Three-dimensional echocardiography: technical aspects and imaging modalities.

Real-time three-dimensional echocardiography (RT3DE) is increasingly available in the veterinary field due to continuous reduction in costs and improvement of equipment. Much like its motion-mode and bi-dimensional counterparts, acquisition and analysis of RT3DE images and datasets is greatly improved by a thorough understanding of the technological aspects, basic physic principles, and knowledge of available modalities with their advantages and drawbacks. In this review, the authors aim to describe how the currently available RT3DE technology has evolved, explain technical aspects of the equipment, and illustrate the most commonly available modalities for image acquisition and visualization.

Current use of real-time three-dimensional transthoracic echocardiography in animals.

This review includes 36 studies of transthoracic real-time three-dimensional echocardiography (RT3DE) in animals. Most of these studies concern cardiac chamber quantification of the left atrium and left ventricle, in dogs. Comparisons of RT3DE and different two-dimensional echocardiographic (2DE) methods have been reported in dogs with myxomatous mitral valve disease (MMVD), dilated cardiomyopathy, and in healthy control dogs. Comparisons of RT3DE and standard reference methods have been reported in healthy control dogs. In dogs with MMVD, volumetric RT3DE measurements of left atrium do not appear to provide superior prognostic value compared with 2DE methods using Simpson's method of discs in dogs with MMVD. The major advantages of RT3DE compared to 2DE include improvements in visualization of the complex morphology of the mitral valve, the estimation of mitral valve regurgitation, and improved visualization of complex congenital cardiac abnormalities.

Prevalence of mitral valve regurgitation in 102 asymptomatic Chinese Crested dogs.

INTRODUCTION: Mitral regurgitation (MR) is one of the main features of myxomatous mitral valve disease (MMVD), which is the most common heart disease in dogs. Myxomatous mitral valve disease affects many small breed dogs, and some breeds such as Cavalier King Charles Spaniels, Dachshunds, Yorkshire terriers, and Miniature Schnauzers have been studied more in detail. Breed-specific information regarding MMVD is valuable for providing appropriate advice on management and breeding. Data, based on insurance statistics in Sweden, show that Chinese Crested dogs (CCD) are twice as likely to visit the veterinarian for a heart-related problem than other breeds. ANIMALS: One-hundred two privately owned, healthy CCD were recruited via the Swedish CCD club. MATERIALS AND METHODS: This was a prospective observational study, in which clinical examinations, blood pressure measurements, and echocardiographic and Doppler examinations were performed in all dogs. Pulsed wave tissue Doppler imaging was performed in 87 dogs. RESULTS: Mitral regurgitation was present in 39 (38%) dogs, whereas a systolic murmur was present in 35 (34%) dogs. Mitral valve prolapse was present in 32 (31%) dogs. Tricuspid regurgitation was found in 29 (28%) dogs. Dogs in the MR group were older (median 9.5 years), and males were overrepresented compared with the non-MR group. Differences were also found between groups regarding left atrial size and transmitral E wave velocity. CONCLUSIONS: The prevalence of MR in CCD is similar to reports in other small breeds. Whether the MR detected in these dogs is a sign of MMVD is unknown.

Impact of blood tube additives and timing of sampling on blood taurine concentrations in clinically healthy dogs.

INTRODUCTION: Dilated cardiomyopathy can be associated with taurine deficiency in dogs. Blood taurine concentrations can be analyzed in whole blood (WB) and plasma. The study objectives were to investigate agreement between taurine concentrations measured in WB, heparin plasma, and EDTA plasma, determine intraindividual variation in healthy dogs, and evaluate if time from feeding to sampling impacts concentrations. ANIMALS: Ten English Cocker spaniels and 10 dogs of various breeds. MATERIALS AND METHODS: Dogs were fasted 12 h prior to initial blood sampling, and the blood was collected at five occasions over eight h. Food was offered immediately after first and one h after fourth sampling time point. RESULTS: Agreement between taurine concentrations in EDTA plasma and heparinized plasma was good (mean difference 4.5 nmol/mL, 95% confidence interval (CI) 36.8-45.8 nmol/mL). Whole blood concentrations were systematically higher than EDTA and heparin plasma concentrations (mean difference 132.7 nmol/mL, 95% CI 23.6-241.8 nmol/mL, and 127.6 nmol/mL, 95% CI 28.6-226.6 nmol/mL, respectively, all P < 0.001). Intraindividual daily variations in taurine concentration were seen in all additives, with largest variations in plasma (P < 0.001). Taurine concentration in heparinized plasma was higher at first and fifth sampling time points compared to the fourth (P = 0.014). DISCUSSION: Agreement was found between taurine concentrations measured in different additives, with expected higher concentration in WB than plasma. Taurine concentrations measured in heparinized plasma varied with sampling time point. Intraindividual daily variations were observed in all additives, but mainly in plasma samples. CONCLUSION: Taurine concentrations in dogs with suspected deficiency should be interpreted with caution.

Prognostic value of selected one-, two- and three-dimensional and Doppler echocardiographic methods to assess severity in dogs with myxomatous mitral valve disease.

INTRODUCTION: Although challenging, predicting outcomes in dogs with myxomatous mitral valve disease (MMVD) is of importance to owners and veterinarians. Our aim was to compare the prognostic value of selected one-, two-, and three-dimensional and Doppler echocardiographic methods to predict cardiac-related and all-cause mortality in MMVD dogs. We hypothesize that three-dimensional methods would better predict prognosis than one- and two-dimensional methods. ANIMALS: One-hundred thirty-eight privately-owned dogs with MMVD. MATERIALS AND METHODS: Cox proportional Hazard analyses and Kaplan-Meier curves were used to investigate the predictive value of 14 variables; left atrial (LA) volume indexed to body weight (BW) measured by real-time three-dimensional echocardiography (RT3DE) and calculated using Simpson's modified method of discs (SMOD) and the area-length method; LA diameter in short-axis and long-axis to aortic in short-axis ratio, effective regurgitant orifice area indexed to body surface area measured in RT3DE en face view and calculated using four-chamber (4Ch) and two-chamber views alone or in combination; percentage increase in left ventricular end-diastolic and systolic internal diameters; fractional shortening; E wave velocity; regurgitant jet area/LA area. RESULTS: All 14 variables were significantly predictive of cardiac-related mortality, and 11 were predictive of all-cause mortality. The prognosis was best predicted by LA volume/BW estimated by SMOD or RT3DE, consistently showing the highest predictive value in all analyses. CONCLUSIONS: Left atrial volume calculated by SMOD showed a similar predictive value compared to RT3DE. Performing SMOD from apical 4Ch images should be considered an alternative to RT3DE for echocardiographic examinations where prognostication of disease outcome is sought.

The effects of activity, body weight, sex and age on echocardiographic values in English setter dogs.

BACKGROUND: Breed-specific reference intervals improve echocardiographic interpretation and thereby reduce misdiagnoses, especially in athletic breeds. OBJECTIVES: The objectives of the study were to examine transthoracic echocardiographic values in healthy adult English setter dogs and determine the effects of activity, body weight, sex and age on these values. ANIMALS, MATERIALS AND METHODS: One hundred and one adult English setter dogs, recruited from local veterinary clinics and from the Norwegian English setter club, underwent routine transthoracic echocardiography. The population was stratified into two groups based on the reported level of activity. The effects of activity level, body weight, sex and age on echocardiographic variables were examined. Results were compared with published data from other breeds and from a pre-existing species-wide allometric model. RESULTS: Of the 100 dogs between 19 months and 10 years of age included in the study, 72 were reported as very active and 28 as less active. Echocardiographic intervals were calculated for body size-independent echocardiographic variables. The upper limits of the intervals for left-atrial-to-aortic ratios and normalised left ventricular volumes exceeded those of various, previously published studies of other breeds. Normalised left ventricular dimensions exceeded published allometric 95th percentile upper reference values in 13% of dogs in diastole and 32% of dogs in systole. More active dogs had larger cardiac dimensions than less active dogs; however, the activity level did not predict echocardiographic variables when included in a multiple regression model. CONCLUSIONS: The study provides breed specific transthoracic echocardiographic values for English setter dogs, thereby contributing to improve diagnostic assessment of cardiac health in this breed.

Comparisons of 3-, 2-dimensional, and M-mode echocardiographical methods for estimation of left chamber volumes in dogs with and without acquired heart disease.

BACKGROUND: Real-time 3-dimensional echocardiography (RT3D) is a recent technique based on volumetric scanning, eliminating the need for geometric modeling of the cardiac chambers and minimizing the errors caused by foreshortened views. HYPOTHESIS: Estimations of left ventricular (LV) end-diastolic (EDV) and end-systolic volume (ESV), and left atrial (LA) size, differ depending on the echocardiographic technique of estimation. ANIMALS: Fifty-one dogs with acquired heart disease and 34 healthy control dogs. METHODS: Prospective observational study by M-mode (Teichholz method), Simpson's modified 2-dimensional (2D) method, and RT3D methods for estimation of LV volumes. LA size was evaluated by 2D and RT3D methods. RESULTS: RT3D showed good agreement with 2D for EDV and ESV, whereas Teichholz method overestimated LV volumes in comparison with the other 2 methods by approximately a factor 2. There were no statistically significant differences among the 3 methods in estimating ejection fraction. Comparison between RT3D assessment of LA end-systolic volume per kilogram (LAs/kg) and LA to aortic ratio (LA/Ao) measured by 2D relative to each other showed that the RT3D method underestimated LAs/kg at lower values, and overestimated it at higher values. The difference between methods increased with increasing LA size. CONCLUSIONS AND CLINICAL IMPORTANCE: There was good agreement between RT3D and 2D methods of estimating EDV and ESV, whereas the Teichholz method overestimated LV volumes by approximately a factor 2. In comparison with RT3D, LA/Ao underestimated LA size, especially when LA was enlarged.

Cardiac troponin I is associated with severity of myxomatous mitral valve disease, age, and C-reactive protein in dogs.

BACKGROUND: Concentrations of cardiac troponin I (cTnI) and C-reactive protein (CRP) might be associated with cardiac remodeling in dogs with myxomatous mitral valve disease (MMVD). Age- and sex-dependent variations in cTnI concentration have been described. OBJECTIVE: To investigate whether plasma concentrations of cTnI and CRP are associated with severity of MMVD, and investigate potential associations of dog characteristics on cTnI and CRP concentrations. ANIMALS: Eighty-one client-owned dogs with MMVD of varying severity. METHODS: Dogs were prospectively recruited for the study. Dogs were classified according to severity of MMVD. Plasma cTnI was analyzed by a high sensitivity cTnI assay with a lower limit of detection of 0.001 ng/mL, and plasma CRP was analyzed by a canine-specific CRP ELISA. RESULTS: Higher cTnI concentrations were detected in dogs with moderate (0.014 [interquartile range 0.008-0.029] ng/mL, P = .0011) and severe (0.043 [0.031-0.087] ng/mL, P < .0001) MMVD, compared with healthy dogs (0.001 [0.001-0.004]ng/mL). Dogs with severe MMVD also had higher cTnI concentrations than dogs with mild (0.003 [0.001-0.024] ng/mL, P < .0001) and moderate (P = .0019) MMVD. There were significant associations of age, CRP, heart rate, and left ventricular end-diastolic diameter, on cTnI concentration C-reactive protein did not differ among severity groups, but was significantly associated with cTnI, breed, and systolic blood pressure on CRP concentration. CONCLUSIONS AND CLINICAL IMPORTANCE: Analysis of cTnI concentration has potential to increase knowledge of overall cardiac remodeling in dogs with MMVD. However, effect of age on cTnI needs consideration when assessing cTnI.

Tissue Doppler and strain imaging in dogs with myxomatous mitral valve disease in different stages of congestive heart failure.

BACKGROUND: Tissue Doppler imaging (TDI) including strain and strain rate (SR) assess systolic and diastolic myocardial function. HYPOTHESIS: TDI, strain, and SR variables of the left ventricle (LV) and the interventricular septum (IVS) differ significantly between dogs with myxomatous mitral valve disease (MMVD) with and without congestive heart failure (CHF). ANIMALS: Sixty-one dogs with MMVD with and without CHF. Ten healthy control dogs. METHODS: Prospective observational study. RESULTS: Radial motion: None of the systolic variables were altered and 3 of the diastolic velocities were significantly increased in dogs with CHF compared with dogs without CHF and control dogs. Longitudinal motion: 2 systolic velocities and 3 diastolic velocities were significantly increased in dogs with CHF compared with dogs without CHF and control dogs. Difference in systolic velocity time-to-peak between LV and IVS was significantly increased in dogs with MMVD with and without CHF compared with control dogs. In total, 11 (23%) of 48 TDI and strain variables differed significantly between groups. Left atrial to aortic ratio was positively correlated to early diastolic velocities, percentage increase in left ventricular internal diameter in systole was positively correlated to systolic and diastolic velocities, and mitral E wave to peak early diastolic velocity in the LV basal segment (E/Em) was positively correlated to radial strain and SR. CONCLUSIONS AND CLINICAL IMPORTANCE: Few TDI and strain variables were changed in dogs with MMVD with and without CHF. Intraventricular dyssynchrony may be an early sign of MMVD or may be an age-related finding.

Effect of pimobendan or benazepril hydrochloride on survival times in dogs with congestive heart failure caused by naturally occurring myxomatous mitral valve disease: the QUEST study.

BACKGROUND: Myxomatous mitral valve disease (MMVD) continues to be an important cause of morbidity and mortality in geriatric dogs despite conventional therapy. HYPOTHESIS: Pimobendan in addition to conventional therapy will extend time to sudden cardiac death, euthanasia for cardiac reasons, or treatment failure when compared with conventional therapy plus benazepril in dogs with congestive heart failure (CHF) attributable to MMVD. ANIMALS: Two hundred and sixty client-owned dogs in CHF caused by MMVD were recruited from 28 centers in Europe, Canada, and Australia. METHODS: A prospective single-blinded study with dogs randomized to PO receive pimobendan (0.4-0.6 mg/kg/d) or benazepril hydrochloride (0.25-1.0 mg/kg/d). The primary endpoint was a composite of cardiac death, euthanized for heart failure, or treatment failure. RESULTS: Eight dogs were excluded from analysis. One hundred and twenty-four dogs were randomized to pimobendan and 128 to benazepril. One hundred and ninety dogs reached the primary endpoint; the median time was 188 days (267 days for pimobendan, 140 days for benazepril hazard ratio = 0.688, 95% confidence limits [CL]=0.516-0.916, P= .0099). The benefit of pimobendan persisted after adjusting for all baseline variables. A longer time to reach the endpoint was also associated with being a Cavalier King Charles Spaniel, requiring a lower furosemide dose, and having a higher creatinine concentration. Increases in several indicators of cardiac enlargement (left atrial to aortic root ratio, vertebral heart scale, and percentage increase in left ventricular internal diameter in systole) were associated with a shorter time to endpoint, as was a worse tolerance for exercise. CONCLUSIONS AND CLINICAL IMPORTANCE: Pimobendan plus conventional therapy prolongs time to sudden death, euthanasia for cardiac reasons, or treatment failure in dogs with CHF caused by MMVD compared with benazepril plus conventional therapy.

Longitudinal Analysis of Quality of Life, Clinical, Radiographic, Echocardiographic, and Laboratory Variables in Dogs with Preclinical Myxomatous Mitral Valve Disease Receiving Pimobendan or Placebo: The EPIC Study.

BACKGROUND: Changes in clinical variables associated with the administration of pimobendan to dogs with preclinical myxomatous mitral valve disease (MMVD) and cardiomegaly have not been described. OBJECTIVES: To investigate the effect of pimobendan on clinical variables and the relationship between a change in heart size and the time to congestive heart failure (CHF) or cardiac-related death (CRD) in dogs with MMVD and cardiomegaly. To determine whether pimobendan-treated dogs differ from dogs receiving placebo at onset of CHF. ANIMALS: Three hundred and fifty-four dogs with MMVD and cardiomegaly. MATERIALS AND METHODS: Prospective, blinded study with dogs randomized (ratio 1:1) to pimobendan (0.4-0.6 mg/kg/d) or placebo. Clinical, laboratory, and heart-size variables in both groups were measured and compared at different time points (day 35 and onset of CHF) and over the study duration. Relationships between short-term changes in echocardiographic variables and time to CHF or CRD were explored. RESULTS: At day 35, heart size had reduced in the pimobendan group: median change in (Δ) LVIDDN -0.06 (IQR: -0.15 to +0.02), P < 0.0001, and LA:Ao -0.08 (IQR: -0.23 to +0.03), P < 0.0001. Reduction in heart size was associated with increased time to CHF or CRD. Hazard ratio for a 0.1 increase in ΔLVIDDN was 1.26, P = 0.0003. Hazard ratio for a 0.1 increase in ΔLA:Ao was 1.14, P = 0.0002. At onset of CHF, groups were similar. CONCLUSIONS AND CLINICAL IMPORTANCE: Pimobendan treatment reduces heart size. Reduced heart size is associated with improved outcome. At the onset of CHF, dogs treated with pimobendan were indistinguishable from those receiving placebo.

Prevalence of mitral valve regurgitation in 79 asymptomatic Norfolk terriers.

OBJECTIVES: To determine the prevalence of mitral valve regurgitation (MR) in asymptomatic Swedish Norfolk terriers. ANIMALS: Seventy-nine privately owned Norfolk terriers. MATERIALS AND METHODS: A prospective observational study was conducted where dogs were recruited via the Swedish Norfolk terrier club. All dogs were examined using the same protocol including physical examination and Doppler echocardiography. RESULTS: Fifteen dogs (19%) had a murmur at the time of the examination. A total of 35 dogs (44%) had MR, including 23 dogs (29%) with both MR and tricuspid valve regurgitation and 12 dogs (15%) with MR only, identified on Doppler echocardiography. In addition, 7 dogs (9%) had tricuspid valve regurgitation only. The prevalence of MR increased with increasing age (p < 0.0001). CONCLUSIONS: Mitral valve regurgitation is common in asymptomatic Norfolk terriers with and without murmurs and the prevalence increases with age. The impact of MR in this breed on survival remains to be elucidated by a longitudinal study.

Real-Time 3-Dimensional Echocardiographic Assessment of Effective Regurgitant Orifice Area in Dogs With Myxomatous Mitral Valve Disease.

BACKGROUND: Effective regurgitant orifice area (EROA), calculated from the vena contracta width (VCW) as the narrowest portion of the proximal regurgitant jet, might be used to estimate severity of mitral regurgitation. However, this simplified assumption only holds when the EROA is circular, which might not be true in dogs with myxomatous mitral valve disease (MMVD). HYPOTHESIS: Effective regurgitant orifice area in dogs with MMVD is noncircular, and using color Doppler real-time 3-dimensional (RT3D) echocardiography, measured EROA in the en face view will be significantly different from calculated EROA. ANIMALS: Hundred and fifty-eight privately owned dogs with naturally occurring MMVD. MATERIALS AND METHODS: Prospective observational study comparing en face view of EROA with calculated EROA using VCW in 4-chamber (4Ch) and 2-chamber (2Ch) view only or combined 4Ch and 2Ch views using RT3D echocardiography. RESULTS: The calculated EROA using the 2Ch view showed a systematic underestimation of 17% compared with the measured en face EROA corrected for body surface area. The calculated EROA using 4Ch and 4Ch + 2Ch views showed less agreement with the en face EROA, and the difference between methods increased with increasing EROA. The difference between calculated and measured EROA showed a systematic underestimation of the calculated EROA by 36% (4Ch) and 33% (4Ch + 2Ch), respectively, compared to measured en face EROA. CONCLUSION AND CLINICAL IMPORTANCE: When replacing measured EROA with calculated EROA using VCW measurements, the 2Ch view is preferred in dogs with MMVD.

Effect of Body Weight on Echocardiographic Measurements in 19,866 Pure-Bred Cats with or without Heart Disease.

BACKGROUND: Echocardiography is a cost-efficient method to screen cats for presence of heart disease. Current reference intervals for feline cardiac dimensions do not account for body weight (BW). OBJECTIVE: To study the effect of BW on heart rate (HR), aortic (Ao), left atrial (LA) and ventricular (LV) linear dimensions in cats, and to calculate 95% prediction intervals for these variables in normal adult pure-bred cats. ANIMALS: 19 866 pure-bred cats. METHODS: Clinical data from heart screens conducted between 1999 and 2014 were included. Associations between BW, HR, and cardiac dimensions were assessed using univariate linear models and allometric scaling, including all cats, and only those considered normal, respectively. Prediction intervals were created using 95% confidence intervals obtained from regression curves. RESULTS: Associations between BW and echocardiographic dimensions were best described by allometric scaling, and all dimensions increased with increasing BW (all P<0.001). Strongest associations were found between BW and Ao, LV end diastolic, LA dimensions, and thickness of LV free wall. Weak linear associations were found between BW and HR and left atrial to aortic ratio (LA:Ao), for which HR decreased with increasing BW (P<0.001), and LA:Ao increased with increasing BW (P<0.001). Marginal differences were found for prediction formulas and prediction intervals when the dataset included all cats versus only those considered normal. CONCLUSIONS AND IMPORTANCE: BW had a clinically relevant effect on echocardiographic dimensions in cats, and BW based 95% prediction intervals may help in screening cats for heart disease.

Effect of Pimobendan in Dogs with Preclinical Myxomatous Mitral Valve Disease and Cardiomegaly: The EPIC Study-A Randomized Clinical Trial.

BACKGROUND: Pimobendan is effective in treatment of dogs with congestive heart failure (CHF) secondary to myxomatous mitral valve disease (MMVD). Its effect on dogs before the onset of CHF is unknown. HYPOTHESIS/OBJECTIVES: Administration of pimobendan (0.4-0.6 mg/kg/d in divided doses) to dogs with increased heart size secondary to preclinical MMVD, not receiving other cardiovascular medications, will delay the onset of signs of CHF, cardiac-related death, or euthanasia. ANIMALS: 360 client-owned dogs with MMVD with left atrial-to-aortic ratio ≥1.6, normalized left ventricular internal diameter in diastole ≥1.7, and vertebral heart sum >10.5. METHODS: Prospective, randomized, placebo-controlled, blinded, multicenter clinical trial. Primary outcome variable was time to a composite of the onset of CHF, cardiac-related death, or euthanasia. RESULTS: Median time to primary endpoint was 1228 days (95% CI: 856-NA) in the pimobendan group and 766 days (95% CI: 667-875) in the placebo group (P = .0038). Hazard ratio for the pimobendan group was 0.64 (95% CI: 0.47-0.87) compared with the placebo group. The benefit persisted after adjustment for other variables. Adverse events were not different between treatment groups. Dogs in the pimobendan group lived longer (median survival time was 1059 days (95% CI: 952-NA) in the pimobendan group and 902 days (95% CI: 747-1061) in the placebo group) (P = .012). CONCLUSIONS AND CLINICAL IMPORTANCE: Administration of pimobendan to dogs with MMVD and echocardiographic and radiographic evidence of cardiomegaly results in prolongation of preclinical period and is safe and well tolerated. Prolongation of preclinical period by approximately 15 months represents substantial clinical benefit.

Diagnostic Value of Selected Echocardiographic Variables to Identify Pulmonary Hypertension in Dogs with Myxomatous Mitral Valve Disease.

BACKGROUND: Pulmonary hypertension (PH) is commonly associated with myxomatous mitral valve disease (MMVD). Because dogs with PH present without measureable tricuspid regurgitation (TR), it would be useful to investigate echocardiographic variables that can identify PH. AIM: To investigate associations between estimated systolic TR pressure gradient (TRPG) and dog characteristics and selected echocardiographic variables. ANIMALS: 156 privately owned dogs. MATERIALS AND METHODS: Prospective observational study comparing the estimations of TRPG with dog characteristics and selected echocardiographic variables in dogs with MMVD and measureable TR. RESULTS: Tricuspid regurgitation pressure gradient was significantly (P < .05) associated with body weight corrected right (RVIDDn) and left (LVIDDn) ventricular end-diastolic and systolic (LVIDSn) internal diameters, pulmonary arterial (PA) acceleration to deceleration time ratio (AT/DT), heart rate, left atrial to aortic root ratio (LA/Ao), and the presence of congestive heart failure. Four variables remained significant in the multiple regression analysis with TRPG as a dependent variable: modeled as linear variables LA/Ao (P < .0001) and RVIDDn (P = .041), modeled as second order polynomial variables: AT/DT (P = .0039) and LVIDDn (P < .0001) The adjusted R(2) -value for the final model was 0.45 and receiver operating characteristic curve analysis suggested the model's performance to predict PH, defined as 36, 45, and 55 mmHg as fair (area under the curve [AUC] = 0.80), good (AUC = 0.86), and excellent (AUC = 0.92), respectively. CONCLUSION AND CLINICAL IMPORTANCE: In dogs with MMVD, the presence of PH might be suspected with the combination of decreased PA AT/DT, increased RVIDDn and LA/Ao, and a small or great LVIDDn.

Canine idiopathic dilated cardiomyopathy. Part I: Aetiology, clinical characteristics, epidemiology and pathology.

Dilated cardiomyopathy (DCM), characterized by chamber dilatation and myocardial systolic and diastolic dysfunction, is one of the most common heart diseases in dogs. The aetiology of the myocardial hypokineis is seldom known in the individual case of DCM, although several theories concerning genetic, nutritional, metabolic, inflammatory, infectious, or drug- or toxin-induced myocardial disease have been discussed. DCM is often referred to as being breed-specific for Boxers, Doberman Pinschers, English Cocker Spaniels and other breeds. Review of reports on histopathologic findings in canine DCM reveals two histologically distinct forms of DCM; (1) cardiomyopathy of boxers and of Doberman pinschers, corresponding to the "fatty infiltration-degenerative" type, and (2) the form seen in many giant, large- and medium-sized breeds, including some boxers and Doberman pinschers, which can be classified as the "attenuated wavy fiber" type of DCM. The classification of canine idiopathic DCM according to histologic findigns seems superior to classification suggesting breed-specific syndromes, as some breeds (i.e. boxers and Doberman pinschers) may be affected by both diseases. However, ante mortem aetiological diagnosis of DCM is difficult. DCM carries a poor prognosis in dogs, and few prognostic indicators have been identified.

Canine idiopathic dilated cardiomyopathy. Part II: pathophysiology and therapy.

Dilated cardiomyopathy (DCM) in dogs is characterized by ventricular and atrial enlargement, and systolic and diastolic dysfunction, with congestive heart failure (CHF) often developing at some stage. With greater understanding of the impact of neuroendocrine stimulation in heart disease, the understanding of the pathophysiology for CHF has changed considerably. It is no longer considered only to be a simple haemodynamic consequence of pump dysfunction, but is now characterized as a complex clinical syndrome with release of many neurohormones, which are believed to have impact on the progression of disease. This change in our understanding of the pathophysiology of CHF has important therapeutic implications. There are strong indications, although not yet proven, that drugs designed to influence the neuroendocrine activity, such as Angiotensin Converting Enzyme (ACE) inhibitors and beta-receptors antagonists, are efficacious as adjunct therapy of heart failure attributable to DCM in dogs. The benefits of drugs designed to influence the myocardial contractile state (positive inotropes) have not been fully evaluated. However, evidence has emerged in recent years indicating that new types of positive inotropes may be beneficial in dogs with DCM. This review focuses on the neuroendocrine aspects of DCM and their possible therapeutic implications and the place for long-term inotropic support in dogs with DCM.

Detection of attenuated wavy fibers in the myocardium of Newfoundlands without clinical or echocardiographic evidence of heart disease.

OBJECTIVES: To determine whether attenuated wavy fibers may be found in the myocardium of Newfoundlands without clinical or echocardiographic evidence of heart disease. ANIMALS: 15 Newfoundlands from a kennel with a known predisposition to dilated cardiomyopathy (DCM) and 32 dogs of other breeds that died suddenly or were euthanatized for reasons unrelated to heart disease and did not have gross postmortem evidence of heart disease. PROCEDURE: Echocardiography was performed on all Newfoundlands on a yearly basis. Necropsy specimens from all dogs were evaluated for attenuated wavy fibers (i.e., myocardial cells <6 microm in diameter with a wavy appearance). RESULTS: None of the Newfoundlands had clinical signs of heart disease, and results of echocardiographic examinations were within reference ranges. Seven Newfoundlands had histologic evidence of attenuated wavy fibers, whereas attenuated wavy fibers were not found in the remaining 8 Newfoundlands or in any of the 32 dogs of other breeds. CONCLUSIONS AND CLINICAL RELEVANCE: Findings suggest that attenuated wavy fibers in dogs with a known predisposition for DCM may indicate an early stage of the disease. However, further studies on a larger number of dogs are needed to confirm this hypothesis.

Effects of dilated cardiomyopathy on the renin-angiotensin-aldosterone system, atrial natriuretic peptide activity, and thyroid hormone concentrations in dogs.

OBJECTIVE: To evaluate the effect of dilated cardiomyopathy (DCM) on activity of the renin-angiotensin-aldosterone system (RAAS), the N-terminal fragment of proatrial natriuretic peptide (NT-proANP), and thyroid hormone concentrations in dogs. ANIMALS: 15 dogs with clinical signs of DCM, 15 dogs without clinical signs of DCM, and 15 age-, breed-, and sex-matched control dogs. PROCEDURE: Physical examinations, thoracic radiography, ECG, and echocardiography were performed on all dogs, and blood and urine samples were collected. RESULTS: Plasma renin activity (PRA), plasma aldosterone concentration (PAC), urine aldosterone-to-creatinine ratio, and NT-proANP concentrations were significantly increased in dogs with clinical signs of DCM, compared with dogs without clinical signs and control dogs. Thyroid-stimulating hormone and total thyroxine concentrations did not differ significantly among groups; however, free thyroxine (FT4) concentrations were significantly decreased in dogs with clinical signs of DCM, compared with control dogs and DCM-dogs without clinical signs. Concentrations of PRA, PAC, FT4, and urine aldosterone-to-creatinine ratio were significantly correlated, whereas plasma concentrations of NT-proANP only correlated with FT4 concentration. CONCLUSION AND CLINICAL RELEVANCE: In dogs with clinical signs of DCM, increased concentrations of components of the RAAS were associated with increased concentrations of NT-proANP Analysis of the neurohormonal system may aid in identification of clinical stages of DCM for groups of dogs, but the range is too great and there are too many dogs that have neurohormonal concentrations within reference ranges to assess dogs on an individual basis.