Factors influencing pulmonary venous flow velocity patterns in mitral regurgitation: an in vitro study

OBJECTIVES

The aim of this study was to investigate factors affecting pulmonary venous flow patterns in mitral regurgitation.

BACKGROUND

Although pulmonary venous flow velocity patterns have been reported to be helpful in assessing the severity of mitral regurgitation, the influence of regurgitant jet direction, pulmonary venous location and left atrial pressures on pulmonary venous flow patterns has yet to be clarified.

METHODS

The mitral regurgitant jet was produced by a pulsatile piston pump at 10, 30 and 40 ml/beat through a circular orifice, whereas the pulmonary venous flow was driven by gravity. Four different patterns of pulmonary venous flow and mitral regurgitation were examined. The V wave pressure was set at 10, 30 and 50 mm Hg and pulmonary venous flow velocity at 30 cm/s. Color and pulsed Doppler recordings were obtained with a VingMed 800 scanner interfaced with a computer facilitating digital analysis.

RESULTS

The decrease in the velocity time integral of pulmonary venous flow was more prominent for any given volume of mitral regurgitation at higher left atrial pressure. When the mitral regurgitant jet was directed toward the pulmonary vein, a more prominent decrease in the velocity time integral was seen, especially for severe mitral regurgitation (40 ml) with high left atrial pressure (95% vs. 55%, p < 0.001); and the time to peak deceleration of forward flow was significantly shorter (485 vs. 523 ms, respectively, p < 0.01). Also, two different types (laminar and turbulent) of reversed pulmonary venous flow were observed.

CONCLUSIONS

Multiple factors, including jet direction, mitral regurgitant volume and left atrial pressure, determine the effect of mitral regurgitation on pulmonary venous flow velocity patterns.

[Effect of hyaluronic acid-stimulating factor on scar formation in wound healing process of deep partial thickness burns]

Hyaluronic acid-stimulating factor (HASF) was purified from the amniotic fluid and fetal serum of the gestational rabbit by means of affinity chromatography. After topical application of HASF on the deep partial thickness burn wounds, the level of hyaluronic acid (HA) in wound exudate was determined daily during the early period of healing. One month after wound healing, the local skin was harvested for collagen analysis. Histologic study was made to check the outline of collagen fibrils. The HASF was also used in rabbit fibroblast culture. The HA level contained in the supernatant was assayed. Result showed that HASF could elevate and maintain the HA level in the extracellular matrix of burn wound. In vitro, HASF was able to stimulate the fibroblast to produce hualuronic acid. The presence of HA in extracellular matrix then modulated collagen synthesis in the process of wound repair resulting in a higher content of type III collagen, thus bringing about a scarless healing of the deep patrial thickness burns.

Dynamic change in mitral regurgitant orifice area: comparison of color Doppler echocardiographic and electromagnetic flowmeter-based methods in a chronic animal model

OBJECTIVES

The aim of the present study was to investigate dynamic changes in the mitral regurgitant orifice using electromagnetic flow probes and flowmeters and the color Doppler flow convergence method.

BACKGROUND

Methods for determining mitral regurgitant orifice areas have been described using flow convergence imaging with a hemispheric isovelocity surface assumption. However, the shape of flow convergence isovelocity surfaces depends on many factors that change during regurgitation.

METHODS

In seven sheep with surgically created mitral regurgitation, 18 hemodynamic states were studied. The aliasing distances of flow convergence were measured at 10 sequential points using two ranges of aliasing velocities (0.20 to 0.32 and 0.56 to 0.72 m/s), and instantaneous flow rates were calculated using the hemispheric assumption. Instantaneous regurgitant areas were determined from the regurgitant flow rates obtained from both electromagnetic flowmeters and flow convergence divided by the corresponding continuous wave velocities.

RESULTS

The regurgitant orifice sizes obtained using the electromagnetic flow method usually increased to maximal size in early to midsystole and then decreased in late systole. Patterns of dynamic changes in orifice area obtained by flow convergence were not the same as those delineated by the electromagnetic flow method. Time-averaged regurgitant orifice areas obtained by flow convergence using lower aliasing velocities overestimated the areas obtained by the electromagnetic flow method ([mean +/- SD] 0.27 +/- 0.14 vs. 0.12 +/- 0.06 cm2, p < 0.001), whereas flow convergence, using higher aliasing velocities, estimated the reference areas more reliably (0.15 +/- 0.06 cm2).

CONCLUSIONS

The electromagnetic flow method studies uniformly demonstrated dynamic change in mitral regurgitant orifice area and suggested limitations of the flow convergence method.

[Changes in myocardial ATPase activity and Ca2+ content in burned rats]

The myocardial ATPase activity and Ca2+ content were investigated in rats with full thickness skin burn injury of 30% TBSA. The results showed that there were significant inhibitions of Na+, K(+)-ATPase,Ca2+, Mg(2+)-ATPase, and Ca(2+)-ATPase activities of myocardium after burn injury. The burn injury could result in increase of calcium content in myocardium. Burned rats also had a higher level of MDA in heart tissue when compared to controls. This study demonstrates that the membrane defects with respect to ATPase activity, oxygen free radical, and Ca2+ overload in myocardium may be associated with damage of myocardium after burns.

[Isolation and identification of a pathogen of grasshoppers]

A pathogen was isolated from natural dead pests of Ceracris kiangsu in Geleshan farm of Chongqin. Its pathogenecity was confirmed by the law of KOCK. It was identified as Pseudomonas pseudoalcaligenes according to its physiological and biochemical properties as well as the G + C content of DNA (63.73mol%). The results of preliminary bioassay show that the pathogen can infect the grasshoppers and Ceracris kiangsu, and also can infect other pests of grassland in a certain extent.

Estimation of regurgitant flow volume based on centerline velocity/distance profiles using digital color M-Q Doppler: application to orifices of different shapes

OBJECTIVES

In this study we investigated the centerline velocity profile method for flow computation as applied to noncircular, as well as circular, orifices using digital color flow data.

BACKGROUND

Recently it has been suggested that flow volume through an orifice can be estimated more accurately by computing the axial "centerline" flow velocity/distance profile proximal to the orifice.

METHODS

A total of seven different orifices were mounted in a constant-flow model: four circular orifices, two rectangular orifices with a major/minor axis ratio of 4:1 and 8:1 and an ovoid orifice having a major/minor axis ratio of 2:1. Three different flow rates were examined (1.68, 3.48 and 6.48 liters/min). Digital measurements of flow velocity at discrete positions along the centerline progressing toward the orifice were analyzed to yield complete flow velocity profiles for each orifice at each flow rate.

RESULTS

A clear separation of the flow profiles for the three different flow rates was observed independent of orifice size for all of the circular orifices. The velocity/distance acceleration curves showed highly significant correlations using multiplicative regression fits (y = ax-b, r = 0.94 to 0.99, all p < 0.0001). An equation for quantitatively correlating the a and b coefficients from the multiplicative regression fits with flow rates was derived from stepwise regression analysis: Flow rate = 23a + 3.3b - 1.5 (r = 0.97, p < 0.0001, SEE 0.46 liter/min).

CONCLUSIONS

In view of the various sizes and shapes encountered clinically for regurgitant orifices, the simplicity of this method for the estimation of the severity of regurgitant lesions might be of importance for clinical applications of this method.

Evaluation of mitral regurgitation using a digitally determined color Doppler flow convergence 'centerline' acceleration method. Studies in an animal model with quantified mitral regurgitation

BACKGROUND

The imaging and measurement of the proximal flow convergence region in the left ventricle have been reported to be useful for identifying the site of mitral regurgitation (MR) and for evaluating its severity. However, the application of this method has not gained general acceptance. There have been few in vivo studies with quantified reference standards for determining regurgitant volume, and those that have been reported used spectral Doppler standards and/or nonsimultaneously performed contrast ventriculography. The purpose of the present study was to evaluate the proximal flow convergence centerline velocity-distance profile method applied to chronic MR resulting from flail mitral leaflets in an animal model in which regurgitant flow rates and regurgitant volumes were determined simultaneously with electromagnetic flow probes and flowmeters.

METHODS AND RESULTS

In six sheep, a total of 18 hemodynamically different states were obtained when the animals were restudied 6 months after surgical induction of MR produced by severing chordae tendineae to the anterior (three sheep) or posterior (three sheep) mitral leaflet. Echocardiographic studies with a Vingmed 750 were performed to obtain complete proximal axial flow acceleration velocity-distance profiles for each hemodynamic state. The color Doppler velocity data were directly transferred in digital format from the ultrasound instrumentation to a microcomputer. The severity of MR was assessed by the magnitude of the mitral regurgitant fraction determined using both mitral and aortic electromagnetic flow probes balanced against each other to yield regurgitant volume. MR was classified as grade I when the regurgitant fraction was < 20%, as grade II when it was 20% to 35%, and as grade III to IV when it was > 35%. Thus, of the 18 hemodynamic states, 4 (from two sheep) were grade I, 7 (from five sheep) were grade II, and 7 (from three sheep) were grade III to IV. All of the velocity-distance acceleration curves showed organized acceleration fields with highly significant correlations using multiplicative regression fits (y = a.x-b, r = .90 to .99, all P < .01). Grade III to IV MR resulted in rightward and upward shifts of the velocity-distance profile curves compared with those produced by grade II and grade I MR. All of the centerline velocity-distance profiles for grade III or IV regurgitation resided in a domain encompassed by velocities > 0.5 m/s at distances from the orifice > 0.6 cm; the profiles for grade I regurgitation resided in a domain encompassed by velocities < 0.3 m/s at distances from the orifice of < 0.45 cm. The profiles for grade II regurgitations resided in a domain between them. Regression analysis for the distance at which a velocity of 0.5 m/s was first reached bore a close relation to regurgitant fraction (r = .92, P < .0001) and peak regurgitant flow rate (r = .89, P < .0001). In addition, an equation for quantitatively correlating both a and b (coefficients from the multiplicative regression fits) with the peak regurgitant flow rate (Qpeak in L/min) was derived from stepwise regression analysis: Qpeak = 12a + 2.7b-2.4 (r = .96, P < .0001, SEE = .45 L/min).

CONCLUSIONS

In this study, using quantified MR volume, we demonstrate that the proximal flow convergence axial centerline velocity-distance profile method can be used for evaluating the severity of MR without any assumption about isovelocity surface shape geometry.

[Erythrocyte membrane during shock stage in burned rats]

The anion transport property is the one of the most important functions of the erythrocyte. In this paper a new method is used to measure the NO2- and Cl- ions transport across the erythrocyte membrane in burned rats. It was found that the NO2- and Cl- transport rate across erythrocyte membrane became slower during shock stage in burned rats, being contrary to the results found in heat-treated erythrocytes in vitro. By using a specific inhibitor of anion transport, DIDS, it was shown that the abnormality of NO2- transport across the erythrocyte membrane in burned rats is due probably to a damage of extracellular domain of band 3 protein. The authors consider that the influence of membranotoxic factors and the disturbance of energy metabolism during burn shock stage are accounted for all the noticed alterations.

[Experimental study of antiinfection effect of topical "moist ointment" in burn wound infection]

A controversy on the therapeutic effect of topical "moist ointment" in burns has been noticed recently. An experimental study is designed for the evaluation of its antibacterial and antiinfection effect. A 20% fullthickness burn wound is produced on SD rat back, and they are seeded with 10(9) CFU of Pseudomonas aeruginosa ATCC-27853. "Moist ointment", cream base, 1% silver sulfadiazine (Ag-SD) cream or 1.2% silver norfloxacin (Ag-FLX) cream is topically applied to the burn wounds at various time interval of 10 min, 8h, 24h, and 48h, after the inoculation of Pseudomonas aeruginosa. Topical therapy lasted for 48h, with dressing change once a day but twice a day for "moist ointment" therapy only. Bacterial counts of subeschar tissue and heart blood culture, and histopathologic study of the wounds are made as laboratory criteria. A modified agar well diffusion (AWD) test is performed as a bacterial inhibitory study using Pseudomonas aeruginosa ATCC-27853, E. coli ATCC-25922, or Staphylococcus aureus ATCC-25923. Results of the study show that Ag-FLX cream has a strong antibacterial effect and Ag-SD cream a moderate effect. However, "moist ointment" and cream base do not show antibacterial effect. Bacterial counts of subeschar tissue and histopathologic study of the infected burn wounds show that more than 70% of the animals in the "moist ointment" group have invasive wound infection, and the incidence of septicemia with Pseudomonas aeruginosa is 50% as determined by blood cultures. The above mentioned results indicate that "moist ointment" has no antibacterial and anti-infection effect.

Growth cycle-induced changes in sensitivity of Staphylococcus aureus to bactericidal lipids from abscesses

Three Staphylococcus aureus strains (303, 18Z and TG), exhibiting various patterns of survival within abscesses, were significantly more sensitive to the bactericidal activity of oleic acid during the log phase of growth than at other stages of the growth cycle. Cells entering the stationary phase showed diminished sensitivity to the fatty acid. These changes were reflected by changes in the LD50 and also by differences in the rate of killing by oleic acid. Additional changes were noted: the rate of killing by oleic acid declined over a 4-day period; a progressively greater proportion of the staphylococcal population became resistant to even high concentrations of oleic acid; from the fourth day onwards c. 50-55% of the cocci were totally resistant to the fatty acid. Strains 303 and 18Z became more sensitive to mono-olein during the log phase of growth, but strain TG was very resistant to mono-olein throughout the growth cycle. Growth in the presence of glycine 6% to reduce cross-links in the peptidoglycan did not alter bacterial sensitivity to oleic acid. However, all three S. aureus strains exhibited significant increases in membrane fluidity during the log phase of growth, but upon entering the stationary phase membrane fluidity again decreased. Concomitant changes in carotenoid content occurred during the growth cycle, but these changes did not appear to be solely responsible for the changes in sensitivity to the lipids.