Evaluation of cardioprotective effects of carvedilol in dogs receiving doxorubicin chemotherapy: A prospective, randomized, double-blind, placebo controlled pilot study

The aim of this pilot study was to evaluate the cardioprotective effects of carvedilol in dogs receiving doxorubicin chemotherapy and provide suggestions to future studies based on results and limitations of our study. Thirteen dogs were randomized into two experimental groups: 6 dogs in carvedilol group and 7 dogs in placebo group. In carvedilol group, 0.39 mg/kg ± 0.04 twice-daily oral carvedilol was started on the day of the first doxorubicin treatment and continued throughout the chemotherapy protocol until the final cardiological evaluation. Cardiological evaluations were performed before the first doxorubicin administration and then 10 to 15 days after each subsequent dose. Troponin I and oxidative stress tests were performed with serum collected from dogs at the initial and final cardiological evaluation. Carvedilol produced some echocardiographic and electrocardiographic changes (reduced E velocity and E/IVRT ratio, as well reduced heart rate and increased PR and QT interval) due to its beta-block effect. In placebo group Doppler study showed a significant increase in mitral flow deceleration time (EDT), as well increased amplitude of the S wave in the right, and R wave in the left, precordial chest leads. There were significant difference in the EDT, E/IVRT and A' velocity, as well heart rate, PR interval and R wave in V4/CV6LU precordial chest lead between groups. In conclusion, some indexes of diastolic function and in precordial chest leads were less affected by doxorubicin in carvedilol than in control group. This suggests that carvedilol may have a beneficial effect in canine cancer patients receiving doxorubicin.

Diagnostic value of the pulmonary vein-to-right pulmonary artery ratio in dogs with pulmonary hypertension of precapillary origin

INTRODUCTION

Non-invasive diagnosis of pulmonary hypertension (PH) relies on estimation of pulmonary arterial pressure (PAP) via Doppler echocardiographic measurement of tricuspid regurgitation pressure gradient (TRPG). The pulmonary vein-to-right pulmonary artery ratio (PV/PA) recently has been described for the detection of pulmonary venous congestion. Whether this variable could be used to detect the presence of precapillary PH is unknown. The objective of the present study was to investigate the diagnostic value of PV/PA for prediction of TRPG, as a surrogate of PAP, in dogs with PH of precapillary origin.

ANIMALS

Sixty-seven client-owned dogs were included in the study.

METHODS

This was a retrospective study. Dogs with a measurable TRPG were included and classified into group 1 (TRPG < 30 mmHg), group 2 (TRPG 30-49 mmHg), group 3 (TRPG 50-80 mmHg), or group 4 (TRPG > 80 mmHg). The PV/PA, acceleration time-to-ejection time ratio of pulmonary artery flow, main pulmonary artery diameter-to-aortic diameter ratio, and right pulmonary artery distensibility index were measured retrospectively from cineloops in each dog.

RESULTS

The PV/PA measured by both two-dimensional (2D) and time-motion mode(MM) echocardiography decreased proportionally with PH severity. Using regression analysis, PV/PA (2D) was identified as the strongest predictor for TRPG (R² = 0.70, p < 0.0001) among other variables studied, with a good diagnostic accuracy (area under the curve = 0.94) for moderate PH (TRPG > 50 mmHg) using a cutoff value of < 0.70 (sensitivity = 96%, specificity = 82%).

CONCLUSIONS

Results of the present study suggest that PV/PA can be useful as an additional, non-invasive, and indirect variable to identify precapillary PH in dogs.

Doppler-derived echocardiographic evidence of pulmonary hypertension in cats with left-sided congestive heart failure

INTRODUCTION

Pulmonary hypertension (PH) caused by left-sided congestive heart failure (L-CHF) is common in dogs and contributes to clinical signs and outcome. The aim of this study was to evaluate the prevalence of Doppler echocardiography-derived PH in a population of cats with L-CHF.

ANIMALS

The study involved 131 cats with L-CHF and 56 control cats.

METHODS

The study design is retrospective, observational study. Tricuspid regurgitation velocity, right atrial dimension, right ventricular (RV) dimension and function, RV wall thickness, pulmonary artery (PA) dimension, Doppler-derived systolic time intervals of PA flow, and presence of septal flattening were evaluated. Pulmonary hypertension was considered if tricuspid regurgitation velocity was >2.7 m/s.

RESULTS

Tricuspid regurgitation was present in 57/131 (44%) of cats with L-CHF and 24/56 (43%) in control cats based on color flow Doppler. Doppler-derived of PH was identified in 22/131 cats with L-CHF (17%). In 15/22 cats, PH was associated with cardiomyopathy, in 5/22 cases with congenital heart disease, and in 2/22 cases with other causes. Cats with Doppler-derived PH more often had chronic L-CHF, as opposed to acute L-CHF (p<0.05). All cats with Doppler-derived PH had subjectively-assessed right-sided heart enlargement, with larger right atrial and RV diameters (p<0.001), increased RV wall thickness (p<0.05), and higher prevalence of septal flattening (<0.001) and PA enlargement (p<0.05).

CONCLUSIONS

Pulmonary hypertension identified by Doppler echocardiography is not a common finding in cats with L-CHF. Right-sided heart enlargement, more frequently observed, may raise the suspicion of PH in cats with L-CHF.

Diastolic heart failure associated with hemangiosarcoma infiltrating left ventricular walls in a dog

A 9-year-old Shetland sheepdog was diagnosed with cardiogenic pulmonary edema. Echocardiography revealed focally thickened left ventricular free wall and interventricular septum and left atrial dilation. Left ventricular systolic function was preserved. Doppler echocardiography of transmitral flow indicated restrictive left ventricular filling. Cardiac histopathology demonstrated hemangiosarcoma infiltrating the left ventricular walls.

Echocardiographic Parameters of Clinically Normal Geriatric Rhesus Macaques (Macacamulatta)

The goal of this study was to generate reference intervals for echocardiographic variables in a population of clinically normal geriatric rhesus macaques (Macaca mulatta). To do this, we studied 51 animals (age, 18-29 y; weight, 5.24-17.04 kg). The normal values for cardiac indices, including geometry and systolic and diastolic function, were determined by 2D, M-mode, spectral Doppler, and tissue Doppler echocardiography under ketamine hydrochloride sedation. Statistical correlations between the echocardiographic parameters and age, body weight, sex, and heart rate were investigated. All echocardiographic indices were acquired, and their reference intervals were established. Multiple weak to strong correlations emerged between variables and echocardiographic parameters, but no moderate or strong correlations between body weight or sex and these parameters were noted. Of the 51 geriatric rhesus macaques evaluated, 36 (71%) fulfilled the criteria for diastolic dysfunction. Valve regurgitation, especially tricuspid regurgitation (43%), and aortic regurgitation (51%) also were common in geriatric rhesus macaques. Although these findings merit follow-up, they are unlikely to have clinical significance given their prevalence in these apparently healthy animals.

A study of the adult zebrafish ventricular function by retrospective Doppler-gated ultrahigh-frame-rate echocardiography

The zebrafish (Danio rerio) has become a preferred animal model for studying various human diseases, particularly those related to cardiovascular regeneration; therefore, a noninvasive imaging modality is needed for observing the cardiac function of zebrafish. Because of its high resolution, high-frequency ultrasound B-mode imaging has recently been used successfully to observe the heart of adult zebrafish. However, ultrahigh-frame-rate echocardiography combining Bmode imaging and color flow imaging is still needed to observe the detailed transient motions of the zebrafish ventricle. This study develops an 80-MHz ultrahigh-frame-rate echocardiography system for this purpose, based on retrospective Doppler- gated technology. B-mode and color flow images of the cardiovascular system of the zebrafish were reconstructed by two-dimensional autocorrelation at maximum frame rates of up to 40,000 and 400 fps, respectively. The timings of end diastole (E(D)) and end systole (E(S)) of ventricle can be determined by using this high-resolution image system. Two ventricular function parameters-fractional shortening (FS) and fractional area change (FAC)-were measured for evaluating the ventricular function by using E(D) and E(S) with their corresponding ventricular dimensions. The experimental results indicated that the measured FS values were 42 ± 4% (mean ± standard deviation) and 60 ± 13% for the long axis and short axis of the ventricle, respectively, and that FAC was 77 ± 9%. This is the first report of these ventricular function parameters for a normal adult zebrafish. The results showed that retrospective high-frequency echocardiography is a useful tool for studying the cardiac function of normal adult zebrafish.

External splinting for treatment of pectus excavatum in a dog with right ventricular outflow obstruction

Right ventricular outflow tract obstruction was diagnosed by Doppler echocardiography in a young dog with a cardiac murmur, severe dyspnea, and a prominent sternal depression. Thoracic radiography confirmed a diagnosis of pectus excavatum involving the caudal third of the sternum. The right ventricular outflow obstruction was attributed to cardiac compression from the dorsally deviated sternum. External surgical splinting of the sternabrae, demonstrated by video in this report, was used to treat the pectus excavatum. Radiographic and Doppler echocardiographic examination 3 weeks and 4 months post-splinting documented resolution of both pectus excavatum and right ventricular outflow obstruction.

Cardiac Effects of Pulmonary Disease

Pulmonary hypertension (PHT) is the primary cardiac consequence of pulmonary disease. It develops as alveolar hypoxia of pulmonary disease, coupled with vasoactive and mitogenic substances released from pulmonary endothelial and vascular smooth muscle cells damaged by the primary disease process, mediates arterial vasoconstriction and vascular remodeling to raise pulmonary vascular resistance. Independent of the underlying pulmonary disease, PHT produces clinical signs of respiratory distress, exercise intolerance, syncope, and right heart failure. Diagnosis of PHT is made by estimation of pulmonary artery pressures by means of continuous-wave Doppler echocardiographic assessment of tricuspid or pulmonic regurgitant flow velocity. Treatment of PHT is directed at the underlying pulmonary disease but may also aim to attenuate pulmonary artery pressure and limit the clinical sequelae of PHT. No treatments are of proven benefit in veterinary patients; irrespective of the nature of the inciting pulmonary disease, the prognosis is often grave.

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

OBJECTIVES

To 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 METHODS

Medical records and digitally recorded echocardiographic examinations were reviewed for RVSH and two-dimensional (2DE) or M-mode echocardiographic evidence of SAM.

RESULTS

SAM 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.

CONCLUSIONS

In 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.

Assessment of diastolic function by Doppler echocardiography in normal Doberman Pinschers and Doberman Pinschers with dilated cardiomyopathy

BACKGROUND

Assessment of diastolic function in patients with dilated cardiomyopathy (DCM) has the potential to add valuable information regarding hemodynamics, disease severity, and prognosis. The purpose of this study was to determine transmitral flow (TMF), isovolumic relaxation time (IVRT), pulmonary venous flow (PVF), flow propagation velocity (Vp), and mitral annular velocities by tissue Doppler in Doberman Pinschers with and without DCM.

HYPOTHESIS

It was anticipated that normal and DCM Dobermans would differ with respect to these parameters, and that associations with time to congestive heart failure (CHF) or death would be found.

ANIMALS

Thirty client-owned Doberman Pinschers (10 each of normal, occult DCM, and overt DCM) were studied.

METHODS

Each dog underwent echocardiography with or without thoracic radiography (to confirm CHF) for classification as normal or DCM-affected, followed by collection of echocardiographic diastolic parameters.

RESULTS

The group with occult DCM exhibited features of pseudonormal TMF, reduced systolic to diastolic PVF ratio, and reduced Vp. Shorter early TMF deceleration time (DTE) was associated with shorter time to CHF or sudden death. The group with overt DCM exhibited restrictive TMF, blunted systolic PVF, and reduced early and late diastolic mitral annular velocities.

CONCLUSIONS AND CLINICAL IMPORTANCE

Doberman Pinschers showed evidence of moderate and severe diastolic dysfunction in occult and overt DCM, respectively. Short DTE may be a useful predictor of onset of CHF or sudden death.

Echocardiographic evaluation of the bottlenose dolphin (Tursiops truncatus)

Safe and effective echocardiography would represent a valuable tool for marine mammal veterinarians and physiologists evaluating the dolphin heart. Unfortunately, conventional ultrasound technology (transthoracic echocardiography) has been limited by logistic, anatomic, and behavioral challenges. Five mature male Atlantic bottlenose dolphins (Tursiops truncatus) were trained for echocardiographic imaging (four for both transthoracic and transesophageal imaging, and one for only transthoracic imaging). It was noted that transesophageal image quality transiently improved when the dolphins spontaneously exhaled. Subsequently, dolphins were conditioned to hold their breath following forced exhalation, and imaging proceeded during such behavioral breath holds. Over 25 transthoracic and 100 transesophageal echocardiographic studies were performed, including both two-dimensional imaging and color flow mapping. Transthoracic imaging yielded poor-quality images of only small portions of the heart. In contrast, transesophageal imaging, which improved dramatically with behavioral breath holding following exhalation, yielded consistently high-quality images of the entire heart (mitral, tricuspid, aortic, and pulmonary valves, atrial and ventricular septa, left and right atria, left and right ventricles, and ascending aorta and main pulmonary artery). Color flow mapping demonstrated mild tricuspid regurgitation in all dolphins, and mild aortic regurgitation in one dolphin found to have a pedunculated mass arising from the sinutubular junction just above the aortic valve. There were no complications in nonsedated dolphins. The heart of the bottlenose dolphin can be safely, effectively, and reproducibly evaluated with the use of transesophageal echocardiography in conjunction with behavioral breath holding following forced exhalation. This approach, and the normative echocardiographic data generated from this work, lays the foundation for future echocardiographic studies of cetaceans.

Prospective screening for occult cardiomyopathy in dogs by measurement of plasma atrial natriuretic peptide, B-type natriuretic peptide, and cardiac troponin-I concentrations

OBJECTIVE

To evaluate the use of measuring plasma concentrations of atrial natriuretic peptide (ANP), B-type natriuretic peptide (BNP), and cardiac troponin-I (cTnI) to detect dogs with occult dilated cardiomyopathy (DCM).

ANIMALS

118 client-owned dogs.

PROCEDURES

Dogs were prospectively examined by use of ECG; echocardiography; and evaluation of concentrations of ANP, BNP, and cTnI. Occult DCM was diagnosed by evaluation of echocardiographic left ventricular dimensions and detection of ventricular arrhythmias on ECG. Sensitivity and specificity of assays for measurement of plasma concentrations of ANP, BNP, and cTnI to detect dogs with occult DCM were determined.

RESULTS

Occult DCM was diagnosed in 21 dogs. A concentration of > 6.21 pg/mL for BNP had a sensitivity of 95.2% and specificity of 61.9% for identifying dogs with occult DCM. In contrast, concentrations of ANP and cTnI had relatively low predictive values.

CONCLUSIONS AND CLINICAL RELEVANCE

Blood-based screening for occult DCM in dogs can be accomplished by use of a BNP assay. Additional studies should be performed to optimize this method of screening dogs to detect occult DCM.

Effects of Pimobendan for Mitral Valve Regurgitation in Dogs

Pimobendan has a dual mechanism of action: it increases myocardial contractility by increasing calcium sensitization to troponin C and it promotes vasodilation by inhibiting PDEIII. This study examined the effects of pimobendan on cardiac function, hemodynamics, and neurohormonal factors in dogs with mild mitral regurgitation (MR). The dogs were given 0.25 mg/kg of pimobendan orally every 12 hr for 4 weeks. With pimobendan, the heart rate and stroke volume did not change, but the systolic blood pressure gradually decreased and the degree of mitral valve regurgitation tended to decrease. Renal blood flow was significantly increased and the glomerular filtration rate was slightly increased at 2 and 4 weeks. Furthermore, over the 4-week period, the plasma norepinephrine concentration decreased significantly, the systolic index increased slightly, the left atrial diameter and the left ventricular diameters decreased significantly, and the heart size improved. Given these results, pimobendan appears to be useful for treating MR in dogs. However, further long-term studies of pimobendan involving a larger number of dogs with mild and moderate MR are needed to establish the safety of pimobendan and document improvements in quality of life.

ASSESSMENT OF THE REPEATABILITY OF FELINE ECHOCARDIOGRAPHY USING CONVENTIONAL ECHOCARDIOGRAPHY AND SPECTRAL PULSE-WAVE DOPPLER TISSUE IMAGING TECHNIQUES

The objective of this study was to determine the intraoperator, intraobserver, and interobserver repeatability in a series of conventional echocardiographic parameters and in some of the newer measurements of diastolic function, including color M-mode flow propagation velocity, isovolumic relaxation time and pulsed-wave Doppler tissue imaging velocities. Four healthy cats were each scanned five times over a 3-day period. The repeatability of these echocardiographic analyses was compared using Bland-Altman analysis (intraoperator repeatability). After a minimum of 5 weeks, one scan was randomly selected from each cat, and was remeasured by the original observer and the results compared using a standard paired Student's t-test (intraobserver repeatability). One scan from each cat was then randomly selected and two observers, with similar levels of experience, measured each of these scans. The repeatability of these echocardiographic analyses was compared using Bland-Altman analysis (interobserver repeatability). The conventional two-dimensional (2D), M-mode and spectral Doppler measurements were repeatable in both their acquisition and measurement by a single investigator; there was a greater degree of variation between the two observers. The predominant (S', E', and A') pulsed-wave Doppler tissue imaging velocities from the left apical four-chambered view, generally had a coefficient of variation of approximately 20% (range 9.62-34.08%). However, with pulsed-wave Doppler tissue imaging, velocities recorded during the isovolumic phases, the velocity of the tricuspid annulus, and the radial fiber velocity within the interventricular septum, frequently had coefficients of variation in excess of 20% and should therefore be interpreted with caution.

Doppler echocardiography–derived evidence of pulmonary arterial hypertension in dogs with degenerative mitral valve disease: 86 cases (2001–2005)

OBJECTIVE

To determine the prevalence of Doppler echocardiography-derived evidence of pulmonary arterial hypertension (DEE-PAH) in dogs with mitral valve disease (MVD) classified according to the International Small Animal Cardiac Health Council (ISACHC) heart failure classification scheme and various echocardiographic and Doppler indices of MVD severity.

DESIGN

Retrospective case series.

ANIMALS

617 dogs examined from 2001 to 2005 with MVD in ISACHC classes I to III.

PROCEDURES

Dogs were examined echocardiographically. Criteria used for systolic and diastolic DEE-PAH were detection of high tricuspid (> or = 2.5 m/s) and telediastolic pulmonic (> or = 2.0 m/s) valvular peak regurgitant jet velocities, respectively, by use of continuous-wave Doppler echocardiography.

RESULTS

86 (13.9%) dogs with MVD had a diagnosis of DEE-PAH. Severity and prevalence of DEE-PAH increased with ISACHC class (3.0%, 16.9%, 26.7%, and 72.2% prevalences for ISACHC classes Ia, Ib, II, and III, respectively). A significant correlation between systolic or diastolic pulmonary arterial pressure and left atrial-to-aortic diameter ratio (LA/Ao) was detected. Doppler echocardiography-derived evidence of pulmonary arterial hypertension was detected in 18 dogs with values of LA/Ao within reference range, all of which had moderate (n = 2 dogs) or severe (16) mitral valve regurgitation on color Doppler imaging.

CONCLUSIONS AND CLINICAL RELEVANCE

The prevalence and degree of DEE-PAH were related to the severity of MVD. Changes associated with DEEPAH may be detected in early stages of the disease, but only in dogs with severe mitral valve regurgitation.

The effect of ramipril on left ventricular mass, myocardial fibrosis, diastolic function, and plasma neurohormones in Maine Coon cats with familial hypertrophic cardiomyopathy without heart failure

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is the most common heart disease of cats, resulting in left ventricular (LV) hypertrophy, myocardial fibrosis, and diastolic dysfunction.

HYPOTHESIS

Ramipril will reduce LV mass, improve diastolic function, and reduce myocardial fibrosis in cats with HCM without congestive heart failure (CHF).

ANIMALS

This prospective, blinded, placebo-controlled study included 26 Maine Coon and Maine Coon cross-bred cats with familial HCM but without CHF.

METHODS

Cats were matched for LV mass index (LVMI) and were randomized to receive ramipril (0.5 mg/kg) or placebo q24h for 1 year, with investigators blinded. Plasma brain natriuretic peptide (BNP) concentration, plasma aldosterone concentration, Doppler tissue imaging (DTI), and systolic blood pressure were measured at baseline and every 3 months for 1 year. Cardiac magnetic resonance imaging (cMRI) was performed to quantify LV mass and myocardial fibrosis by delayed enhancement (DE) cMRI at baseline and 6 and 12 months. Plasma angiotensin-converting enzyme (ACE) activity was measured on 16 cats 1 hour after PO administration.

RESULTS

Plasma ACE activity was adequately suppressed (97%) in cats treated with ramipril. LV mass, LVMI, DTI, DE, blood pressure, plasma BNP, and plasma aldosterone were not different in cats treated with ramipril compared with placebo (P = .85, P = .94, P = .91, P = .89, P = .28, P = .18, and P = .25, respectively).

CONCLUSION

Treatment of Maine Coon cats with HCM without CHF with ramipril did not change LV mass, improve diastolic function, alter DE, or alter plasma BNP or aldosterone concentrations in a relevant manner.

Doppler echocardiographic prediction of pulmonary hypertension in West Highland white terriers with chronic pulmonary disease

BACKGROUND

Pulmonary hypertension (PH) is commonly diagnosed by Doppler echocardiography (DE) of tricuspid regurgitation (TR). However, TR may be absent or difficult to measure.

HYPOTHESIS

Doppler-derived systolic time intervals of pulmonary artery (PA) flow may be used to predict PH in dogs.

ANIMALS

Seventy-three healthy dogs and 45 West Highland white terriers (WHWT) with interstitial pulmonary disease (IPD).

METHODS

Echocardiographic studies, including determination of right ventricular acceleration time (AT), ejection time (ET), and AT : ET ratio; right ventricular shortening fraction (RV-SF); and TR velocity, were performed. Pulmonary hypertension was defined by TR >3.1 m/s.

RESULTS

In healthy WHWT, AT (median, range) was 73 ms (53 to 104) and AT : ET was 0.40 (0.28 to 0.55). AT : ET was minimally affected by age (R2 = 0.04, 95% confidence interval [CI] 0.01-0.07, P < .001) but not by heart rate, body weight, or RV-SF. In all WHWT with TR, AT and AT : ET were inversely related to calculated systolic PA pressure (R2 = 0.52, 95% CI 0.42-0.62, P < .001 and R2 = 0.36, 95% CI 0.29-0.42, P = .001). Clinical cutoffs to predict systolic PH were defined for AT (58 ms; sensitivity [Se] 88% and specificity [Sp] 80%) and AT : ET (0.31; Se 73% and Sp 87%).

CONCLUSION AND CLINICAL IMPORTANCE

PH is common in WHWT with IPD. Analysis of right ventricular AT and AT : ET may be predictive of PH and should be particularly useful if TR is absent.

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.

Congenital Heart Diseases in the Boxer Dog: A Retrospective Study of 105 Cases (1998–2005)

Subaortic stenosis (SAS) is one of the most common congenital heart diseases (CHD) in dogs with Boxers being predominantly affected. However, the increasing availability of modern diagnostic imaging systems now allows a better assessment of cardiac morphology and function, thereby facilitating early detection of CHD in awake animals. In this context, the case records of Boxer dogs diagnosed with CHD using echocardiography combined with Doppler mode, were retrospectively reviewed (1998-2005). One hundred and five Boxers exhibiting either a single CHD (53/105, 50.5%) or association of several CHD (52/105, 49.5%) were included. The most common CHD was atrial septal defect (ASD) observed in 56.2% of these animals (59/105), followed by mitral dysplasia (58/105, 55.2%), and SAS (49/105, 46.7%). SAS was associated with one or two CHD in 29.5% of cases (31/105). Most of the dogs with a low intensity left heart base systolic murmur had an isolated ASD whereas most of the dogs with a similar but high intensity murmur had SAS, either isolated or associated with a concurrent CHD. The incidence of ASD and mitral dysplasia in Boxer dogs is higher than previously assumed, and ASD is a common cause of left heart base systolic murmur in this breed of dog. This confirms that the detection of such a murmur should not be used as the unique criterion for diagnostic confirmation of SAS.

Severe pulmonary arterial hypertension due to Angiostrongylosus vasorum in a dog

A dog was presented with a history of dyspnea, coughing, and ascites. Angiostrongylosis and severe pulmonary arterial hypertension (PAH) were found, as well as a marked discordance between the electrical and mechanical events of the heart. Pulmonary arterial hypertension related to Angiostrongylus vasorum has rarely been reported.

Correlation between activation of the sympathetic nervous system estimated by plasma concentrations of norepinephrine and Doppler echocardiographic variables in dogs with acquired heart disease

OBJECTIVE

To evaluate correlations between plasma concentrations of norepinephrine and Doppler echocardiographic variables for dogs with degenerative mitral valve disease (DMVD) or dilatative cardiomyopathy (DCM) to better understand the time course and magnitude of sympathetic activation in dogs with heart failure (HF).

ANIMALS

15 healthy dogs, 15 dogs with DMVD, and 15 dogs with DCM.

PROCEDURES

Dogs were positioned in lateral recumbency with minimal restraint for at least 20 minutes. Plasma samples were obtained and assayed by use of high-performance liquid chromatography. Concentrations were correlated with HF classification and with the main Doppler echocardiographic variables for each group.

RESULTS

Mean +/- SD norepinephrine concentration was significantly higher in dogs with DMVD (494.4 +/- 204.8 pg/mL) or DCM (655.7 +/- 652.5 pg/mL) than in healthy dogs (205.8 +/- 78.9 pg/mL), but concentrations did not differ significantly between the 2 groups with HF. Correlations were not detected between norepinephrine and heart rate or any M-mode echocardiographic variables evaluated, except for fractional shortening (FS) in DCM dogs. In that group, norepinephrine was inversely correlated with FS values. In DMVD dogs, no significant correlation was found between norepinephrine and the left atrium-to-aortic root ratio or mitral regurgitation.

CONCLUSIONS AND CLINICAL RELEVANCE

A proportional inverse correlation exists between norepinephrine and FS values in dogs with DCM. However, norepinephrine concentration was not correlated with the evaluated echocardiographic variables in dogs with DMVD. Sympathetic antagonists should be evaluated as a treatment option because of the increased plasma concentrations of norepinephrine detected in dogs with HF.

Tissue Doppler imaging and gradient echo cardiac magnetic resonance imaging in normal cats and cats with hypertrophic cardiomyopathy

Cats with hypertrophic cardiomyopathy (HCM) often develop diastolic dysfunction, which can lead to development of left congestive heart failure. Tissue Doppler imaging (TDI) echocardiography has emerged as a useful, noninvasive method for assessing diastolic function in cats. Cardiac magnetic resonance imaging (cMRI) has been performed in cats and accurately quantifies left ventricular (LV) mass in normal cats. However, assessment of cardiac function in cats by cMRI has not been performed. Six normal Domestic Shorthair cats and 7 Maine Coon cats with moderate to severe HCM were sedated, and TDI of the lateral mitral annulus was performed. Peak early diastolic velocity (Em) was measured from 5 nonconsecutive beats. Cats were anesthetized with propofol and electrocardiogram-gated gradient echo cMRI was performed during apnea after hyperventilation. Short-axis images of the LV extending from the mitral annulus to the apex were obtained throughout the cardiac cycle. LV mass at end systole and LV volumes throughout the cardiac cycle were quantified according to Simpson's rule. To assess the possible influence of propofol on diastolic function, TDI was performed on the 7 cats with HCM while sedated and then while anesthetized with propofol. Em was significantly lower in cats with HCM than normal cats (6.7 +/- 1.3 cm/s versus 11.6 +/- 1.9 cm/s, P < .001, respectively). There was no difference in the cMRI indices of diastolic function in normal and HCM cats. Propofol did not reduce diastolic function (Em) in cats with HCM but mildly reduced systolic myocardial velocity (S) in Maine Coon cats with HCM that were anesthetized with propofol (P = .87 and P = .03, respectively).

Quantitative assessment of regional right ventricular myocardial velocities in awake dogs by Doppler tissue imaging: repeatability, reproducibility, effect of body weight and breed, and comparison with left ventricular myocardial velocities

Right ventricular myocardial (RVM) motion is poorly documented. The objective of this study was to determine the variability of RVM velocities by tissue Doppler imaging (TDI) in healthy dogs (study 1), to analyze RVM motion in a large healthy canine population (study 2), and to compare the results with those obtained for the left ventricular free wall. Six healthy Beagle Dogs were monitored in study 1, and 64 healthy dogs of 14 different breeds were monitored in study 2. Velocities were recorded in 2 segments (basal and apical) of the right and left myocardial walls. In study 1, 36 TDI examinations were performed for 4 days, whereas a single TDI examination was performed on each dog in study 2. All velocity profiles included 1 positive systolic wave and 2 negative diastolic waves. The lowest intraday and interday coefficient of variation values of the right TDI variables were observed at the base (3.5-16.1%). The variability of the right apical velocities was much higher, with most coefficient of variation values > 15%. RVM velocities were higher in the basal than in the apical segments (P < .001) and were higher than the left velocities of the corresponding segment (P < .01). Body weight and breed had an effect on only a few right and left TDI variables. TDI provides a repeatable and reproducible method for evaluating basal RV function in the dog. These data also demonstrate the heterogeneity of the myocardial velocities between the left and the right ventricles and between the base and the apex.

Tei index of myocardial performance applied to the right ventricle in normal dogs

Right ventricular (RV) dysfunction is a cause of exercise intolerance, hypotension, syncope, and heart failure in dogs with cardiac and respiratory disorders. The study objective was to determine Doppler-derived reference values that reflect global RV function in healthy dogs. We measured systolic time intervals and an RV index of myocardial performance (IMP) in 45 healthy dogs between 8 months and 8 years of age. Pulsed-wave Doppler recordings of mitral, tricuspid, aortic, and pulmonic were acquired. Pre-ejection period (PEP), ejection time (ET), PEP/ET, and IMP were determined for both ventricles by separate cardiac cycles. Compared to the mean left ventricular (LV) IMP (0.410; 95% confidence intervals [CI] 0.378-0.442), mean RV IMP (0.250; 95% CI 0.222-0.278) was significantly smaller, and mean ET for the RV (187 millisecond [ms]; 95% CI 182-192) was significantly longer than the LV (173 ms; 95% CI 168-179). A clinically relevant correlation was not found among RV IMP and body weight, heart rate, RV ET, RV PEP, or RV PEP/ET. Calculation of LV IMP with 2 separate sample volumes yielded smaller values than from a single sample volume, with a difference in means of 0.040. We conclude that the RV IMP is relatively independent of body weight and heart rate within the ranges studied and is consistently lower than values derived from the LV in healthy dogs. This study provides additional reference values for RV function in dogs and may be useful for identification of RV dysfunction in dogs.

Echocardiographic and Doppler echocardiographic findings in 11 wolves (Canis lupus )

Two-dimensional real-time, M-mode and Doppler echocardiographic measurements were made in 11 adult wolves (Canis lupus) anaesthetised with an intramuscular combination of medetomidine, ketamine, butorphanol and acepromazine followed by isoflurane in oxygen. M-mode measurements of the left ventricle, B-mode measurements of the left atrium and aorta, systolic indices, and Doppler measurements of aortic and pulmonary blood outflow, and of mitral and tricuspid blood inflow, were recorded. The values obtained were compared with those reported for dogs of similar bodyweight and body type. The diastolic measurements of the cardiac chambers and walls were similar to those reported for healthy, conscious dogs, but the use of anaesthesia probably resulted in the markedly different systolic cardiac measurements, systolic indices and Doppler blood flow velocities observed in the wolves. Mild mitral regurgitation, probably due to mitral endocardiosis, was observed in one wolf, and trivial functional mitral insufficiency was observed in five others.

Comparison of myocardial contrast enhancement via cardiac magnetic resonance imaging in healthy cats and cats with hypertrophic cardiomyopathy

OBJECTIVE

To quantify myocardial contrast enhancement (MCE) of the left ventricle (LV) by use of cardiac magnetic resonance imaging (CMRI) in healthy cats and cats with hypertrophic cardiomyopathy (HCM) and to compare MCE between the 2 groups.

ANIMALS

10 healthy cats and 26 Maine Coon cats with moderate to severe HCM but without clinical evidence of congestive heart failure.

PROCEDURE

Anesthetized cats underwent gradient echo CMRI examination. Short-axis images of the LV were acquired before and 7 minutes after IV administration of gadolinium dimeglumine. Regions of interest were manually traced in the quadrants of 5 mid-LV slices acquired at end systole, and the MCE percentage was calculated from summed weight-averaged data from all slices. Doppler tissue imaging echocardiography was performed to measure the early diastolic myocardial velocity (Em) as an index of diastolic function. Three-way repeated-measures ANOVA was used to determine differences in MCE between cats with HCM and healthy cats. Simple linear regression was used to assess whether MCE was correlated with LV mass, LV mass index (LVMI), or Em. A Student t test was used to compare the SDs of the postcontrast myocardial signal intensity between the 2 groups.

RESULTS

There was no difference in MCE between cats with HCM and healthy cats. There was no correlation of MCE with LV mass, LVMI, or Em. There was no difference in heterogeneity of signal intensities of LV myocardium between the 2 groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Contrast-enhancement CMRI was not useful in detecting diffuse myocardial fibrosis in cats with HCM.

Cardiac output measurement by partial carbon dioxide rebreathing, 2-dimensional echocardiography, and lithium-dilution method in anesthetized neonatal foals

The objective of this study was to assess 2 noninvasive methods of measuring cardiac output (CO) in neonatal foals by comparing results to that of the lithium-dilution method. Ten neonatal foals were anesthetized and CO was manipulated by varying the depth of anesthesia and infusion of dobutamine. Concurrent CO measurements were obtained by lithium dilution (reference method), partial carbon dioxide (CO2) rebreathing, volumetric echocardiography (cubic, Teichholz, Bullet, area-length, and single and biplane modified Simpson formulas), and transthoracic Doppler echocardiography. Thirty pairs of lithium-dilution/noninvasive CO measurements were taken from the 10 foals. For each method, relative bias was calculated as a percentage of the average CO. Lithium determinations of CO ranged between 3.09 and 1 1.1 L/min (mean +/- SD = 6.39 +/- 2.1 L/min), resulting in cardiac indices ranging between 79.0 and 209 mL/kg/min (mean +/- SD = 131 +/- 35.9 mL/kg/min). Relative bias of Doppler echocardiography significantly increased (P < .05), whereas that of partial CO2 rebreathing significantly decreased (P = .03) with increasing CO. Other methods were not influenced by the level of CO. Among methods not influenced by the level of CO, relative bias of the Bullet method (-4.2 +/- 20.9%; limits of agreement -45.2 to 36.7%) was significantly lower (P < .05) than that of each of the other noninvasive methods evaluated. Volumetric echocardiography using the Bullet method provides an accurate and noninvasive estimate of CO in anesthetized neonatal foals and warrants investigation in critically ill conscious foals.

Chronic myocardial infarction due to arteriosclerosis of coronary arteries followed by acute thromboembolism of caudal abdominal aorta in a cat

A 10-year-old cat with the paresis of hind limbs was initially diagnosed as a hypertrophic cardiomyopathy followed by acute thromboembolism of caudal abdominal aorta from the findings of the medical examinations. However, this case was proved to be an chronic myocardial infarction due to arteriosclerosis of coronary arteries by the pathologic diagnosis. In the left ventricular, the hypertrophy and the narrowing were slight, and a coagulative infarction was seen obviously. The intramural coronary arteriosclerosis showed thickening of the wall due to medial hyperplasia by fibrosis, and arterial stenosis. Myocardial infarction and arteriosclerosis are scarcely any reports of these lesions in cats. This case is valuable for an extremely rare case of myocardial infarction in the cat.

Percutaneous transcatheter coil embolization of a ventricular septal defect in a dog

A 4-month-old male French Bulldog weighing 5.0 kg (11 lb) was referred for a heart murmur. A grade 3/6 systolic murmur was detected at the left heart base and a grade 4/6 systolic murmur was detected at the right heart base. By use of color-flow Doppler ultrasonography and cardiac catheterization, a diagnosis of supracristal ventricular septal defect (VSD) with accompanying aortic regurgitation was made. Percutaneous transcatheter coil embolization was used to close the VSD. Because residual shunt was detected via echocardiography after coil implantation, the residual shunt was followed periodically via echocardiography to detect spontaneous closure of the VSD. Volume overload in the left ventricle was detected in the dog 131 days after admission. Additional coils were placed 137 days after admission. Hemolysis resulting in hemoglobinuria was detected, but this complication was mild. In the dog of this report, results of coil occlusion for correction of VSD were promising. Thus, coil occlusion should be considered as an alternative treatment for VSD in dogs.

Pulmonic stenosis in dogs: balloon dilation improves clinical outcome

Medical records of 81 dogs with severe pulmonic stenosis from 2 referral centers were examined retrospectively. Forty dogs underwent balloon valvuloplasty (BV), which was performed by 1 operator, whereas 41 did not. The mean age at latest follow-up was 41.5 months. A statistical comparison of the clinical outcome and survival was performed. Dogs revealing clinical signs at presentation showed a 16-fold increase in risk of death compared with asymptomatic dogs (P < .001). Statistical analyses demonstrated that an increase of 1 mm Hg in transstenotic pressure gradient (PG) at presentation was associated with a 3% increase in hazard rate (P < .001). Thirty-seven dogs survived BV with a median reduction in PG of 46%. The median preoperative PG was 120 mm Hg, and median PG 24 hours postoperatively was 55 mm Hg with a median of 55 mm Hg 6 months post-BV. Twenty (49%) of the non-BV (NBV) dogs remained asymptomatic at last follow-up. Fourteen (34%) of the NBV dogs died or were euthanized because of heart disease related to pulmonic stenosis. Twelve of these dogs died suddenly, whereas only 1 of the BV dogs died suddenly. After adjusting for PG, clinical signs at presentation, and age, BV or dilation was associated with a 53% reduction in hazard rate (P = .005). This study indicates that BV, when performed by an experienced operator, appears to be successful both in alleviating clinical signs and in prolonging survival in dogs with severe pulmonic stenosis.

Echocardiographic estimation of mean left atrial pressure in a canine model of acute mitral valve insufficiency

High mean left atrial pressure (MLAP) due to canine degenerative mitral valve disease is associated with clinically relevant morbidity and mortality. The ability to noninvasively measure MLAP would assist in the diagnosis and treatment of disease. Doppler echocardiography allows measurement of early transmitral blood flow (E) and the velocity of the mitral valve annulus (Ea). The ratio of early mitral inflow velocity to early mitral annular velocity (E: Ea) correlates well with MLAP in human subjects. We sought to determine the ability of E: Ea to predict MLAP in dogs with experimentally induced mitral regurgitation. Nine anesthetized purpose-bred dogs underwent placement of a Swan-Ganz catheter into the left atrium and recording of MLAP. Simultaneous transthoracic echocardiographic and hemodynamic studies were performed after acute chordae tendineae rupture and during IV infusion with nitroprusside (2.5-5.0 microg x kg(-1) x min(-1)) or hydralazine (1-1.5 mg/kg). Mitral regurgitant fraction, measured by single-plane angiography and thermodilution, ranged from 17% to 81%. MLAP increased from 5.4 +/- 2.5 mm Hg to 17.4 +/- 9.4 mm Hg after creation of mitral valve regurgitation (MR; P = .018). Forty sets of echocardiographic measurements were obtained from 7 dogs, and E, as well as E: Ea, were linearly related to MLAP. The R2 value for the linear regression equation containing E: Ea as the dependent variable (0.83) was greater than that for E (0.73). The 95% confidence intervals were calculated for predicting MLAP = 20 mm Hg from E:Ea, and E:Ea >9.1 or <6.0 indicated a 95% probability that MLAP was >20 mm Hg or <20 mm Hg, respectively. Echocardiography can be used to predict MLAP in isoflurane-anesthetized dogs with experimentally induced acute mitral valve insufficiency.

Use of tissue Doppler imaging to confirm the diagnosis of dilated cardiomyopathy in a dog with equivocal echocardiographic findings

A 1-year-old healthy female Great Dane was referred for an echocardiographic examination prior to anesthesia and surgical correction of prolapse of the right third eyelid gland. Findings of a physical examination were normal. Conventional 2-dimensional and M-mode echocardiography revealed equivocal findings of dilated cardiomyopathy (DCM). Conversely, tissue Doppler imaging revealed a dramatic decrease in systolic and early diastolic radial myocardial velocity gradients, which were related to a decrease in endocardial velocities. Four months later, the diagnosis of DCM was confirmed via conventional echocardiography. In dogs with equivocal conventional echocardiographic findings of DCM, severe myocardial alterations may be detected via tissue Doppler imaging and this technique may enable early diagnosis of radial myocardial dysfunction.

[Transesophageal echocardiography: principles, technique and potential indications in veterinary medicine]

Transesophageal echocardiography (TEE) is a recent ultrasound technique using an endoscopic transducer to image the heart from within the esophagus. TEE avoids the anatomical structures that may affect the quality of the conventional transthoracic echocardiography. The quality of cardiovascular images obtained with TEE is therefore superior to transthoracic views. The potential indications of TEE in veterinary medicine include analysis of specific abnormalities (thrombosis, aneurism, cardiac tumors), cardiac monitoring during anesthesia or catheterization, and evaluation of cardiovascular surgical procedures.

Comparison of systolic cardiac function before and after treatment of atrial fibrillation in horses with and without additional cardiac valve insufficiencies

Clinical, electrocardiographic and echocardiographic examinations were conducted before therapy and 4 days after conversion to normal sinus rhythm in 15 horses with a history of atrial fibrillation of 2-6 months duration. Seven horses showed no other signs of cardiac disease. Four horses suffered additionally from mitral valve insufficiency, while six horses had aortic valve insufficiency, including two of the four horses with mitral valve insufficiency, but none had signs of congestive heart failure. Doppler echocardiographic estimates of various variables were made for assessment of systolic heart function. These included heart rate, stroke volume, cardiac output and cardiac output per kg of body weight (heart index). After conversion to normal sinus rhythm, the horses without heart valve insufficiency showed a statistically significantly decreased heart rate (-24%) and cardiac output (-3%), but an increase in stroke volume (+8.4%) and heart index (+9%). The horses with heart valve insufficiency experienced a statistically significant decrease in heart rate (-21%) after conversion to normal sinus rhythm, but showed an increase in all other variables. Cardiac output increased statistically significantly by 20%, stroke volume by 54% and heart index by 58%.

Quantification of mitral regurgitation using proximal isovelocity surface area method in dogs

The present study was performed to determine the accuracy and reproducibility of calculating the mitral regurgitant orifice area with the proximal isovelocity surface area (PISA) method in dogs with experimental mitral regurgitation and in canine patients with chronic mitral insufficiency and to evaluate the effect of general anesthesia on mitral regurgitation. Eight adult, Beagle dogs for experimental mitral regurgitation and 11 small breed dogs with spontaneous mitral regurgitation were used. In 8 Beagle dogs, mild mitral regurgitation was created by disrupting mitral chordae or leaflets. Effective regurgitant orifice (ERO) area was measured by the PISA method and compared with the measurements simultaneously obtained by quantitative Doppler echocardiography 4 weeks after creation of mitral regurgitation. The same procedure was performed in 11 patients with isolated mitral regurgitation and in 8 Beagle dogs under two different protocols of general anesthesia. ERO and regurgitant stroke volume (RSV) by the PISA method correlated well with values by the quantitative Doppler technique with a small error in experimental dogs (r = 0.914 and r = 0.839) and 11 patients (r = 0.990 and r = 0.996). The isoflurane anesthetic echocardiography demonstrated a significant decrease of RSV, and there was no significant change in fractional shortening (FS), ERO area, LV end-diastolic and LV end-systolic volume. ERO area showed increasing tendency after ketamine-xylazine administration, but not statistically significant. RSV, LV end-systolic and LV end-diastolic volume increased significantly (p < 0.01), whereas FS significantly decreased (p < 0.01). The PISA method is accurate and reproducible in experimental mitral regurgitation model and in a clinical setting. ERO area is considered and preferred as a hemodynamic-nondependent factor than other traditional measurements.

[Influence of detomidine on echocardiographic function parameters and cardiac hemodynamics in horses with and without heart murmur]

30 warmblood horses were examined before and after sedation with 20 micrograms/kg BW detomidine, to determine changes of cardiac function parameters, using B-mode, M-mode and Doppler echocardiography. 15 horses showed a heart murmur, but no clinical signs of cardiac heart failure, 15 horses had neither a heart murmur nor other signs of cardiac disease. After sedation with detomidine we could recognise a significant increase of end-diastolic left atrium diameter, an increase of end-systolic left ventricular diameter and aortic root diameter. The end-systolic thickness of papillary muscle and interventricular septum showed a decrease. Fractional shortening and amplitude of left ventricular wall motion was decreased after sedation. The mitral valve echogram revealed a presystolic valve closure and an inflection in the Ac slope (B-notch) in xy horses before sedation. Both increased after sedation with detomidine. Doppler echocardiography showed a decrease of blood flow velocity and velocity time integral (VTI) in the left and right ventricular outflow tract after sedation. Regurgitant flow signals were intensified following sedation in xy horses, especially at the mitral valve.

Reversible pulmonary hypertension presenting simultaneously with an atrial septal defect and angiostrongylosis in a dog

A one-year-old female neutered beagle was presented with marked abdominal effusion. Echocardiography showed marked dilatation of the right cardiac chambers, an atrial septal defect and severe tricuspid insufficiency. Systolic pulmonary arterial pressure (sPAP), evaluated by continuous wave Doppler echocardiography, was very high (80 mmHg), with a right to left interatrial shunt. The radiographic images were compatible with widespread pneumonitis. Numerous larvae of Angiostrongylus vasorum were visible on direct faecal examination. The animal was given fenbendazole for 15 days, combined with diuretics, an antibiotic and a vasodilator. Two weeks later, the dog showed a marked improvement. The treatment, except the anthelmintic, was continued for seven weeks and then stopped. At that stage, Doppler echocardiography revealed that the sPAP had returned to normal (20 mmHg) and the interatrial shunt had reversed (left to right). Eighteen months later, clinical and Doppler echocardiographic examinations were normal.

Determinants of weak femoral artery pulse in dogs with mitral valve prolapse

In three substudies encompassing 247 dogs from two breeds predisposed to myxomatous mitral valve disease (MMVD), femoral artery pulse strength was palpated and related to potential explanatory factors, including quantitative echocardiographic measures of MMVD, aortic and femoral artery diameter and wall thickness and blood pressure. In addition, in 109 Cavalier King Charles Spaniels (of which 61 were included in the three substudies mentioned above), the relation between femoral artery pulse strength and presence of thrombocytopenia was investigated. In 26% of the dogs, a pulse </=50% of normal strength was detected; six dogs (2.0%) had an absent pulse unilaterally or bilaterally. Mitral valve prolapse severity, degree of obesity, heart rate and age all influenced femoral artery pulse strength negatively. Weak femoral artery pulses were not related to clinical signs or to decreased pulse pressure or stroke volume. A weak femoral artery pulse reflected reduced artery diameter and/or distension rather than occlusion. In conclusion, weak femoral artery pulses in dogs with MMVD seem to be associated with regional/local reductions in blood flow and not arteriosclerosis or platelet count.

[Exploration of a third degree atrioventricular block by standard echocardiography, tissue Doppler imaging, and treatment with a cardiac pacemaker in a German wire-haired pointer]

A nine-year-old intact male Drathaar was evaluated for syncope and extreme weakness, and was found to have a third degree atrioventricular (AV) block. As there were no biochemic, serologic, organic (thoracic radiographs, abdominal echography, standard and tissue Doppler echocardiographies) and histologic (interventricular septum biopsy) anomalies, the dog was treated with a permanently implanted cardiac pacemaker.

The relationship of resting S-T segment depression to the severity of subvalvular aortic stenosis and the presence of ventricular premature complexes in the dog

Electrocardiograms (ECG) from 35 dogs with subvalvular aortic stenosis (SAS) with a left ventricular outflow tract pressure gradient (PG) of > or =50 mm Hg were retrospectively evaluated for S-T segment depression (STD, > or =0.2 mV in lead II). Pressure gradient, age, heart rate (HR), and number of ventricular premature complexes (VPCs) on a 24-hour ambulatory ECG for dogs with STD were not significantly different from those for dogs without STD. The S-T segment deviation did not correlate significantly with PG, age, HR, or VPCs. The significance of STD in the dog with SAS remains uncertain. Long-term prospective studies are needed to fully understand this observation.

COMPARISON OF DOPPLER-DERIVED PEAK AORTIC VELOCITIES OBTAINED FROM SUBCOSTAL AND APICAL TRANSDUCER SITES IN HEALTHY DOGS

The accuracy of Doppler-derived blood flow velocity depends on the angle of incidence between the ultrasound beam and the direction of flow. In dogs with subaortic stenosis, it is known that the subcostal transducer site provides higher left ventricular ejection velocities than does the apical site. Left ventricular ejection velocities obtained from the subcostal site in healthy dogs have not been reported; accordingly, we examined healthy, random-source dogs to test the hypothesis that aortic velocities obtained from the subcostal and apical transducer sites differ. In 38 unsedated dogs, high-pulsed repetition frequency (HPRF) and continuous-wave (CW) Doppler studies of the proximal aorta and left ventricular outflow tract were performed using two-dimensional echocardiographic guidance. The effects of Doppler modality, transducer site, and their interaction on peak aortic velocity were tested through the use of analysis of variance. P values less than 0.05 were considered to indicate significance. The mean (+/-SE) peak aortic velocities were as follows: subcostal site (HPRF) = 1.44 +/- 0.03; apical site (HPRF) = 1.39 +/- 0.03; subcostal site (CW) = 1.48 +/- 0.03; apical site (CW) = 1.39 +/- 0.03. Aortic velocities obtained from the subcostal site were significantly greater than those obtained from the cardiac apex (P = 0.0001). Lower and upper limits of 95% reference intervals for aortic velocities by method of measurement and transducer location are proposed. In a population of healthy dogs, peak aortic velocities obtained from the subcostal site exceeded those obtained from the cardiac apex but did so only to a marginal degree.

Right-to-left shunting patent ductus arteriosus with pulmonary hypertension in a cat

A 16-month-old, neutered female domestic shorthaired cat had tachypnoea, inappetence and a heart murmur, which had been first detected at eight weeks old. Diagnosis of reverse shunting patent ductus arteriosus and pulmonary hypertension was based on a detailed two-dimensional and Doppler echocardiographic examination. This report documents the clinical and imaging findings in this rare feline condition.

Effect of handling-induced stress on the results of spectral Doppler echocardiography in falcons

In order to evaluate the effects of habituation to handling on the Doppler-derived velocity of diastolic ventricular inflow and systolic aortic outflow, falcons that were accustomed to regular handling were compared with falcons that had been handled very little. The mean heart rate of the frequently handled birds was 111 beats per minute less than the non-habituated birds. All the mean blood flow velocities recorded were much higher in the non-habituated birds than those accustomed to handling. Taking into account the difficulty of objectively quantifying the level of stress suffered by any individual bird, the question is, if meaningful clinical or reference values for Doppler-derived blood flow velocities may be obtained in unsedated or non-anaesthetized birds?

Aortic ejection velocity in healthy Boxers with soft cardiac murmurs and Boxers without cardiac murmurs: 201 cases (1997-2001)

OBJECTIVE

To determine aortic ejection velocity in healthy adult Boxers with soft ejection murmurs without overt structural evidence of left ventricular outflow tract obstruction and in healthy Boxers without cardiac murmurs.

DESIGN

Retrospective study.

ANIMALS

201 Boxers.

PROCEDURE

Dogs were examined independently by 2 individuals for evidence of a cardiac murmur, and a murmur grade was assigned. Maximal instantaneous (peak) aortic ejection velocity was measured by means of continuous-wave Doppler echocardiography from a subcostal location. Forty-eight dogs were reexamined approximately 1 year later.

RESULTS

A soft (grade 1, 2, or 3) left-basilar ejection murmur was detected in 113 (56%) dogs. Overall median aortic ejection velocity was 1.91 m/s (range, 1.31 to 4.02 m/s). Dogs with murmurs had significantly higher aortic ejection velocities than did those without murmurs (median, 2.11 and 1.72 m/s, respectively). Auscultation of a murmur was 87% sensitive and 66% specific for the identification of aortic ejection velocity > 2.0 m/s. An ejection murmur and aortic ejection velocity > 2.0 m/s were identified in 73 (36%) dogs. For most dogs, observed changes in murmur grade and aortic ejection velocity during a follow-up examination 1 year later were not clinically important.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that ejection murmurs were common among healthy adult Boxers and that Boxers with murmurs were likely to have high (> 2.0 m/s) aortic ejection velocities. The cause of the murmurs in these dogs is unknown.

Morphologic and functional characterization of Chagasic heart disease in non-human primates

Chagasic heart disease has been documented in non-human primates, but noninvasive characterization of systolic and diastolic function has not been previously reported. Seventeen seropositive (12 females; mean age, 20) and 13 age- and gender-matched seronegative baboons underwent Doppler echocardiography. Systolic function indices included left ventricular (LV) fractional shortening (FS %), velocity of circumferential fiber shortening (VCF, circ/sec), LV mass index, and left and right ventricular ejection fractions (RVEF %). Diastolic function indices included transmitral E-wave, A-wave, E/A ratio, E-deceleration time, and isovolumic relaxation time. Twelve-lead electrocardiographic (ECG) recordings were obtained. There were no significant differences between groups for body size or blood pressure. Seropositive and seronegative groups revealed diffuse non-specific T wave changes precluding differentiation; however, tall "P" waves were seen in four seropositive and two seronegative baboons. Four of the 17 (24%) seropositive baboons had decreased FS (25 +/- 8% versus 40 +/- 5%, P < 0.005) and VCF (1.05 +/- 0.36 circ/sec versus 1.84 +/- 0.23 circ/sec, P < 0.0001), prolonged isovolumic relaxation time (71 +/- 16 msec versus 55 +/- 9 msec, P < 0.02), and reduced RVEF (44 +/- 9% versus 54 +/- 4%, P < 0.05), as compared with the other seropositive baboons. We conclude that chagasic heart disease is present in 24% of the naturally infected baboons in this study. ECG evidence of right atrial enlargement was more common in the seropositive animals. There were systolic and diastolic abnormalities of both ventricles. The LV systolic dysfunction may be segmental or diffuse.