Echocardiographic characteristics of dogs with pulmonary hypertension secondary to respiratory diseases.

BACKGROUND: Pulmonary hypertension (PH) secondary to respiratory disease is caused by pulmonary vascular remodeling and hypoxia. Severe PH can induce various clinical signs, including syncope and right-sided heart failure. HYPOTHESIS/OBJECTIVES: To investigate the echocardiographic characteristics in dogs with PH secondary to respiratory diseases. ANIMALS: Thirty-one dogs with respiratory diseases with or without PH and 15 healthy dogs. METHODS: Prospective cross-sectional study. Dogs were classified according to respiratory disease (obstructive airway/lung disease [OALD] or restrictive lung disease [RLD]) and PH-relevant signs. The association between echocardiographic variables and PH (classified by respiratory disease and PH-relevant signs) was investigated. RESULTS: Twenty-one dogs were diagnosed with PH; of these, 11 showed PH-related signs (OALD, n = 2; RLD, n = 9), 14 had right ventricular hypertrophy, and 19 had pulmonary arterial enlargement. Right ventricular dysfunction and dilatation were observed only in dogs with PH-related signs (n = 10). Left and right ventricular stroke volumes were significantly lower in dogs with PH (median [interquartile range]: 17.2 [12.4-20.8] and 16.8 [15.3-29.5] mL/m2 , respectively). Dogs with RLD had higher echocardiography-estimated pulmonary vascular resistance than those with OALD (median [interquartile range]: 3.1 [1.9-3.3] and 1.6 [1.3-2.2], respectively). CONCLUSIONS AND CLINICAL IMPORTANCE: Pulmonary arterial enlargement was the most common echocardiographic finding in dogs with PH secondary to respiratory diseases. Right ventricular dysfunction, dilatation, and decreased left and right ventricular stroke volume were significantly associated with the PH-related signs, indicating that comprehensive echocardiography is recommended in dogs with respiratory disease. Restricted lung disease might induce more severe PH than OALD.

Influence of heart rate on right ventricular function assessed by right heart catheterization and echocardiography in healthy anesthetized dogs.

BACKGROUND: Right ventricular (RV) functional assessment has received considerable attention in veterinary medicine since various diseases, such as cardiovascular, respiratory, endocrine, and neoplastic disease, may affect RV function. Heart rate (HR) is an important factor that can influence RV function through changes in loading condition and contractility. However, no study has yet evaluated the association between HR and RV function in the same individuals. This study aimed to evaluate the influence of elevated HR on RV function using right heart catheterization and echocardiography, and investigate the association between right heart catheterization and echocardiographic indices. RESULTS: Right atrial pacing was performed in eight dogs at 120, 140, 160, and 180 bpm. With an increase in HR, the RV systolic volume, RV diastolic volume, and stroke volume significantly decreased; however, the cardiac output, end-systolic elastance (Ees), and effective arterial elastance (Ea) significantly increased. Significant changes were not observed in RV pressure and Ees/Ea. The RV area normalized by body weight, RV fractional area change normalized by body weight (RV FACn), and tricuspid annular plane systolic excursion normalized by body weight (TAPSEn) significantly decreased with increased HR. Peak systolic myocardial velocity of the lateral tricuspid annulus (RV s'), RV strain, and RV strain rate of only the RV free wall analysis (RV-SrL3seg) showed no significant changes with the increase in HR; however, there was an increase in the RV strain rate of the RV global analysis (RV-SrL6seg). Multiple regression analysis revealed that HR, RV FACn, and RV- SrL6seg had significant associations with the Ees, and the TAPSEn and RV-SrL3seg with Ees/Ea. CONCLUSIONS: Decreased venous return and shortened relaxation time decreased the RV FAC, TAPSE, RV s', and RV strain, and might underestimate the RV function. Ees increased with the increase in HR, reflecting the myocardial force-frequency relation; as a result, RV-SrL6seg could be a useful tool for Ees estimation. Additionally, the RV-SrL3seg could detect RV performance, reflecting the balance between RV contractility and RV afterload.

Echocardiographic reference intervals for right ventricular indices, including 3-dimensional volume and 2-dimensional strain measurements in healthy dogs.

BACKGROUND: There is currently a lack of reference intervals (RIs) for the novel measures like 3-dimensional (3D) echocardiography or speckle-tracking strain for assessment of right ventricular (RV) structure and function. OBJECTIVES: To generate RIs and to determine the influence of age, heart rate, and body weight (BW) on various RV function indices using a dedicated RV software for 3D RV end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), global and free wall RV longitudinal strain (RVLS), end-diastolic area (RVEDA), end-systolic area (RVESA), fractional area change (FAC), tricuspid annular plane systolic excursion (TAPSE), and tissue Doppler imaging (TVI)-derived systolic myocardial velocity of the lateral tricuspid annulus (S'). ANIMALS: Healthy adult client-owned dogs (n = 211) of various breeds and ages. METHODS: Prospective study. Reference intervals were estimated as statistical prediction intervals using allometric scaling for BW-dependent variables. Right-sided (upper limit) or left-sided (lower limit) 95% RIs were calculated for every variable. Inter- and intraobserver variability was determined. RESULTS: Most variables showed clinically acceptable repeatability with coefficient of variation less than 10. Upper or respectively lower RI after allometric scaling to normalize for different BWs were: EDVn ≤ 2.5 mL/kg0.942 , ESVn ≤ 1.2 mL/kg0.962 , TAPSEn ≥ 4.5 mm0.285 , RVEDAn ≤ 1.4 cm2 /kg0.665 , RVESAn ≤ 0.8 cm2 /kg0.695 , and TVI S'n ≥ 5.6 cm/s/kg0.186 . The calculated limits for indices without allometric normalization were: EF > 42.1%, FAC > 30.0%, free wall RVLS < -20.8%, and global RVLS < -18.3%. CONCLUSIONS: Echocardiographic RIs for RV structure and function are provided.

Investigation of the influence of manual ventilation-controlled respiration on right ventricular pressure-volume loops and echocardiographic variables in healthy anesthetized dogs.

OBJECTIVE: To evaluate the influence of manual ventilation-controlled respiration on right ventricular (RV) pressure-volume loop-derived and echocardiographic variables in dogs. ANIMALS: 8 healthy, anesthetized Beagles. PROCEDURES: In a prospective experimental study, pressure-volume catheters were percutaneously inserted into the right ventricle of each dog, and manual ventilation was performed; RV pressure-volume loop (hemodynamic) data and conventional echocardiographic variables were assessed. Two-dimensional speckle tracking echocardiography-derived RV strain (RVS) and RV systolic strain rate (RVSR) were obtained with RV free wall-only analysis (free wall) and RV global analysis (RVGA; interventricular septum). Variables were compared between end-inspiratory and end-expiratory phases of respiration by statistical methods. Multiple regression analysis was used to assess associations between selected hemodynamic and echocardiographic variables. RESULTS: The RV pressure significantly increased, and RV volume, stroke volume, tricuspid annular plane systolic excursion, RV fractional area change, peak myocardial systolic velocity of the lateral tricuspid annulus, and RV free wall only-assessed RVS and RVSR significantly decreased in the inspiratory phase, compared with the expiratory phase. There were no significant differences in end-systolic elastance or RVGA-assessed RVS or RVSR between respiratory phases. The RVGA-assessed RVSR was significantly associated with stroke volume and end-systolic elastance. CONCLUSIONS AND CLINICAL RELEVANCE: Specific RV echocardiographic variables were significantly affected by respiration. In contrast, RVS and RVSR determined with RVGA were not affected by respiration and were associated with hemodynamic indicators of RV contractility.

Utility of tricuspid annular plane systolic excursion normalized by right ventricular size indices in dogs with postcapillary pulmonary hypertension.

BACKGROUND: Tricuspid annular plane systolic excursion (TAPSE) is a common right ventricular (RV) function indicator. However, TAPSE was not decreased in dogs with myxomatous mitral valve disease (MMVD) and postcapillary pulmonary hypertension (PH) because of its load, angle, and body weight dependency, and TAPSE was considered a preload-dependent index. OBJECTIVES: To evaluate the utility of TAPSE normalized by RV size in dogs with postcapillary PH. ANIMALS: Twenty healthy dogs and 71 MMVD dogs with or without PH. METHODS: In this prospective observational study, end-diastolic RV internal dimension (RVIDd), end-diastolic and end-systolic RV area, and end-diastolic RV wall thickness were measured as RV size indices. The TAPSE was measured using B-mode and M-mode methods. Normalized TAPSE was calculated by dividing TAPSE by each RV size index. The RV strain was obtained as the detailed RV function using 2-dimensional speckle tracking echocardiography. All indices were compared among the PH severity groups and in the presence of right-sided congestive heart failure (R-CHF). RESULTS: Although nonnormalized TAPSE was higher with PH severity progression, each normalized TAPSE showed a significant decrease in the severe PH group (P < .05). The TAPSEB-mode /RVIDd ratio had high area under the curve to predict R-CHF and had moderate correlation with RV strain (P < .05). The TAPSEB-mode /RVIDd and left atrial-to-aortic diameter ratios were independent predictors for R-CHF. CONCLUSIONS AND CLINICAL IMPORTANCE: Normalized TAPSE could reflect RV systolic dysfunction in dogs with severe PH, which could not be detected by nonnormalized TAPSE. The TAPSEB-mode /RVIDd ratio might predict R-CHF with high sensitivity and reproducibility.

Acute effects of intravenous pimobendan administration in dog models of chronic precapillary pulmonary hypertension.

INTRODUCTION: Pulmonary hypertension (PH) is a progressive and potentially life-threatening disease. Several drugs are used for the treatment of dogs with precapillary PH. Pimobendan is an inotropic drug with phosphodiesterase 3 inhibitory and calcium-sensitizing effects. Pimobendan administration improved right ventricular (RV) function and lowered pulmonary arterial pressure in some human patients with precapillary PH. However, the efficacy of pimobendan in dogs with precapillary PH is unknown. ANIMALS, MATERIAL, AND METHODS: An implantable port device was percutaneously placed in the cranial vena cava of five laboratory beagles. Chronic embolic precapillary PH was induced via the repeated injection of microspheres every 1-2 days. Microsphere injection was continued until systolic pulmonary arterial pressure reached 50 mmHg. Right heart catheterization and echocardiography were performed at baseline and after injections of placebo and pimobendan (0.15 mg/kg). RESULTS: Repeated injections of microspheres caused an increase in pulmonary vascular resistance, a decrease in stroke volume, RV dilation, left ventricular (LV) and RV dysfunction, and RV dyssynchrony as assessed using echocardiography. Compared with placebo, pimobendan improved LV and RV function based on the LV Tei index from 0.48 to 0.38 (p=0.002) and the RV Tei index from 0.76 to 0.61 (p=0.008), as well as the stroke volume index from 29.4 to 36.7 ml/m2 (p=0.012), respectively. CONCLUSIONS: In dog models of chronic PH, intravenous pimobendan effectively improved RV and LV function and increased stroke volume. However, pimobendan administration did not decrease pulmonary arterial pressure or produce hypotension.

Survival characteristics and prognostic importance of echocardiographic measurements of right heart size and function in dogs with pulmonary hypertension.

BACKGROUND: The clinical relevance of echocardiographic measurements of right heart size and function in dogs with pulmonary hypertension (PH) is unknown. OBJECTIVE: To determine if echocardiographic measurements of right heart size and right ventricular (RV) function are associated with survival times in dogs with PH. ANIMALS: Eighty-two client-owned dogs. METHODS: Retrospective study where data from medical records and baseline echocardiographic examinations were collected and measured in a standardized manner. Owners or primary veterinarians were contacted for outcome data. RESULTS: Enlargement of the right atrium (88%), RV (69%), and pulmonary artery (72%) was common. One-third of the cases had reduced RV function quantified by two-dimensional echocardiography-derived tricuspid annular plane systolic excursion (TAPSE). Decreased TAPSE was significantly (P = .008) more common in dogs with PH not secondary to left heart disease (LHD; 43%) compared to dogs with PH secondary to LHD (14%) but median survival times (182, 95% confidence interval [CI] = 39-309 versus 298, 95% CI = 85-314 days, respectively) were not significantly different (P = .78). Right atrial area (hazard ratio [HR] = 2.72, 95% CI = 1.58-4.70), TAPSE < 3.23 mm/kg0.284 (HR = 2.19, 95% CI = 1.28-3.74), and right heart failure (HR = 2.05, 95% CI = 1.18-3.57) were independently associated with shorter survival time (P ≤ .04). CONCLUSIONS AND CLINICAL IMPORTANCE: Right atrial area, RV function (TAPSE < 3.23 mm/kg0.284 ), and right heart failure offer clinically relevant prognostic information in dogs with PH. Results support the quantitative assessment of right heart size and function in dogs with PH.

Echocardiographic assessment of right heart size and function in dogs with pulmonary valve stenosis.

INTRODUCTION/OBJECTIVES: We sought to determine the prevalence and clinical significance of right heart remodeling and right ventricular (RV) dysfunction in dogs with pulmonary valve stenosis (PS). We also sought to evaluate repeatability of several measurements of severity of PS, right heart size, and RV function in dogs with PS. ANIMALS, MATERIALS AND METHODS: Several indices of right atrial (RA) size and RV size and function were prospectively evaluated in 48 dogs with PS. Regression analysis was used to determine if indices of right heart size and function were independently associated with maximum transpulmonary pressure gradient (max PG) and adverse clinical findings (exercise intolerance, syncope, or right heart failure). Eight dogs underwent a second echocardiogram performed by the same operator to assess repeatability of the echocardiographic indices, which was quantified by coefficient of variation (CV) and repeatability coefficient. RESULTS: Increased RA size (81%), increased RV wall thickness (83%), and decreased tricuspid annular plane systolic excursion (TAPSE [81%]) were common. Right atrial size, end-diastolic RV area, and RV wall thickness were independently associated with max PG. Decreased TAPSE was independently associated with adverse clinical findings. All indices except RA area (18.6%) and RV systolic velocity (20.7%) had CVs <15%. Repeatability coefficients are available to help distinguish a true change versus measurement variability during serially obtained exams. CONCLUSIONS: Right heart remodeling and RV dysfunction are common in dogs with PS and are associated with echocardiographic and clinical severity. Results support the quantitative assessment of right heart size and function in dogs with PS.

Change in right ventricular function in an American cocker spaniel with acute pulmonary thromboembolism.

A 12-year-old neutered female American cocker spaniel weighing 9.9 kg was presented for evaluation with a 2-day history of dyspnea and anorexia. Echocardiography revealed severe pulmonary hypertension (estimated systolic pulmonary arterial pressure, 93.4 mmHg) with right heart enlargement, pulmonary arterial dilation, and right ventricular dysfunction. The dilation of left heart and congenital cardiac shunt were not observed. Pulmonary thromboembolism (PTE) was confirmed by computed tomographic angiography. After treatment with antiplatelet and anticoagulant, the clinical sign and the echocardiographic abnormality of right heart were improved. These echocardiographic findings are not specific for PTE, but it can be useful as a rule-in test for PTE when other causes of pulmonary hypertension are excluded and a monitor of therapeutic efficacy.

Right ventricular function and dyssynchrony measured by echocardiography in dogs with precapillary pulmonary hypertension.

INTRODUCTION: Assessment of the right ventricular (RV) function by echocardiography is important in dogs with pulmonary hypertension (PH). Few reports are available on RV function and dyssynchrony in dogs, especially in the context of precapillary PH. ANIMALS: The study included 79 client-owned dogs: 25 dogs with precapillary PH and 54 control dogs. METHODS: Dogs with precapillary PH were prospectively enrolled between December 2013 and February 2017. The echocardiographic indices of RV function, including RV strain and the dyssynchrony index by speckle-tracking echocardiography, were measured. Multivariate analysis was used to determine independent predictors of the RV dyssynchrony index. RESULTS: Dogs with precapillary PH showed RV dilation, hypertrophy and right atrial dilation. Impaired echocardiographic indices of RV function, including RV strain, were observed. In addition, RV dyssynchrony occurred in dogs with precapillary PH. Multivariate analysis revealed that tricuspid regurgitation velocity and RV dilation were independent predictors of the RV dyssynchrony index. CONCLUSIONS: Echocardiographic RV function indices are impaired in dogs with precapillary PH. In addition, RV dilation and elevated systolic pulmonary arterial pressure estimated by echocardiography are associated with RV dyssynchrony.

Effect of acute volume overload on echocardiographic indices of right ventricular function and dyssynchrony assessed by use of speckle tracking echocardiography in healthy dogs.

OBJECTIVE To determine the relationship between acute volume overload and echocardiographic indices of right ventricular (RV) function and dyssynchrony in healthy dogs. ANIMALS 7 healthy Beagles. PROCEDURES Right heart catheterization and echocardiography were performed in 7 healthy anesthetized Beagles at baseline and after induction of volume overload. Volume overload was induced by IV infusion of lactated Ringer solution (150 mL/kg/h for 90 minutes). Echocardiographic indices of RV function, including peak velocity of systolic tricuspid annular motion, tricuspid annulus plane systolic excursion, fractional area change, RV Tei index, RV longitudinal strain (RVLS), and systolic RV longitudinal strain rate (RVLSR), were obtained by use of speckle tracking echocardiography (STE). In addition, SD of the systolic shortening time of the right ventricle for the 6 segments (RV-SD6) was determined with STE. RESULTS Volume overload significantly increased the RV end-diastolic pressure, compared with the baseline value. Echocardiographic indices of RV function, except for septal RVLSR, were significantly enhanced by volume overload. In contrast, RV-SD6 did not change with volume overload. Although echocardiographic indices of RV function, except for septal RVLSR, were correlated with RV end-diastolic pressure, RV-SD6 was not correlated. CONCLUSIONS AND CLINICAL RELEVANCE Echocardiographic indices of RV function, including RVLS and RVLSR, were affected by acute short-term volume overload. Therefore, results for assessment of RV function by use of STE in dogs with clinical conditions associated with right-sided chronic volume overload, such as tricuspid and pulmonic regurgitation, should be interpreted with caution.

Right ventricular outflow tract fractional shortening: an echocardiographic index of right ventricular systolic function in dogs with pulmonary hypertension.

OBJECTIVES: To create reference intervals for right ventricular outflow tract fractional shortening (RVOT-FS) in healthy dogs and examine diagnostic performance of this index in dogs with pulmonary hypertension (PH). In addition, we examine the impact of myxomatous mitral valve disease (MMVD) without PH on RVOT-FS. ANIMALS, MATERIALS AND METHODS: The study population included 52 healthy adult dogs, 51 dogs with MMVD but without PH, and 51 dogs with PH. This is a prospective study. Complete echocardiographic evaluations were performed on all dogs. Right ventricular outflow tract fractional shortening was obtained by two-dimensional guided M-mode recordings from the right parasternal short axis view. Right ventricular outflow tract fractional shortening was evaluated in healthy dogs of various breeds, and reference intervals were generated. We examined the effect of PH on RVOT-FS with receiver operating characteristic analysis and evaluated the effect of MMVD on RVOT-FS in dogs without PH. Intraobserver and interobserver reproducibility was calculated. RESULTS: Healthy dogs had RVOT-FS > 44%. Right ventricular outflow tract fractional shortening values of healthy dogs and MMVD dogs without PH did not differ (p=0.84). In dogs with PH, RVOT-FS decreased with increasing tricuspid regurgitation velocity (p<0.0001). Pimobendan use in dogs with PH increased RVOT-FS as PH worsened. Right ventricular outflow tract fractional shortening was acquired with clinically acceptable intraobserver and interobserver reproducibility. CONCLUSIONS: Right ventricular outflow tract fractional shortening is a novel, easy applicable, and repeatable index for evaluating RV systolic function. Studies comparing this index with common echocardiographic indices used to assess RV function in dogs are needed.

Arrhythmogenic right ventricular cardiomyopathy in Boxer dogs: the diagnosis as a link to the human disease.

BACKGROUND: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a myocardial disease with an increased risk for ventricular arrhythmias. The condition, which occurs in Boxer dogs, shares phenotypic features with the human disease arrhythmogenic cardiomyopathy (ACM) suggesting its potential as a natural animal model. However, there are currently no universally accepted clinical criteria to diagnose ARVC in Boxer dogs. We aimed to identify diagnostic criteria for ARVC in Boxer dogs defining a more uniform and consistent phenotype. METHODS AND RESULTS: Clinical records from 264 Boxer dogs from a referral veterinary hospital were retrospectively analysed. ARVC was initially diagnosed according to the number of ventricular premature complexes (VPCs) in the 24-hour-Holter-ECG in the absence of another obvious cause. Dogs diagnosed this way had more VPCs, polymorphic VPCs, couplets, triplets, VTs and R-on-T-phenomenon and syncope, decreased right ventricular function and dilatation in comparison to a control group of all other Boxer dogs seen by the Cardiology Service over the same period. Presence of couplets and R-on-T-phenomenon on a 24h-ECG were identified as independent predictors of the diagnosis. A diagnosis based on ≥100 VPCs in 24 hours, presence of couplets and R-on-T phenomenon on a 24h-ECG was able to select Boxer dogs with a phenotype most similar to human ACM. CONCLUSION: We suggest the diagnosis of ARVC in Boxer dogs requires two out of the three following criteria: presence of ≥ 100 VPCs, presence of couplets or R-on-T-phenomenon on a 24 h-ECG. This results in a uniform phenotype similar to that described in human ACM and may result in the adoption of the term ACM for this analogous condition in Boxer dogs.

Pulmonary hypertension and right ventricular failure in broiler chickens reared at high altitude is affected by dietary source of n-6 and n-3 fatty acids.

The present study evaluated the development of pulmonary hypertension and right ventricular failure in broiler chickens reared at high altitude (2100 m) as affected by dietary intake of n-3 and n-6 fatty acid sources. Flax oil and soy oil were used as sources of n-3 and n-6 fatty acids, respectively, either with or without α-tocopheryl acetate. A total of 192 day-old broiler chicks (Ross 308) were used in a completely randomized design using isoenergetic and isonitrogenous experimental diets. Results showed that dietary flax oil significantly (p < 0.05) improved feed conversion ratio during 21-42 days of age. However, body weight gain did not significantly differ among the experimental groups in entire trial. Birds received flax oil had significantly higher serum concentration of nitric oxide (NO) but they had lower serum concentration of malondialdehyde when compared with their counterparts fed with soy oil. Liver and abdominal fat weights were significantly (p < 0.05) reduced by substitution of soy oil for flax oil. The right-to-total ventricle weight ratio (RV/TV) and mortality from pulmonary arterial hypertension (PAH) were significantly (p < 0.05) decreased in birds that received flax oil. In conclusion, n-3 fatty acids could significantly reduce RV:TV and PAH mortality in birds by increasing circulatory level of NO and suppressing hepatic lipogenesis.

Tricuspid annular plane systolic excursion (TAPSE) in dogs: reference values and impact of pulmonary hypertension.

BACKGROUND: The impact of pulmonary hypertension (PH) on right ventricular systolic function is difficult to assess. Tricuspid annular plane systolic excursion (TAPSE) is an echocardiographic measurement of right ventricular systolic function and a strong predictor of outcome in human PH patients. HYPOTHESIS/OBJECTIVES: Determine a reference range for TAPSE in healthy dogs, and quantify TAPSE in dogs with PH. It is hypothesized that TAPSE is lower in dogs with PH compared with a reference group, and decreases as PH worsens. ANIMALS: Fifty normal dogs and 30 dogs with PH. METHODS: TAPSE was measured by 2-dimensional echocardiography-guided M-mode from the left apical 4-chamber view. Peak systolic tricuspid valve regurgitation jet velocity was measured by continuous-wave Doppler to estimate right ventricular-to-right atrial pressure gradient. PH was subjectively classified as mild, moderate, and severe. RESULTS: There was a curvilinear correlation between TAPSE and body weight. The upper and lower limits of the 95% reference interval were determined by quantile regression. Interobserver and intraobserver agreement was adequate with a coefficient of variation <10%. There were significant differences when comparing dogs with PH and the healthy group, as well as between the PH subgroups (P < .01), except between dogs with mild and moderate PH (P = .99). Only dogs in the severe PH group had TAPSE values that were mostly below the lower limit of the reference interval. CONCLUSIONS AND CLINICAL IMPORTANCE: TAPSE is easily obtainable with acceptable inter and intraobserver agreement. TAPSE is decreased in PH and below the reference interval in most dogs with severe PH.

Uhl's anomaly in a domestic shorthair cat.

A 2-year-old, neutered male, domestic shorthair cat was presented for investigation of dyspnea and episodic weakness. Clinical and ultrasonographic features were consistent with right ventricular cardiomyopathy. Pathological findings documented Uhl's anomaly. Although rare, Uhl's anomaly should be a differential diagnosis for cats with right-sided congestive heart failure. In particular, Uhl's anomaly could be misdiagnosed as arrhythmogenic right ventricular cardiomyopathy due to the similarity of clinical and echocardiographic findings.

Outflow tract segmental arrhythmogenic right ventricular cardiomyopathy in an English Bulldog.

A 5-year-old English Bulldog was presented for acute onset of syncope and fatigue caused by sustained ventricular tachycardia with left bundle block morphology and inferior axis. This arrhythmia had the electrocardiographic features of a ventricular tachycardia arising from the right ventricular outflow tract (RVOT), as described in an experimental canine model and in people. Since a RVOT aneurysm was identified by echocardiography, a segmental form of arrhythmogenic right ventricular cardiomyopathy (ARVC) was suspected. Gross examination of the heart confirmed the bulging of the RVOT and histological examination of the ventricular myocardium revealed segmental involvement of the RVOT with transmural fibro-fatty degeneration. To the authors' knowledge, this is the first reported case of AVRC in an English Bulldog and the first example of segmental AVRC described in the dog.

Arrhythmogenic right ventricular cardiomyopathy associated with severe left ventricular involvement in a cat.

An 8-year-old, 4 kg, intact female, domestic shorthaired cat was referred for tachypnea and pleural effusion. A 24-h Holter recording showed numerous polymorphic ventricular premature complexes with left and right bundle branch block morphology. Echocardiographic examination revealed right atrial and ventricular dilation. The right ventricular free wall was thin and aneurysmal. The cat died 10 days after initiation of antiarrhythmic therapy. Gross and histopathological findings were consistent with arrhythmogenic right ventricular cardiomyopathy (ARVC) associated with severe left ventricular involvement.

An index of myocardial performance applied to the right ventricle of Boxers with arrhythmogenic right ventricular cardiomyopathy.

OBJECTIVE: To use an index of myocardial performance (IMP) to assess right ventricular function in Boxers with arrhythmogenic right ventricular cardiomyopathy (ARVC). ANIMALS: 22 Boxers (12 Boxers with ARVC diagnosed by the detection of > or = 1,000 ventricular premature complexes (VPCs)/24 h and 10 Boxers with < or = 5 VPCs/24 h (control dogs). Procedures-Pulsed-wave Doppler recordings of tricuspid inflow and pulmonic outflow were acquired. Preejection period (PEP), ejection time (ET), PEP/ET, and IMP were determined for the right ventricle by use of data from separate cardiac cycles. RESULTS: A significant difference was not identified between groups for right ventricular PEP, right ventricular ET, right ventricular PEP/ET, or right ventricular IMP. Right ventricular IMP was not significantly correlated with VPC number (r = 0.21) or VPC grade (r = -0.3) in Boxers with ARVC. CONCLUSIONS AND CLINICAL RELEVANCE: Boxers with ARVC did not have significant differences in right ventricular IMP, compared with results for control Boxers. This would suggest that right ventricular dysfunction does not develop in Boxers with ARVC or that a more severe phenotype of the disease may be necessary for detection of dysfunction. Additional studies that use more sensitive techniques to evaluate myocardial function may be warranted.