Objective—To determine the influence of age, body
weight (BW), heart rate (HR), sex, and left ventricular
shortening fraction (LVSF) on transmitral and pulmonary
venous flow in clinically normal dogs.
Animals—92 client-owned dogs 3 months to 19
Procedure—Transthoracic Doppler echocardiography
recordings of transmitral flow and pulmonary venous
flow were obtained in conscious unsedated dogs.
Influence of age, BW, HR, sex, and LVSF on diastolic
variables was assessed, using statistical methods
such as ANOVA on ranks and univariate and multivariate
forward stepwise linear regression analyses.
Results—Age significantly influenced isovolumic
relaxation time (IVRT; r = 0.56), ratio between peak
velocity of the early diastolic mitral flow wave-to-peak
velocity of late diastolic mitral flow wave (E:A;
r = –0.44), deceleration time of early diastolic mitral
flow (DTE; r = 0.26), and peak velocity of atrial reversal
pulmonary venous flow wave (AR-wave; r= 0.37).
Significant changes of mitral inflow and pulmonary
venous flow variables were evident only in dogs > 6
and > 10 years old, respectively. Body weight significantly
influenced DTE ( r = 0.63), late diastolic flow
duration ( r= 0.60), and AR duration ( r= 0.47), whereas
HR significantly affected DTE ( r = –0.34), IVRT
( r= –0.33), and peak velocity of AR ( r= 0.24). Sex or
LVSF (range 22 to 48%) did not influence any echocardiographic
Conclusions and Clinical Relevance—Age, BW, and
HR are important factors that affect filling of the left
atrium and left ventricle in clinically normal dogs. (Am
J Vet Res 2001;62:1447–1454)
Objective—To compare Doppler echocardiographic
variables of left ventricular (LV) function with those
obtained invasively via cardiac catheterization under
a range of hemodynamic conditions.
Animals—7 healthy anesthetized cats (1 to 3 years of
Procedure—Cats were anesthetized and instrumented
to measure the time constant of isovolumic
relaxation (tau ), LV end-diastolic pressure
(LVEDP), peak negative and positive rate of change
of LV pressure, arterial blood pressure, and cardiac
output. Echocardiographic variables of diastolic function
(isovolumic relaxation time [IVRT], early LV flow
propagation velocity [Vp], transmitral and pulmonary
venous flow velocity indices, and LV tissue Doppler
imaging indices) were measured simultaneously
over a range of hemodynamic states induced by
treatments with esmolol, dobutamine, cilobradine,
and volume loading. Correlation between invasive
and noninvasive measures of LV filling was determined
by univariate and multivariate regression
Results—Significant correlations were found
between and IVRT, peak Vp, peak late transmitral
flow velocity, and peak systolic pulmonary venous
flow velocity. A significant correlation was found
between LVEDP and early diastolic transmitral flow
velocity (peak E) and the ratio of peak E to peak Vp,
but not between LVEDP and peak Vp.
Conclusion and Clinical Relevance—IVRT and Vp
can be used as noninvasive indices of LV relaxation;
Vp was independent of preload and heart rate in
this study. The E:Vp ratio may be useful as an indicator
of LV filling pressure. (Am J Vet Res 2003;64:93–103)
Objective—To compare echocardiographic indices of myocardial strain with invasive measurements of left ventricular (LV) systolic function in anesthetized healthy dogs.
Animals—7 healthy dogs.
Procedures—In each anesthetized dog, preload and inotropic conditions were manipulated sequentially to induce 6 hemodynamic states; in each state, longitudinal, radial, and global strains and strain rate (SR), derived via 2-D speckle-tracking echocardiography, were evaluated along with conventional echocardiographic indices of LV function and maximum rate of rise (first derivative) of LV systolic pressure (LV+dp/dtmax). Catheter-derived and echocardiographic data were acquired simultaneously. Partial and semipartial correlation coefficients were calculated to determine the correlation between LV+dp/dtmax and each echocardiographic variable. Global longitudinal strain was compared with conventional echocardiographic indices via partial correlation analysis.
Results—All myocardial segments could be analyzed in all dogs. Significant semipartial correlations were identified between conventional echocardiographic strain indices and LV+dp/dtmax. Correlation coefficients for longitudinal deformation and global strain, segmental longitudinal strain, and segmental SR were −0.773, −0.562 to −0.786, and −0.777 to −0.875, respectively. Correlation coefficients for radial segments and strain or SR were 0.654 to 0.811 and 0.748 to 0.775, respectively. Correlation coefficients for traditional echocardiographic indices and LV+dp/dtmax (−0.586 to 0.821) and semipartial correlation coefficients for global strain and echocardiographic indices of LV systolic function (−0.656 [shortening fraction], −0.726 [shortening area], and −0.744 [ejection fraction]) were also significant.
Conclusions and Clinical Relevance—Results indicated that LV systolic function can be predicted by myocardial strain and SR derived via 2-D speckle-tracking echocardiographic analysis in anesthetized healthy dogs.
Objective—To assess the feasibility, describe the techniques, and determine the reliability of transthoracic echocardiography for characterization of left atrial (LA) size and LA mechanical function in horses.
Animals—6 healthy adult horses.
Procedures—Repeated echocardiographic examinations were performed independently by 2 observers in standing, unsedated horses by use of 2-dimensional echocardiography, pulsed-wave flow Doppler, and tissue Doppler imaging (TDI) techniques. Test reliability was determined by estimating measurement variability, within-day interobserver variability, and between-day inter- and intraobserver variability of all echocardiographic variables. Variability was expressed as the coefficient of variation (CV) and the absolute value below which the difference between 2 measurements will lie with 95% probability.
Results—Most echocardiographic variables of LA size had low overall variability (CV, < 15%). Among the 2-dimensional indices of LA mechanical function, area-based and volume-based ejection phase indices had moderate between-day variability (CV usually < 25%). Transmitral Doppler flow indices were characterized by low to high between-day variability (CV, 6% to 35%). The TDI wall motion velocities had high between-day variability (CV, > 25%), whereas most TDI-derived time intervals had low variability (CV, < 15%).
Conclusions and Clinical Relevance—LA size and mechanical function can be reliably assessed in standing, unsedated horses by use of 2-dimensional echocardiography, transmitral blood flow velocity profiles, and analyses of LA wall motion by use of TDI. These results may provide useful recommendations for echocardiographic assessment of LA size and function in horses.
Objective—To determine whether serum concentrations
of cardiac troponin I (cTnI) and cardiac troponin
T (cTnT) are increased in dogs with gastric dilatationvolvulus
(GDV) and whether concentrations correlate
with severity of ECG abnormalities or outcome.
Design—Prospective case series.
Animals—85 dogs with GDV.
Procedure—Serum cTnI and cTnT concentrations
were measured 12 to 24, 48, 72, and 96 hours after
surgery. Dogs were grouped on the basis of severity
of ECG abnormalities and outcome.
Results—cTnI and cTnT were detected in serum
from 74 (87%) and 43 (51%) dogs, respectively.
Concentrations were significantly different among
groups when dogs were grouped on the basis of
severity of ECG abnormalities (none or mild vs moderate
vs severe). Dogs that died (n = 16) had significantly
higher serum cTnI (24.9 ng/ml) and cTnT (0.18
ng/ml) concentrations than did dogs that survived
(2.05 and < 0.01 ng/ml, respectively). Myocardial cell
injury was confirmed at necropsy in 4 dogs with high
serum cardiac troponin concentrations.
Conclusions and Clinical Relevance—Results indicate
that concentrations of cTnI and cTnT suggestive
of myocardial cell injury can commonly be found in
serum from dogs with GDV and that serum cardiac
troponin concentrations are associated with severity
of ECG abnormalities and outcome. (J Am Vet Med
Objective—To identify Doppler echocardiographic (DE) variables that correlate with left ventricular filling pressure (LVFP).
Animals—7 healthy dogs (1 to 3 years old).
Procedures—Dogs were anesthetized and instrumented to measure left atrial pressure (LAP), left ventricular pressures, and cardiac output. Nine DE variables of LVFP derived from diastolic time intervals, transmitral and pulmonary venous flow, and tissue Doppler images were measured over a range of hemodynamic states induced by volume loading and right atrial pacing. Associations between simultaneous invasive measures of LVFP and DE measures of LVFP were determined by use of regression analysis. Receiver operating characteristic analysis was used to predict increases in mean LAP on the basis of DE variables.
Results—Mean LAP was correlated with several DE variables: the ratio between peak velocity during early diastolic transmitral flow and left ventricular isovolumic relaxation time (peak E:IVRT) during sinus rhythm and during right atrial pacing, IVRT, the ratio between late diastolic transmitral flow velocity and pulmonary venous flow duration, and the interval between onset of early diastolic mitral annulus motion and onset of early diastolic transmitral flow. Cutoff values of 2.20 and 2.17, for peak E:IVRT in dogs with sinus rhythm and atrial pacing predicted increases in mean LAP (≥ 15 mm Hg) with sensitivities of 90% and 100% and specificities of 92% and 100%, respectively.
Conclusions and Clinical Relevance—Doppler echocardiography can be used to predict an increase in LVFP in healthy anesthetized dogs subjected to volume loading.
Case Description—4 dogs with acquired pulmonary artery stenosis (PAS) were examined for various clinical signs. One was a mixed-breed dog with congenital valvular PAS that subsequently developed peripheral PAS, one was a Golden Retriever with pulmonary valve fibrosarcoma, one was a Pembroke Welsh Corgi in which the left pulmonary artery had inadvertently been ligated during surgery for correction of patent ductus arteriosus, and one was a Boston Terrier with a heart-base mass compressing the pulmonary arteries.
Clinical Findings—All 4 dogs were evaluated with 2-dimensional and Doppler echocardiography to characterize the nature and severity of the stenoses; other diagnostic tests were also performed.
Treatment and Outcome—The mixed-breed dog with valvular and peripheral PAS was euthanized, surgical resection of the pulmonic valve mass was performed in the Golden Retriever, corrective surgery was performed on the Pembroke Welsh Corgi with left pulmonary artery ligation, and the Boston Terrier with the heart-base mass was managed medically.
Clinical Relevance—Acquired PAS in dogs may manifest as a clinically silent heart murmur, syncope, or right-sided heart failure. The diagnosis is made on the basis of imaging findings, particularly results of 2-dimensional and Doppler echocardiography. Treatment may include surgical, interventional, or medical modalities and is targeted at resolving the inciting cause.
Objective—To evaluate the effects of the pacemaker funny current (If) inhibitor ivabradine on heart rate (HR), left ventricular (LV) systolic and diastolic function, and left atrial performance in healthy cats and cats with hypertrophic cardiomyopathy (HCM).
Animals—6 healthy cats and 6 cats with subclinical HCM.
Procedures—Anesthetized cats underwent cardiac catheterization and were studied over a range of hemodynamic states induced by treatment with esmolol (200 to 400 μg/kg/min, IV), esmolol and dobutamine (5 μg/kg/min, IV), ivabradine (0.3 mg/kg, IV), and ivabradine and dobutamine. Left ventricular systolic and diastolic function, cardiac output, and left atrial function were studied via catheter-based methods and echocardiography.
Results—Treatment with ivabradine resulted in a significant reduction of HR, rate-pressure product, and LV contractile function and a significant increase in LV end-diastolic pressure, LV end-diastolic wall stress, and LV relaxation time constant (tau) in cats with HCM. Concurrent administration of ivabradine and dobutamine resulted in a significant increase of LV contractility and lusitropy, with blunted chronotropic effects of the catecholamine. Left atrial performance was not significantly altered by ivabradine in cats with HCM. Regression analysis revealed an association between maximum rate of LV pressure rise and tau in cats with HCM.
Conclusions and Clinical Relevance—Ivabradine had significant effects on several cardiovascular variables in anesthetized cats with HCM. Studies in awake cats with HCM are needed to clinically validate these findings.
Objective—To evaluate the accuracy of a commercial ultrasonographic cardiac output (CO) monitoring system (UCOMS) in anesthetized Beagles as assessed by comparison with thermodilution CO (TDCO).
Animals—8 healthy anesthetized Beagles.
Procedures—Simultaneous UCOMS and TDCO measurements of CO were obtained during 4 hemodynamic states: baseline anesthesia (0.5% to 1.5% isoflurane), a higher depth of anesthesia (2% to 3.5% isoflurane) to yield a ≥ 15% reduction in systolic arterial blood pressure, IV infusion of colloidal solution to a mean right atrial pressure of ≥ 15 mm Hg, and IV infusion of dobutamine at 5 μg/kg/min. Measurements were obtained at 2 probe positions: the subxiphoid region and the right thoracic inlet. Correlation and agreement of results between methods were determined via linear regression analysis and Bland-Altman plots.
Results—A significant positive correlation was detected between UCOMS andTDCO measurements obtained at the subxiphoid (R = 0.86) and thoracic inlet (R = 0.83) positions. Bland-Altman plots revealed minimal bias between methods (bias ± SD, −0.03 ± 0.73 L/min and −0.20 ± 0.80 L/min for subxiphoid and thoracic inlet measurements, respectively). However, the percentage error associated with UCOMS measurements made at the 2 positions was > 45%.
Conclusions and Clinical Relevance—When compared with the results of TDCO, CO measured with the UCOMS exceeded commonly accepted limits of error in healthy dogs. The UCOMS was, however, able to track changes in CO across hemodynamic states. Additional research is needed to assess the usefulness of the UCOMS for monitoring CO in critically ill dogs.