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 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 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 determine survival times in dogs with
severe subvalvular aortic stenosis (SAS) treated by
means of balloon valvuloplasty or with atenolol, a
β-adrenoceptor blocking drug.
Animals—38 dogs < 24 months old with severe SAS
(peak systolic pressure gradient ≥ 80 mm Hg).
Procedure—10 dogs underwent balloon valvuloplasty
and were reexamined 6 weeks later to determine the
feasibility of the procedure. The remaining 28 dogs
were randomly assigned to undergo balloon valvuloplasty
(n = 15) or to be treated with atenolol long term
(13) and were reexamined annually for 9 years or until
the time of death.
Results—For the first 10 dogs, mean pressure gradient
6 weeks after balloon valvuloplasty (mean ± SD,
119 ± 32.6 mm Hg) was significantly decreased, compared
with mean baseline pressure gradient (167 ±
40.1 mm Hg). Median survival time for dogs that
underwent balloon valvuloplasty (55 months) was not
significantly different from median survival time for
dogs treated with atenolol (56 months).
Conclusions and Clinical Relevance—Results suggest
that balloon valvuloplasty can result in a significant
decrease in the peak systolic pressure gradient
in dogs with severe SAS, at least for the short term.
No clear benefit in survival times was seen for dogs
that underwent balloon valvuloplasty versus dogs that
were treated with atenolol. (J Am Vet Med Assoc
Objectives—To quantify direction and velocity of
blood flow in hepatic veins in dogs under different
hemodynamic conditions by use of pulsed-wave
Animals—10 healthy dogs.
Procedure—Dogs were anesthetized, and venous
flow velocities in the quadrate lobe were measured.
Arterial blood pressure, right atrial pressure,
pulmonary artery pressure, and cardiac output
were measured simultaneously. The timing of each
waveform during the cardiac cycle was used to
identify velocity profiles. Peak waveform velocities
were measured during conditions of light anesthesia
with isoflurane (baseline; period 1), cardiovascular
depression following administration of highdose
isoflurane and esmolol IV (period 2), cardiovascular
depression with crystalloid volume expansion
(period 3), and high cardiac output induced
with dobutamine (period 4). Hemodynamic measurements
and maximum waveform velocities
were compared among the 4 periods by use of an
ANOVA and univariate and multivariate linear
Results—During each study period, 4 distinct, lowvelocity
waves were identified. Mean velocities
recorded during period 1 were as follows: retrograde
atrial contraction a-wave, 7.3 cm/s; antegrade systolic
S-wave, 15.0 cm/s; retrograde venous return v-wave,
2.7 cm/s; and antegrade diastolic D-wave, 11.4 cm/s.
Mean S:D ratio was 1.27. During periods 3 and 4, Swave
velocity increased; D-wave velocity was highest
during period 4.
Conclusions and Clinical Relevance—Consistent
hepatic venous velocity profiles were observed in
healthy dogs under different hemodynamic conditions.
These findings provide baseline values that may
be useful in evaluating clinical cases, but further study
involving healthy, awake dogs and dogs with cardiac
and hepatic diseases is required. (Am J Vet Res
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 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
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
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. (J Am Vet Med Assoc
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.