Pulse oximetry screening for critical congenital heart diseases at two different hospital settings in Thailand.

OBJECTIVE: To evaluate the predictive abilities of pulse oximetry screening (POS) for critical congenital heart disease (CRIT.CHD) at two different hospital settings in Thailand. STUDY DESIGN: The study was conducted in healthy newborns at Ramathibodi Hospital (RH), a university hospital and Maharat Nakhon Ratchasima Hospital (MH), a regional hospital. Positive POS was defined as oxygen saturation (SpO2) <95% or difference between pre- and postductal SpO2 >3%. RESULTS: Of 11 407 live births, 10 603 (92.9%) newborns were enrolled with a follow-up rate at 1 month of 78.3%. Incidence of CRIT.CHD (per 1000 live births) at RH and MH were 5.7 and 2.7, respectively. POS could detect three newborns who would have had a missed diagnosis. Sensitivity of POS for CRIT.CHD at RH was 82.3% vs 100% at MH. Overall specificity was 99.9% and false-positive rate was 0.009%. Combination of POS and physical examination (PE) enhanced detection ability to 100% at both hospitals. CONCLUSION: POS combined with PE improved detection of CRIT.CHD. Routine POS is useful in personnel-limited settings.

Case report: Giant coronary aneurysm caused by Kawasaki disease: follow-up with echocardiography and multidetector CT angiography.

Giant coronary artery aneurysms caused by Kawasaki disease are not common; however, they are one of the most serious complications and can be fatal. Here, we describe a 5-year-old girl with Kawasaki disease who initially had normal coronary arteries. Despite intravenous immunoglobulin, she developed progressive giant coronary artery aneurysms. Echocardiography is a non-invasive tool for imaging the condition but it does have some limitations, whereas selective coronary angiography is the gold standard. However, multidetector CT may be a better non-invasive tool, alternate to invasive catheterized selective coronary angiography, in the long-term follow-up of patients with a giant coronary aneurysm.

Surface integration of velocity vectors from 3D digital colour Doppler: an angle independent method for laminar flow measurements.

BACKGROUND: The study was designed to test the angle independence of a dynamic three-dimensional digital colour Doppler method for laminar flow measurement. The technique acquired three-dimensional data by rotational acquisition and used surface integration of Doppler vector velocities and flow areas in time and space for flow computation. METHOD: A series of pulsatile flows (peak flow 55-180 ml/s) through a curved tube were studied with reference flow rates obtained using an ultrasonic flow meter. Colour Doppler imaging was performed at three angles to the direction of flow (20 degrees, 30 degrees, 40 degrees), using a multiplane transoesophageal probe controlled by an ATL HDI5000 system. Integration of digital velocity vectors over a curved three-dimensional surface across the tube for each of the 11 flow rates at each angle was performed off-line to compute peak flow. RESULTS: Peak flow rates correlated closely (r=0.99) with the flow meter with the mean difference from the reference being -0.8+/-2 x 4 ml/s, 0.9+/-2.6 ml/s, 1.0+/-2 x 3 ml/s for 20 degrees, 30 degrees and 40 degrees respectively. Comparison of the three angle groups showed no significant differences (P=0.15, ANOVA). When sampled obliquely, the flow area on the curved surface increased while the velocities measured decreased. CONCLUSION: Surface integration of velocity vectors to compute three-dimensional Doppler flow data is less angle dependent than conventional Doppler methods.

Evaluation of systolic and diastolic ventricular performance of the right ventricle in fetuses with ductal constriction using the Doppler Tei index.

Fetal ductal constriction (DC) can depress right ventricular (RV) function. However, noninvasive assessment of fetal RV function remains difficult. We evaluated RV and left ventricular (LV) performance in fetuses with DC using the Doppler-derived Tei index. The Tei index measures the ratio of total time spent in isovolumic contraction and relaxation (isovolumic time) to the ejection time. Tricuspid inflow and RV outflow Doppler traces for the derivation of RV Tei indexes and mitral inflow and LV outflow traces for LV Tei indexes were measured in 78 fetuses of pregnant women who received indomethacin and 70 normal fetuses (gestational ages ranging from 20 to 39 weeks). DC occurred in 23 fetuses, defined as pulsatility index <1.9. In fetuses with DC, the RV isovolumic time was prolonged and RV ejection time was shortened, and the RV Tei index was high compared with those in fetuses that received indomethacin without DC and normal fetuses. Also, the RV Tei index clearly separated the fetuses with DC from normal and fetuses that received indomethacin without DC (0.74 +/- 0.14 vs 0.35 +/- 0.07 and 0.37 +/- 0.06, respectively; p <0.0001). The LV Tei index was not affected by DC. Serial study in 7 fetuses with DC showed that the RV Tei index decreased from 0.69 +/- 0.12 to 0.38 +/- 0.04 (p = 0.0002) after discontinuation of indomethacin coincident with ductal relaxation, although it remained elevated in 2 cases at the time of ductal relaxation. Thus, the Tei index is a useful and sensitive indicator for detecting abnormal RV performance in fetuses with DC.

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.

Direct computation of multiple 3D flow convergence isovelocity surfaces from digital 3D reconstruction of colour Doppler data of the flow convergence region: an in vitro study with differently shaped orifices.

AIMS: Evaluation of the accuracy of direct computation of multiple three-dimensional (3D) flow convergence (FC) isovelocities by using digital reconstruction of colour Doppler data of the flow convergence region. METHODS AND RESULTS: We used a conventional ultrasound system (ATL HDI 3000) connected to a computer workstation via Ethernet link. The digital 3D datasets were directly transferred to a Silicon Graphic Imaging Octane workstation for later measurement. We generated nine pulsatile flows (20-60 ml/beat), with peak flow rates (67-180 ml/s), through three orifices (circular, rectangular and triangular, S=0.24 cm(2)). The 3D reconstructions of FC surface areas from multi-threshold velocities, including aliasing velocities were analysed to quantify the peak flow rate. For all orifices, linear regression demonstrated excellent correlation between the 3D calculated and electromagnetic flow meter recorded data. While there was a high correlation for 3D computation of flow rate from the single best Nyquist of 24 cm/s (r=0.97-0.98, SEE=7 .75-12.58 ml/s), the ability to average three threshold velocities (15, 18 and 24 cm/s) yielded an improved correlation (r=0.98-0.99, SEE=5.70-7.73 ml/s). CONCLUSIONS: Direct computation of multiple 3D FC isovelocities from digital reconstruction of colour Doppler data of the FC region provides the potential to accurately quantify the complex asymmetric spatial flow events at any selected velocity.

Acoustically stimulated transient power scattering explains enhanced detection of the very low velocities in myocardial capillaries by power Doppler imaging: an in vitro study.

BACKGROUND: Although enhanced detection of myocardial perfusion signals by power Doppler imaging during contrast echocardiography has been noted, flow velocities in the coronary microvasculature should generally be below the threshold for Doppler motion detection. It has been suggested that in this situation nonlinear scattering related to acoustically stimulated microsphere oscillation or destruction may be responsible for the detected Doppler shift. METHODS AND RESULTS: This study examined the behavior of MRX 115 (ImaRx Pharmaceuticals) microbubbles during harmonic and nonharmonic power Doppler imaging at varying power outputs (mechanical indexes 0. 3, 0.5, 0.7, and 0.9) in a perfusion tube model under zero-flow conditions. Boluses of MRX 115 0.5-mL suspension were introduced into the model, and flow was halted during each imaging period. Once power Doppler imaging was implemented, a signal was detected as unique sparkling color pixels corresponding to individual bubble destruction events, even in the absence of contrast movement. This phenomenon continued until all contrast bubbles disappeared from the region subjected to power Doppler imaging, usually within 35 to 40 seconds. Off-line videointensity measurements showed that initial power Doppler signal intensity and maximum signal decay rates increased parallel to increasing power output and were substantially greater for nonharmonic than for harmonic imaging modes. CONCLUSION: This relationship between signal intensity and decay rate and acoustic power output suggests that transient scattering related to bubble destruction is responsible for generation of the power Doppler signal in the absence of flow. This would explain the enhanced detection of the very low velocity flows in the myocardial capillaries by power Doppler contrast imaging.

Evaluation of descending aortic flow volumes and effective orifice area through aortic coarctation by spatiotemporal integration of color Doppler data: An in vitro study.

Flow volumes in an in vitro model of the aorta with 3 different degrees of stiffness (stiff, moderately stiff, and compliant) proximal to a coarctation were calculated by using a digital color Doppler echocardiography flow calculation method that semiautomatically integrates spatial and temporal color flow velocity data. These flow volumes were compared with those obtained by the conventional pulsed Doppler method with reference to ultrasonic flowmeter. Flow volumes determined by the automated method agreed well with those obtained by ultrasonic flowmeter, even in this compliant aorta model with vessel size changing with pulsation, whereas the pulsed Doppler method overestimated the reference data, especially for more compliant descending aortic segments. The combination of flow data with continuous wave Doppler allows definition of effective orifice area for coarctation.

Three-dimensional reconstruction of the color Doppler-imaged vena contracta for quantifying aortic regurgitation: studies in a chronic animal model.

BACKGROUND: The purpose of this study was to investigate the use of 3-dimensional (3D) reconstruction of color Doppler flow maps to image and extract the vena contracta cross-sectional area to determine the severity of aortic regurgitation (AR) in an animal model. Evaluation of the vena contracta with 2-dimensional imaging systems may not be sufficiently robust to fully characterize this region, which may be asymmetrically shaped. METHODS AND RESULTS: In 6 sheep with surgically induced chronic AR, 18 hemodynamically different states were studied. Instantaneous regurgitant flow rates were obtained by aortic and pulmonary electromagnetic flowmeters (EMFs) as reference standards, and aortic regurgitant effective orifice areas (EOAs) were determined from EMF regurgitant flow rates divided by continuous-wave (CW) Doppler velocities. Composite video data for color Doppler imaging of the aortic regurgitant flows were transferred into a TomTec computer after computer-controlled 180 degrees rotational acquisition. After the 3D data transverse to the flow jet were sectioned, the smallest proximal jet cross section was identified for direct measurement of the vena contracta area. Peak regurgitant flow rates and regurgitant stroke volumes were calculated as the product of these areas and the CW Doppler peak velocities and velocity-time integrals, respectively. There was an excellent correlation between the 3D-derived vena contracta areas and reference EOAs (r=0.99, SEE=0.01 cm2) and between 3D and reference peak regurgitant flow rates and regurgitant stroke volumes (r=0.99, difference=0.11 L/min; r=0.99, difference=1.5 mL/beat, respectively). CONCLUSIONS: 3D-based determination of the vena contracta cross-sectional area can provide accurate quantification of the severity of AR.