RESUMEN
Continuously operating thermo-electrochemical cells (thermocells) are of interest for harvesting low-grade waste thermal energy because of their potentially low cost compared with conventional thermoelectrics. Pt-free thermocells devised here provide an output power of 12 W m-2 for an interelectrode temperature difference (ΔT) of 81 °C, which is sixfold higher power than previously reported for planar thermocells operating at ambient pressure.
RESUMEN
BACKGROUND AND AIM OF THE STUDY: The mitral valve edge-to-edge repair (ETER) procedure inevitably alters mitral valve leaflet mechanics. The study aim was to quantify the effects of papillary muscle (PM) position on stretches in the central area of the anterior leaflet after mitral valve ETER. METHODS: Sixteen markers of a 4x4 array were attached onto the central area of the mitral valve anterior leaflet. The free edges of the mitral valve leaflets were sutured together with a single stitch to mimic the ETER. The mitral valve was then mounted in an in-vitro flow loop that was capable of simulating physiological loading conditions. The PM of the mitral valve was set in slack, normal, and taut positions. Displacements of the markers were obtained from the images of the markers, in order to calculate the stretches and stretch rates. RESULTS: The major principal stretch during systole was significantly greater than that during diastole in the three PM positions. The major principal (radial) stretch was significantly greater in the taut PM position than in the normal and slack PM positions during diastole. However, there was no significant difference in the minor principal (circumferential) stretch during diastole in the three PM positions. The loading and unloading stretch rates were not affected by the PM position, except for the major principal stretch rate during loading. CONCLUSION: With regards to the central region of the mitral valve anterior leaflet, the radial stretch during diastole was significantly less than that during systole. Therefore, the load on the anterior leaflet during systole, rather than that during diastole, should be considered when evaluating ETER durability, especially in the taut PM position. The circumferential stretch during diastole was not influenced by the PM positions.
Asunto(s)
Válvula Mitral/cirugía , Modelos Cardiovasculares , Músculos Papilares/cirugía , Técnicas de Sutura , Animales , Presión Sanguínea/fisiología , Diástole/fisiología , Válvula Mitral/fisiología , Modelos Animales , Músculos Papilares/fisiología , Estrés Mecánico , Porcinos , Sístole/fisiología , Resistencia a la Tracción/fisiologíaRESUMEN
Mitral valve edge-to-edge repair (ETER) alters valve mechanics, which may impact efficacy and durability of the repair. The objective of this paper was to quantify stretches in the central region of the anterior leaflet of the mitral valve after ETER with a single suture and 6 mm suture. Sixteen markers, forming a 4x4 array, were attached onto the central region of the mitral valve anterior leaflet. The mitral valve was subjected to ETER with a single suture and 6 mm suture, and mounted in an in vitro flow loop simulating physiological conditions. Images of the marker array were used to calculate marker displacement and stretch. A total of 9 mitral valves were tested. Two peak stretches were observed during a cardiac cycle, one in systole and the other in diastole under mitral valve edge-to-edge repair condition. The major principal (radial) stretch during systole was significantly greater than that during diastole. However, there was no significant difference between the minor principal (circumferential) stretch during diastole and that during systole. In addition, there were no significant differences in the radial and circumferential, or areal stretches and stretch rates during diastole between the single suture and 6 mm suture. The ETER subjects the mitral valve leaflets to double frequency of loading and unloading. Minor change in suture length may not result in a significant load difference in the central region of the anterior leaflet during diastole.