New semiautomated Doppler method for quantification of volumetric flow: intraoperative validation with multiplane transesophageal color Doppler imaging

Measurement of Volumetric Flow by Real-time 3-Dimensional Doppler Echocardiography in Children

BACKGROUND

We sought to assess the accuracy and reproducibility of an automated real-time (RT) 3-dimensional (3D) Doppler echocardiography (RT3DDE) technique for measuring volumetric flow (VF) in children.

METHODS

A total of 19 healthy children (age = 11.5 +/- 3.5 years) were studied to measure VF through mitral valve (MV), aortic valve (AV), pulmonary valve (PV), and tricuspid valve (TV) by RT3DDE. RT 3D echocardiography was also performed to measure left ventricular (LV) end-systolic volume, LV end-diastolic volume, and stroke volume (stroke volume = LV end-diastolic volume--LV end-systolic volume), which served as a reference standard for comparison with VF by RT3DDE.

RESULTS

Compared with stroke volume by RT 3D echocardiography, the correlation with VF was excellent for MV (r = 0.91), good for AV (r = 0.89) and PV (r = 0.89), but poor for TV (r = 0.20) by RT3DDE. There were good agreements for AV (bias = 0.9 +/- 5.0 mL), PV (bias = -0.4 +/- 5.7 mL), and MV (bias = 4.1 +/- 4.7 mL), and marked underestimation for TV (bias = -24.4 +/- 14.6 mL).

CONCLUSIONS

Our data demonstrated that VF measurement by RT3DDE is feasible and reasonably accurate for MV, AV, and PV but problematic for TV.

A real-time 3-dimensional digital Doppler method for measurement of flow rate and volume through mitral valve in children: A validation study compared with magnetic resonance imaging

We developed and assessed a real-time 3-dimensional (3D) digital Doppler method for measurement of flow volumes through the mitral valve in children. A total of 13 children (aged 10.46 +/- 2.5 years; 8 boys/5 girls) were enrolled. An ultrasound system (Sonos 7500, Philips, Andover, Mass) was used to acquire raw 3D velocity data for flow measurement based on Gaussian control surface theorem [flow (mL/s) = mean velocity x flow area]. Stroke volume (SV) measured by real-time 3D digital Doppler with the control surface at the mitral valve annulus or orifice was compared with the SV by phase velocity cine magnetic resonance imaging (MRI) at the ascending aorta and by left ventricular volumetric MRI measurement. The best correlation and agreement were seen at the mitral valve orifice by real-time 3D digital Doppler compared with SV by phase velocity cine MRI at the ascending aorta (r = 0.92, mean difference = -5.2 +/- 12.0 mL) and SV by left ventricular volumetric MRI measurement (r = 0.94, mean difference = -0.2 +/- 10.3 mL).

Automated volumetric flow quantification using angle-corrected color Doppler image

We have developed a fully automated method for measuring volumetric blood flow with angle-corrected blood velocity from a color Doppler image. By computing the blood flow vector through a conduit, the angle of incidence between the direction of ultrasound beam and the direction of blood flow can be measured to correct the underestimated blood velocity. This correction immediately contributes to the improvement of measurement accuracy. The developed method also enhances the conduit identification procedure that is one of the most important factors affecting the accuracy of volumetric measurement. To evaluate the validity of the developed algorithm, experimental studies had been applied to 21 healthy subjects and 10 patients. Volumetric flows were measured from a color Doppler image of the left ventricular outflow track, which were compared with blood volumes that were measured by traditional pulsed-wave (PW)-Doppler technique. The mean stroke volume difference between two methods was -0.45 +/- 11.7 (mean +/- SD). The proposed algorithm is a viable method for determining blood flow volume in an automated fashion.

A new dynamic three-dimensional digital color doppler method for quantification of pulmonary regurgitation: validation study in an animal model

OBJECTIVES

The purpose of the present study was to validate a newly developed three-dimensional (3D) digital color Doppler method for quantifying pulmonary regurgitation (PR), using an animal model of chronic PR.

BACKGROUND

Spectral Doppler methods cannot reliably be used to assess pulmonary regurgitation.

METHODS

In eight sheep with surgically created PR, 27 different hemodynamic states were studied. Pulmonary and aortic electromagnetic (EM) probes and meters were used to provide reference right ventricular (RV) forward and pulmonary regurgitant stroke volumes. A multiplane transesophageal probe was placed directly on the RV and aimed at the RV outflow tract. Electrocardiogram-gated and rotational 3D scans were performed for acquiring dynamic 3D digital velocity data. After 3D digital Doppler data were transferred to a computer workstation, the RV forward and pulmonary regurgitant flow volumes were obtained by a program that computes the velocity vectors over a spherical surface perpendicular to the direction of scanning.

RESULTS

Pulmonary regurgitant volumes and RV forward stroke volumes computed by the 3D method correlated well with those by the EM method (r = 0.95, mean difference = 0.51 +/- 1.89 ml/beat for the pulmonary regurgitant volume; and r = 0.91, mean difference = -0.22 +/- 3.44 ml/beat for the RV stroke volume). As a result of these measurements, the regurgitant fractions derived by the 3D method agreed well with the reference data (r = 0.94, mean difference = 2.06 +/- 6.11%).

CONCLUSIONS

The 3D digital color Doppler technique is a promising method for determining pulmonary regurgitant volumes and regurgitant fractions. It should have an important application in clinical settings.

Blood flow velocity profiles in the aortic annulus: a 3-dimensional freehand color flow Doppler imaging study

BACKGROUND

The use of a single sample volume in Doppler measurements of the velocity time integral (VTI) in the aortic annulus may introduce errors in calculations of stroke volumes, shunts, regurgitant fractions, and aortic valve area. To study the blood flow velocity distribution and assess this potential error, we used a dynamic 3-dimensional color flow Doppler imaging method.

METHODS AND RESULTS

Seventeen healthy volunteers were studied. The ultrasound data were captured from 10 to 20 heartbeats at a high frame rate (mean 57 frames per second) while freely tilting the transducer in the apical position. A magnetic position-sensor system recorded the spatial position and orientation of the probe. The raw digital ultrasound data were analyzed off-line with no loss of temporal resolution. Blood flow velocities were integrated across a spherical surface that tracked the aortic annulus during systole. The ratios of the systolic maximum to the systolic mean VTI ranged from 1.2 to 1.5 (mean 1.4). At the time of systolic peak flow, the ratios of the maximum to the mean velocity ranged from 1.1 to 2.0 (mean 1.5). The location of the maximum velocities and VTI showed individual variation.

CONCLUSION

The blood flow velocity profile was nonuniform. By using a single sample volume in Doppler measurements of the VTI in the aortic annulus, errors ranging from 20% to 50% may be introduced in calculations of stroke volumes.

Transoesophageal echocardiographic monitoring during paediatric cardiac surgery: obtainable information and feasibility in 532 children

BACKGROUND

We hypothesized that transoesophageal echocardiography (TOE) performed by the anaesthesiologists would be beneficial for monitoring purposes during paediatric cardiac surgery. We present the results for the first 5 years in 532 consecutive children.

METHODS

The probe was successfully inserted in 99% of cases and remained in the oesophagus for 211 min on average (range 10-555 min).

RESULTS

Insignificant valve leak, single- or biventricular failure and volume depletion were the most common new findings due to TOE. Changes in inotropic strategy and volume replacement were the most frequent interventions. In 45% of the cases, new information was disclosed and, in a total of 8% of cases, decisive information was provided. Except for tracheal extubation in one child who was uneventfully reintubated, no severe complications were identified.

CONCLUSIONS

These data stress the safety and ease of performing TOE in children undergoing cardiac surgery. There is evidence for benefit from TOE findings to potentially enhance the therapeutic basis.

Three dimensional echocardiography documents haemodynamic improvement by biventricular pacing in patients with severe heart failure

OBJECTIVES

To quantify the short term haemodynamic effects of biventricular pacing in patients with heart failure and left bundle branch block by using three dimensional echocardiography.

DESIGN

Three dimensional echocardiography was performed in 15 consecutive heart failure patients (New York Heart Association functional class III or IV) with an implanted biventricular pacing system. Six minute walk tests were performed to investigate the effect of biventricular pacing on exercise capacity. Data were acquired at sinus rhythm and after short term (2–7 days) biventricular pacing.

RESULTS

Compared with baseline values, biventricular pacing significantly reduced left ventricular end diastolic volume (EDV) by mean (SD) 4.0 (5.1)% (p < 0.01) and end systolic volume (ESV) by 5.6 (6.4)% (p < 0.02). Mitral regurgitant fraction was significantly reduced by 11 (12.1)% (p < 0.003) and forward stroke volume (FSV) increased by 13.9 (18.6)% (p < 0.02). Exercise capacity was significantly improved with biventricular pacing by 48.4 (43.3)% (p < 0.00001). Regression analyses showed that the percentage increase in FSV independently predicted percentage improvement in walking distance (r2 = 0.73, p < 0.0002). Both basal QRS duration and QRS narrowing predicted pacing efficacy, showing a significant correlation with %ΔEDV, %ΔESV, and %ΔFSV.

CONCLUSIONS

In five of 15 consecutive patients with heart failure and left bundle branch block, biventricular pacing induced a more than 15% increase in FSV, which predicted a more than 25% increase in walking distance and was accompanied by an immediate reduction in left ventricular chamber size and mitral regurgitation.

Three dimensional echocardiography documents haemodynamic improvement by biventricular pacing in patients with severe heart failure

OBJECTIVES

To quantify the short term haemodynamic effects of biventricular pacing in patients with heart failure and left bundle branch block by using three dimensional echocardiography.

DESIGN

Three dimensional echocardiography was performed in 15 consecutive heart failure patients (New York Heart Association functional class III or IV) with an implanted biventricular pacing system. Six minute walk tests were performed to investigate the effect of biventricular pacing on exercise capacity. Data were acquired at sinus rhythm and after short term (2-7 days) biventricular pacing.

RESULTS

Compared with baseline values, biventricular pacing significantly reduced left ventricular end diastolic volume (EDV) by mean (SD) 4.0 (5.1)% (p < 0.01) and end systolic volume (ESV) by 5.6 (6.4)% (p < 0.02). Mitral regurgitant fraction was significantly reduced by 11 (12.1)% (p < 0.003) and forward stroke volume (FSV) increased by 13.9 (18.6)% (p < 0.02). Exercise capacity was significantly improved with biventricular pacing by 48.4 (43.3)% (p < 0.00001). Regression analyses showed that the percentage increase in FSV independently predicted percentage improvement in walking distance (r(2) = 0.73, p < 0.0002). Both basal QRS duration and QRS narrowing predicted pacing efficacy, showing a significant correlation with %DeltaEDV, %DeltaESV, and %DeltaFSV.

CONCLUSIONS

In five of 15 consecutive patients with heart failure and left bundle branch block, biventricular pacing induced a more than 15% increase in FSV, which predicted a more than 25% increase in walking distance and was accompanied by an immediate reduction in left ventricular chamber size and mitral regurgitation.

Transesophageal echocardiography (TEE) in the critical care patient

Critically ill patients often pose special diagnostic problems to the clinician, intensified by limited physical examination findings and difficulty in transportation to imaging suites. Mechanical ventilation and the limited ability to position the patient make transthoracic echocardiography difficult. Transesophageal echocardiographic (TEE) imaging, however, is well suited to the critical care patient and is frequently used to evaluate hemodynamic status, the presence of vegetations, a cardioembolic source, and an intracardiac cause of hypoxemia. Using proper precautions, TEE can be performed safely in unstable patients and frequently leads to important changes in management.

A digital 3-dimensional method for computing great artery flows: in vitro validation studies

BACKGROUND

Conventional 2-dimensional Doppler large vessels are prone to inaccuracy. Three-dimensional (3D) volume imaging provides the opportunity to make cross-sectional flow calculations through digital spatiotemporal integration of flow velocity, area, and profile.

METHODS

A new digital 3D color Doppler reconstruction method was used to generate radially acquired flow data sets. Raw scanline data with digital velocity assignments, obtained by scanning parallel to flow, were transferred from a specially programmed but otherwise conventional ultrasonographic system, which controlled a multiplane transesophageal probe, to a computer workstation via an Ethernet link for assimilation into color 3D data sets. This configuration was used to study 20 pulsatile laminar flows (stroke volumes 30 to 70 mL and peak flow rates 65 to 205 mL/s) in a curved tube model with an oval cross-sectional geometry. After generation of the color 3D data set, flow velocity values from cross sections perpendicular to the tubes were analyzed to determine flow rate and stroke volume.

RESULTS

The flows from 3D digital velocity profiles showed close correlation with peak instantaneous flow rates (r = 0.99, y = 1.01x-0.9, standard error of estimate 4.1 mL/s). When interpreted with pulsed wave Doppler data obtained through the cardiac cycle, they also allowed computation of stroke volume (r = 0.98, y = 1.44x-2.5, standard error of estimate 3.8 mL).

CONCLUSION

The ability to compute laminar flows from 3D digital data sets obtained parallel to the direction of flow and without the need for geometric assumptions represents an important opportunity for and advantage of 3D color Doppler echocardiography.

Comparison of esophageal Doppler monitor generated minute distance and cardiac output in a porcine model of ventricular fibrillation

The primary goal of cardiopulmonary resuscitation (CPR) is to increase cardiac output (CO), providing adequate tissue perfusion and oxygenation to maintain normal organ function. A non-invasive, easy to use, commercially available esophageal doppler monitor (EDM, Deltex) has been found to provide minute distance (MD), which is the distance moved by a column of blood through the aorta in 1 min. The goal of our study was to determine if CO measurements correlate with the EDM MD, before and during cardiac arrest, in a porcine model of ventricular fibrillation. Twenty pigs were anesthetized and an EDM was placed. MD measurement using EDM, and CO measurement using florescent microsphere injections were compared before and during CPR. MD correlated well with CO (r2 = 0.96) before and during CPR. Based on the excellent correlation between MD as determined by EDM and CO by florescent microsphere technique, it appears that the non-invasive use of the EDM may play a valuable role in determination of CO during CPR.