Assessment of the total artificial heart (TAH) pulsatility: the coalition between pulsatility and ejection time in TAH in vitro study.

There are many types of pulsatile pumps with various pulsatile flow waveforms. These authors perceived that pulsatility was an important characteristic for a pulsatile pump. The effect of a total artificial heart (TAH) was estimated using a pulse power index (PPI) in a mock loop. This method helps in the development of a standard criterion for measurement of a pulsatile waveform. The pulsatility of the TAH was found to be useful as a physiological control method. At first the relationship between ejection time and dp/dt was examined and then the relation between PPI, ejection time and preload. The dp/dt was unchanged by ejection time and PPI was unchanged by preload. However, PPI was changed by the ejection time. There was an inverse correlation between ejection time and PPI (r = 0.80). The PPI at ejection time 150 msec was significantly higher than the other ejection time's PPI. These results suggest that the TAH should be driven with an ejection time of 150 msec, because this ejection time has a high pulsatility and can obtain a higher flow. This happens without increasing the dp/dt and this ejection time can be preplanned, because a fixed ejection time improves the durability of the actuator.

[Three-dimensional transesophageal echocardiographic assessment for prosthetic valves].

We evaluated three-dimensional transesophageal echocardiographic assessment of the implanted mechanical valves by rotational scanning method. Patients were 7 mitral valve replacement and one aortic valve replacement, 2 mitral and aortic valve replacement. In 2 cases of 7 mitral valve replacement, the prosthetic valve regurgitation was evaluated using by color Doppler echocardiography. In this study, multiplane transesophageal probe was used. It rotated at 2-degree intervals from 0 to 180 degrees and the three-dimensional reconstruction was performed by echo scan workstation system (TOMTEC Inc, Munich, Germany). In mitral valve replacement cases, the valve motion of bileaflet valve (St. Jude Medical valve and ATS valve) were showed very clearly. The struts was easily recognized in the St. Jude Medical valve (SJM valve) cases. In one of SJM valve cases, the pannus formation was revealed, but it did not disturb valve motion. The prosthetic valve regurgitation can be seen accurately. However, aortic valve and ball valve cases cannot be reconstructed because of artifact from prosthetic valve and ultrasonic direction. The prosthetic valve regurgitation, pannus formation which was difficult to be showed in two-dimensional echocardiography and relationship between annulus and sewing cuff can be evaluated by this three-dimensional echocardiography. In this study, this system has some problems, for example real-time evaluation is impossible, aortic valve and ball valve cases cannot be reconstructed. However, we think that this new technology is suitable for evaluating valve thrombus, valve dysfunction and paravalvular leakage. In conclusion, the three-dimensional echo-cardiography demonstrated, reliable and accurate examination, and it can evaluate various complications of prosthetic valve.

Assessment of the significance of virulence factors of uropathogenic Escherichia coli in experimental urinary tract infection in mice.

Four Escherichia coli strains, isolated from cystitis patients, belonging to serotype 02:H- and possessing different combinations of urovirulence factors were examined in an experimental pyelonephritis mouse model to assess the relative importance of virulence factors in causation of urinary tract infections (UTI). The results suggest not only that the each virulence factor has a role in causation of UTI but also that the presence of P fimbriae and production of hemolysin significantly reduced the LD50 and ID50 of the strains in the mouse model. The results also demonstrate that the presence of additional virulence factors acts in an additive or synergetic fashion enhancing the cumulative impact of the strain.