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.

Aorto-septal angle, isolated basal septal hypertrophy, and systolic murmur in 122 cats.

INTRODUCTION/OBJECTIVES: Systolic murmurs in the absence of cardiac structural abnormalities are common in cats. Narrow aorto-septal angle (AoSA) and septal remodeling can be a cause of a systolic murmur in elderly human beings. The aim of this study was to measure the AoSA in cats and to investigate the association between the AoSA and the presence of a murmur and isolated basal septal hypertrophy (IBSH). ANIMALS: The study population comprised 122 cats. MATERIALS AND METHODS: A physical exam, blood pressure measurement, chest radiographs, and echocardiography were performed. RESULTS: A systolic murmur was audible in 39/122 cats. A difference between cats with and without a murmur was found for age (P=0.0001), interventricular basal septal thickness (BIVSd) (P=0.004), AoSA (P=0.003), aortic (P<0.0001), and pulmonic (P=0.021) flow velocity, the presence of IBSH (P<0.0001), and systolic anterior motion of the mitral valve (P=0.0002). More than 50% of cats with a murmur had an AoSA ≤122°. Less than 25% of the cats with an AoSA ≥137° had a murmur. The AoSA narrowed 0.55°/year of age (P<0.001), whereas the BIVSd increased 0.11 mm/year of age (P<0.0001); the BIVSd increased as the AoSA narrowed. In all cats with AoSA < 120°, IBSH was present. CONCLUSIONS: This study demonstrates that the probability of having a systolic murmur in cats is increased by the presence of a narrow AoSA. Aging was associated with a narrower AoSA and a thicker basal septum; these findings might represent an age-related heart remodeling.

The longitudinal outcome of canine (K9) myxomatous mitral valve disease (LOOK-Mitral) registry: Baseline treatment characteristics.

OBJECTIVES: To describe the medical treatment prescribed or modified by veterinary cardiologists at the enrollment visit in dogs included in the longitudinal outcome of canine (K9) myxomatous mitral valve disease (MMVD) registry (LOOK-mitral registry) and to evaluate the influence of the EPIC trial and other selected variables on cardiologist prescription habits. ANIMALS: The medical records of 6,102 dogs enrolled in the LOOK_mitral registry between 2015 and 2018 were retrospectively reviewed and 6,016 dogs were included. RESULTS: A medical treatment was prescribed by a cardiologist to 2,599 dogs (15% Stage-B1, 90% Stage-B2 and to all dogs in Stage-C). Angiotensin converting enzyme inhibitors (Ace-i) were the treatment most commonly prescribed for dogs in Stage-B1 (n = 352, 9%). The combination of pimobendan and an Ace-i was the most common treatment in Stage-B2 dogs (n = 367, 41%). Furosemide, an Ace-i, and pimobendan was the most common cardiac medical treatment prescribed for ACVIM Stage-C dogs (n = 704, 57%). Within each stage, dogs with larger left atrial and left ventricular dimensions were more likely to receive Ace-i, pimobendan or spironolactone. There was a four-fold increase in pimobendan prescription in Stage-B2 dogs after the publication of the EPIC trial. Moreover, a 15% reduction in Ace-i prescription and a 30% reduction in spironolactone prescription occurred after EPIC. In 974 dogs, a medical treatment was prescribed by the referring veterinarian. This was not changed (12%), modified (74%), or discontinued (14%) by the cardiologist. CONCLUSIONS: The EPIC trial and the echocardiographic assessment of left atrial and ventricular dimensions influence cardiologists' prescription habits.

Trifascicular block in a cat infected with Cytauxzoon felis.

A 3-year-old female spayed indoor/outdoor Siamese cat was diagnosed with cytauxzoonosis and irregular heart rhythm was appreciated during a physical examination. On electrocardiogram, the cat had an average ventricular rate of 144 beats/min with Wenckebach type (Mobitz type I) atrioventricular block. The QRS complexes of sinus conducted beats had left anterior fascicular block morphology, they were followed by two subsequent beats presented with a prolonged P-R interval and QRS conducted with a left bundle branch block. The finding of alternating left anterior fascicular block and left bundle branch block along with atrioventricular block is consistent with trifascicular block. No structural heart changes were noted on echocardiography. Approximately 48 h after presentation to the emergency service, the cat acutely decompensated and spontaneously died.

Heart rhythm characterization during sudden cardiac death in dogs.

INTRODUCTION/OBJECTIVES: Inherited or acquired arrhythmic disorders and cardiac disease have been associated with sudden cardiac death (SCD) in dogs. The electrical mechanism related to death in most of these cases is unknown. This retrospective study aimed to describe arrhythmic events in dogs that experienced SCD during Holter monitoring. ANIMALS, MATERIALS AND METHODS: Nineteen client-owned dogs that experienced SCD during Holter examination were included. Clinical records from a Holter service database were reviewed, and both the rhythm preceding death and the dominant rhythm causing SCD were analysed. Clinical data, Holter diaries and echocardiographic diagnosis were also evaluated. RESULTS: Structural heart disease was identified in 12/19 dogs (dilated cardiomyopathy in five dogs, arrhythmogenic right ventricular cardiomyopathy in four dogs, myxomatous mitral valve disease in two dogs, and suspected myocarditis in one dog), five of which had concurrent congestive heart failure. Sudden cardiac death was related to ventricular premature complexes or monomorphic ventricular tachycardia degenerating into ventricular fibrillation in 42% of dogs, polymorphic ventricular tachycardia, or torsade de pointes-like inducing ventricular fibrillation in 21%, and asystole or presumptive agonal pulseless electrical activity triggered by malignant bradyarrhythmias in 37%. CONCLUSIONS: The most common rhythm associated with SCD in our population of dogs was ventricular tachycardia leading to ventricular fibrillation, although bradyarrhythmia-related SCD, possibly related to inappropriate vagal reflexes, was also a notable cause.

Accuracy of echocardiographically estimated pulmonary artery pressure in dogs with myxomatous mitral valve disease.

INTRODUCTION: Echocardiographically identified pulmonary hypertension is an independent predictor of poor outcome in dogs affected by myxomatous valvular degeneration (MMVD). Systolic pulmonary arterial pressure is routinely estimated based on its relationship with the Doppler-determined velocity of tricuspid regurgitation as defined by the simplified Bernoulli equation (sPAP_D). Experimental studies suggest that the method is imperfect, but its accuracy in dogs with MMVD is not known. ANIMALS: Twenty dogs affected by MMVD that had cardiac remodeling and measurable tricuspid regurgitation. METHODS: A flow-directed thermodilution monitoring catheter was percutaneously placed in the right external jugular vein and advanced to the main pulmonary artery. Pulmonary arterial systolic pressure was recorded (systolic pulmonary arterial pressure obtained by right heart catheterization [sPAP_C]). A second operator contemporaneously acquired tricuspid regurgitant velocity spectra to calculate sPAP_D. Each operator was blinded to the result of the other techniques. RESULTS: Technical difficulties prevented the analysis of catheterization data in two dogs. Eighteen measurement pairs were therefore used for comparison of sPAP_C and sPAP_D through correlation and Bland-Altman analysis. A statistically significant bias between sPAP_C and sPAP_D (mean difference = 0.5 mmHg; confidence interval = -6.5 mmHg, +7.5 mmHg) was not detected. The interval of agreement between the techniques was wide (-27.3 mmHg, +28.2 mmHg). A significant linear association between the two techniques was not identified (r = 0.11, p=0.17). CONCLUSION: Echocardiographically estimated pulmonary artery pressure poorly agrees with sPAP_C measurement in dogs affected by MMVD and cardiac remodeling with or without previously diagnosed congestive heart failure. In these dogs, sPAP_D could under- or over-estimate sPAP_C by more than 20 mmHg, and therefore caution should be used when interpreting sPAP_D.

The Longitudinal Outcome Of Canine (K9) myxomatous mitral valve disease (LOOK-Mitral registry): Baseline characteristics.

INTRODUCTION: The Longitudinal Outcome Of Canine (K9) myxomatous mitral valve disease (MMVD) registry (LOOK-Mitral registry) was established to describe the natural history and predictors of outcome in dogs affected by MMVD. This study was intended to describe the baseline characteristics of dogs in the LOOK-mitral registry. ANIMALS: Dogs with echocardiographic evidence of MMVD were prospectively enrolled by thirteen referral centers. RESULTS: A total of 6102 dogs with MMVD were included. The median age was 10 years (1-19 years), and mixed breed was the most common breed (n = 1,360, 22%). Concomitant diseases were reported in 2459 dogs with chronic respiratory diseases occurring most frequently (14%), followed by the presence of azotemia (6%) and orthopedic diseases (5%). Regarding disease severity, 65% of dogs were in ACVIM Stage-B1, 15% in Stage-B2, and 20% in Stage-C. Dogs in Stage-B1 were younger (p<0.001) than dogs in other stages. Murmur intensity, heart rate during physical examination, and radiographic vertebral heart score were positively associated with the stage. Dogs in Stage-C were more likely to have tachypnea (p<0.001), dyspnea (p<0.001), cough (p<0.001), syncopal episodes (p<0.001), and tachyarrhythmias (p<0.001) compared to dogs in Stage-B1 and B2. Echocardiographic indices of left atrial and ventricular size were positively correlated with the ACVIM stage. Interestingly, 4% of dogs that weighed <20 kg had an increased normalized end-systolic left ventricle internal diameter (>1.26). CONCLUSIONS: This study contributes to a better understanding of the clinical characteristics of dogs affected by MMVD and provides new findings that may be of clinical relevance.

Predictors of reoccurrence of congestive signs within 180 days after successful treatment of the first episode of congestive heart failure in dogs with myxomatous mitral valve disease.

INTRODUCTION: Myxomatous mitral valve disease (MMVD) is the most common cause of left-sided congestive heart failure in dogs. We sought to identify predictors of first reoccurrence of congestive signs (CS) within 180 days in dogs with MMVD and clinically stable heart failure. ANIMALS: A total of 445 dogs affected by stable American College of Veterinary Internal Medicine (ACVIM)-Stage-C MMVD were included, 106 in the reoccurrence group (RG) and 339 in no reoccurrence group (NRG). Patients were considered "stable" if medical treatment had been unchanged for at least 4 weeks since the first identification of CS. METHODS: Medical records of dogs with stable ACVIM-Stage-C MMVD included in a registry of dogs affected by MMVD were reviewed. Follow-up was required for inclusion in this investigation. Logistic regression was used to identify clinical and echocardiographic variables that independently predict first reoccurrence of CS. RESULTS: Baseline left atrial-aortic ratio (p=0.022, OR: 1.89, 90% CI: 1.20-2.98), left ventricular internal diameter at end-diastole (LVIDd_N) (p=0.014, OR: 2.84, 90% CI: 1.41-5.77), peak velocity of early diastolic transmitral flow (p=0.049, OR: 1.81, 90% CI: 1.10-3.00) and furosemide daily dosage (p=0.039, OR: 1.19, 90% CI: 1.04-1.37) were associated with reoccurrence of CS in univariable analyses. The LVIDd_N (p=0.014) remained significant in the multivariable analysis, but the area under the receiver operator characteristic curve was 0.57. CONCLUSION: This study failed to identify accurate predictors of reoccurrence of CS. However, dogs with larger value of LVIDd_N are more likely to have reoccurrence of CS within 180 days.

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.

Effects of combined aging and heart failure on visceral sympathetic nerve and cardiovascular responses to progressive hyperthermia in F344 rats.

Sympathetic nerve discharge (SND) responses to hyperthermia are attenuated in aged rats without heart failure (HF) and in young HF (Y(HF)) rats, demonstrating that individually aging and HF alter SND regulation. However, the combined effects of aging and HF on SND regulation to heat stress are unknown, despite the high prevalence of HF in aged individuals. We hypothesized that SND responses to heating would be additive when aging and HF are combined, demonstrated by marked reductions in SND and mean arterial pressure (MAP) responses to heating in aged HF (A(HF)) compared with aged sham HF (A(SHAM)) rats, and in A(HF) compared with Y(HF) rats. Renal and splenic SND responses to hyperthermia (colonic temperature increased to 41.5°C) were determined in anesthetized Y(HF), young sham (Y(SHAM)), A(HF), and A(SHAM) Fischer rats. HF was induced by myocardial infarction and documented using echocardiographic, invasive, and postmortem measures. The severity of HF was similar in Y(HF) and A(HF) rats. SND responses to heating were attenuated in Y(HF) compared with Y(SHAM) rats, demonstrating an effect of HF on SND regulation in young rats. In contrast, A(HF) and A(SHAM) rats demonstrated similar SND responses to heating, suggesting a prominent influence of age on SND regulation in A(HF) rats. Splenic SND and MAP responses to heating were similar in Y(HF), A(HF), and A(SHAM) rats, indicating that the imposition of HF in young rats changes the regulatory status of these variables to one consistent with aged rats. These data suggest that the effect of HF on SND regulation to hyperthermia is age dependent.

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.

Cardiovascular images: constrictive pericarditis and tricavitary effusion in a dog with pericardial mesothelioma.

This report describes the transthoracic echocardiographic findings and computed tomography features of a 12-year-old West Highland white terrier with constrictive pericarditis (CP) secondary to pericardial mesothelioma. Although pericardial mesothelioma is well described in dogs, its association with CP in the canine population is not as widely reported. In this clinical case, a multidisciplinary imaging approach was helpful to identify anatomical and hemodynamic abnormalities that allowed for a diagnosis of CP.

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.

Survival characteristics and prognostic variables of dogs with mitral regurgitation attributable to myxomatous valve disease.

BACKGROUND: There are few studies evaluating the natural history and prognostic variables in chronic mitral valve disease (CMVI) in a heterogeneous population of dogs. OBJECTIVES: To estimate survival and prognostic value of clinical and echocardiographic variables in dogs with CMVI of varying severity. Five hundred and fifty-eight dogs belonging to 36 breeds were studied. METHODS: Dogs were included after clinical examination and echocardiography. Long-term outcome was assessed by telephone interview with the owner. RESULTS: The mean follow-up time was 22.7 +/- 13.6 months, and the median survival time was 19.5 +/- 13.2 months. In univariate analysis, age>8 years, syncope, HR>140 bpm, dyspnea, arrhythmias, class of heart failure (International Small Animal Cardiac Health Council), furosemide therapy, end-systolic volume-index (ESV-I)>30 mL/m(2), left atrial to aortic root ratio (LA/Ao)>1.7, E wave transmitral peak velocity (Emax)>1.2 m/s, and bilateral mitral valve leaflet engagement were associated with survival time when all causes of death were included. For the cardiac-related deaths, all the previous variables except dyspnea and EDV-I>100 mL/m(2) were significantly associated with survival time. Significant variables in multivariate analysis (all causes of death) were syncope, LA/Ao>1.7 m/s, and Emax>1.2 m/s. For cardiac-related death, the only significant variable was LA/Ao>1.7. CONCLUSIONS AND CLINICAL IMPORTANCE: Mild CMVI is a relatively benign condition in dogs. However, some clinical variables can identify dogs at a higher risk of death; these variables might be useful to identify individuals that need more frequent monitoring or therapeutic intervention.

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.

Migration of a Kirschner wire to the heart in a Yorkshire terrier.

A 12-year-old, male Yorkshire terrier was presented for acute pulmonary oedema. Thoracic radiographs showed a linear metallic foreign body within the cardiac silhouette. Echocardiogram showed a hyperechoic line extending through the left ventricle, the mitral valve, leading into the left atrium. A 4 cm long Kirschner wire was surgically removed by left fourth thoracotomy. The dog died two days after surgery for acute pulmonary oedema. Necropsy showed thrombi on the mitral leaflets that impeded their movement.

Anatomic regurgitant orifice area obtained using 3D-echocardiography as an indicator of severity of mitral regurgitation in dogs with myxomatous mitral valve disease.

OBJECTIVES: To determine feasibility and repeatability of measuring the anatomic regurgitant orifice area (AROA) using real-time three-dimensional transthoracic echocardiography (RT3DE) in dogs with myxomatous mitral valve disease (MMVD), and to investigate differences in the AROA of dogs with different disease severity and in different American College of Veterinary Internal Medicine (ACVIM) stages. ANIMALS: Sixty privately-owned dogs diagnosed with MMVD. METHODS: The echocardiographic database of our institution was retrospectively searched for dogs diagnosed with MMVD and RT3DE data set acquisition. Dogs were classified into mild, moderate, or severe MMVD according to a Mitral Regurgitation Severity Score (MRSS), and into stage B1, B2 or C according to ACVIM staging. The RT3DE data sets were imported into dedicated software and a short axis plane crossing the regurgitant orifice was used to measure the AROA. Feasibility, inter- and intra-observer variability of measuring the AROA was calculated. Differences in the AROA between dogs in different MRSS and ACVIM stages were investigated. RESULTS: The AROA was measurable in 60 data sets of 81 selected to be included in the study (74%). The inter- and intra-observer coefficients of variation were 26% and 21%, respectively. The AROA was significantly greater in dogs with a severe MRSS compared with dogs with mild MRSS (p=0.045). There was no difference between the AROA of dogs in different ACVIM clinical stages. CONCLUSIONS: Obtaining the AROA using RT3DE is feasible and might provide additional information to stratify mitral regurgitation severity in dogs with MMVD. Diagnostic and prognostic utility of the AROA deserves further investigation.

Presumptive partial atrial standstill secondary to atrial cardiomyopathy in a Greyhound.

Persistent atrial standstill is a rare arrhythmia in both human and veterinary patients. In recent decades, cases of partial atrial standstill have been recognized in humans. We describe a case of presumptive partial atrial standstill in a Greyhound, in which there was disparate left and right atrial electromechanical function and rapid progression to congestive heart failure over the span of fourteen weeks. An atrial cardiomyopathy characterized by severe, diffuse, fibrofatty replacement of the atrial myocardium was identified histologically.

Mitral valve morphology assessed by three-dimensional transthoracic echocardiography in healthy dogs and dogs with myxomatous mitral valve disease.

OBJECTIVE: To assess differences in morphology of the mitral valve (MV) between healthy dogs and dogs affected by myxomatous mitral valve disease (MMVD) using real-time transthoracic three-dimensional echocardiography (RT3DE). ANIMALS: Thirty-four were normal dogs and 79 dogs were affected by MMVD. METHODS: Real-time transthoracic three-dimensional echocardiography mitral datasets were digitally recorded and analyzed using dedicated software. The following variables were obtained and compared between healthy dogs and dogs with MMVD at different stages: antero-posterior annulus diameter, anterolateral-posteromedial annulus diameter, commissural diameter, annulus height, annulus circumference, annulus area, anterior leaflet length, anterior leaflet area, posterior leaflet length, posterior leaflet area, non-planar angle, annulus sphericity index, tenting height, tenting area, tenting volume, the ratio of annulus height and commissural diameter. RESULTS: Dogs with MMVD had a more circular MV annulus compared to healthy dogs as demonstrated by an increased annulus sphericity index (p=0.0179). Affected dogs had a less saddle-shaped MV manifest as a decreased annulus height to commissural width ratio (p=0.0004). Tenting height (p<0.0001), area (p<0.0001), and volume (p<0.0001) were less in affected dogs. CONCLUSIONS: Real-time transthoracic three-dimensional echocardiography analysis demonstrated that dogs affected by MMVD had a more circular and less saddle-shaped MV annulus, as well as reduced tenting height area and volume, compared to healthy dogs. Multiple variables differed between dogs at different stages of MMVD. Diagnostic and prognostic utility of these variables, and the significance of these changes in the pathogenesis and natural history of MMVD, require further attention.