Biomedical subjects

I Yamada

Publications and source records attributed to I Yamada.

At least 73 records · Page 4Linked to original sources

PubMed1998

Diagnostic accuracy of technetium-99m-pertechnetate scintigraphy with lemon juice stimulation to evaluate Warthin's tumor.

UNLABELLED: This study investigated the diagnostic accuracy of 99mTc-pertechnetate scintigraphy with lemon juice stimulation for evaluating parotid gland Warthin's tumor. METHODS: Technetium-99m-pertechnetate scintigraphy with intraoral lemon juice stimulation was used to evaluate a total of 68 parotid gland lesions clinically suspected of being Warthin's tumor in 62 patients. Twenty-three of the 68 lesions were subsequently histologically confirmed to be Warthin's tumor, whereas the remaining 45 lesions were histologically diagnosed as being other lesions. RESULTS: Technetium-99m-pertechnetate scintigraphy with lemon juice stimulation correctly diagnosed 18 of 23 Warthin's tumors as being Warthin's tumor but was unable to diagnose the other five Warthin's tumors. Further, scintigraphy correctly diagnosed 41 of 45 non-Warthin's tumors as being non-Warthin's tumor but misdiagnosed other four non-Warthin's tumors as Warthin's tumor. Thus, the sensitivity of scintigraphy for diagnosing Warthin's tumor was found to be 78%, its specificity 91% and its accuracy 87%. On the basis of prestimulation images alone, however, the sensitivity was estimated to be 65%, its specificity 93% and its accuracy 84%. CONCLUSION: For evaluating Warthin's tumor, the sensitivity of 99mTc-pertechnetate scintigraphy was relatively low, although the specificity was sufficiently high. Lemon juice stimulation improved the sensitivity markedly but decreased the specificity slightly. Thus, 99mTc-pertechnetate scintigraphy with lemon juice stimulation should be carefully performed for diagnosis of Warthin's tumor.

Adenolymphoma↗

PubMed1998

A method for estimating aortic regurgitant effective orifice area by digital Doppler color flow mapping.

BACKGROUND AND AIMS OF THE STUDY: Although non-invasive assessment of the severity of aortic regurgitation (AR) is important, quantitative evaluation of AR can be difficult in clinical settings. Most Doppler echocardiographic methods have been compared with angiographic grading of AR severity. However, while aortic angiography is used widely for grading AR severity, the method is only semi-quantitative. A computed semi-automatic digital color Doppler method has recently been described for calculating stroke volume and cardiac output. The study aim was to develop a method of evaluating AR severity by using a digital automated color Doppler method (ACM) along with continuous wave (CW) Doppler for estimating aortic regurgitant effective orifice area. METHODS: A total of 22 different hemodynamic conditions were studied in six sheep. Regurgitant volumes (RV) were determined by electromagnetic flowmetry (EM) and by ACM. AR effective orifice areas (EOAs) were determined by dividing each of the RVs by the time integrals of the AR continuous wave velocities. AR EOAs by ACM were compared with those obtained by EM and with other EM indices of regurgitant severity. ACM was accurate for quantifying AR EOAs (r = 0.96). RESULTS AND CONCLUSIONS: Calculated AR EOA correlated well with peak AR flow and regurgitant fraction by EM. The combined ACM/CW Doppler method can be useful for estimating non-invasively the aortic regurgitant EOA and for evaluating the severity of AR.

Anatomy, Cross-Sectional↗

PubMed1998

[A case of nodular fasciitis of the chest wall].

We present a case of nodular fasciitis of chest wall origin. A 62-year-old woman visited our hospital because of a rapidly growing hard tumor fixed to her right chest wall, measuring 7 x 8 cm in size. Although incisional biopsy specimen revealed that the tumor was suggestive of nodular fasciitis, the possibility that the tumor had a malignant component could not be excluded. Total excision of the mass with combined resection of 3rd, 4th, 5th ribs was performed to establish the histological diagnosis and treatment plan. We believe that the tumor proved to be malignant by excisional biopsy, should then undergo further excision with sufficient surgical margin. Nodular fasciitis may be misdiagnosed as a sarcoma due to its rich cellularity, mitotic activity and poorly circumscribed nature. Awareness of the histological features of nodular fasciitis, and its predilection for presenting as a rapidly growing mass, should decrease the likelihood of misdiagnosis and the attendant risk of over surgery.

Diagnosis, Differential↗

PubMed1997

Direct measurement of three-dimensionally reconstructed flow convergence surface area and regurgitant flow in aortic regurgitation: in vitro and chronic animal model studies.

BACKGROUND: Evaluation of flow convergence (FC) with two-dimensional (2D) imaging systems may not be sufficiently accurate to characterize these often asymmetric, complex phenomena. The aim of this study was to validate a three-dimensional (3D) method for determining the severity of aortic regurgitation (AR) in an experimental animal model. METHODS AND RESULTS: In six sheep with surgically induced chronic AR, 20 hemodynamically different states were studied. Instantaneous regurgitant flow rates were obtained by aortic and pulmonary electromagnetic flow meters. Video composite data of color Doppler flow mapping images were transferred into a TomTec computer after computer-controlled 180 degrees rotational acquisition. Direct measurement of the 3D reconstructed FC surface areas as well as measurements of FC areas estimated with 2D methods with hemispherical and hemielliptical assumptions were performed, and values were multiplied by the aliasing velocity to obtain peak regurgitant flow rates. There was better agreement between 3D and electromagnetically derived flow rates than there was between the 2D and the reference values (r=.94, y=1.0x-0.16, difference=0.02 L/min for the 3D method; r=.80, y=1.6x-0.3, difference=1.2 L/min for the 2D hemispherical method; r=.75, y=0.90x+0.2, difference=-0.20 L/min for the 2D hemielliptical method). CONCLUSIONS: Without any geometrical assumption, the 3D method provided better delineation of the FC zones and direct measurements of FC surface areas, permitting more accurate quantification of the severity of AR than the 2D methods.

Animals↗

PubMed1997

Vena contracta imaged by Doppler color flow mapping predicts the severity of eccentric mitral regurgitation better than color jet area: a chronic animal study.

OBJECTIVES: This study sought to evaluate the relation between the color Doppler-imaged vena contracta and the severity of mitral regurgitation (MR) in a chronic animal model of MR. BACKGROUND: The vena contracta, which is defined as the smallest connection between the laminar flow acceleration zone and the turbulent regurgitant jet, has been reported to be a clinically useful marker for evaluating the severity of valvular regurgitation. METHODS: Six sheep with chronic MR produced by previous operation severing the chordae tendineae were examined. MR jet flows and vena contracta widths were imaged using a Vingmed 775 scanner with a 5-MHz transducer. Image data were directly transferred in digital format to a microcomputer for off-line measurement. MR was quantified as peak and mean regurgitant flow rates, regurgitant stroke volumes and regurgitant fractions determined using mitral and aortic electromagnetic flow probes and flowmeters balanced against each other. RESULTS: Vena contracta width correlated well with regurgitant severity determined by electromagnetic flowmeters (r = 0.95, SEE = 0.05 cm, p < 0.0001 for peak regurgitant flow rate; r = 0.85, SEE = 0.08 cm, p < 0.0001 for regurgitant stroke volume; r = 0.90, SEE = 0.07 cm, p < 0.0001 for regurgitant fraction). CONCLUSIONS: This study shows that the vena contracta width method is useful for predicting the severity of MR. It is simple and conveniently available with high resolution equipment. The quantitative comparisons in the present study lay the foundation for future clinical and research studies using this vena contracta technique.

Animals↗

PubMed1997

Quantifying aortic regurgitation by using the color Doppler-imaged vena contracta: a chronic animal model study.

BACKGROUND: The aim of the present study was to evaluate the accuracy of determining aortic effective regurgitant orifice area (EROA) and aortic regurgitant volume by using the color Doppler-imaged vena contracta (CDVC). METHODS AND RESULTS: Twenty-nine hemodynamically different states were obtained pharmacologically in eight sheep with surgically induced aortic regurgitation. Instantaneous regurgitant flow rates (RFRs) were obtained with aortic and pulmonary electromagnetic flowmeters (EFMs), and aortic EROAs were determined from EFM RFRs divided by continuous wave Doppler velocities. Color Doppler-derived EROAs were estimated by measuring the maximal diameters of the CDVC. Peak and mean RFRs and regurgitant volumes per beat were calculated from vena contracta area continuous wave diastolic Doppler velocity curves. Peak EFM-derived RFRs varied from 1.8 to 13.6 (6.3+/-3.2) L/min (range [mean+/-SD]), mean RFRs varied from 0.7 to 4.9 (2.7+/-1.3) L/min, regurgitant volumes per beat varied from 7.0 to 48.0 (26.9+/-12.2) mL/beat, and the regurgitant fractions varied from 23% to 78% (55+/-16%). EROAs determined by using CDVC measurements correlated well with reference EROAs obtained by using the EFM method (r=.91, SEE=0.07 cm2). Excellent correlations and agreements between peak and mean RFR and regurgitant volumes per beat as determined by Doppler echocardiography and EFM were also demonstrated (r=.95 to .96). CONCLUSIONS: Our study indicates that the CDVC method can be used to quantify both aortic EROAs and regurgitant flow rates.

Animals↗

PubMed1997

Preparation of radiotherapy glass by phosphorus ion implantation at 100 keV.

A chemically durable glass containing a large amount of phosphorus is useful for in situ irradiation of cancers. It can be activated to be a beta emitter (half-life of 14.3 days) by neutron bombardment. Microspheres of the activated glass injected into the tumors can irradiate the tumors directly with beta rays without irradiating neighboring normal tissues. In the present study a P+ ion was implanted into a pure silica glass in a plate form at 100 keV in order to find the fundamental conditions for obtaining such a glass. Little phosphorus was present in the surface region, at least to a depth of 2.4 nm for doses of 5 x 10(16) and 1 x 10(17) cm-2, whereas an appreciable amount of it was distributed on the glass surface and a part of it was oxidized for doses above 5 x 10(17) cm-2. The glasses implanted with doses of 5 x 10(16) and 1 x 10(17) cm-2 hardly released the P and Si into water at 95 degrees C, even after 7 days, whereas the glasses implanted with doses above 5 x 10(17) cm-2 released appreciable amounts of these elements. Implantation energies of 20 and 50 keV (even at doses of 5 x 10(16) and 1 x 10(17) cm-2, respectively), formed oxidized phosphorus on the glass surfaces and gave appreciable release of the P and Si into the hot water. This indicates that a chemically durable glass containing a larger amount of phosphorus could be obtained if a P+ ion is implanted at higher energies to localize in a deeper region of the glass surface.

Biocompatible Materials↗

PubMed1997

Internal derangements of the temporomandibular joint: comparison of assessment with three-dimensional gradient-echo and spin-echo MRI.

Our purpose was to assess the diagnostic accuracy of three-dimensional (3D) gradient-echo (GRE) MRI in the diagnosis of internal derangements of the temporomandibular joint (TMJ). We studied 140 joints in 70 patients with TMJ internal derangements. We obtained 3D-GRE and spin-echo (SE) images in the closed-mouth position; the images were reviewed for disc displacement as well as bone and cartilage abnormalities. The 3D-GRE and SE images were interpreted independently by different radiologists. The sensitivity and specificity of 3D-GRE imaging for assessing mediolateral disc displacement was 100%, whereas the sensitivity and specificity of sagittal SE images were 82% and 72%, respectively (P < 0.001). The 3D-GRE images also demonstrated more bone abnormalities (in 112 condyles or 80%) than did SE images (in 79 condyles or 56%) (P < 0.001). Furthermore, 3D-GRE imaging revealed articular cartilage abnormalities in 46 condyles (33%) that were not visible on SE images. The frequency of pain was significantly higher in joints with bone and cartilage abnormalities (P < 0.05 and P < 0.001, respectively). For assessment of disc displacement, 3D-GRE images were superior to sagittal SE images alone, and comparable to combined sagittal and coronal SE images, while for bone and cartilage abnormalities, they were superior to sagittal and coronal SE images.

Adolescent↗

PubMed1997

Calculation of aortic regurgitant volume by a new digital Doppler color flow mapping method: an animal study with quantified chronic aortic regurgitation.

OBJECTIVES: The aim of the present study was to quantitate aortic regurgitant volume and regurgitant fraction in a chronic animal model with surgically created aortic regurgitation using a new semiautomated color Doppler flow calculation method. BACKGROUND: The conventional noninvasive methods for evaluating the severity of aortic regurgitation have not been accepted widely nor compared with truly quantitative reference standards. METHODS: Eight to 20 weeks after aortic regurgitation was surgically induced in six sheep, a total of 22 hemodynamic states were studied. Electromagnetic flow probes and meters provided reference flow data. Epicardial color Doppler echocardiographic studies were performed to image left ventricular outflow tract forward and aortic regurgitant blood flows. The new method digitally integrated spatial and temporal color flow velocity data for left ventricular outflow tract forward flow and ascending aortic regurgitant flow. The pulsed Doppler method using the velocity-time integral was also used to obtain regurgitant volumes and regurgitant fractions. RESULTS: Regurgitant volumes and regurgitant fractions by the new method agreed well with those obtained electromagnetically, whereas the pulsed Doppler method overestimated these reference data (mean [+/-SD] difference 0.23 +/- 2.9 ml vs. 11 +/- 5.8 ml, p < 0.0001 for regurgitant volume; mean difference 1.2 +/- 7.6% vs. 19 +/- 13%, p < 0.0001 for regurgitant fraction). CONCLUSIONS: This animal study, using strictly quantified aortic regurgitant volumes, demonstrated that the digital color Doppler method provides accurate aortic regurgitant volumes and regurgitant fractions without cumbersome measurements.

Animals↗

PubMed1997

Vestibular schwannoma showing a dural tail on contrast-enhanced magnetic resonance images.

The dural tail on contrast-enhanced magnetic resonance (MR) images, frequently observed in meningiomas, has been used to distinguish between cerebellopontine angle meningiomas and vestibular schwannomas. We report on a 66-year-old female with vestibular schwannoma showing the dural tail on contrast-enhanced MR images. Histological examination revealed that the dural tail corresponded to the thickened dura mater comprising of collagen fibres and scattered hyalinization with no tumoral invasion.

Aged↗

PubMed1997

The use of three-phase scintigraphy for diagnosing hemangiomas of the extremities. A clinical evaluation.

Five hemangiomas were found in four patients and were assessed by three-phase blood perfusion and blood-pool scintigraphy to determine the usefulness of this method for the imaging characteristics of different types of hemangiomas of the extremities. After injecting Tc-99m RBC or Tc-99m DTPA HSA, dynamic perfusion and early and delayed pool images were obtained and analyzed. The perfusion images of one cavernous hemangioma and two venous hemangiomas showed normal activity, but blood-pool imaging showed increased activity, whereas on perfusion imaging and early blood-pool imaging, another cavernous hemangioma showed a partial increase in activity in its periphery and on delayed blood-pool imaging, diffuse increase in activity. Further, the remaining hemangioma, a mixed-type hemangioma, showed, diffuse increase in activity on both perfusion and blood-pool imaging. Thus, three-phase scintigraphy was found useful in evaluating and achieving a diagnosis of a hemangioma of the extremities.

Adolescent↗

PubMed1997

Staging of esophageal carcinoma in vitro with 4.7-T MR imaging.

PURPOSE: To determine the accuracy of 4.7-T magnetic resonance (MR) imaging for evaluating the mural invasion of esophageal carcinoma. MATERIALS AND METHODS: Sixty-seven esophageal specimens containing 70 squamous cell carcinomas were studied with a 4.7-T MR system with a 4-cm-diameter surface coil. Spin-echo MR images were obtained with a field of view of 4-6 cm, matrix size of 256 x 256, and section thickness of 3 mm, which resulted in a voxel size of 0.08-0.16 mm3. MR findings were compared with histopathologic findings, which served as the standard of reference. Tumor invasion on MR images was determined by consensus of two radiologists. RESULTS: T2-weighted images depicted six to eight layers of the normal esophageal wall; these correlated well with layers identified with histologic examination. In 66 (94%) of 70 cases of esophageal carcinoma, the depth of mural invasion visualized with MR imaging correlated well with that determined with histopathologic examination. The stage determined with MR imaging, however, was higher in two (3%) and lower in two (3%) cases than that determined with histopathologic examination. MR imaging enabled visualization of the gross features of tumor growth pattern, tumor ulceration, and adjacent lymph node involvement. CONCLUSION: MR imaging in vitro allows accurate assessment of the mural invasion of esophageal carcinoma and thus potentially enables preoperative histopathologic staging.

Carcinoma, Squamous Cell↗

PubMed1997

Perfusion and blood-pool scintigraphy in the evaluation of head and neck hemangiomas.

UNLABELLED: We investigated the sensitivity and specificity of perfusion and blood-pool scintigraphy in the detection of head and neck hemangiomas and evaluated their histopathologic types. METHODS: Perfusion and blood-pool scintigraphy with 99mTc-red blood cells (RBCs) or 99mTc-human serum albumin combined with DTPA (HSA-D) were used to evaluate 51 head and neck lesions clinically suspected of being hemangiomas in 48 patients. Thirty-three of the 51 lesions were subsequently histologically confirmed to be hemangiomas, whereas the remaining 18 were histologically diagnosed as other lesions. RESULTS: Perfusion and blood-pool scintigraphy correctly diagnosed 30 of 33 hemangiomas as being hemangiomas but could not detect the remaining 3 hemangiomas. Perfusion and blood-pool scintigraphy correctly diagnosed 12 of 18 lesions as nonhemangiomas, but the remaining 6 lesions were misdiagnosed as hemangiomas. Thus, the sensitivity for detecting hemangiomas was 91%, with a specificity and accuracy of 67% and 82%, respectively. Twenty-five (89%) of 28 cavernous or venous hemangiomas demonstrated normal activity on the perfusion images and increased activity on the delayed blood-pool images, whereas the remaining 3 (11%) showed normal activity on both perfusion and blood-pool images. Finally, 5 of 5 (100%) capillary or recemose hemangiomas showed increased activity on the perfusion and blood-pool images. CONCLUSION: Perfusion and blood-pool scintigraphy demonstrated sufficiently high sensitivity but relatively low specificity for detecting head and neck hemangiomas. Additionally, perfusion and blood-pool scintigraphy can clearly differentiate between cavernous and venous hemangiomas and capillary and recemose hemangiomas and are extremely useful for the detection and evaluation of head and neck hemangiomas.

Adult↗

PubMed1997

Nonlinear intestinal absorption of 5-hydroxytryptamine receptor antagonist caused by absorptive and secretory transporters.

The mechanism of the nonlinear concentration dependence of intestinal absorption of the 5-hydroxytryptamine receptor antagonist azasetron was studied by use of rat in situ intestinal perfusion, as well as an in vitro Ussing-type chamber method mounted with rat intestinal tissue and cultured monolayers of human adenocarcinoma Caco-2 cells. The intestinal absorption rate constant of azasetron evaluated by the Doluisio method increased significantly with increasing concentration of azasetron up to 10 mM in a nonlinear fashion and tended to decrease at higher concentrations. Mucosal-to-serosal directed permeation of [14C]azasetron across rat ileal sheets evaluated by the in vitro Ussing-type chamber method also increased in a nonlinear fashion in a low concentration range, followed by a decrease as the concentration was further increased, whereas serosal-to-mucosal directed permeation decreased in a concentration-dependent manner. Vectorial transport of [14C]azasetron across a Caco-2 cell monolayer was observed, with higher transport in the basolateral-to-apical direction at a trace concentration of azasetron. When the initial uptake rate of azasetron by Caco-2 cells was measured, it was saturable with an apparent half-saturation concentration of 15 mM and was reduced in the presence of several cationic compounds. These observations suggest that azasetron is taken up by a carrier-mediated transport mechanism across the intestinal epithelial cells. When the steady-state uptake of [14C]azasetron was measured, it was increased in the presence of unlabeled azasetron and ondansetron. In addition, the steady-state uptake was enhanced in the presence of a P-glycoprotein inhibitor, cyclosporin A, and by ATP-depletion of the cells, although these treatments had no effect on the initial uptake of [14C]azasetron. Furthermore, the multidrug-resistant cancer cell line K562/ADM that overexpresses P-glycoprotein accumulated azasetron less extensively than did the parental drug-sensitive K562 cells. These results strongly suggest that azasetron is secreted into the intestinal lumen predominantly by P-glycoprotein. We conclude that intestinal transport of azasetron involves specialized transporters in both the absorptive and secretory directions, and the complex nonlinear intestinal absorption characteristics can be ascribed to the participation of multiple transport mechanisms.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1997

Left ventricular stroke work in mitral regurgitation: an animal experimental study.

BACKGROUND AND AIMS OF THE STUDY: Most studies on mitral regurgitation have focused on evaluating the regurgitant volume. The effects of mitral regurgitation and its associated cardiac workload on left ventricular function and mechanics may be equally important both in assessing the impact of regurgitation as well as in planning and evaluating therapy. The present study was undertaken to investigate the interrelationships of the regurgitant volume, hemodynamics and left ventricular work in an experimental animal model of chronic mitral regurgitation in which the regurgitant volume could be measured directly with electromagnetic flow probes. METHODS: A total of 21 hemodynamic states were studied in six sheep with surgically created mitral regurgitation. Regurgitant flow rates were obtained from electromagnetic flow meters. Left ventricular and atrial pressures were recorded using high-fidelity catheters. Regurgitant jet velocity was recorded by continuous wave Doppler. Left ventricular stroke work and energy losses due to the regurgitation were calculated. RESULTS: There was a close correlation between left ventricular stroke work and both jet energy and left atrial systolic pressure rise (r = 0.81, p = 0.0001 and r = 0.92, p = 0.0001, respectively). A moderate correlation to the regurgitant volume was found (r = 0.52, p = 0.01). CONCLUSIONS: The regurgitant volume itself is only one of the determinants of left ventricular stroke work in mitral regurgitation. Other factors such as left atrial mechanical properties and the regurgitant kinetic jet energy are at least as important for assessing cardiac work in patients with mitral regurgitation.

Animals↗

PubMed1996

Turbulent/viscous interactions control Doppler/catheter pressure discrepancies in aortic stenosis. The role of the Reynolds number.

BACKGROUND: Despite good correlation between Doppler and catheter pressure drops in numerous reports, it is well known that Doppler tends to apparently overestimate pressure drops obtained by cardiac catheterization. Neither (1) simplification of the Bernoulli equation nor (2) pressure recovery effects can explain this dilemma when taken alone. This study addressed the hypothesis that a Reynolds number-based approach, which characterizes (1) and (2), provides a first step toward better agreement of catheter and Doppler assessments of pressure drops. METHODS AND RESULTS: Doppler and catheter pressure drops were studied in an in vitro model designed to isolate the proposed Reynolds number effect and in a sheep model with varying degrees of stenosis. Doppler pressure drops in vitro correlated with the directly measured pressure drop for individual valves (r = .935, .960, .985, .984, .989, and .975) but with markedly different slopes and intercepts. A Bland-Altman type plot showed no useful pattern of discrepancy. The Reynolds number was successful in collapsing the data into the profile proposed in the hypothesis. Parallel results were found in the animal model. CONCLUSIONS: Apparent overestimation of net pressure drop by Doppler is due to pressure recovery effects, and these effects are countered by both viscous effects and inertial/turbulent effects. Only by reconciliation of discrepancies by use of a quantity such as Reynolds number that embodies the relative importance of competing factors can the noninvasive and invasive methods be connected. This study shows that a Reynolds number-based approach accomplishes this goal both in the idealized in vitro setting and in a biological system.

Animals↗

PubMed1996

Seeding of vascular grafts with genetically modified endothelial cells. Secretion of recombinant TPA results in decreased seeded cell retention in vitro and in vivo.

BACKGROUND: Seeding of small-diameter vascular grafts with endothelial cells (ECs) genetically engineered to secrete fibrinolytic or antithrombotic proteins offers the potential to improve graft patency rates. METHODS AND RESULTS: Sheep venous ECs were transduced with a retroviral vector encoding human tissue plasminogen activator (TPA). The ECs were seeded onto 4-mm-ID synthetic (Dacron) grafts. Retention of the seeded ECs was measured 2 hours after placement of the seeded grafts both in vitro in a nonpulsatile flow system and in vivo (in sheep) as femoral and carotid interposition grafts. On exposure to flow in vitro, ECs transduced with TPA were retained at a significantly lower rate (median, 67%) than either untransduced ECs (81%) or ECs transduced with a control retroviral vector producing beta-galactosidase (beta-Gal) (80%) (P < .05 for TPA versus either control). On implantation in vivo, ECs transduced with TPA were retained at a very low rate (median, 0%), significantly less than the retention of ECs transduced with the beta-Gal vector (32%; P < .00001). Decreased in vivo retention of ECs transduced with TPA correlated modestly with increased in vitro cellular passage level (r2 = .48; P < .0001) but not with in vivo blood flow rate (P = .45). Addition of the protease inhibitor aprotinin to the cell culture and graft perfusion media resulted in a significant (P < .05) increase in in vitro retention of ECs transduced with TPA. CONCLUSIONS: Increased TPA expression significantly decreases seeded EC adherence in vitro and in vivo. Gene therapy strategies for decreasing graft thrombosis may require expression of antithrombotic molecules that lack proteolytic activity.

Animals↗

PubMed1996

Effective regurgitant orifice area by the color Doppler flow convergence method for evaluating the severity of chronic aortic regurgitation. An animal study.

BACKGROUND: The aim of the present study was to evaluate dynamic changes in aortic regurgitant (AR) orifice area with the use of calibrated electromagnetic (EM) flowmeters and to validate a color Doppler flow convergence (FC) method for evaluating effective AR orifice area and regurgitant volume. METHODS AND RESULTS: In 6 sheep, 8 to 20 weeks after surgically induced AR, 22 hemodynamically different states were studied. Instantaneous regurgitant flow rates were obtained by aortic and pulmonary EM flowmeters balanced against each other. Instantaneous AR orifice areas were determined by dividing these actual AR flow rates by the corresponding continuous wave velocities (over 25 to 40 points during each diastole) matched for each steady state. Echo studies were performed to obtain maximal aliasing distances of the FC in a low range (0.20 to 0.32 m/s) and a high range (0.70 to 0.89 m/s) of aliasing velocities; the corresponding maximal AR flow rates were calculated using the hemispheric flow convergence assumption for the FC isovelocity surface. AR orifice areas were derived by dividing the maximal flow rates by the maximal continuous wave Doppler velocities. AR orifice sizes obtained with the use of EM flowmeters showed little change during diastole. Maximal and time-averaged AR orifice areas during diastole obtained by EM flowmeters ranged from 0.06 to 0.44 cm2 (mean, 0.24 +/- 0.11 cm2) and from 0.05 to 0.43 cm2 (mean, 0.21 +/- 0.06 cm2), respectively. Maximal AR orifice areas by FC using low aliasing velocities overestimated reference EM orifice areas; however, at high AV, FC predicted the reference areas more reliably (0.25 +/- 0.16 cm2, r = .82, difference = 0.04 +/- 0.07 cm2). The product of the maximal orifice area obtained by the FC method using high AV and the velocity time integral of the regurgitant orifice velocity showed good agreement with regurgitant volumes per beat (r = .81, difference = 0.9 +/- 7.9 mL/beat). CONCLUSIONS: This study, using strictly quantified AR volume, demonstrated little change in AR orifice size during diastole. When high aliasing velocities are chosen, the FC method can be useful for determining effective AR orifice size and regurgitant volume.

Animals↗