Biomedical subjects
Publications and source records attributed to Yoshiki Mori.
This study was performed to evaluate left ventricular (LV) diastolic function in patients with Ebstein's anomaly using Doppler echocardiography. We found that LV abnormal relaxation in this anomaly cannot be explained by right ventricular volume overload alone. Furthermore, LV diastolic dysfunction persists even after intracardiac repair.
Little is known about the growth potential of pulmonary stenotic lesions after balloon angioplasty (BA) in patients after the arterial switch operation. The aim of this study was to evaluate the growth potential of pulmonary stenotic lesions after BA and assess the midterm results of BA for pulmonary artery stenosis after the arterial switch operation. Thirty-seven patients who had undergone 52 procedures had repeat catheterization at a median of 43 years (range 1.2 to 9.3 ys) after BA. To adjust growth-related changes in the size of the pulmonary artery, the stenotic diameter was expressed as a percentage of normal (%N). An immediate increase of 63 +/- 45% in the stenotic diameter and a reduction of 51 +/- 33% in the pressure gradient occurred across the stenotic lesions after BA. The right ventricular-aortic systolic pressure ratio decreased from 0.67 +/- 0.24 to 0.51 +/- 0.12 after BA (p <0.0001). Compared with immediate data after BA, there was no significant change in the growth-adjusted diameter of the stenotic lesions (68 +/- 26 %N after BA vs 65 +/- 25 %N at follow-up, p = 0.08), and the pressure gradient (16 +/- 13 mm Hg after BA vs 20 +/- 21 mm Hg at follow-up, p = 0.10). The ventricular-aortic systolic pressure ratio also did not change (0.51 +/- 0.12 after BA vs 0.50 +/- 0.21 at follow-up, p = 0.57). Restenosis occurred in 3 of 26 vessels (12%) after successful BA in which the diameter increased >50% after BA. Our data suggest that pulmonary stenotic lesions after BA develop with age in growing children after the arterial switch operation, and the efficacy of the BA may be long lasting.
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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.
OBJECTIVE: Although long-term prostacyclin(PGI2) therapy in patients with severe pulmonary hypertension (PH)reduces pulmonary vascular resistance (PVR), there have been no reports on its therapeutic effects in patients with mild PH. We investigated the chronic effect of beraprost sodium (BPS), an oral PGI2 analog, in children with mild PH. METHODS: We studied 20 patients who were destined for a Fontan procedure with a mean pulmonary arterial pressure(PAP) of>20 mmHg and/or PVR of>3.0 Wood units. Both the PAP and the PVR in these cases were too high for patients to undergo a successful Fontan procedure. Seven patients received BPS (PG group) and 13 did not (control group). All patients underwent repeat cardiac catheterization to examine pulmonary hemodynamics. RESULTS: In the PG group, the pulmonary-to-systemic flow ratio (Qp/Qs) did not change after BPS administration(1.1 +/- 0.6 vs 1.3 +/- 0.9);however, the mean PAP decreased significantly (25.3 +/- 8.2 vs 19.9 +/- 6.5 mmHg; P < 0.05),as did PVR (3.7 +/- 1.3 vs 2.3 +/- 0.9 Wood units; P < 0.05), whereas the pulmonary artery (PA) index increased significantly (312 +/- 136 vs 375 +/- 165; P < 0.05). In the control group, the mean PAP decreased significantly (24.9 +/- 4.7 vs 19.8 +/- 6.3 mmHg; P < 0.05)and the PA index increased significantly (295 +/- 72 vs 362 +/- 114; P < 0.05). No significant changes in Qp/Qs (1.5 +/- 0.8 vs 1.4 +/- 0.6)or PVR (2.9 +/- 1.3 vs 2.5 +/- 0.8 Wood units) were observed. CONCLUSION: We conclude that long-term BPS administration probably reduces PVR in potential candidates for a Fontan procedure with mild PH. This treatment would reduce the risks associated with the Fontan procedure and would also improve its outcome.
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.
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 degrees 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.
Accurately quantifying transmitral flow volume is clinically important not only as a measure of cardiac output, but also as a value from which to subtract aortic flow, for determining the severity of mitral regurgitation. However, controversy exists over the accuracy of pulsed Doppler for mitral flow quantification because of the complexity of mitral flow geometry and dynamic changes in flow profile and flow area. To explore the feasibility of directly quantifying transmitral flow volume with a newly developed dynamic 3-dimensional digital color Doppler technique, this in vivo experimental study was conducted to validate the method. Eight open chest sheep were imaged with a multiplane transesophageal (TEE) probe placed on the heart for digital 3-dimensional gated acquisition of mitral inflow over a 180-degree acquisition. The digital velocity data were contour detected for flow area after computing the velocity vectors and flow profile perpendicular to a spherical 3-dimensional surface across the mitral annulus. Flow areas and actual velocities were then integrated in time and space and the resulting flow volumes were compared with those obtained by a reference electromagnetic flowmeter on the aorta for 26 steady hemodynamic states. The flow volumes correlated closely to the electromagnetic references (y = 0.87x + 2.49, r = 0.92, SEE = 1.9 Ml per beat). Our study shows that transmitral flow volume can be accurately determined in vivo by this dynamic 3-dimensional digital color Doppler flow quantification method.
OBJECTIVE: To explore the feasibility of directly quantifying transaortic stroke volume with a newly developed dynamic 3-dimensional (3D) color Doppler flow measurement technique, an in vivo experimental study was performed. BACKGROUND: Traditional methods for flow quantification require geometric assumptions about flow area and flow profiles. Accurate quantification of flow across the aortic valve is clinically important as a means of estimating cardiac output. METHODS: Eight open-chest sheep were scanned with apical epicardial placement of a 7 to 4 MHz multiplane transesophageal probe scanning parallel to aortic flow and running on an ATL HDI 5000 system. An electromagnetic flow meter implanted on the ascending aorta was used as reference. Thirty different hemodynamic conditions were studied after steady states were obtained in the animals by administration of blood, angiotensin, and sodium nitroprusside. Electrocardiogram-gated digital color 3D velocity data were acquired for each of the 30 steady states. The aortic stroke volumes were computed by temporal and spatial integration of flow areas and actual velocities across a projected surface perpendicular to the direction of flow, at a level just below the aortic valve. RESULTS: There was close correlation between the 3D color Doppler calculated aortic stroke volumes and the electromagnetic data (r = 0.91, y = 0.96x + 1.01, standard error of the estimate = 2.6 mL/beat). CONCLUSION: Our results showed that dynamic 3D color Doppler measurements obtained in an open-chest animals provide the basis for accurate, geometry-independent quantitative evaluation of the aortic flow. Therefore, 3D digital color Doppler flow computation could potentially represent an important method for noninvasively determining cardiac output in patients.
OBJECTIVE: Our study was intended to test the accuracy of a 3-dimensional (3D) digital color Doppler flow convergence (FC) method for assessing the effective orifice area (EOA) in a new dynamic orifice model mimicking a variety of mitral regurgitation. BACKGROUND: FC surface area methods for detecting EOA have been reported to be useful for quantifying the severity of valvular regurgitation. With our new 3D digital direct FC method, all raw velocity data are available and variable Nyquist limits can be selected for computation of direct FC surface area for computing instantaneous flow rate and temporal change of EOA. METHODS: A 7.0-MHz multiplane transesophageal probe from an ultrasound system (ATL HDI 5000) was linked and controlled by a computer workstation to provide 3D images. Three differently shaped latex orifices (zigzag, arc, and straight slit, each with cutting-edge length of 1 cm) were used to mimic the dynamic orifice of mitral regurgitation. 3D FC surface computation was performed on parallel slices through the 3D data set at aliasing velocities (14-48 cm/s) selected to maximize the regularity and minimize lateral dropout of the visualized 3D FC at 5 points per cardiac cycle. Using continuous wave velocity for each, 3D-calculated EOA was compared with EOA determined by using continuous wave Doppler and the flow rate from a reference ultrasonic flow meter. Simultaneous digital video images were also recorded to define the actual orifice size for 9 stroke volumes (15-55 mL/beat with maximum flow rates 45-182 mL/s). RESULTS: Over the 9 pulsatile flow states and 3 orifices, 3D FC EOAs (0.05-0.63 cm(2)) from different phases of the cardiac cycle in each pump setting correlated well with reference EOA (r = 0.89-0.92, SEE = 0.027-0.055cm(2)) and they also correlated well with digital video images of the actual orifice peak (r = 0.97-0.98, SEE = 0.016-0.019 cm(2)), although they were consistently smaller, as expected by the contraction coefficient. CONCLUSION: The digital 3D FC method can accurately predict flow rate, and, thus, EOA (in conjunction with continuous wave Doppler), because it allows direct FC surface measurement despite temporal variability of FC shape.