Early echocardiographic predictors of myxomatous mitral valve disease in dachshunds

Myxomatous mitral valve disease in dogs is heritable, and it is therefore important to detect the early signs of the disease. This study was conducted to assess the predictive value of early echocardiographic and auscultatory signs of mitral valve prolapse, measured in terms of the leaflet thickness, the area of the regurgitant jet, and the intensity of the murmur, on the increases in left ventricular end diastolic diameter (LVEDD) and left atrial diameter (LAD) in a population of 190 clinically healthy dachshunds followed up for three years. The most significant predictor of an increase in LVEDD was the interaction between the index of mitral valve prolapse and the area of the regurgitant jet (P < 0.0001). In dogs with a jet area greater than 50 per cent of the left atrium, the disease progressed more quickly in terms of increases in LVEDD in relation to the severity of the prolapse at the initial examination. In dogs with smaller jets, the initial prolapse index was not significantly associated with increases in LVEDD. The initial index of mitral valve prolapse, the area of the jet and the intensity of the heart murmur were all significant predictors of an increase in LAD.     

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.     

OBSERVER VARIATION IN THE TWO-DIMENSIONAL ECHOCARDIOGRAPHIC EVALUATION OF MITRAL VALVE PROLAPSE IN DOGS

In this study, the observer variation and the influence of observer experience in diagnosing mitral valve prolapse in dogs was assessed by having three observers with different degrees of echocardiographic experience (10 years, 4 years, and no prior experience) analyze 303 mitral valve video recordings from 253 dogs, both with and without mitral regurgitation. To assess intraobserver variation, 16 recordings were analyzed twice, and 34 dogs were scanned twice at intervals of a few days. By consensus, 90 dogs had no mitral valve prolapse, 130 had mild and 33 had severe mitral valve prolapse. Intraobserver repeatabilities ranged from 88% to 100% and interobserver repeatabilities from 70% to 78%. In 79% to 94% of the dogs that were scanned twice, the observers diagnosed both recordings identically. All repeatabilities were reduced by approximately 10% when mitral valve prolapse was graded into mild and severe. The three observers differed significantly in diagnosing mitral valve prolapse when compared with each other in pairs (all p-values < 0.01). The unexperienced observer had the highest and most unsystematic occurrence of false diagnoses. It is possible that the interobserver repeatabilities would have been lower had each sonographer obtained his own echocardiograms. We conclude, that mitral valve prolapse in dogs can be diagnosed using two-dimensional echocardiography with the same degree of observer variation as reported in human studies, and that education and training of staff is mandatory to ensure proper ultrasonographic evaluation.     

Comparison of primary mitral valve disease in German Shepherd dogs and in small breeds

The case records of 58 German Shepherds (GS group) affected by mitral valve prolapse (MVP) and/or mitral valve regurgitation (MR), and 49 dogs weighing < 15 kg (D group), affected by chronic valvular disease (CVD) were reviewed. The dogs of the GS group were presented more often without a detectable heart murmur (p < 0.01), and less frequently with a high intensity heart murmur (p < 0.01). Atrial fibrillation (AF) was more common in the GS group (p < 0.001). MVP associated with mitral valve thickening was more common in the D group (p < 0.001). Fractional shortening (FS) was lower (p < 0.0001) and end-systolic volume index (ESV-I) was increased (p < 0.0001) in the GS group, whereas end-diastolic volume index (EDV-I) did not differ between the 2 groups. Prevalence and severity of pulmonary hypertension were similar in the 2 groups. Dogs with mitral valve disease weighing more than 20 kg had a 5.8 higher chance of developing decreased FS, increased ESV-I, AF and ventricular arrhythmias. In the GS group, the decreased FS and increased ESV-I were not associated with the presence of AF or ventricular arrhythmias (p > 0.05). It appears that GS may be affected both by mitral valve prolapse and mitral insufficiency. It also appears that a comparatively large proportion of GS shows no major mitral valve thickening or MVP, but still presents with significant mitral regurgitation, possibly suggesting a different cause for the important incompetence observed in most cases.     

Evaluation of collagenase-induced mitral valve regurgitation in dogs

OBJECTIVE: To investigate the hemodynamic changes induced by injecting collagenase into the mitral valve to induce mitral valve regurgitation (MVR) in dogs. ANIMALS: 9 healthy Beagles. PROCEDURE: Dogs were randomly assigned to 3 groups: control (saline [0.9% NaCl] solution; n = 3), single collagenase injection (C1; 3), and 2 collagenase injections (C2; 3). Open-heart surgery was performed, and saline or collagenase solutions were injected into the mitral valve. Before and weekly for 11 weeks after surgery, radiography, echocardiography, and phonocardiography were performed. Mean pulmonary arterial pressure and mean pulmonary arterial wedge pressure (mPAWP) were measured before and 11 weeks after surgery. Postmortem examinations were performed after dogs were euthanatized. RESULTS: No changes were detected in the control group during the 11-week follow-up period. A systolic murmur and MVR developed 1 week after surgery in groups C1 and C2. The murmur changed from a protosystolic to a pansystolic murmur, and left atrial diameter and the left atrial-to-aortic root diameter ratio increased with time. Mean pulmonary arterial pressure and mPAWP were greater 11 weeks after surgery in groups C1 and C2, compared with presurgery values. During necropsy, tissue loss was detected in the mitral valve at the site of collagenase injection. Degree of regurgitation corresponded to lesion size. CONCLUSIONS AND CLINICAL RELEVANCE: Injection of collagenase into the mitral valve of healthy dogs induced MVR, and dogs with MVR developed progressive hemodynamic changes without acute overload. Collagenase-induced MVR may be an appropriate model for evaluation of prognostic markers of idiopathic MVR in dogs.     

ECHOCARDIOGRAPHIC ASSESSMENT OF 537 DOGS WITH MITRAL VALVE PROLAPSE AND LEAFLET INVOLVEMENT

In this work we investigated which mitral valve leaflet was most often involved in mitral valve prolapse with degenerative mitral valve disease and whether there was an association with breed, age, gender, or weight. Five hundred and thirty-seven dogs with mitral valve prolapse-degenerative mitral valve disease were assessed; the cross-breed dog was the most represented breed (248 dogs, 46.2%). Mitral valve prolapse was more common in male dogs, and the average age was 11.3±2.8 years. Prolapse of the anterior leaflet was present in 48.4% of dogs, prolapse of the the posterior leaflet in 7.1%, and bileaflet prolapse was present in 44.5%; this distribution is different than that typically found in humans. There was a significant correlation between severity of mitral regurgitation and severity of mitral valve prolapse or ISACHC class, and between severity of mitral valve prolapse and ISACHC class. There was no relationship between the particular affected leaflet(s) and severity of mitral regurgitation, severity of mitral valve prolapse, or ISACHC class. Our findings suggest that the susceptibility to the mitral valve prolapse-degenerative mitral valve disease is not confined to a specific breeds and that the specific leaflet prolapsing is different in dogs compared with humans.     

Quantification of mitral valve regurgitation in dogs with degenerative mitral valve disease by use of the proximal isovelocity surface area method

OBJECTIVE: To determine the within-day and between-day variability of regurgitant fraction (RF) assessed by use of the proximal isovelocity surface area (PISA) method in awake dogs with degenerative mitral valve disease (MVD), measure RF in dogs with MVD, and assess the correlation between RF and several clinical and Doppler echocardiographic variables. DESIGN: Prospective study. ANIMALS: 6 MVD-affected dogs with no clinical signs and 67 dogs with MVD of differing severity (International Small Animal Cardiac Health Council [ISACHC] classification). PROCEDURES: The 6 dogs were used to determine the repeatability and reproducibility of the PISA method, and RF was then assessed in 67 dogs of various ISACHC classes. Mitral valve regurgitation was also assessed from the maximum area of regurgitant jet signal-to-left atrium area (ARJ/LAA) ratio determined via color Doppler echocardiographic mapping. RESULTS: Within- and between-day coefficients of variation of RF were 8% and 11%, respectively. Regurgitation fraction was significantly correlated with ISACHC classification and heart murmur grade and was higher in ISACHC class III dogs (mean +/- SD, 72.8 +/- 9.5%) than class II (57.9 +/- 20.1%) or I (40.7 +/- 19.2%) dogs. Regurgitation fraction and left atriumto-aorta ratio, fractional shortening, systolic pulmonary arterial pressure, and ARJ/LAA ratio were significantly correlated. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that RF is a repeatable and reproducible variable for noninvasive quantitative evaluation of mitral valve regurgitation in awake dogs. Regurgitation fraction also correlated well with disease severity. It appears that this Doppler echocardiographic index may be useful in longitudinal studies of MVD in dogs.     

Genome-wide analysis of mitral valve disease in Cavalier King Charles Spaniels

The Cavalier King Charles Spaniel (CKCS) is prone to severe early onset mitral valve disease. In this study, 36 purebred CKCS dogs were evaluated for mitral valve murmur and divided into early and late onset groups. A genome-wide genetic approach was used to assess whether the condition is determined by a small number of genetic factors. There were no regions of highly discrepant homo/heterozygosity in the two groups. Similarly, there was no evidence for loci associated with mitral valve murmur in a genome-wide association study. This analysis suggests that familial occurrence of mitral valve murmur in the CKCS breed is not due to a single major gene effect, indicating that breeding strategies to eliminate the disease cannot be based on genotype information at this time.     

Epidemiology and Inheritance of Mitral Valve Prolapse in Dachshunds

One hundred ninety consecutive Dachshunds >2 years of age, including 18 families consisting of both parents and 4 or more offspring, were examined clinically and echocardiographically to study the epidemiology and inheritance of mitral valve prolapse (MVP) and other signs of myxomatous mitral valve disease in the dog. From video-recorded echocardiograms, MVP severity, jet size (color Doppler), and leaflet thickness were assessed. With regard to murmur intensity and each of these 3 echocardiographic measurements. the inheritance and the influence of age, gender, coat type, body weight, degree of obesity, heart rate, and thorax dimensions were evaluated. MVP severity correlated positively with age (P < .0001) and heart rate (P = .002), negatively with thorax circumference (P = .0005), and was related to coat type (P = .006). MVP severity progressed faster in males than in females (P = .0002). The other measures of disease severity (jet size, leaflet thickness, and murmur intensity) also correlated positively with age (all P < .0001). When compared in pairs, all 4 measures of disease severity correlated significantly with one other. Pedigree analyses did not disclose agreement with simple Mendelian models, but high disease prevalence made interpretation difficult. Mean parental MVP severity correlated significantly with MVP severity in the offspring (P = .03). The epidemiology of MVP in Dachshunds resembles that of MVP in humans, MVP severity correlates significantly with other measures of the degree of myxomatous mitral valve disease, and MVP is an inherited condition in Dachshunds. A polygenic mode of inheritance is suggested.     

Neuroendocrine changes in Dachshunds with mitral valve prolapse examined under different study conditions

Neuroendocrine changes associated with canine mitral valve prolapse (MVP) were studied in 159 Dachshunds older than two years. In study 1, 102 dogs were sampled without controlling diet or fasting period. In good accordance with human findings, the MVP severity correlated positively with plasma renin activity and tended to correlate negatively with plasma aldosterone. These findings were not attributable to any coexistent mitral regurgitation (MR). In study 2, in which diet and fasting period were controlled, 57 Dachshunds younger than seven years were sampled twice through an i.v. cannula: once after approximately 15 minutes in lateral recumbency and again after 10 minutes of walking. In both study 2 settings, neither MVP nor MR correlated significantly with plasma levels of renin, aldosterone, angiotensin-converting enzyme, norepinephrine, epinephrine, or cortisol. We conclude that the increased renin release found in early canine mitral disease is not reproducible under all study conditions, and that it correlates with the severity of MVP and not of MR.     

Long‐term outcome in dogs undergoing mitral valve repair with suture annuloplasty and chordae tendinae replacement

Mitral valve repair under cardiopulmonary bypass was performed in three dogs with clinical signs associated with mitral regurgitation that were not controlled by medication. Mitral valve repair comprised circumferential annuloplasty and chordal replacement with expanded polytetrafluoroethylene. One dog died 2 years after surgery because of severe mitral regurgitation resulting from partial circumferential suture detachment. The others survived for over 5 years, but mild mitral valve stenosis persisted in one. The replaced chordae did not rupture in any dog. Mitral valve repair appears to be an effective treatment for mitral regurgitation in dogs. Chordal replacement with expanded polytetrafluoroethylene is a feasible technique, demonstrating long‐term durability in dogs. However, mitral annuloplasty techniques need improvement.     

Increased NT-proANP predicts risk of congestive heart failure in Cavalier King Charles spaniels with mitral regurgitation caused by myxomatous valve disease

ObjectivesTo evaluate the predictive value of plasma N-terminal pro-atrial natriuretic peptide (NT-proANP) and nitric oxide end-products (NOx) as markers for progression of mitral regurgitation caused by myxomatous mitral valve disease.AnimalsSeventy-eight privately owned Cavalier King Charles spaniels with naturally occurring myxomatous mitral valve disease.MethodsProspective longitudinal study comprising 312 measurements over a 4.5 year period. Clinical values were recorded, NT-proANP concentrations were measured by radioimmunoassay, and NOx were analyzed colorimetrically. To predict congestive heart failure (CHF), Cox proportional hazards models with time-varying covariates were constructed.ResultsThe hazard ratio for NT-proANP (per 1000 pmol/l increase) to predict future CHF was 6.7 (95% confidence interval, 3.6–12.5; p < 0.001). The median time to CHF for dogs with NT-proANP levels >1000 pmol/l was 11 months (95% confidence interval, 5.6–12.6 months), compared to 54 months (46 – infinity) for dogs with concentrations ≤1000 pmol/l (p < 0.001). Due to intra- and inter-individual variability, most corresponding analyses for NOx were insignificant but dogs reaching CHF had a lower mean NOx concentration than dogs not reaching CHF (23 vs. 28 μmol/l, p = 0.016). Risk of CHF increased with increase in heart rate (>130 beats per minute) and grade of murmur (≥3/6).ConclusionsThe risk of CHF due to mitral regurgitation is increased in dogs with blood NT-proANP concentrations above 1000 pmol/l. Measurement of NT-proANP can be a valuable tool to identify dogs that may develop CHF within months.     

Prevalence of fragmented medial coronoid process of the ulna in lame adult dogs

Over a period of three years, a diagnosis of fragmented medial coronoid process of the ulna was confirmed by arthroscopy in 263 dogs, in 69 of which both elbow joints were affected, giving a total of 332 affected joints; 39 of the joints were also affected by osteochondrosis dissecans of the trochlea of the humerus. More than half of the dogs (51.7 per cent) were over one year old when first examined. In 259 (78 per cent) of the joints there were radiographic changes of secondary osteoarthrosis of different severity, but the other 73 (22 per cent) had no signs of osteophytosis except for a mild sclerosis. Among these 73 there were 14 joints in 13 dogs between 19 and 36 months old and 11 joints in 10 dogs over three years old. A further 12 joints in 11 dogs over three years old showed only mild arthrosis. In five of the 11 joints of the dogs over three years old which had no radiological signs of arthrosis, the fragment was already dislocated. Among the dogs over 18 months old with no arthrosis and the dogs over three years old with mild arthrosis, the most commonly affected breeds were the Bernese mountain dog, rottweiler and boxer.     

Efficacy and safet of pimobendan in canine heart failure caused by myxomatous mitral valve disease

OBJECTIVES: To evaluate the clinical efficacy and safety of pimobendan by comparing it with ramipril over a six-month period in dogs with mild to moderate heart failure (HF) caused by myxomatous mitral valve disease (MMVD). METHODS: This was a prospective randomised, single-blind, parallel-group trial. Client-owned dogs (n = 43) with mild to moderate HF caused by MMVD were randomly assigned to one of two groups, which received either pimobendan (P dogs) or ramipril (R dogs) for six months. The outcome measures studied were: adverse HF outcome, defined as failure to complete the trial as a direct consequence of HF; maximum furosemide dose (mg/kg/day) administered during the study period; and any requirement for additional visits to the clinic as a direct consequence of HF. RESULTS: Treatment with pimobendan was well tolerated compared with treatment with ramipril. P dogs were 25 per cent as likely as R dogs to have an adverse HF outcome (odds ratio 4.09, 95 per cent confidence interval 1.03 to 16.3, P = 0.046). CLINICAL SIGNIFICANCE: R dogs had a higher overall score and thus may have had more advanced disease than P dogs at baseline (P = 0.04). These results should be interpreted cautiously but such a high odds ratio warrants further investigation.     

Hemilaminectomy for the treatment of thoracolumbar disc disease in the dog: a follow-uo studv of 40 cases

A study was made of dogs with Hansen type I thoracolumbar disc extrusions that had been treated by hemilaminectomy and fenestration of the affected disc. Follow-up information was available for 40 dogs undergoing treatment over a five-year period. The follow-up period ranged from 12 to 72 months (mean 34 months). The case details and the results of treatment of these 40 dogs are presented. All dogs were graded according to the degree of neurological dysfunction at the time of initial presentation and at the conclusion of the study period. Twenty-seven dogs (68 per cent) had no detectable signs of neurological dysfunction or thoracolumbar pain at the final assessment and a further eight dogs (20 per cent) had mild ambulatory paraparesis but were regarded by their owners as functional pets. Recurrence of neurological signs consistent with thoracolumbar disc disease was seen in five dogs (13 per cent) and was successfully resolved completely in one of three dogs that were treated.     

Retrospective study of 155 cases of prolapse of the nictitating membrane gland in dogs

A retrospective study of 155 cases (114 dogs). The breed, sex and age at the time of the first and opposite onset of nictitans gland prolapse were recorded. Long-term follow-up with a minimum of one-year duration was performed by telephone conversations. One hundred and fourteen dogs representing 155 nictitans gland prolapses were included. 75.4 per cent of the first prolapse occur before one year of age. Unilateral nictitans gland prolapse was observed in 64 per cent of cases. When the condition was bilateral, it occurred simultaneously in 41.4 per cent. When it was bilateral but not simultaneous (24/41), the opposite gland prolapse occurred within three months in 70.8 per cent of the cases. Five breeds were most commonly affected by the bilateral condition: French bulldog, shar pei, great dane, English bulldog and cane corso.     

Lumbosacral osteochondrosis: radiological features and surgical management in 34 dogs

Lumbosacral osteochondrosis has been diagnosed with increasing frequency over the past few years. Nevertheless, poor recognition of the condition continues to lead to frequent misdiagnosis. A study was therefore undertaken over a 12-year period (1986 to 1998) to describe the use of a variety of radiological studies to define the syndrome and the use of different surgical techniques for optimal treatment of the condition. Dogs with clinical signs of cauda equina neuropathy and radiological signs of lumbosacral osteochondrosis were older than 14 months (mean age 6.3 years). German shepherd dogs, boxers and rottweilers were heavily represented. Of the 34 dogs with osteochondrosis in this study, the lesion appeared to be related to the sacrum in 31 dogs (91 per cent) and the seventh lumbar vertebra in the remaining three dogs (9 per cent). Twenty-seven male and seven female dogs were affected (4:1). Out of the 34 dogs, six (18 per cent) were treated conservatively and the remaining 28 (82 per cent) were treated surgically. The outcome of surgical treatment was considered to be satisfactory in 24 (86 per cent) of these latter dogs.     

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.     

Relationships between the histological grade of cutaneous mast cell tumours in dogs, their survival and the efficacy of surgical resection

The histological grade of 340 cutaneous mast cell tumours derived from 280 dogs was determined by an established histological grading system; 87 of the tumours (26 per cent) were well differentiated, 199 (59 per cent) were intermediately differentiated and 54 (16 per cent) were poorly differentiated. The one-year survival rates for the dogs with tumours of these three grades were significantly different (P = 0.0001), being 100 per cent, 92 per cent and 46 per cent, respectively. The median survival time for the dogs with poorly differentiated tumours was 278 days, significantly shorter than that for the dogs with either intermediately or well-differentiated tumours, which were both over 1300 days. Regrowth of the tumours was identified in 10 (19 per cent) of the dogs with poorly differentiated tumours, 12 (6 per cent) of the dogs with intermediately differentiated tumours and one of the dogs with well-differentiated tumours; only three of the tumours which regrew had initially had complete margins. The results suggest that wide surgical margins are not a prerequisite for a successful long-term outcome in dogs with well-differentiated cutaneous mast cell tumours.     

Identification of surface morphologic changes in the mitral valve leaflets and chordae tendineae of dogs with myxomatous degeneration

OBJECTIVE: To describe structural changes in the left atrioventricular (mitral) valve complex of dogs with endocardiosis by use of scanning electron microscopy. ANIMALS: 5 clinically normal dogs and 4 dogs with mitral valve endocardiosis. PROCEDURE: The mitral valve complex from each dog was fixed and prepared for examination via scanning electron microscopy. Findings in valves from clinically normal and affected dogs were compared to identify surface changes associated with endocardiosis. RESULTS: Compared with findings in valves from clinically normal dogs, endocardiosis-affected mitral valve complexes had several morphologic abnormalities. Tissue swelling on the edge of valve leaflets, chordae tendineae, and the chordal-papillary muscle junction was evident. Damage to the valve complex endothelium was unevenly distributed; in some areas, denudation of endothelial cells had exposed the basement membrane or subendothelial valve collagen matrix. This damage was most noticeable on the leaflet edges and extended more to the ventricular aspect of the valve than the atrial side. Cell loss also extended to the chordae tendineae but was less apparent at the chordal-papillary muscle junction. The remaining endothelial cells on affected valves were arranged in less-ordered rows and had more plasmalemmal microappendages, compared with cells on unaffected valves. CONCLUSIONS AND CLINICAL RELEVANCE: Morphologic changes associated with mitral valve endocardiosis in dogs were similar to those observed in humans with mitral valve prolapse. In dogs with mitral valve endocardiosis, gross changes in the valve complex may affect hemodynamics in the heart; alterations in the leaflet and chordal endothelium may contribute to pathogenesis of this disease.