Left ventricular radial colour and longitudinal pulsed-wave tissue Doppler echocardiography in 39 healthy domestic pet rabbits

This paper reports radial colour and longitudinal mitral annulus pulsed-wave tissue Doppler findings in a large cohort of healthy, adult pet rabbits. Thirty-nine rabbits (22 Dwarf Lops, 14 French Lops and three Alaskans) underwent conscious echocardiography. The median age of the rabbits was 22 months and the median weight was 2.8 kg (Dwarf Lop 2.4 kg/French Lop 6.0 kg). Adequate radial colour and longitudinal pulsed-wave tissue Doppler traces were obtained in 100% and 85% of cases, respectively. Most systolic tissue Doppler parameters were significantly higher in French Lops than in Dwarf Lops. Separation of mitral inflow diastolic waves was present in 40% of cases using conventional spectral Doppler and in >60% of cases using pulsed-wave tissue Doppler which could be beneficial when evaluating diastolic function in rabbits. This study can be used as a reference for normal echocardiographic tissue Doppler values for adult rabbits undergoing conscious echocardiography in clinical practice.     

Comparison of the Repeatability of Echocardiographic Measurements from Different Modes and Views in Horses of Various Breeds and Sizes

The objective of this study was to compare the repeatability of echocardiographic measurements obtained from different echocardiographic modes and views in healthy adult equids of various sizes, breeds, and thorax shapes. Ten equids (body weight: 120–662 kg; age: 1–26 years) from various breeds, free of cardiac disease, were used in this study. Each animal was submitted to a standardized echocardiographic and Doppler protocol 3 times at 1 day interval. This protocol included the measurements of left and right ventricular, aortic, pulmonary, and left atrial parameters obtained from different views using the bidimensional (2D) or the motion (M) modes, and the measurement of several parameters of blood flow obtained from the pulsed wave Doppler mode. Repeatability of each measurement was estimated on the basis of the residual variance using a linear model and the coefficient of variation of repeated measurements. A two by two comparison of the repeatability of measurements performed in different views was performed using the residual variances in a variance ratio F test. Results showed that repeatability of echocardiographic or Doppler measurements in equids of various sizes, breeds, and thorax shapes are comparable to previously reported results in thoroughbred and standardbred horses. Left ventricular morphologic parameters showed a good repeatability in the classic M-mode right parasternal short axis view at the level of the chordae tendineae, but the 2D-mode right parasternal long axis four-chamber view appeared to offer an interesting alternative measurement. This latter view also allowed obtaining the most repeatable measurement of right ventricular internal diameter. The left atrial diameter was maximal and most repeatable in the 2D-mode left parasternal long axis four-chamber angled view, and the repeatability of the aortic diameter was best in the 2D-mode right parasternal long axis five-chamber view. Finally, aortic systolic time intervals were more repeatable when measured from the Doppler mode as compared with the M-mode. In conclusion, repeatability of echocardiographic measurements in horses could be optimized after the following protocol: (1) M-mode right parasternal short axis view at the level of chordae tendineae to measure left ventricular morphologic parameters, and 2D-mode right parasternal long axis four-chamber as an alternative view; (2) 2D-mode right parasternal long axis five-chambers to measure the aortic diameter; (3) 2D-mode left parasternal long axis four-chambers angled view to measure the left atrial diameter.     

An echocardiographic study of healthy Border Collies with normal reference ranges for the breed

ObjectivesThe objectives of this study were to obtain standard echocardiographic measurements from healthy Border Collies and to compare these measurements to those previously reported for a general population of dogs.AnimalsStandard echocardiographic data were obtained from twenty apparently healthy Border Collie dogs. These data (n = 20) were compared to data obtained from a general population of healthy dogs (n = 69).MethodsBorder Collies were deemed healthy based on normal history, physical examination, complete blood count, serum biochemical profile, electrocardiogram, and blood pressure, with no evidence of congenital or acquired heart disease on echocardiographic examination. Standard two dimensional, M-mode, and Doppler echocardiographic measurements were obtained and normal ranges determined. The data were compared to data previously obtained at our hospital from a general population of normal dogs.ResultsTwo dimensional, M-mode, and Doppler reference ranges for healthy Border Collies are presented in tabular form. Comparison of the weight adjusted M-mode echocardiographic means from Border Collies to those from the general population of dogs showed Border Collies to have larger left ventricular systolic and diastolic dimensions, smaller interventricular septal thickness, and lower fractional shortening.ConclusionsThere are differences in some echocardiographic parameters between healthy Border Collies and the general dog population, and the echocardiographic reference ranges provided in this study should be used as breed specific reference values for Border Collies.     

R-R interval variations influence the degree of mitral regurgitation in dogs with myxomatous mitral valve disease

Mitral regurgitation (MR) due to myxomatous mitral valve disease (MMVD) is a frequent finding in Cavalier King Charles Spaniels (CKCSs). Sinus arrhythmia and atrial premature complexes leading to R-R interval variations occur in dogs. The aim of the study was to evaluate whether the duration of the R-R interval immediately influences the degree of MR assessed by echocardiography in dogs. Clinical examination including echocardiography was performed in 103 privately-owned dogs: 16 control Beagles, 70 CKCSs with different degree of MR and 17 dogs of different breeds with clinical signs of congestive heart failure due to MMVD. The severity of MR was evaluated in apical four-chamber view using colour Doppler flow mapping (maximum % of the left atrium area) and colour Doppler M-mode (duration in ms). The influence of the ratio between present and preceding R-R interval on MR severity was evaluated in 10 consecutive R-R intervals using a linear mixed model for repeated measurements.MR severity was increased when a short R-R interval was followed by a long R-R interval in CKCSs with different degrees of MR (P < 0.005 when adjusted for multiple testing). The relationship was not significant in control dogs with minimal MR and in dogs with severe MR and clinical signs of heart failure. In conclusion, MR severity increases in long R-R intervals when these follow a short R-R interval in CKCSs with different degrees of MR due to asymptomatic MMVD. Thus, R-R interval variations may affect the echocardiographic grading of MR in CKCSs.     

Cardiovascular variables in eventing and endurance horses over a season

IntroductionThe objectives of this study were to describe the changes in clinical cardiovascular examination variables over a competition season in groups of competitive eventing and endurance horses and to compare these findings to non-competitive controls of the same breeds.AnimalsThis study included two eventing horses, 11 endurance horses, and 13 eventing and seven endurance control breed-matched horses.Materials and methodsCardiovascular examinations were performed before starting the competition season, in the middle and at the peak/end of the competition season. Examinations included auscultation of the heart; M-mode echocardiographic measurements and calculated values; left atrial, pulmonary artery, and aortic diameters; color flow Doppler; exercise electrocardiograms (ECG) measuring peak heart rates and quantifying premature complexes; and 24-h continuous ECGs quantifying premature complexes per hour.ResultsAuscultation, echocardiograms, arrhythmias during exercise, and 24-h continuous ECGs did not change significantly throughout the season (p > 0.05 for all variables).ConclusionCardiovascular examination variables of eventing and endurance horses throughout a competition season are reported here for the first time. Although the present study did not reveal significant changes, data should be interpreted carefully as only a small number of horses were examined.     

M-mode and Doppler echocardiographic reference values for male New Zealand white rabbits

OBJECTIVE: To determine M-mode and Doppler echocardiographic reference values in healthy New Zealand white rabbits. ANIMALS: 52 healthy male rabbits. PROCEDURES: The rabbits were anesthetized and M-mode measurements of the left ventricle, left atrium, and aorta and Doppler measurements of pulmonary and aortic outflow and mitral inflow were recorded. RESULTS: Mean +/- SD heart rate during echocardiographic examination was 155 +/- 29 beats/min. Mean +/- SD measurements in diastole and systole for the interventricular septum thickness, left ventricular internal diameter, and left ventricular free wall thickness were 2.03 +/- 0.37 mm and 3.05 +/- 0.45 mm; 14.37 +/- 1.49 mm and 10.25 +/- 1.22 mm; and 2.16 +/- 0.25 and 3.48 +/- 0.55 mm, respectively. Mean +/- SD left atrial-to-aortic diameter ratio was 1.17 +/- 0.14, and mean +/- SD mitral valve E-point-to-septal separation interval was 1.71 +/- 0.29 mm. Mean +/- SD for fractional shortening and ejection fraction were 30.13 +/- 2.98% and 61.29 +/- 4.66%, respectively. Mean +/- SD maximal aortic and pulmonary artery outflow velocities were 0.85 +/- 0.11 m/s and 0.59 +/- 0.10 m/s, respectively, and the peak E-to-peak A wave velocity ratio of the mitral valve was 2.19 +/- 0.46. CONCLUSIONS AND CLINICAL RELEVANCE: Results provide echocardiographic reference values for young adult male New Zealand white rabbits anesthetized with ketamine and medetomidine. Values obtained from unanesthetized rabbits, rabbits sedated with other agents, or rabbits of different size may differ from those reported here.     

Clinical, echocardiographic, and Doppler imaging characteristics of mitral valve stenosis in two dogs.

Mitral stenosis was diagnosed noninvasively by echocardiography and Doppler imaging in 2 Bull Terriers. Two-dimensional echocardiography revealed severe atrial and moderate left ventricular dilatation; severely reduced mitral valve opening excursion; doming of the cranial mitral valve leaflet into the left ventricle during diastole; thickened, nodular cranial mitral valve leaflets; and reduced mitral valve orifice. M-mode echocardiographic findings additionally indicated greatly diminished mitral valve E to F slope and abnormal caudal mitral valve leaflet motion. Color flow Doppler imaging revealed bright bursts of color with aliasing originating from the stenotic mitral valve orifice, extending into the left atrium during systole, and into the left atrium during diastole. Spectral Doppler recordings revealed transvalvular mitral valve gradients and prolonged pressure half-times. Necropsy performed on 1 dog revealed extremely thickened, nodular, and stiff mitral valves with short, thickened, and fused chordae tendineae. The diagnosis of mitral valve stenosis was easily facilitated with diagnostic ultrasonography.     

Two-dimensional and M-mode echocardiographic measurements of cardiac dimensions in healthy standardbred trotters

The aim of the study was to establish normal echocardiographic values of healthy Standardbred trotters not published previously. Twenty-three clinically normal horses weighing between 350 and 490 kg were examined in the same manner: first a thorough physical and then detailed echocardiographic examination were performed. Standardised two-dimensional (2D) and guided M-mode echocardiographic imaging techniques were used to measure interventricular septal thickness (IVS), left ventricular internal diameter (LVID), left ventricular wall thickness (LVW), left atrial internal diameter (LAID) in end-systole (s) and end-diastole (d) and aortic diameter (AOD) in end-diastole. Mean, range and standard deviation of the different parameters were calculated. The mean values (in centimetres) were as follow (2D/M-mode): IVSs: 4.6/4.7; IVSd: 3.1/3.0; LVIDs: 7.0/7.0; LVIDd: 10.7/10.7; LVWs: 3.9/3.9; LVWd: 2.7/2.7; LAIDs: 10.4/-; LAIDd: 11.3/-; AODd: 7.2/-. Results of two-dimensional and M-mode measurements were compared to each other and to normal values obtained from other breeds.     

Feasibility and clinical utility of transvenous intracardiac echocardiography in conscious,sedated horses

Introduction/objectivesIntracardiac echocardiography (ICE) is a method of obtaining echocardiographic images with a steerable ultrasound catheter placed within the heart via a venous or arterial approach. The objectives of this study were to assess the feasibility of a 5–10 MHz, 8 French, 90 cm ICE catheter to evaluate cardiac structures and function in standing, sedated horses, and describe standard views in this species.AnimalsTen apparently healthy horses weighing 458.1–618.2 kg from a university teaching herd.Materials and methodsEach horse had a physical examination, transthoracic echocardiography, and ICE performed through a 10 French introducer percutaneously placed in the right jugular vein in the proximal third of the neck with continuous ECG monitoring using telemetry.ResultsThree intracardiac echocardiography positions (cranial right atrium, mid right atrium, and right ventricle) with seven views were described with the associated 2D, pulse wave Doppler, continuous wave Doppler, color Doppler, and M-mode image acquisition standardized by referencing the intracardiac positions and common landmarks. The positions were confirmed with simultaneous transthoracic echocardiography. The procedure was well tolerated with only mild, occasional ventricular, and supraventricular arrhythmias that resolved with intracardiac echocardiography catheter repositioning.ConclusionsIntracardiac echocardiography is feasible, safe, and allows for the acquisition of diagnostic images in conscious, sedated horses.     

First Description of Partial Atrioventricular Septal Defect in a Rabbit

Congenital heart diseases have rarely been described in rabbits. The purpose of the present case report is to describe the clinical, radiographic, echocardiographic, and pathological features of a partial atrioventricular septal defect in a pet rabbit. A 3-month-old, 380-g male vaccinated pet rabbit was presented for decreased activity, increased respiratory rate and effort, anorexia, and decreased fecal output of 2 days duration. Total body radiographic images revealed severe cardiomegaly associated with enlarged caudal pulmonary vessels and increased interstitial to alveolar lung pattern. Echocardiographic imaging showed evidence of distended heart chambers, abnormal flow through the atria, and mitral valve regurgitation. The rabbit was treated with furosemide and an angiotensin-converting enzyme inhibitor but rapidly deteriorated and died. Necropsy confirmed the dilation of both ventricles and the presence of a partial atrioventricular septal defect associated with an ostium primum atrial septal defect just over the tricuspid valve and the mitral valve.     

Echocardiographic parameters and indices in 23 healthy Maltese dogs

BackgroundEchocardiography is a primary tool used by veterinarians to evaluate heart diseases. In recent years, various studies have targeted standard echocardiographic values for different breeds. Reference data are currently lacking in Maltese dogs and it is important to fill this gap as this breed is predisposed to myxomatous mitral valve disease, which is a volume overload disease.ObjectivesTo establish the normal echocardiographic parameters for Maltese dogs.MethodsIn total, 23 healthy Maltese dogs were involved in this study. Blood pressure measurements, thoracic radiography, and complete transthoracic echocardiography were performed. The effects of body weight, age and sex were evaluated, and the correlations between weight and linear and volumetric dimensions were calculated by regression analysis.ResultsThe mean vertebral heart size was 9.1 ± 0.4. Aside from the ejection fraction, fractional shortening, and the left atrial to aorta root ratio, all the other echocardiographic parameters were significantly correlated with weight.ConclusionThis study describes normal echocardiographic parameters that may be useful in the echocardiographic evaluation of Maltese dogs.     

Echocardiographic indices in normal German shepherd dogs

Sixty clinically normal German shepherd dogs, 31 males and 29 females, ranging in age from 1 and 5 years and with a body weight ranging from 22 to 37.2 kg, were examined by the two-dimensional mode, M-mode, and Doppler echocardiography. In Doppler mode, the mitral valve flows were obtained, where the aim was to determine the velocity peaks and ratios of the E and A waves and the mitral E wave deceleration time. The velocity peaks were obtained for the tricuspid, pulmonary and aortic valves. On the left ventricular outflow tract flow, the time velocity integral and aortic cross-sectional area was used to calculate the cardiac output. A statistically significant correlation with the body weight was found for the systolic left atrial and diastolic aortic diameter on two-dimensional mode. On M-mode, there was a significant correlation between the body weight and the systolic left atrium and diastolic aortic dimension, systolic and diastolic left ventricular, septal and posterior wall dimensions. Doppler echocardiography showed that there was no significant correlation between the body weight and the mitral, tricuspid, pulmonary and aortic valves flows. These results demonstrate that it is important to know the normal echocardiographic values for German shepherd dogs because there are some characteristics peculiar to this particular breed. The data obtained is expected to be helpful for studies on small animal cardiology.     

Echocardiographic detection of tricuspid atresia in two foals

M-mode, 2-dimensional, and contrast echocardiographic studies were used to detect tricuspid atresia in 2 foals. M-mode echocardiographic findings included a small right ventricle, large left ventricle, large mitral valve excursion, large left atrium (foal 2), dropout of the cranial aspect of the aortic root, and a thick band of echoes in the tricuspid valve region. These findings were confirmed by 2-dimensional echocardiography. In addition, a large right atrium, persistent foramen ovale, ventricular septal defect, and large mitral valve apparatus were imaged. One foal also had a thick right atrial wall. Contrast echocardiography confirmed the intracardiac flow of blood from right to left atrium and then to the left ventricle, followed by simultaneous opacification of the right ventricle and aorta. The use of these echocardiographic techniques enables accurate antemortem diagnosis and prognosis of tricuspid atresia in the foal.     

Echocardiographic and radiographic findings in a cohort of healthy adult green iguanas (Iguana iguana)

ObjectivesTo describe characteristics of echocardiography and cranial coelomic radiography in a cohort of iguanas.AnimalsTwenty apparently healthy adult green iguanas (Iguana iguana) from a reptile sanctuary.MethodsPhysical examination, radiography, two-dimensional and color Doppler echocardiography were performed to assess cardiac structures and function, and any related normal or abnormal findings were recorded.ResultsEchocardiographic examination was possible without sedation and allowed visualization of the great vessels, atria, and ventricle. Some structures could not be evaluated in a minority of the iguanas due to individual differences in bony conformation and imaging quality. Suspected abnormal echocardiographic findings in 3 iguanas included pericardial effusion (n = 1) and enlarged caudal vena cava and/or sinus venosus (n = 2). Objective measurements were repeatable as assessed by within-subject coefficient of variation, and reliable as assessed by intra-observer intraclass correlation coefficient. Left atrial and ventricular measurements were significantly correlated with body weight. Valve regurgitation was common, with atrioventricular valve regurgitation present in 53% (9/17) and aortic or pulmonic valve regurgitation in 71% (12/17) of otherwise normal iguanas. A heart murmur was not appreciated during examination of any of the iguanas. Heart size cannot be measured radiographically due to superimposition and silhouetting of other coelomic structures. Echocardiographic or radiographic findings consistent with mineralization of the great vessels were present in 76% of iguanas (13/17).ConclusionsEchocardiography in iguanas is well tolerated without sedation and allowed both subjective evaluation and structural measurements. Valve regurgitation and great vessel mineralization were commonly observed in this cohort of apparently healthy adult iguanas.     

Systolic anterior motion of the mitral valve associated with right ventricular systolic hypertension in 9 dogs

ObjectivesTo describe the zoographic and echocardiographic characteristics of canine patients in which systolic anterior motion of the mitral valve (SAM) was identified in association with right ventricular systolic hypertension (RVSH).Animals, materials and methodsMedical records and digitally recorded echocardiographic examinations were reviewed for RVSH and two-dimensional (2DE) or M-mode echocardiographic evidence of SAM.ResultsSAM was identified in association with RSVH in 9 patients; 5 had pulmonic stenosis, 2 had tetralogy of Fallot and 2, pulmonary hypertension. Relative to body weight, the end-diastolic and end-systolic left ventricular dimensions were subnormal in all patients. Hyperdynamic left ventricular systolic performance was identified in 8 of 9 patients.In 5 of the 9 patients, SAM was mild or moderate in degree. Left ventricular outflow tract (LVOT) obstruction and mitral valve regurgitation were documented by Doppler studies in only 3 of the 4 patients with marked SAM. However, late systolic acceleration within the LVOT was recorded in 2 additional patients for whom peak velocities were normal.ConclusionsIn the cases described here, the presence of SAM is likely explained by alterations in left ventricular geometry and function associated with diminished pulmonary venous return together with sympathetic activation resulting from subnormal stroke volume. Although the hemodynamic consequences were apparently minor, the association of SAM with right-sided heart disease might be of interest to those engaged in the practice of veterinary echocardiography.     

Mitral valve stenosis in three cats

Two-dimensional and M-mode echocardiography were used to diagnose mitral stenosis in two cats with heart failure. This appeared to be related to mitral valve complex malformation. Ultrasound findings included thickened mitral valve leaflets with inhibited mobility, reduced mitral valve orifice size, abnormal upward (cranial) motion of the caudal mitral leaflet during diastole and severe left atrial enlargement. Colour-flow and spectral Doppler imaging helped characterise this condition. Colour-flow Doppler mapping showed turbulence and increased mitral filling velocity (aliasing) at the site of stenosis and related jets of mitral regurgitation. Spectral Doppler recordings showed increased diastolic mitral filling velocities with spectral broadening and prolonged pressure half-time. Mitral stenosis should be included in the differential diagnosis of cats with severe left atrial enlargement when congenital or acquired mitral valve disease is detected; it may represent an advanced form of mitral valve complex malformation in some cases.     

M-MODE ECHOCARDIOGRAPHY AS A DIAGNOSTIC AID FOR FELINE CARDIOMYOPATHY

Normal cats and cats with congestive cardiomyopathy (CCM) and hypertrophic cardiomyopathy (HCM) were examined using M-mode echocardiography to determine its diagnostic capabilities. Sixteen normal cats were examined to verify previously reported data and to add further echocardiographic inforamtion (left atrial/aortic root ratio, left posterior wall thickness at end systole and end diastole, amplitude of mitral valve excursions, and velocity of valve opening and closure) to aid in differential diagnosis. Significant (p<0.05) changes were detected between the normal cats and those with cardiomyopathy. In each type of cardiomyopathy, alterations in left atrial dimension, left atrial/aortic root ratio, left ventricular dimension, left ventricular wall thickness and percentage of ventricular dimensional change were identified. Altered mitral valve motion was found with HCM. Echocardiography was found to be an accurate technique for definitive diagnosis of feline cardiomyopathy.     

Non-invasive assessment of left ventricular relaxation property using color M-mode-derived intraventricular pressure gradients in cats

IntroductionDiastolic dysfunction is an early clinical feature of feline hypertrophic cardiomyopathy (HCM). The left ventricular filling in early diastole is facilitated by the diastolic intraventricular pressure gradient (IVPG). The study objectives were to evaluate color Doppler M-mode-derived IVPG calculation in cats as a non-invasive assessment of the left ventricular relaxation property to determine the normal ranges of peak IVPG in cats and investigate the influence of left ventricular function and heart rate (HR).AnimalsOne hundred and six client-owned apparently healthy cats.MethodsProspective cross-sectional study. Quantitative analysis of color Doppler M-mode images was used to estimate total and segmental IVPGs non-invasively.ResultsThe total IVPG was 0.76 mmHg (95% reference interval (RI): 0.28–1.29 mmHg), the basal IVPG 0.34 mmHg (95% RI: 0.07–0.63 mmHg), and the mid-apical IVPG 0.42 mmHg (95% RI: 0.15–0.71 mmHg). Total and segmental IVPG increased with HR (P < 0.003), while segmental percent IVPG was HR independent. A short isovolumic relaxation time (IVRT) and a high mitral annular velocity in early diastole were associated with an increase in total IVPG (P = 0.008 and P = 0.009, respectively) adjusted for HR. An increase in IVPG was associated with an increase in mitral inflow velocity (P < 0.001).ConclusionsFeline IVPGs increase with HR and a short IVRT, which was believed to be a normal physiologic adrenergic response associated with an increased sympathetic tone. Future studies of segmental IVPG changes in feline HCM are needed to evaluate the clinical applicability of color Doppler M-mode estimated IVPGs in feline cardiology.     

Atrial septal defect in five dogs

The clinical, electrocardiographic, radiographic, and two-dimensional, M-mode and Doppler echocardiographic findings of five cases of canine ostium secundum type atrial septal defect (ASD) are described. The atrial septal anomaly was associated with other congenital cardiac abnormalities in two dogs: ventricular septal defect in one case and tricuspid dysplasia in the other. ASD was found in addition to dilated cardiomyopathy and suspected atrial thrombosis in one geriatric dog, but was the only cardiac abnormality detected in the remaining two dogs. Colour Doppler imaging facilitated the diagnosis of ASD in all subjects. The long-term prognosis for dogs with isolated and small-sized ASD is usually good, but can be compromised by the presence of concurrent congenital or acquired cardiac diseases.