Doppler echocardiographic measurement of mitral flow volume: validation of a new method in adult patients

Terlipressin improves pulmonary pressures in cirrhotic patients with pulmonary hypertension and variceal bleeding or hepatorenal syndrome

Terlipressin has been shown to improve both pulmonary and systemic hemodynamics in stable cirrhotic patients with pulmonary hypertension, whereas other vasoconstrictors may cause pulmonary pressures to deteriorate. We investigated the pulmonary and systemic hemodynamic effects of the first terlipressin dose (2 mg) in 7 cirrhotic patients with PH presenting with variceal bleeding (n=4) or hepatorenal syndrome (n=3). Terlipressin decreased pulmonary vascular resistance (158.8+/-8.9 vs 186.5+/-13.9 dynes · sec · cm-5; P=0.003) together with an increase in systemic vascular resistance (2143+/-126 vs 1643+/-126 dynes · sec · cm-5; P<0.001). Terlipressin should be the vasoconstrictor treatment of choice when patients present with variceal bleeding or HRS.

Assessment of ventricular filling volumes with an automated color Doppler method: validation in a pulsatile flow model

OBJECTIVE

Determination of ventricular filling volumes with the use of Doppler echocardiographic measurements critically depends on the presence of a circular-shaped flow area and a flat velocity profile across it because evaluation of flow volume is usually based on echocardiographic measurements of its diameter and pulsed Doppler recordings within the center of this area. The approach may be limited at the mitral and tricuspid ring levels as a result of their noncircular shape and because nonflat velocity profiles are present. The purpose of this study was to examine in a pulsatile flow model simulating ventricular inflow conditions the accuracy of an automated method based on the analysis of color Doppler flow velocities for evaluation of flow volumes.

MATERIALS AND METHODS

A recently-developed automated Doppler method that takes into account the velocity distribution across a region of interest was examined in a pulsatile flow model by using flows with waveforms characteristic for ventricular inflow through tubes with elliptically-shaped cross-sectional areas. Color Doppler imaging was performed against flow direction along the major and minor axes of the tubes with major diameters ranging between 3 and 5 cm and major-to-minor diameter ratios of 1.5 and 2.0.

RESULTS

A close correlation was found between flow volumes measured by the Doppler technique for registrations along the minor or major axis of the ellipses and actual values (r = 0.99, standard error of the estimate = 0.44 to 1.98 mL), with a systematic underestimation or overestimation, respectively, depending on the diameter ratio. Averaging of the data derived from 2 orthogonal measurements by using the geometric mean value yielded an excellent agreement between Doppler data and actual flow volumes.

CONCLUSION

This automated color Doppler method enables reliable determination of flow volumes in a pulsatile flow model simulating ventricular inflow conditions with the use of 2 orthogonal imaging views. The data indicate that the method may improve the noninvasive evaluation of ventricular filling volumes.

Transgastric, pulsed Doppler echocardiographic determination of cardiac output

OBJECTIVE

The aim of this study was to evaluate the accuracy of cardiac output measurement with transesophageal echocardiography (TEE) using a transgastric, pulsed Doppler method in acutely ill patients.

DESIGN

Cardiac output was simultaneously measured by thermodilution (TD) and a transgastric, pulsed Doppler method.

SETTING

The study was carried out in a surgical intensive care unit as part of the management protocol of the patients.

PATIENTS

Thirty consecutive acutely ill patients with a Swan-Ganz catheter, mechanically ventilated, sedated and with a stable hemodynamic condition were included.

MEASUREMENTS

Pulsed Doppler TEE was performed using a transgastric approach in order to obtain a long axis view of the left ventricle. Cardiac output was calculated from the left ventricular outflow tract diameter, the velocity time integral of the blood flow profile and heart rate.

RESULTS

One patient was excluded because of the presence of aortic regurgitation and another, because of the impossibility of obtaining a transgastric view. Twenty-eight simultaneous measurements were performed in 28 patients. A clinically acceptable correlation and agreement were found between the two methods (Doppler cardiac output = 0.889 thermodilution cardiac output +0.74 l/min, r = 0.975, p <0.0001).

CONCLUSION

Transgastric pulsed Doppler measurement across the left ventricular outflow tract with TEE is a very feasible and clinically acceptable method for cardiac output measurement in acutely ill patients.

M mode and Doppler echocardiographic assessment of left ventricular diastolic function in primary antiphospholipid syndrome

BACKGROUND

High titres of serum antiphospholipid antibodies are a possible pathogenic factor for cardiac lesions in patients with systemic lupus erythematosus.

OBJECTIVE

To test the hypothesis of a causal link between high titres of antiphospholipid antibodies in the serum and myocardial involvement in patients without systemic lupus erythematosus.

PATIENTS AND DESIGN

18 patients with primary antiphospholipid syndrome (recurrent fetal loss, arterial and/or venous thrombosis, high titres of antiphospholipid antibodies, and no criteria for systemic lupus erythematosus) were prospectively studied by cross sectional, M mode, and pulsed Doppler echocardiography, and compared with 18 healthy controls. The pulsed Doppler indices of left ventricular diastolic function included isovolumic relaxation time and four mitral outflow indices: peak velocity of early flow, peak velocity of late flow, early to late peak flow velocity ratio, and rate of deceleration of early flow. Four computerised M mode indices were also measured: peak rate of left ventricular enlargement in diastole, peak rate of posterior wall thinning, peak velocity of lengthening of the posterior wall, and velocity of circumferential chamber lengthening.

RESULTS

Compared with controls, patients with primary antiphospholipid syndrome had higher values for isovolumic relaxation time and peak velocity of late mitral outflow and lower values for early to late mitral peak outflow velocity ratio, rate of deceleration of early mitral outflow, peak rate of left ventricular enlargement in diastole, peak rate of posterior wall thinning, peak velocity of lengthening of the posterior wall and velocity of circumferential chamber lengthening.

CONCLUSION

This abnormal pattern reflects an impairment of myocardial relaxation and filling dynamics of the left ventricle in patients with primary antiphospholipid syndrome who were free of any clinically detectable heart disease. These data suggest that high serum titres of antiphospholipid antibodies may be associated with subclinical myocardial damage.

Detection and localization of early diastolic forces within the left ventricle from inflow jet dynamics. A comparison between normal subjects and patients with dilated cardiomyopathy

We studied the properties of the jet of blood entering the left ventricle from the left atrium during early diastole in 32 patients with dilated cardiomyopathy, and 24 normal subjects of similar age. The diameter of the jet was measured from the cross-sectional color Doppler image and its cross-sectional area (JA) was derived. Pulsed Doppler records of flow velocity were made at 1-cm intervals into the ventricle from the mitral ring. Peak (Vp) and mean (Vm) E wave velocity and time velocity integral (TVI) were determined. At any level in the ventricle, therefore, the early diastolic volume of blood remaining in the jet, i.e., the flow time integral, is given by JA.TVI; the local flow rate, Q, by JA.Vm; and jet momentum along the long axis of the ventricle by Q.Vp. In normals, the jet cross-sectional area fell from 5.9 (1.3) cm2 at the mitral ring to 4.9 (0.7) cm2 at 4 cm (P < 0.05), but the flow time integral fell proportionately more, from 46.0 (15.2) ml at the ring level to 15.9 (3.4) ml at 4 cm (P < 0.01). Axial momentum flux was 44 (13) x 10(2) cm4s-2 at the ring level, falling to 28 (10) x 10(2) cm4s-2 at 4 cm (P < 0.01). In dilated cardiomyopathy, the jet cross-sectional area was much smaller than normal, 1.9 (0.8) cm2 at the ring level, and it remained effectively constant, being 2.0 (0.9) cm2 at 6 cm (P < 0.01 vs normals).(ABSTRACT TRUNCATED AT 250 WORDS)

Two-dimensional mitral flow velocity profiles in pig models using epicardial Doppler echocardiography

OBJECTIVES

This study investigated the velocity distribution across the natural mitral valve.

BACKGROUND

Information about the blood velocity distribution across the mitral valve is of interest in basic fluid dynamic studies of the natural mitral valve and is needed for precise cardiac output estimates by Doppler echocardiography.

METHODS

The velocity distribution across the mitral valve was measured by epicardial Doppler echocardiography in ten 90-kg anesthetized pigs. By rotating the ultrasound transducer in 30 degrees intervals from the apical position, we constructed two-dimensional velocity profiles across the left ventricular inflow tract from diameters from each rotation arranged around a reference point. The time-averaged mitral velocity profile was calculated to estimate the error in cardiac output calculations that may occur with pulsed Doppler ultrasound when a single sample volume is used to record the mean velocity across the mitral orifice.

RESULTS

The time-averaged diastolic cross-sectional mitral velocity profiles at the level of the mitral annulus and leaflet tips were variably skewed because of the development of a large anterior vortex in the left ventricle during the deceleration of early diastolic inflow and atrial systole. The ratio of the time-velocity integral of the center sample volume to the spatially averaged time-velocity integral was 1.13 +/- 0.15 (mean +/- SD) (range 0.80 to 1.32). Using regression analysis, we found a correlation between the degree of nonuniformity of the cross-sectional velocity distribution and the peak velocity of the anterior vortex (r = 0.65, p < 0.01).

CONCLUSIONS

The assumption of a flat mean velocity profile across the mitral valve can introduce errors of +13 +/- 15% (mean +/- SD) in cardiac output measured with pulsed Doppler ultrasound when one is interrogating a single center sample volume.

Quantitative Doppler assessment of valvular regurgitation

BACKGROUND

Quantitation of valvular regurgitation remains a challenge. The accuracy of quantitative Doppler is controversial, and its ability to measure regurgitant volume is unknown; therefore, it is not widely used.

METHODS AND RESULTS

In 120 patients (20 without regurgitation, 19 with aortic regurgitation, and 81 with mitral regurgitation), the stroke volume through the mitral annulus and left ventricular outflow tract were measured using pulsed-wave Doppler concurrently with left ventricular stroke volume calculated using left ventricular volumes measured by two-dimensional echocardiography Simpson's biapical method. Regurgitant volume and fraction were thus computed using Doppler or ventricular methods. In normal patients there were good correlations between Doppler and left ventricular measurements of stroke volume. Doppler regurgitant volume and fraction were 4.4 +/- 4.4 mL and 5.3 +/- 4.5%, respectively. In patients with aortic regurgitation, there were good correlations between Doppler and left ventricular measurements of stroke volume, regurgitant volume, and regurgitant fraction (r = 0.97, r = 0.95, and r = 0.93, respectively; p < 0.0001). In patients with mitral regurgitation, despite good correlations between Doppler and ventricular methods for stroke volume, regurgitant volume, and regurgitant fraction (r = 0.94, r = 0.93, and r = 0.94, respectively; p < 0.001), these variables were overestimated by Doppler. However, in the last 54 patients compared with the first 27, overestimation decreased significantly for regurgitant volume (5 +/- 10 mL versus 18 +/- 27 mL, p < 0.05) and regurgitant fraction (3.3 +/- 6.7% versus 6.2 +/- 6.8%, p = 0.05).

CONCLUSIONS

Quantitative Doppler can be performed in large numbers of patients in a clinical laboratory. Its potential limitation was identified as overestimation of mitral regurgitation, which is overcome with increased experience. Its achieved accuracy in mitral and aortic regurgitation allows measurement not only of regurgitant fraction but most importantly of regurgitant volume.

Cross-sectional early mitral flow-velocity profiles from color Doppler in patients with mitral valve disease

BACKGROUND

Cross-sectional flow-velocity profiles from early mitral flow in 20 patients (10 with mitral regurgitation and 10 with mitral stenosis) were constructed from the velocity data from each point in sequentially delayed two-dimensional digital Doppler ultrasound maps.

METHODS AND RESULTS

The data suggested that the early mitral flow studied in an apical four-chamber view was variably skewed in both patient groups. The maximum flow velocity overestimated the cross-sectional mean velocity at the same time by a factor of 1.12-1.86. The maximum time-velocity integral was 1.13-1.77-fold greater than the cross-sectional mean time-velocity integral. In patients with mitral regurgitation, the cross-sectional flow-velocity profile appeared to be most skewed at the level of the mitral leaflet tips. The level of the mitral annulus appeared to give the most homogenous flow-velocity distribution in both patient groups.

CONCLUSIONS

When calculations of volume flow are based on pulsed Doppler ultrasound recordings with a single sample volume, the possibility of a skewed flow-velocity profile must be taken into account.

A theoretical model for the noninvasive assessment of the transmitral pressure-flow relation

The purpose of this paper is to formulate from the equations of fluid mechanics an equation which describes the transmitral pressure-flow relationship. According to the linear momentum equation applied to the atrioventricular coupling, the left-atrium-left-ventricle pressure difference (Pa-Pv) can be written as Pa-P v = A delta v/delta t + B v 2 + C v, where v is the transmitral blood velocity and A, B, and C are variables related to the geometry of the atrium, ventricle and mitral orifice, respectively. Based on this theory, Pa-Pv is calculated noninvasively in a patient with a nonobstructive mitral valve. Mitral flow and cardiac dimensions recorded by Doppler echocardiography are digitized and analyzed. Calculation shows that Pa-Pv reaches its peak value at the time of flow peak acceleration and has already considerably decreased at the time of peak velocity. The time course of calculated Pa-Pv is in close agreement with the published experimental catherization data. Numerical computation of early diastolic left atrium and left ventricle pressure curves based on the experimental data of others for the time constant of left ventricular relaxation, left atrial and ventricular chambers stiffness constants, combined with sine-waveform-simulated mitral flow, verifies the time course and the magnitude of Pa-Pv as predicted from flow equations. This paper provides a theoretical method for the noninvasive assessment of the transmitral pressure-flow relationship using ultrasound technique and might help to achieve a better understanding of the diastolic function as assessed by Doppler echocardiography.

Impact of changes in heart rate and stroke volume on the cross sectional flow velocity distribution of diastolic mitral blood flow. A study on 6 patients with pacemakers programmed at different heart rates

The effect of changes in stroke volume on the cross sectional velocity distribution in the mitral orifice during passive mitral inflow was studied in six patients with total atrioventricular block, atrial fibrillation and VVI pacemakers during periods with different heart rates. The time velocity integrals recorded both in the left ventricular outflow tract and at the mitral orifice decreased significantly as the heart rate was increased from 60 to 80 and from 80 to 100 beats per minute. Instantaneous cross sectional flow velocity profiles were constructed by time interpolation of the velocity data from each point in sequentially delayed two dimensional digital ultrasound maps. Each patient had a characteristic cross sectional flow velocity profile in the mitral orifice recorded at the level of the leaflet tips in a four chamber view. The velocity profiles varied between the patients. With increase in heart rate only minimal changes in the flow profiles from individual patients were seen. The maximum velocity through the mitral orifice overestimated the cross sectional mean velocity at the same time by a factor of 1.4-1.9. The maximum time velocity integral overestimated the cross sectional mean by a factor of 1.4-1.8. The observed cross sectional skew varied between patients but did not change significantly with increasing heart rate and decrease in stroke volume.

Non-invasive measurement of the regurgitant fraction by pulsed Doppler echocardiography in isolated pure mitral regurgitation

OBJECTIVE

To assess the usefulness of pulsed Doppler echocardiography as a method of measuring the regurgitant fraction in patients with mitral regurgitation.

PATIENTS AND METHODS

Twenty controls and 27 patients with isolated mitral regurgitation underwent Doppler studies. In the patients the study was performed within 48 hours of cardiac catheterisation. Aortic outflow was measured in the centre of the aortic annulus, and mitral inflow was derived from the flow velocity at the tip of the leaflets and the area of the elliptical mitral opening. The regurgitant fraction was calculated as the difference between the two flows divided by the mtiral inflow.

RESULTS

In the 20 controls the two flows were almost identical (mitral inflow, 4.44 (SD 0.88) l/min; aortic outflow, 4.58 (SD 0.84) l/min), with a mean regurgitant fraction of 4.2 (SD 8.4)%. In patients with mitral regurgitation, the mitral inflow was significantly higher than the aortic outflow (8.8 (3.6) v 4.3 (1.1) l/min). In most patients the Doppler-derived regurgitant fraction (45.8 (19.2)%) accorded closely with the regurgitant fraction (41.3 (SD 17.8)%) determined by the haemodynamic technique.

CONCLUSION

Pulsed Doppler echocardiography, with an instantaneous velocity-valve area method for calculating mitral inflow, reliably measured the severity of regurgitation in patients with mitral regurgitation.

Relations between posterior wall kinetics during diastole and left ventricular filling

M-mode echocardiography reveals an abrupt change between early and late left ventricular posterior wall kinetics during relaxation. No attempt has been previously made to relate this wall kinetic change and transmitral flow rate. In 25 normal subjects, 14 patients with dilated cardiomyopathy (Group 1) and 17 patients with hypertrophic cardiomyopathy (Group 2), M-mode echocardiographic studies were performed on the posterior wall and mitral valve. Transient values of mitral orifice area were calculated and transmitral flow velocities were recorded: area and velocity data yielded transmitral flow rates. Time intervals were determined from mitral opening to peak early area, velocity and flow rate and to posterior wall slope change. An additional group included five patients with a mitral prosthesis. The posterior wall slope change was present when part of the myocardial structures were almost akinetic or when mitral chordae tendineae were absent; slope change appeared as a regional phenomenon in the free wall. In the normal subjects, close values were found for the four time intervals. In the patients with dilated and hypertrophic cardiomyopathy, peak early velocity (95.7 +/- 16.7 and 146.2 +/- 31.4 ms, respectively), peak flow rate (84.7 +/- 18.2 and 137.4 +/- 29.5 ms) and time to slope change (91.4 +/- 18.6 and 133.6 +/- 32.7 ms) were significantly delayed (p less than 0.001) in comparison with peak area (56.6 +/- 9.5 and 84.3 +/- 22.5 ms). Slope change does not indicate the end of the early filling phase but, rather, its transition from acceleration to deceleration. Time to peak velocity or time to peak filling rate must be considered in a relaxation analysis.

Cross sectional early mitral flow velocity profiles from colour Doppler

Instantaneous cross sectional flow velocity profiles from early mitral flow in 10 healthy men were constructed by time interpolation of the velocity data from each point in sequentially delayed two dimensional digital Doppler ultrasound maps. This interpolation allows correction of the artificially produced skewness of velocities across the flow sector caused by the time taken to scan the flow sector for velocity recording of pulsatile blood flow. These results suggested that early mitral flow studied in an apical four chamber view is variably skewed both at the leaflet tips and at the annulus. The maximum flow velocity overestimated the cross sectional mean velocity at the same time by a factor of 1.2-2.2. Also the maximum time velocity integral overestimated the cross sectional mean time velocity integral to the same extent. This cross sectional skew must be taken into account when calculation of blood flow is based on recordings with pulsed wave Doppler ultrasound from a single sample volume.