Estimation of left ventricular filling pressure by Doppler echocardiography in dogs with pacing-induced heart failure

BACKGROUND: Congestive heart failure (CHF) is a common clinical syndrome characterized by elevated filling pressure. HYPOTHESIS: Doppler echocardiographic (DE) variables of left ventricular (LV) filling can predict a decline of LV end-diastolic pressure (LVEDP) induced by acute preload reduction in dogs with compensated CHF. ANIMALS: Five male hound dogs. METHODS: Dogs previously instrumented with a transvenous cardiac pacemaker and a LV pressure gauge were paced at 160-180 bpm to induce mild CHF characterized by LVEDP > 20 mmHg. LVEDP and 9 DE variables of LV filling derived from diastolic time intervals, transmitral and pulmonary venous flow, and tissue Doppler imaging were measured simultaneously at baseline and 30, 60, 120, and 240 minutes after furosemide (4 mg/kg, IV) or placebo (0.9% saline, IV). Repeated measures analysis of variance and correlation analysis were used to determine the association between the decline of LVEDP after furosemide and DE measures of LV filling pressure (LVFP). RESULTS: Furosemide but not placebo decreased LVEDP (P < .001). The ratio of early transmitral flow velocity to LV isovolumic relaxation time (E : IVRT) predicted LVEDP best (R(2)= .50; P < .001). Correlations were also found between LVEDP and IVRT, E, ratio between E and late diastolic transmitral flow velocity (E : A), and early diastolic velocity of the mitral annulus (Ea). The ratio of E to Ea (E : Ea) was not useful in the prediction of LVEDP in this model. CONCLUSION AND CLINICAL IMPORTANCE: E : IVRT can be used to predict LVFP in dogs with mild left-sided CHF induced by rapid pacing.     

Comparison between invasive hemodynamic measurements and noninvasive assessment of left ventricular diastolic function by use of Doppler echocardiography in healthy anesthetized cats

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 age). PROCEDURE: Cats were anesthetized and instrumented to measure the time constant of isovolumic relaxation (tau [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 analyses. RESULTS: Significant correlations were found between tau 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. CONCLUSIONS 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.     

Comparison of left ventricular ejection fractions determined in healthy anesthetized dogs by echocardiography and gated equilibrium radionuclide ventriculography

Left ventricular ejection fractions (LVEF) of 8 pentobarbital-anesthetized dogs were calculated by gated equilibrium radionuclide ventriculography (RVG) and by M-mode and two-dimensional echocardiography (2-DE) prior to and during constant IV infusion of isoproterenol. Mean LVEF (+/- SD), determined with RVG by use of an automatic edge detection algorithm (RVG-auto) to define the left ventricular region of interest, increased from a resting value of 53.5% (+/- 4.9%) to 71.9% (+/- 6.8%) during isoproterenol infusion. Mean LVEF, determined with RVG by use of visual inspection (RVG-manual) to define the left ventricular region of interest increased from a resting value of 51.6% +/- 3.8% to 67.0% +/- 5.6% during isoproterenol infusion. Using 2-DE and the bullet formula to calculate left ventricular volume (LVV = 5/6 x cross-sectional area x length), mean LVEF increased from 52.3% (+/- 3.50) to 74.7% (+/- 5.0%). Using 2-DE area measurements and Teicholz formula, mean LVEF increased from 48.9% (+/- 5.1%) to 69.5% (+/- 6.0%). Using M-mode echocardiographic left ventricular diameter measurements and Teicholz formula, mean LVEF increased from 52.3 (+/- 9.0%) to 78.3% (+/- 8.1%). Before and during isoproterenol infusion, the mean LVEF values calculated by RVG agreed closely with mean LVEF values calculated from M-mode and 2-DE. Correlation coefficients determined from linear regression analysis of LVEF by echocardiography vs LVEF by radionuclide ventriculography ranged from 0.79 to 0.88. Correlation coefficients were higher and SEM were lower when LVEF was determined by RVG-manual, rather than by RVG-auto methods and when LVEF was calculated from 2-DE measurements, rather than from M-mode measurements.     

Pulsed tissue Doppler imaging of the left ventricular septal mitral annulus in healthy dogs

This study evaluated pulsed TDI variables including the isovolumic time interval and duration of the major wave in a population of large healthy dogs. Longitudinal myocardial motion at the septal mitral annulus was evaluated with pulsed TDI in 45 healthy adult dogs. Maximal myocardial velocities, isovolumic time intervals, and duration of the myocardial waves were measured. The correlation between time intervals and velocity variables was also investigated. The mean maximal systolic velocity was 6.92 ± 1.78 cm/sec, the mean early diastolic velocity (Em) was 6.58 ± 1.81 cm/sec, the mean late diastolic velocity (Am) was 5.10 ± 2.00 cm/sec, the mean isovolumic contraction time (IVCT) was 53.61 ± 95.13 msec, and the mean isovolumic relaxation time (IVRT) was 26.74 ± 57.24 msec. The early diastolic mitral inflow velocity (E)/Em ratio was 10.94 ± 3.27 while the Em/Am ratio was 1.40 ± 0.40. There was a negative correlation between Am duration and Am amplitude, and a positive correlation between the IVRT and Em/Am ratio (p < 0.05). The normal LV parameter using pulsed TDI method could be used as the reference range for identifying myocardial dysfunction in dogs.     

Effects of vagal maneuvers on heart rate and Doppler variables of left ventricular filling in healthy cats

BackgroundEvaluation of left ventricular (LV) diastole is clinically important in cats with heart disease. Diastolic dysfunction is a main characteristic of feline cardiomyopathy and is associated with clinical signs and poor outcome. Numerous echocardiographic indices characterizing LV diastole exist, of which Doppler variables of transmitral flow and mitral annular motion are used most often. However, rapid heart rate (HR), a common finding in cats examined in the veterinary hospital environment, may cause summation of flow waves limiting interpretation of diastolic function.ObjectiveTo evaluate the effects of vagal maneuvers (gentle eyeball pressure and nasal planum massage) on HR and Doppler variables of LV diastolic filling.AnimalsTwenty-four healthy client-owned cats with summated transmitral flow waves at baseline.MethodsProspective observational study. Transthoracic echocardiography was performed and Doppler transmitral and mitral annular tissue Doppler velocities recorded both before and during vagal maneuvers. Data were compared using a paired t-test.ResultsApplication of vagal maneuvers temporarily decreased HR in all cats (mean reduction ± SD; 42 ± 22 bpm). The duration of HR reduction (<5 s, 5–10 s, and >10–15 s) was evenly distributed among groups (8 cats in each). Summated Doppler transmitral flow and mitral annular tissue velocity waves were separated during vagal maneuvers in 71% and 72% of cats, respectively. No adverse effects were observed.ConclusionsVagal maneuvers may be utilized as a simple non-pharmacologic tool in the Doppler evaluation of LV diastolic function in healthy cats.     

Comparison of the myocardial performance index derived by use of pulsed Doppler echocardiography and tissue Doppler imaging in dogs with volume overload

OBJECTIVE: To investigate the relationship between the myocardial performance index (MPI) determined by use of pulsed Doppler (PD) echocardiography and tissue Doppler imaging (TDI) in the response to volume overload-related changes in left ventricle (LV) performance. ANIMALS: 7 male Beagles. PROCEDURES: Dogs were anesthetized and intubated. A 6-F fluid-filled catheter was placed in the LV to measure LV peak systolic (LVPs) and LV end-diastolic (LVED) pressures. Preload was increased by IV infusion of lactated Ringer's solution (rate of 200 mL/kg/h for 60 minutes) into a cephalic vein. Transmitral flow velocities and aortic outflow were measured, and TDI velocities were obtained from the 4-chamber view. RESULTS: Acute volume overload induced a significant increase in heart rate, LVPs pressure, and LVED pressure, compared with baseline values. A significant decrease in the PD-MPI and TDI-MPI values and a significant correlation (r = 0.70) between PD-MPI and TDI-MPI were detected. The PD-derived A-wave velocity, ejection time, and isovolumic relaxation time (IRT) and the TDI-derived IRT, MPI, and ratio of the velocity of the E wave to the velocity of the ventricular portion of the E wave during early diastole had equal ability to predict LVED pressure (r(2) = 0.63). CONCLUSIONS AND CLINICAL RELEVANCE: The TDI-MPI was closely correlated with LV filling pressure and may be helpful in evaluating global cardiac function in dogs.     

Assessment of left ventricular function using pulsed tissue Doppler imaging in healthy dogs and dogs with spontaneous mitral regurgitation

Pulsed tissue Doppler imaging (pulsed TDI) has been demonstrated to be useful for the estimation of left ventricular (LV) systolic and diastolic functions in various human cardiac diseases. The objectives of this study were to investigate the relationship between pulsed TDI and LV function by using cardiac catheterization in healthy dogs and to evaluate the clinical usefulness of pulsed TDI in dogs with spontaneous mitral regurgitation (MR). The peak early diastolic velocity (E'), peak atrial systolic velocity (A'), and peak systolic velocity (S') were detectable in the velocity profiles of the mitral annulus in all the dogs. In the healthy dogs, S' and E' were correlated with LV peak +dP/dt and -dP/dt, respectively. E' was lower in dogs with MR than in dogs without cardiac diseases. E/E' in the MR dogs with decompensated heart failure was significantly increased in comparison with those with compensated heart failure. The sensitivity and specificity of the E/E' cutoff value of 13.0 for identifying decompensated heart failure were 80% and 83%, respectively. In addition, E/E' was significantly correlated with the ratio of left atrial to aortic diameter. These findings suggest that canine pulsed TDI can be applied clinically for estimation of cardiac function and detection of cardiac decompensation and left atrial volume overload in dogs with MR.     

Doppler echocardiographic study of left and right ventricular function during dobutamine stress testing in conscious healthy dogs.

OBJECTIVE: To evaluate left and right ventricular filling and ejection performances by use of Doppler echocardiography in healthy, conscious dogs submitted to dobutamine stress testing. ANIMALS: 10 unsedated, healthy adult Beagles. PROCEDURE: Doppler echocardiography was performed during cardiac stress testing on each dog twice at 24-hour intervals. Dobutamine was infused in 10 micrograms/kg of body weight/min incremental dosages, from 12.5 to 42.5 micrograms/kg/min. Duration of each step was 15 minutes. Doppler measurements were recorded at baseline and at each stage of dobutamine infusion, whereas aortic diameter was measured at baseline and at peak dosage by use of two-dimensional echocardiography. RESULTS: Dobutamine infusion induced a significant increase in velocity time integrals and in peak flow velocities at the aortic, pulmonic, mitral, and tricuspid valves. Acceleration time-to-deceleration time ratio at the aortic wave also was increased significantly. On the other hand, ejection time, acceleration time, and deceleration time at the aortic and pulmonic valves and peak flow velocity of the E wave-to-peak flow velocity of the A wave ratio at the mitral and tricuspid valves decreased significantly during the test. The acceleration time-to-deceleration time ratio at the pulmonic wave was unchanged. A significant, progressive increase in cardiac index also was observed during dobutamine infusion, with a maximal increase of 104% from baseline. This was mediated initially by an increase in stroke index and, at higher dosages, by an increase in heart rate. CONCLUSIONS AND CLINICAL RELEVANCE: Doppler echocardiography performed during dobutamine stress testing may be a reliable method of assessing myocardial function in dogs with cardiovascular disease.     

Assessment of left ventricular function by two-dimensional speckle-tracking echocardiography in small breed dogs with hyperadrenocorticism

Background

Hyperadrenocorticism (HAC) is associated with an increased prevalence of hypertension. This study investigated the left ventricular function using two-dimensional speckle-tracking echocardiography (2D-STE) in small breed dogs affected with spontaneous HAC.Age-matched healthy controls (n = 9), dogs with pituitary-dependent hyperadrenocorticism (PDH, n = 10), and dogs with adrenal-dependent hyperadrenocorticism (ADH, n = 9) were included in this study. Conventional echocardiography, global longitudinal and circumferential strain, and strain rate were assessed.

Results

On group-wise comparison, left ventricular free wall (LVFWd) and interventricular septal thickness in diastole (IVSd) were thickest in the ADH group, followed by the PDH and controls (P = 0.014 and P = 0.001, respectively). Neither LVFWd nor IVSd was correlated with systemic blood pressure (P = 0.238 and P = 0.113, respectively). The values of all variables derived from the global strain and strain rate in longitudinal and circumferential directions followed the same pattern: highest in the controls, followed by PDH and then ADH (all P < 0.05, respectively). On multiple regression analyses, global longitudinal strain, global longitudinal strain rate in systole and early diastole, and global circumferential strain all decreased linearly with increased IVSd (all P < 0.05).

Conclusions

Left ventricular hypertrophy (LVH) was more prevalent in the HAC group compared to the control group. Association between hypertension and development of LVH was not identified. Decreased global longitudinal and circumferential strains were associated with increased IVSd. 2D-STE revealed significant decreases in systolic functions that were undetected using conventional echocardiography in the ADH and PDH groups.     

Assessment of global and regional left ventricular volume and shape by real-time 3-dimensional echocardiography in dogs with myxomatous mitral valve disease

Background: Left ventricular (LV) remodeling occurs in response to chronic volume overload. Real‐time 3‐dimensional (RT3D) echocardiography offers new modalities for LV assessment. Objective: To investigate LV changes in shape and volume in response to different severities of naturally acquired myxomatous mitral valve disease (MMVD) in dogs by RT3D echocardiography. Animals: Sixty‐five client‐owned dogs. Methods: Prospectively recruited dogs were classified by standard echocardiography into healthy, mild, moderate, and severe MMVD groups. Endocardial border tracking of LV RT3D dataset was performed, from which global and regional (automatically acquired basal, mid, and apical segments based on LV long‐axis length) end‐diastolic (EDV) and end‐systolic volumes (ESV), LV long‐axis length, and sphericity index were obtained. Results: Global and regional EDV and ESV (indexed to body weight) were most prominently increased in dogs with severe MMVD. All 3 regional LV segments contributed to increased global EDV and ESV with increasing MMVD severity, but mid‐EDV contributed the most to the global EDV increase. Furthermore, LV long‐axis length and LV sphericity index increased with increasing MMVD severity. Basal and apical EDV segments displayed the strongest association with sphericity index (P < .0001). Conclusions and Clinical Importance: The most prominent LV volume expansion was found in dogs with severe MMVD. Increased EDV, primarily in the mid‐segment, leads to rounding of LV apical and basal segments in response to increasing MMVD severity. Assessment of LV volume and shape potentially could allow early detection of dogs at risk for rapid progression into congestive heart failure.     

Comparison of echocardiography and gated equilibrium radionuclide ventriculography in the measurements of left ventricular systolic function parameters in healthy dogs

Left ventricular systolic function was assessed in 12 healthy dogs with equilibrium radionuclide ventriculography. The results of the analysis were compared to traditional echocardiographic measurements. Left ventricular internal dimensions and volume were measured at the time of end-systole and end-diastole. Ejection fraction--one of the most informative parameters of cardiac function--was calculated in each animal. Values (e.g. EDD, ESD, EDV, ESV) measured by the scintigraphic method were significantly (Student's t-test, p < 0.05) higher than the data obtained by echocardiography. Ejection fraction (EF) was the only parameter that did not differ significantly when comparing the two imaging techniques. The difference between the results of parallel measurements was in inverse ratio to the size of the heart.     

Pulsed-wave Doppler ultrasonographic evaluation of hepatic veins during variable hemodynamic states in healthy anesthetized dogs

OBJECTIVES: To quantify direction and velocity of blood flow in hepatic veins in dogs under different hemodynamic conditions by use of pulsed-wave Doppler ultrasonography. 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 high-dose isoflurane and esmolol i.v. (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 regression. RESULTS: During each study period, 4 distinct, low-velocity 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, S-wave 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.     

Influence of sotalol on the time constant of isovolumic left ventricular relaxation in anesthetized dogs.

OBJECTIVE: To determine the effects of various doses of sotalol on myocardial relaxation in healthy dogs. ANIMALS: 12 healthy adult mixed-breed dogs anesthetized with thiopental and alpha-chloralose. PROCEDURES: Left ventricular pressure (LVP), aortic pressure, and aortic flow velocity were measured. The time constant of isovolumic relaxation (tau) was determined by means of linear regression of the natural logarithm of LVP and by means of direct measurement from the LVP-versus-time curve. Sotalol was administered IV at cumulative doses of 1, 2, 4, and 8 mg/kg to 6 dogs; the other 6 were used as controls. Mean systolic aortic pressure was used to assess afterload, and maximal rate of increase in LVP versus time (dP/dt) was used as an index of contractility. RESULTS: After administration of the first dose of sotalol, tau was increased significantly, and maximum dP/dt was decreased significantly, compared with baseline values. Administration of additional doses of sotalol did not result in any additional change in tau, but maximum dP/dt increased, and maximum dP/dt after administration of the final dose of sotalol was significantly higher than maximum dP/dt after administration of the first dose. There were no significant changes in mean systolic aortic pressure. CONCLUSIONS AND CLINICAL RELEVANCE: In healthy dogs, sotalol did not have any negative effect on myocardial relaxation beyond those attributable to its beta-blocking properties, despite an increase in intracellular ionized calcium concentration, as suggested by an increase in maximum dP/dt after an initial decrease.