Rosemary A. Rusk

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.

Quantification of flow volume with a new digital three-dimensional color Doppler flow approach: an in vitro study.

The quantification of flow stroke volume is important for evaluation of patients with cardiac dysfunction and cardiovascular disease. Three‐dimensional digital color Doppler flow imaging allows the acquisition of flow data in an orientation approximately parallel to flow and analysis of the Doppler flow velocities perpendicular to flow (cross‐sectional flow calculation). This in vitro study assessed the applicability of this method for quantifying cardiac output in a funnel‐shaped tube model similar to mitral inflow or the left ventricular outflow tract.

Will a handheld ultrasound scanner be applicable for screening for heart abnormalities in newborns and children

BACKGROUND There is significant interest in opportunities to provide echocardiography services for detection of congenital heart disease with portable, or even handheld, devices in remote areas or third world countries where conventional ultrasound systems may not be available. We tested a handheld system (HHS) (SonoHeart, SonoSite Inc, Bothell, Wash) equipped with a broadband, 7- to 4-MHz, miniaturized, curved, linear-array transducer and implemented with an improved directional Doppler flow map. METHODS All echocardiography scanning was performed in the neonatal nursery, pediatric intensive care department, or pediatric echocardiography laboratory of our institution. We reviewed limited echocardiography view sequences sequentially obtained by the same expert examiner (D.J.S.) in 50 infants and children (age: 1 day to 6 years), with preoperative or postoperative forms of congenital heart disease. Each patient was studied twice, once with a conventional full-feature system (FFS) and then a limited scan with the HHS using similar frequency transducers. The cardiologist (D.J.S.) and blinded research laboratory reviewers (X.L., G.K.M., R.A.R.) read the FFS and HHS image sequences for diagnosis and for grading the quality of the anatomic and flow feature images. The studies were performed and reviewed with the examiner and reviewers blinded to patient diagnosis. RESULTS The major diagnoses (eg, patent ductus arteriosus, atrio-ventricular (AV) canal, peripheral pulmonary valve stenosis, aortic coarctation, atrial septal defect, ventricular septal defect, preoperative or postoperative tetralogy of Fallot, and mitral regurgitation) were made by both readers, who were unaware of each others diagnosis results. Furthermore, the average composite HHS cardiac anatomic feature score on a scale of 0 (not visualized) to 3 (visualized precisely) from the parasternal long-axis and 4- or 5-chamber view for cardiac anatomy were 2.67 +/- 0.49 (SD) and 2.50 +/- 0.55, respectively, versus 2.73 +/- 0.45 and 2.55 +/- 0.54 for the FFS. The mean flow feature score, comprising all views, was 2.67 +/- 0.45 (HHS) versus 2.72 +/- 0.48 (FFS). The P values for all above comparisons were >.05. Image quality of the FFS anatomic structures were, thus, not statistically different from the HHS. Although the color cosmetic was different for the HHS directional (nonvelocity) map, only 9% of 150 total findings (including structural abnormalities and flow features, none of which were critical) were missed, whereas the other 91% regurgitant, shunt, stenosis flow features or heart structure were imaged adequately by the HHS in this population. CONCLUSIONS Implementing high-frequency transducers and programs optimized for tissue and flow imaging on the HHS should provide images of sufficient quality for targeted echocardiography examinations to determine the presence, absence, or status of congenital heart disease in newborns and young children.

Strain rate imaging: an in vitro "validation" study using a physiologic balloon model mimicking the left ventricle.

Background: Strain rate imaging (SRI) can be implemented from digital ultrasound loops of tissue Doppler imaging (TDI) data and is performed as an autocorrelation solution of the distance between intramyocardial targets. As such, it should have better resolution along longer distances of wall segments that are imaged at the length of individual ultrasound scan lines. Methods: We used a new left ventricular double‐balloon phantom with a tissue‐mimicking gel between the walls. Mounted in a water bath and connected to a pulsatile flow pump at four‐stroke volume (30–50 ml/beat), the high frame rate, digital, multiple two‐dimensional/tissue/TDI loops of balloon wall motion were recorded using a GE VingMed system FiVe (3.5 MHz phased array transducer), with the model scanned longitudinally from the apex. The strain rate (SR) values were measured at the apex and the lateral wall using an offline measurement program, and mean SR values for every 100 msec were calculated by averaging three determinations at each point. The excursions of the apex and lateral wall also were measured directly by high speed digital video imaging, and consecutive velocity profiles were calculated every 100 msec. A total of 40 data points for four‐stroke volumes were analyzed. Results: While our balloon model had enough gel targets between the walls to produce a good mimic of myocardial speckle with walls that thickened and thinned, samples immediately across the apex and apex SR values (Hz) varied substantially. In contrast, systematic signals could be obtained from lines imaged >15° from the true apex and crossing a longer length of myocardium. At the lateral wall, there was a close correlation between the video velocities and SR values, as well as a close overlap of the phasic patterns. Conclusions: SRI produces more reliable data from wall segments parallel to scan lines.

Validation of a digital color Doppler flow measurement method for pulmonary regurgitant volumes and regurgitant fractions in an in vitro model and in a chronic animal model of postoperative repaired tetralogy of Fallot

OBJECTIVES The purpose of this study was to validate a digital color Doppler (DCD) automated cardiac flow measurement method for quantifying pulmonary regurgitation (PR) in an in vitro and a chronic animal model of the right ventricular outflow tract of postoperative tetralogy of Fallot (TOF). BACKGROUND There has been no reliable ultrasound method that can accurately quantitate PR. METHODS We developed an in vitro model of mild pulmonary stenosis and wide-open PR that mimics the patterns of flow seen in patients with postoperative TOF. Thirteen different forward and regurgitant stroke volumes (RSVs) across the noncircular shaped cross-sectional outflow tract flow area were estimated using the DCD method in two orthogonal planes. In six sheep with surgically created PR, 24 different hemodynamic states with PR strictly quantified by electromagnetic probes were also studied. RESULTS The RSVs and regurgitant fractions (RFs) obtained by the DCD method using average values from two orthogonal planes correlated well with reference values (RSV: r = 0.99, mean difference = 0.02 +/- 0.39 ml/beat for in vitro model; r = 0.97, mean differences = 1.79 +/- 1.84 ml/beat for animal model, RF: r = 0.98, mean difference = -1.10 +/- 4.34% for in vitro model; r = 0.94, mean difference = 2.73 +/- 6.75% for animal model). However, the DCD method using a single plane had limited accuracy for estimating pulmonary RFs and RSVs. CONCLUSIONS The DCD method using average values from two orthogonal planes provides accurate estimation of RSVs and RFs and should have clinical importance for serially quantifying PR in patients with postoperative TOF.

Lower receiving frequencies than transmitting frequencies could yield improved results for contrast imaging: An in vivo study in closed chest canines

Background: Ultrasonic imaging methods of receiving at higher frequencies, which are multiples of the transmitting frequencies (harmonic imaging), are well established as a means of improving myocardial visualization in association with intravenous contrast administration. This exploratory study examined the effect of using receive frequencies that were lower than the transmit frequencies while imaging closed chest dogs with an Ensemble wideband, phase inversion contrast program on a modified Siemens Elegra scanner. Methods: Intravenous bolus injections of 0.75 mL Definity and 1 mL QW7437 were administered to six anesthetized dogs. Intermittent imaging for contrast visualization was performed using either a broadband array, transmitting at 1.4 MHz and receiving at 2.6–3.2 MHz or a broadband 4–7.5 MHz transducer transmitting at 6.0 MHz and receiving at 4.2–4.5 MHz. Contrast enhancement was measured by videodensitometry, sampling mid‐cavity and within the myocardium before and after injection. The changes in videodensity from control to after injection were calculated for each method. Results: There was no significant difference in the change in intracavity videodensity between the two imaging strategies although there was near full intracavity saturation in all cases. However, the change in myocardial density was significantly greater for both contrast agents when using receiving frequencies lower than transmitting frequencies (P = 0.02 and 0.03). The difference in duration of the myocardial blush did not reach statistical significance but it tended to persist for longer with the lower receiving frequencies. Conclusion: Delivering sound energy at a slightly higher frequency and receiving at lower than the transmit frequency may be an advantageous method of enhancing myocardial perfusion signals during intravenous contrast echocardiography. (ECHOCARDIOGRAPHY, Volume 20, April 2003)

MEDIUM TERM LONGITUDINAL FOLLOW UP OF ALL PATIENTS REFERRED TO A TRANSCATHETER AORTIC VALVE MULTI-DISCIPLINARY TEAM.

Results: Patients (n=26) awaiting treatment / fnal MDT decision were excluded. 17 patients were treated by TAVI (7 transfemoral, 10 transapical), 27 by conventional surgical AVR (csAVR), 9 with balloon valvuloplasty (BAV) and 30 medically. There were no differences in baseline characteristics (but for an excess of prior CABG in the TAVI group vs. csAVR (13/17 vs. 3/27; p <0.001)) nor in logistic EuroSCORE (ES): TAVI: 18.5% (IQR 8.4 27.1%); csAVR: 12.1% (7.5 27.1%); BAV: 30.0% (12.8 39.0%); medical: 20.4% (10.6 40.0%): p= 0.35. 30 day mortalities were: TAVI: 0/17; csAVR: 1/25; BAV: 1/9; medical: 8/30. Adjusting for ES, the observed / expected 30 day mortality indices were: TAVI: 0; csAVR: 0.33; BAV: 0.37; medical: 1.31. Valve replacement patients (TAVI & csAVR) had a lower 30 day mortality than palliative treatment (BAV & medical): 2.38% vs. 25.6%, p = 0.003. This survival beneft persisted upon medium term follow up, log rank p<0.001 (see fgure).

Reconstructive three-dimensional tissue Doppler imaging for quantifying left ventricular myocardial infarction area after coronary artery occlusion: an in vivo chronic animal study

目的通过活体动物实验探讨三维重建组织多普勒超声成像测量心肌梗死面积的方法和可行性.方法用三维重建组织多普勒显像的方法,对8只开胸的心尖部心肌梗死和室壁瘤的活体羊模型在4种不同的血流状态下进行心肌梗死面积的测量.结果重建三维超声组织多普勒成像测量的活体羊心内膜梗死的面积与尸检标本测量的面积密切相关(r=0.90, Y=0.83X+1.33,s=0.92 cm2,P<0.000 1).结论重建三维组织多普勒成像提供了一系列动态空间组织多普勒数据确定室壁异常运动区,并能定量测量心肌梗死面积,在缺血性心脏疾病中,有助于非侵入性心脏功能的估测.