson and Henderson.

STUDY DESIGN

A randomized, prospective study.

ANIMALS

Thirty-five dogs admitted for surgical correction of a left to right shunting PDA.

METHODS

Dogs were randomly assigned: 19 to a standard dissection technique (group S) and 16 to the Jackson and Henderson dissection group (group JH).

RESULTS

Gender ratio, age at surgery, and diameter of the ductus were not statistically different between groups. Breed distribution was also similar. Because 1 dog had fatal intraoperative hemorrhage, only 34 dogs were available for residual flow comparisons. Twenty-one percent of group S dogs had residual flow compared with 53% in group JH. Whereas no intraoperative complications occurred in group S, 3 were encountered in group JH.

CONCLUSIONS

The incidence of residual flow was higher when the Jackson and Henderson dissection was used for PDA ligation compared with a standard method of dissection. This was probably because of entrapment of loose connective tissue within the medial aspect of the ligature, impeding complete closure of the ductus.

CLINICAL RELEVANCE

Ideal PDA closure should result in no residual ductal flow to prevent possible adverse long-term sequelae, such as recanalization and infective endocarditis.

Review of left-to-right shunting patent ductus arteriosus and short term outcome in 98 dogs

The case records of 98 dogs with a left-to-right shunting patent ductus arteriosus (PDA) were reviewed. There were 35 breeds represented, with a female to male ratio of 3:1. Forty per cent of the dogs were older than one year at initial presentation and 31 per cent had clinical signs attributable to PDA. A left heart base continuous murmur of grade IV/VI or higher was noted in 90 per cent of the dogs. On electrocardiography, the most common abnormalities were tall R waves (63 per cent) and deep QII waves (62 per cent). The radiographic triad of dilation of the descending aorta with enlargement of the main pulmonary artery segment and left atrium, typical of PDA, was noted in only 26 per cent of cases. Two-dimensional (2D) and M-mode echocardiography detected left atrial enlargement (35 per cent) and an increased left ventricular diameter in diastole (82 per cent) and systole (84 per cent) as the most common abnormalities. Doppler echocardiography demonstrated increased aortic outflow velocities in 66 per cent of cases. The overall short-term successful outcome in this study was 95 per cent. There was no significant difference between surgical ductal ligation using a standard technique or the Jackson-Henderson technique in terms of survival, occurrence of haemorrhage or residual shunting. The number of interventional procedures used in this study was too low for statistical comparison, but there appeared to be a trend towards a higher rate of residual shunting and a lower fatality rate using a coil occlusion technique.

Atrial septal defect in five dogs

The clinical, electrocardiographic, radiographic, and two-dimensional, M-mode and Doppler echocardiographic findings of five cases of canine ostium secundum type atrial septal defect (ASD) are described. The atrial septal anomaly was associated with other congenital cardiac abnormalities in two dogs: ventricular septal defect in one case and tricuspid dysplasia in the other. ASD was found in addition to dilated cardiomyopathy and suspected atrial thrombosis in one geriatric dog, but was the only cardiac abnormality detected in the remaining two dogs. Colour Doppler imaging facilitated the diagnosis of ASD in all subjects. The long-term prognosis for dogs with isolated and small-sized ASD is usually good, but can be compromised by the presence of concurrent congenital or acquired cardiac diseases.

Postoperative rupture of an aortic aneurysmal dilation associated with a patent ductus arteriosus in a dog

OBJECTIVE

To describe an unusual case of fatal aortic aneurysm rupture after standard ligation of a left-to-right shunting patent ductus arteriosus (PDA) and review the literature concerning the causes of aneurysm and applicable medical physics of blood flow that may contribute to mural failure.

STUDY DESIGN

Clinical case report.

SAMPLE POPULATION

An 11-month-old female Brittany spaniel.

RESULTS

A PDA was diagnosed in the dog after referral for a grade IV/IV cardiac murmur. Diagnostic tests performed included a minimum database, thoracic radiography, and echocardiography. Conventional surgical ligation of the PDA was performed. The postoperative recovery from anesthesia was uneventful. Approximately 5 hours after surgery, the dog vocalized once and collapsed. All resuscitative efforts failed. Necropsy showed a large, spiral rupture of the cranial and dorsal wall of the aorta that extended from the left subclavian artery to 2 cm distal to the PDA-aorta junction. No evidence of intramural, perianeurysmal hemorrhage or inflammation was noted. Histopathologic examination of the ruptured aneurysm showed that the wall lacked a defined tunica intima and endothelial cell layer. A distinct separation of the thinned tunica media parallel to the elastic fibers was noted.

CONCLUSIONS AND CLINICAL RELEVANCE

Dilatation of the aorta near the area of a PDA is one of the recognized abnormalities associated with the condition. Aneurysmal dilatation results from and contributes to abnormal blood flow dynamics and increased aortic wall tension, which promotes expansion. Although an unusual and previously unreported sequela, rupture of the aneurysm should be considered a possible complication when ligation of a PDA with a conspicuous aortic aneurysmal dilation is performed.

Heritability estimations for diseases, coat color, body weight, and height in a birth cohort of Boxers

OBJECTIVE

To obtain heritability estimates for diseases and characteristics in Boxers.

ANIMALS

Birth cohort of 2,929 purebred Boxers from 414 litters.

PROCEDURE

Heritability estimates were determined for cheiloschisis-palatoschisis, cryptorchidism, epilepsy, stifle disorders, cardiac disorders, coat color, birth weight, and adult weight, and height. Binary traits were analyzed by use of a mixed-effects probit model. Some traits also were analyzed by use of a model that postulated monogenic inheritance. Full pedigree analyses were performed. Variation in incidences of disease among clusters of related dogs was evaluated.

RESULTS

Heritability estimates were virtually zero for cardiac disorders, medium (0.17 to 0.36) for most other traits, and high (> 0.55) for coat color, birth weight, and adult height. Litter effects and risk factors affected cheiloschisis-palatoschisis, heart murmur, coat color, broadly defined epilepsy, and adult weight. Litter effects may be attributable to common environmental effects for littermates but also may be attributable to dominance variation caused by a recessive gene. Heritability estimates increased when stricter definitions for epilepsy and stifle disorders were used. The monogenic model did not reveal higher heritability estimates for 6 traits analyzed. Incidences for white coat differed significantly for 10 familial clusters, confirming high heritability and effects of familial lineage.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicate that genetic improvement of most traits should be feasible, except for cardiac disorders. However, because most traits are influenced by environmental effects as well as genetic effects, genetic counseling based on polygenic inheritance and use of familial information rather than strict exclusion of parents is preferred.

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.

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).