Diagnosis of congenital aneurysmal giant right auricle in a dog.

A five-year-old intact male Golden Retriever was sent to our center for a second cardiac evaluation after the diagnosis of right atrial dilatation. Transthoracic and transesophageal echocardiographic evaluation and echo-contrast study were performed. A diagnosis of aneurysmal right auricle was issued without any sign of other cardiac pathologies. The tomographic evaluation was necessary to estimate the dimension of the aneurysmal area and exclude pericardial defects that may justify this anomaly. This report describes a rare case of aneurysmal giant right auricle in dogs. The diagnosis is accurate with the association of echocardiography and computed tomography.

Acute pulmonary edema in a dog with severe pulmonary valve stenosis: A rare complication after balloon valvuloplasty.

Pulmonic stenosis is a frequent congenital heart disease in dogs, and the treatment of choice is balloon valvuloplasty which is usually safe and successful. The authors describe for the first time a severe complication after balloon valvuloplasty in a five-month-old dog. After effective treatment, with a considerable drop in right ventricular pressures, the dog developed hypoxemia and dyspnea due to pulmonary edema. The dog underwent intensive care and symptoms improved after a few hours of oxygen therapy, continuous positive airway pressure, and furosemide. Although this event is rare, it could have a large impact on patient survival and should be considered in the treatment of severe pulmonary valve stenosis in the future.

Repeat balloon valvuloplasty for dogs with recurrent or persistent pulmonary stenosis.

INTRODUCTION/OBJECTIVES: Pulmonary stenosis (PS) is a common congenital defect in the dog. Severe valvar PS can be treated with balloon valvuloplasty (BV) to reduce obstruction severity and improve clinical signs. Repeat BV is often unnecessary, as restenosis is uncommon. Repeated pulmonary BV in people is generally successful and safe, but outcomes in dogs with recurrent or persistent stenosis have not been reported. The objectives of this study were to retrospectively evaluate outcomes of repeat BV in dogs. ANIMALS, MATERIALS, AND METHODS: Medical records and stored echocardiographic images were reviewed from dogs that received repeat BV for pulmonary valvar restenosis or persistent stenosis. Echocardiographic variables included maximum systolic ejection velocity (PVmax), velocity-derived maximal pressure gradient (PGmax) and velocity time integral (VTI) across the pulmonary valve, and ratios of pulmonic to aortic maximum velocity (PVmax/AVmax) and VTI (VTIPV/VTIAV). RESULTS: Twenty-three dogs were included; one underwent three BV procedures. The median time between BV procedures was 18.3 months (interquartile range, 6.3-43.6). One dog died during repeat BV, but no others experienced adverse effects. Reductions in PVmax, PGmax, and VTIPV after initial and repeat BV were 1.85 m/s, 76.2 mmHg, and 44.7 cm and 1.33 m/s, 55.6 mmHg, and 30.2 cm, respectively (all p < 0.01). Differences between pre-BV and post-BV PVmax, PGmax, VTIPV, PVmax/AVmax, and VTIPV/VTIAV were not different comparing initial to repeat BV (all p > 0.10). CONCLUSIONS: Repeat BV for recurrent or persistent PS is well tolerated and effective in a majority of dogs.

The predictive value of clinical, radiographic, echocardiographic variables and cardiac biomarkers for assessing risk of the onset of heart failure or cardiac death in dogs with preclinical myxomatous mitral valve disease enrolled in the DELAY study.

OBJECTIVES: To identify the predictive value on time to onset of heart failure (HF) or cardiac death of clinical, radiographic, and echocardiographic variables, as well as cardiac biomarkers N-terminal pro brain natriuretic peptide (NT-proBNP) and cardiac troponin I in dogs with preclinical myxomatous mitral valve disease (MMVD). ANIMALS: One hundred sixty-eight dogs with preclinical MMVD and left atrium to aortic root ratio ≥1.6 (LA:Ao) and normalized left ventricular end-diastolic diameter ≥1.7 were included. METHODS: Prospective, randomized, multicenter, single-blinded, placebo-controlled study. Clinical, radiographic, echocardiographic variables and plasma cardiac biomarkers concentrations were compared at different time points. Using receiving operating curves analysis, best cutoff for selected variables was identified and the risk to develop the study endpoint at six-month intervals was calculated. RESULTS: Left atrial to aortic root ratio >2.1 (hazard ratio [HR] 3.2, 95% confidence interval [95% CI] 1.9-5.6), normalized left ventricular end-diastolic diameter > 1.9 (HR: 6.3; 95% CI: 3.3-11.8), early transmitral peak velocity (E peak) > 1 m/sec (HR: 3.9; 95% CI: 2.3-6.7), and NT-proBNP > 1500 ρmol/L (HR: 5.7; 95% CI: 3.3-9.5) were associated with increased risk of HF or cardiac death. The best fit model to predict the risk to reach the endpoint was represented by the plasma NT-proBNP concentrations adjusted for LA:Ao and E peak. CONCLUSIONS: Logistic and survival models including echocardiographic variables and NT-proBNP can be used to identify dogs with preclinical MMVD at higher risk to develop HF or cardiac death.

Histologic characterization of dilated cardiomyopathy in Estrela mountain dogs.

Dilated cardiomyopathy (DCM) is the second-most-important acquired cardiovascular disease in dogs (excluding heartworm disease in some geographic regions) and a major cause of morbidity and mortality in Estrela Mountain Dogs. The objective of this study is to describe the histologic features of DCM in Estrela Mountain Dogs, with special attention to the localization and quantification of attenuated wavy fibers (AWFs), fibrosis, and fatty infiltration. Myocardial samples from 10 areas were collected from the hearts of 10 dogs with DCM and 7 dogs without signs of cardiac disease-namely, the basal, middle, and apical portions of the free wall of both cardiac ventricles and the interventricular septum, as well as the left ventricular papillary muscle. In each sample, the presence or absence of AWFs was noted, and fatty infiltration and fibrosis were quantified. Fatty infiltration, fibrosis, and AWFs were observed in the myocardium of all dogs with DCM, in contrast to what has been described in other breeds. The left ventricular myocardium was the best tissue for diagnosis of DCM, based on these histologic features. The authors concluded that quantification of fibrosis and observation of AWFs in the left ventricular myocardium are useful in the histologic diagnosis of DCM in Estrela Mountain dogs.

Real-time three-dimensional echocardiographic study of a cardiac hemangiosarcoma in a dog.

A 7-year-old Golden Retriever was presented for a second opinion regarding a cardiac mass. Two-dimensional transthoracic echocardiography demonstrated presence of a mass in the area of the right atrium. The mass appeared adherent and possibly infiltrative to the external wall of the right atrium. Three-dimensional transthoracic echocardiography allowed better visualization of the neoplasia, suggesting that it was not infiltrative and contributed significantly to the decision to carry out the surgical resection of the cardiac tumor. This case report demonstrates the use of three-dimensional transthoracic echocardiography in the diagnostic evaluation of cardiac masses in dogs without the need for general anesthesia.

Branch pulmonary artery stent placement in a dog with heart base neoplasia.

A 7-year-old French bulldog was presented for evaluation of cardiac neoplasia. Two-dimensional transthoracic echocardiography revealed a mass on the base of the heart, compressing the right pulmonary artery. Computed tomography exam confirmed that a surgical approach to remove the mass would not be viable. Stent placement in the right pulmonary artery was performed to relieve external compression caused by the neoplasia. When surgery is not feasible, pulmonary artery stenting could be one aspect of a multidisciplinary approach to palliative management of heart base neoplasia.

DELay of Appearance of sYmptoms of Canine Degenerative Mitral Valve Disease Treated with Spironolactone and Benazepril: the DELAY Study.

INTRODUCTION: Efficacy of renin-angiotensin-aldosterone system (RAAS) blockade using angiotensin-converting enzyme inhibitors (ACEi) in dogs with preclinical myxomatous mitral valve disease (MMVD) is controversial. HYPOTHESIS: Administration of spironolactone (2-4 mg q 24 h) and benazepril (0.25-0.5 mg q 24 h) in dogs with preclinical MMVD, not receiving any other cardiac medications, delays the onset of heart failure (HF) and cardiac-related death. Moreover, it reduces the progression of the disease as indicated by echocardiographic parameters and level of cardiac biomarkers N-terminal pro brain natriuretic peptide (NT-proBNP) and cardiac troponin I (cTnI). ANIMALS: 184 dogs with pre-clinical MMVD and left atrium-to-aortic root ratio (LA:Ao) ≥1.6 and normalized left ventricular end-diastolic diameter (LVEDDn) ≥1.7. METHODS: This is a prospective, randomized, multicenter, single-blinded, placebo-controlled study. Primary outcome variable was time-to-onset of first occurrence of HF or cardiac death. Secondary end points included effect of treatment on progression of the disease based on echocardiographic and radiographic parameters, as well as variations of NT-proBNP and cTnI concentrations. RESULTS: The median time to primary end point was 902 days (95% confidence interval (CI) 682-not available) for the treatment group and 1139 days (95% CI 732-NA) for the control group (p = 0.45). Vertebral heart score (p = 0.05), LA:Ao (p < 0.001), LVEDDn (p < 0.001), trans-mitral E peak velocity (p = 0.011), and NT-proBNP (p = 0.037) were lower at the end of study in the treatment group. CONCLUSIONS: This study failed in demonstrating that combined administration of spironolactone and benazepril delays onset of HF in dogs with preclinical MMVD. However, such treatment induces beneficial effects on cardiac remodeling and these results could be of clinical relevance.

A new 2D-based method for myocardial velocity strain and strain rate quantification in a normal adult and paediatric population: assessment of reference values.

BACKGROUND: Recent advances in technology have provided the opportunity for off-line analysis of digital video-clips of two-dimensional (2-D) echocardiographic images. Commercially available software that follows the motion of cardiac structures during cardiac cycle computes both regional and global velocity, strain, and strain rate (SR). The present study aims to evaluate the clinical applicability of the software based on the tracking algorithm feature (studied for cardiology purposes) and to derive the reference values for longitudinal and circumferential strain and SR of the left ventricle in a normal population of children and young adults. METHODS: 45 healthy volunteers (30 adults: 19 male, 11 female, mean age 37 +/- 6 years; 15 children: 8 male, 7 female, mean age 8 +/- 2 years) underwent transthoracic echocardiographic examination; 2D cine-loops recordings of apical 4-four 4-chamber (4C) and 2-chamber (2C) views and short axis views were stored for off-line analysis. Computer analyses were performed using specific software relying on the algorithm of optical flow analysis, specifically designed to track the endocardial border, installed on a Windows based computer workstation. Inter and intra-observer variability was assessed. RESULTS: The feasibility of measurements obtained with tissue tracking system was higher in apical view (100% for systolic events; 64% for diastolic events) than in short axis view (70% for systolic events; 52% for diastolic events). Longitudinal systolic velocity decreased from base to apex in all subjects (5.22 +/- 1.01 vs. 1.20 +/- 0.88; p < 0.0001). Longitudinal strain and SR significantly increased from base to apex in all subjects (-12.95 +/- 6.79 vs. -14.87 +/- 6.78; p = 0.002; -0.72 +/- 0.39 vs. -0.94 +/- 0.48, p = 0.0001, respectively). Similarly, circumferential strain and SR increased from base to apex (-21.32 +/- 5.15 vs. -27.02 +/- 5.88, p = 0.002; -1.51 +/- 0.37 vs. -1.95 +/- 0.57, p = 0.003, respectively). Values of global systolic SR, both longitudinal and circumferential, were significantly higher in children than in adults (-1.3 +/- 0.2, vs. -1.11 +/- 0.2, p = 0.006; -1.9 +/- 0.6 vs. -1.6 +/- 0.5, p = 0.0265, respectively). No significant differences in longitudinal and circumferential systolic velocities were identified for any segment when comparing adults with children. CONCLUSION: This 2D based tissue tracking system used for computation is reliable and applicable in adults and children particularly for systolic events. Measured with this technology, we have established reference values for myocardial velocity, Strain and SR for both young adults and children.

Complications during catheter-mediated patent ductus arteriosus closure and pulmonary balloon valvuloplasty.

OBJECTIVES: To evaluate and illustrate complications of cardiac catheterisation and the associated risk factors of the most common cardiac intervention procedures. MATERIALS AND METHODS: Retrospective study of clinical records of client-owned dogs presented to a cardiology referral centre between January 2006 and December 2017. RESULTS: Five hundred and twenty-four dogs were included, 62 of which had complications. Complications were divided into technical complications and those due to unexpected additional anatomical abnormalities. Seven procedures (1.33%) were interrupted; five dogs (0.95%) subsequently underwent surgery, and four dogs died during the interventional procedure, indicating a mortality rate of 0.76% CLINICAL SIGNIFICANCE: There is a low risk of complications following closure of patent ductus arteriosus or pulmonary balloon valvuloplasty when carried out by a trained team using standardised procedures in a referral centre.

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.

Clinical, echocardiographic and advanced imaging characteristics of 13 dogs with systemic-to-pulmonary arteriovenous fistulas.

OBJECTIVES: The objective is to describe the clinical, radiographic, echocardiographic and angiographic findings in dogs with systemic-to-pulmonary arteriovenous fistula (SPAVF). ANIMALS: Thirteen medical records of client-owned dogs with a diagnosis of SPAVF were reviewed/analysed. METHODS: This is a retrospective study of case records. Thoracic radiography, transthoracic echocardiography (TTE), transesophageal echocardiography (TEE), three-dimensional TEE, intracardiac echocardiography, fluoroscopy-guided or computed tomography (CT) angiography were carried out. RESULTS: Based on the TTE, SPAVF was identified in seven of the included dogs. In eight cases, TEE and angiography were both performed and confirmed the diagnosis. Computed tomography angiography was performed in three dogs. A case was diagnosed by TEE alone, another one by three-dimensional TEE and the latter by intracardiac echocardiography. CONCLUSIONS: Transthoracic echocardiography identified seven cases of SPAVF, while definitive diagnosis in the remaining dogs required selective angiography or computed tomography angiography.

Echocardiographic Assessment of Cardiac Function by Conventional and Speckle-Tracking Echocardiography in Dogs with Patent Ductus Arteriosus.

BACKGROUND: Patent ductus arteriosus (PDA) is one of the most common congenital heart defects in dogs. Advanced echocardiographic techniques such as speckle-tracking echocardiography (STE) have not been extensively used to evaluate cardiac function in affected dogs. HYPOTHESIS: Advanced echocardiographic techniques are more sensitive than standard echocardiographic techniques in analyzing systolic function in dogs with PDA. ANIMALS: Forty-four client-owned dogs: 34 dogs with PDA (preoperative evaluation) and 10 healthy sex- and weight-matched controls. METHODS: Prospective study. Dogs were recruited over a 2-year period. Complete echocardiographic evaluation was performed, including conventional (end-diastolic volumes indexed to body surface area in B and M-mode [EDVIB /M ], end-systolic volumes indexed to body surface area in B and M-mode [ESVIB /M ], allometric scaling in diastole and systole [AlloD/S], pulmonary flow to systemic flow [Qp/Qs], ejection fraction [EF] and fractional shortening [FS]) and speckle-tracking echocardiography ([STE]: global longitudinal, radial and circumferential strain [S] and strain rate [SR]). RESULTS: Dogs with PDA had significantly different EDVIB /M , ESVIB /M , AlloD/S, Qp/Qs and all STE-derived parameters (global longitudinal S and SR, global circumferential S and SR, global radial S and SR)compared to healthy dogs. No correlation was found between standard techniques (EDVIB /M , ESVIB /M , AlloD/S, Qp/Qs) and STE-derived parameters (global longitudinal, circumferential and radial S and SR). CONCLUSION AND CLINICAL IMPORTANCE: Conventional parameters routinely used to assess systolic function (EF and FS) were not different between the groups; STE-derived parameters identified subtle changes in cardiac systolic function and contractility between the 2 groups of dogs. Based on these findings, STE may be a more appropriate tool to assess cardiac contractility in dogs with PDA.

Speckle-Tracking Echocardiography in Dogs With Patent Ductus Arteriosus: Effect of Percutaneous Closure on Cardiac Mechanics.

BACKGROUND: Patent ductus arteriosus (PDA) is 1 of the most common congenital heart defects in dogs and percutaneous closure is effective in achieving ductal closure; PDA closure is associated with abrupt hemodynamic changes. HYPOTHESIS: A marked decrease in standard parameters of systolic function as assessed by M- or B-mode echocardiography after PDA closure was identified in previous studies. Speckle tracking echocardiography can provide further insight into the effect of PDA closure on cardiac mechanics in dogs affected by PDA. ANIMALS: Twenty-five client-owned dogs with PDA. METHODS: Prospective study. Dogs were recruited over a 2-year period. Complete echocardiographic evaluation was performed before and 24 hours after PDA closure, including standard (end-diastolic volumes indexed to body surface area in B- and M-mode [EDVIB /M ], end-systolic volumes indexed to body surface area in B- and M-mode [ESVIB /M ], allometric scaling in diastole [AlloD] and systole [AlloS], pulmonary flow to systemic flow [Qs/Qp], ejection fraction [EF], and fractional shortening [FS]), and advanced speckle-tracking echocardiography (STE): global longitudinal, radial, circumferential and transverse strain (S), and strain rate (SR). RESULTS: Patent ductus arteriosus closure was associated with statistically significant decreases in EDVIM /B and ESVIM /B , AlloD and AlloS, SI, EF, and FS. A statistically significant decrease in the absolute values of radial, transverse, and circumferential S and SR was observed, whereas longitudinal S and SR did not change significantly. CONCLUSION AND CLINICAL IMPORTANCE: Patent ductus arteriosus closure by percutaneous approach is associated with marked decreases of conventional echocardiographic parameters as a result of the changes in loading conditions, but no evidence of systolic dysfunction was identified by means of STE, as none of the S and SR values were below reference ranges. In the short term, contractility is enhanced in the long axis (long S/SR values were not statistically different before and after closure) and decreases to normal values in short axis (circumferential, radial, and transversal S/SR decreased to normal reference range).

Use of an Amplatz Canine Ductal Occluder (ACDO) device to close an acquired aortopulmonary fistula with a hybrid approach in a dog.

A 2-year-old recently spayed female Rottweiler was referred as an emergency with cardiac tamponade and the presence of an anomalous retrograde flow in the pulmonary artery. Echocardiography and angiography demonstrated a left-to-right aortopulmonary fistula. Clinical history and data indicated a possible infectious aetiology. Antibiotics and heart failure medications were administered for 30 days before intervention. Initial attempt at insertion of an Amplatz occluder by means of a percutaneous catheterization technique was tried but a safe release of the device was judged to be not possible due to the angle and the fragile and irregular margins of the window. A decision was made to proceed with a hybrid technique combining thoracotomy and direct pulmonary artery catheterization. This hybrid approach was successful with resolution of congestive heart failure with only residual mild paraprosthetic leakage.

Cardiovascular-renal axis disorders in the domestic dog and cat: a veterinary consensus statement.

OBJECTIVES: There is a growing understanding of the complexity of interplay between renal and cardiovascular systems in both health and disease. The medical profession has adopted the term "cardiorenal syndrome" (CRS) to describe the pathophysiological relationship between the kidney and heart in disease. CRS has yet to be formally defined and described by the veterinary profession and its existence and importance in dogs and cats warrant investigation. The CRS Consensus Group, comprising nine veterinary cardiologists and seven nephrologists from Europe and North America, sought to achieve consensus around the definition, pathophysiology, diagnosis and management of dogs and cats with "cardiovascular-renal disorders" (CvRD). To this end, the Delphi formal methodology for defining/building consensus and defining guidelines was utilised. METHODS: Following a literature review, 13 candidate statements regarding CvRD in dogs and cats were tested for consensus, using a modified Delphi method. As a new area of interest, well-designed studies, specific to CRS/CvRD, are lacking, particularly in dogs and cats. Hence, while scientific justification of all the recommendations was sought and used when available, recommendations were largely reliant on theory, expert opinion, small clinical studies and extrapolation from data derived from other species. RESULTS: Of the 13 statements, 11 achieved consensus and 2 did not. The modified Delphi approach worked well to achieve consensus in an objective manner and to develop initial guidelines for CvRD. DISCUSSION: The resultant manuscript describes consensus statements for the definition, classification, diagnosis and management strategies for veterinary patients with CvRD, with an emphasis on the pathological interplay between the two organ systems. By formulating consensus statements regarding CvRD in veterinary medicine, the authors hope to stimulate interest in and advancement of the understanding and management of CvRD in dogs and cats. The use of a formalised method for consensus and guideline development should be considered for other topics in veterinary medicine.

Blood lymphocyte subsets in canine idiopathic pericardial effusion.

The immunophenotype of peripheral blood lymphocytes was investigated in 23 dogs diagnosed with idiopathic pericardial effusion in order to provide information about a possible role of the immune system in this pathology. Flow cytometric analysis showed a significant reduction in nearly all lymphocyte subsets examined and a strong, significant (P < 0.001) reduction of the CD4 subset, which gave rise to a significantly lower CD4/CD8 ratio. Our data suggest that an imbalance in the immune system is present during the course of the disease, preferentially affecting the T helper cell response.

Doppler echocardiographic study of left ventricular diastole in non-anaesthetized healthy cats.

The current study: (1) describes the Doppler technique for the assessment of diastolic function in feline patients; (2) reports normal Doppler diastolic values; and (3) determines the effect of ageing on these parameters. Doppler echocardiography was performed on 20 non-anaesthetized healthy cats. Each diastolic parameter was correlated with age, body weight, body surface area and R-R interval. To assess the isovolumetric relaxation phase of diastole, isovolumetric relaxation time was measured. To assess the filling phase of diastole, we measured peak flow velocities of the E and A waves, diastolic filling time, acceleration and deceleration time of the E wave and the E/A ratio of transmitral flow, peak flow velocity of the S, D and the A retrograde waves, as well as the S/D ratio and the systolic fraction of pulmonary venous flow. We found a significant correlation between age and peak flow velocity of the A wave, normalized peak flow velocity of the A wave, the E/A ratio, the acceleration time of the E wave, the diastolic filling time, the velocity time integral of the E wave, the peak flow velocity of the S wave and the systolic fraction. It was concluded that Doppler echocardiographic analysis of diastole is possible in the cat and that age has most effect on filling parameters.

Lymphocyte beta -adrenoceptor downregulation in great danes with occult dilated cardiomyopathy (DCM) and with DCM and heart failure.

The importance of the adrenergic nervous system in supporting the failing heart has long been known. The adrenergic drive on cardiac structure and function has however some adverse effects, which include myocardial beta-adrenoceptor (beta-AR) downregulation and decreased beta-adrenergic responsiveness to cathecolamines. In dog lymphocytes, beta(1)-AR and beta(2)-AR populations are almost equally represented (with a slight prevalence of beta(2)) and a significant correlation between cardiac and lymphocytic adrenoceptors has been found. The aim of the present study was to investigate possible differences between the concentration of lymphocytic beta-AR in healthy dogs, dogs with dilated cardiomyopathy (DCM) and dogs with occult DCM. Three groups of great danes were considered: a control group (n =10), dogs with DCM (n =9) and dogs with occult DCM (n =4). Lymphocytic beta-AR populations were determined in all dogs. A substantial and significant decrease (P<0.05) in total-AR, beta(1)-AR and beta(2)-AR concentrations in the lymphocytes of dogs with symptomatic DCM and occult DCM compared to the control group was found. Although the mean value of the lymphocyte beta(1)-AR number in the asymptomatic group was double compared to the DCM group, this difference was not statistically significant. We conclude that in dogs beta-AR downregulation occurs early in the course of dilated cardiomyopathy. This finding may suggest the value of early use of a beta-blocker in the therapeutic regimen. Moreover, the continuous monitoring of lymphocytic beta-AR may represent a useful tool for the development of a more effective individual therapy.