Impact of chronic mitral regurgitation on 3D atrial size and mechanics. Insights from the prospective 3D-PRIME study

Background

Chronic mitral regurgitation (MR) leads to progressive left atrial (LA) dilation. Its relative contribution to 3-dimensional (3D) LA structural and functional remodelling and the impact of concomitant clinical and hemodynamic factors, has been less explored.

Aims

To assess 3D LA size and mechanics, as well as mean LA pressure estimated from the pulmonary vein flow, in relation to chronic MR severity.

Methods

In the prospective 3D-PRIME (3D Echocardiography and Cardiovascular Prognosis in Mitral Regurgitation) study, 46 patients with chronic MR (69±13 years, body mass index (BMI) 26.2±4.3kg/m2, 50% women, 26% with atrial fibrillation, 30% with severe MR) recruited at one heart valve center were investigated with 2D and 3D transthoracic and transesophageal echocardiography. MR severity was quantified by the regurgitant volume (RV) and MR classified as organic, atrial functional or ventricular functional, as by current recommendations. LA size was measured by 3D maximum volume (LAV) indexed for body surface area (LAVI), LA mechanics by 3D peak relative increase in longitudinal volume in the reservoir phase (Sr), and mitral size by 3D annulus area and total leaflet area. Pulmonary vein Doppler flow profile was recorded in both right and left upper veins, and mean LA pressure was estimated from the average pulmonary vein systolic/diastolic velocity time integral ratio.

Results

Average mitral RV was 38±26ml, LAVI 53ml/m2, and Sr 17±11%. Increased mitral RV correlated with higher LAV and mean LA pressure (Figure 1), larger mitral annulus area (r=0.42) and total leaflet area (r=0.38) (all p<0.01), but not with Sr. In backward stepwise multivariate linear regression analyses, increased LAVI was independently predicted by larger mitral RV, higher age and atrial fibrillation (R2=0.62), higher mean LAP by larger mitral RV, body mass index and atrial fibrillation (R2=0.55), while lower Sr was associated with higher age and atrial fibrillation (R2=0.62) (all p<0.001). Patients with atrial functional MR (30% of the total group) had the largest LAVs and lowest Sr despite slightly lower mitral RV (Figure 2).

Conclusion

Chronic MR is associated with progressive increase in LA volume, mean LA pressure, and mitral annulus and total leaflet area. While MR is accompanied by low 3D LA longitudinal deformation, impaired LA mechanics is multifactorial and related closely to age and history of atrial arrythmias.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): Haukeland University Hospital Figure 1Figure 2

Detection of microbial contamination in fermentation processes: mass spectrometric determination of gram-negative bacteria in Leuconostoc mesenteroides cultures

Gas chromatography/mass spectrometry was used to detect the presence of Enterobacter cloacae in cultures of Leuconostoc mesenteroides, an organism used in an industrial process for production of dextrane. The penta-fluorobenzoyl-methyl ester derivative of 3-hydroxy-myristic acid, a characteristic compound of gram-negative bacteria, was used as the analyte. By using gas chromatography/mass spectrometry with selected ion monitoring, E. cloacae was determined over the range of 1 ppm to 1% in cultures of L. mesenteroides. The proposed analytical approach represents a useful alternative to conventional methods for determining contaminating organisms in industrial fermentation processes.

Quantification and comparison of some natural sphingomyelins by on-line high-performance liquid chromatography/discharge-assisted thermospray mass spectrometry

Sphingomyelins obtained from bovine brain, chicken egg yolk and bovine milk fat were analysed. Separation was performed by reversed-phase high-performance liquid chromatography utilizing a binary solvent gradient consisting of n-butanol-water-1-propanol-isooctane. Detection was accomplished by light scattering and on-line discharge-assisted thermospray (plasmaspray) ionization mass spectrometry. The positive ion mass spectra exhibit prominent ions related to the amine base structure and fragments which can be utilized for identification of molecular species. The abundance of the fragments containing the fatty acid reflects relatively well the fatty acid composition of natural sphingomyelin mixtures. Bovine brain sphingomyelin has, for example, two distinctive major molecular species composed of C24:1 and C18:0 acids as indicated by the m/z 630.6 and m/z 548.5 ions, respectively. While egg yolk exhibits ions of m/z 520.6 which indicate the presence of C16:0, bovine milk sphingomyelin has several prominent ions of m/z 632.5, 618.6 and 604.7, reflecting the proportions of C24:0, C23:0 and C22:0, respectively.

Cultivation of HeLa cells with fetal bovine serum or Ultroser G: effects on the plasma membrane constitution

Plasma membranes isolated from HeLa cells cultivated in suspension cultures supplemented with 3.5% fetal bovine serum or 2% of the commercially available serum substitute Ultroser G contained the same amounts of protein, cholesterol, and phosphate on a cellular basis. Minor differences in the plasma membrane fatty acid composition were seen, with the most pronounced alteration observed for palmitic acid, which amounted to 27 and 20% in fetal bovine serum- and Ultroser G- supplemented cells, respectively. Plasma membranes from cells grown with Ultroser G contained almost twice as much phosphatidylethanolamine and displayed two thirds of the phosphatidylcholine content, compared to plasma membranes obtained from fetal bovine serum supplemented cells. The former membranes also showed a 3 times higher specific [3H]acetate labeling of cholesterol, indicating a higher de novo synthesis of cholesterol. Both quantitative and qualitative alterations were revealed among the plasma membrane polypeptides when these were subjected to immuno- and lectin blottings. Fluorescence anisotropy measurements at different temperatures produced similar results irrespective of the growth medium supplement when the plasma membrane specific probe 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene was used on intact cells. However, the average cellular rigidity was higher for Ultroser G supplemented cells, determined with 1,6-diphenyl-1,3,5-hexatriene as a probe.

Highly sensitive determination and characterization of intact cellular ester-linked phospholipids using liquid chromatography-plasma spray mass spectrometry

Liquid chromatographic class separations of common cellular phospholipids combined with plasma spray ionization of the effluents were investigated. Comparison with true thermospray ionization involving ammonium acetate buffering revealed a gain in total ionization in the plasma spray of a factor of approximately 10 using a cation-exchange column and a solvent mixture consisting of acetonitrile-methanol-water (400:100:15, v/v). Plasma spray ionization studies of bovine brain polyphosphoinositides interrelated by the phosphate content in the inositol moiety showed almost identical monoglyceride and diglyceride ion clusters, indicating possibilities of studying the biochemical turnover of such phospholipids. Plasma spray ionization liquid chromatography-mass spectrometry of bacterial membrane phospholipids (Pseudomonas fluorescens) revealed possibilities of obtaining indications of individual fatty acid compositions from the spectra of the phosphatidylinositol and phosphatidylethanolamine fractions present. Conventional gas chromatographic fatty acid analysis agreed with the direct mass spectrometric structure elucidations. Interestingly, the two phospholipid classes had different relative fatty acid compositions with a significantly higher degree of cyclic fatty acids in the phosphatidyl ethanolamines. Plasma spray ionization yielded linear dose-response curves for both the monoglyceride and diglyceride fragment signals in the selected-ion monitoring mode. The detection limit for the monoglyceride and diglyceride species of phosphatidylcholine under the chromatographic and mass spectrometric conditions used was found to be in the picogram range.

Model system for studies of microbial dynamics at exuding surfaces such as the rhizosphere

An autoclavable all-glass system for studying microbial dynamics at permeable surfaces is described. Standard hydrophobic or hydrophilic membranes (46-mm diameter) of various pore sizes were supported on a glass frit through which nutrient solutions were pumped by a peristaltic pump. The pump provided a precisely controlled flow at speeds of 0.5 to 500 ml of defined or natural cell exudates per h, which passed through the membrane into a receiving vessel. The construction allowed a choice of membranes, which could be modified. The system was tested with a bacterium, isolated from rape plant roots (Brassica napus L.), that was inoculated on a hydrophilic membrane filter and allowed to develop into a biofilm. A defined medium with a composition resembling that of natural rape root exudate was pumped through the membrane at 0.5 ml/h. Scanning electron microscopic examinations indicated that the inoculum formed microcolonies embedded in exopolymers evenly distributed over the membrane surface. The lipid composition and content of poly-beta-hydroxybutyrate in free-living and adhered cells were determined by gas chromatography. The bacterial consumption of amino acids in the exudate was also studied.