Resumen

ZOCALO, YANINA et al. El endotelio mantiene elevada la capacidad de conducción arterial y reduce la poscarga dinámica ventricular de una manera frecuencia-dependiente. Rev.Urug.Cardiol. [online]. 2007, vol.22, n.1, pp.15-24. ISSN 1688-0420.

SUMMARY Introduction: The geometrical properties, the viscosity (V) and elasticity (E) of the arteries determine the arterial conduit (CF) and buffer (BF) functions, as well as the elastic (W_E) and viscous (W_V) work developed by the ventricle during the ejection (external dynamic afterload). It remains to be established the role of the endothelium in controlling V, CF, BF, W_E and W_V, and if the endothelium’s regulation of the dynamic afterload depends on the frequency. Objetive: To characterize the endothelial role in the regulation of V, CF, BF, W_E and W_V, and to analyze the endothelial control of the dynamic afterload during the increase in the frequency of stimulation. Methods: Ovine brachiocephalic arteries (n=9) were studied in a circulation mock during physiological haemodynamic conditions. Arterial flow, pressure and diameter were measured at 60, 80 and 100 cycles/minute. At each frequency E, V, CF, BF, W_E y Wv, were calculated before and after the endothelium removal. Hystological studies verified the adequacy of the endotelial removal. Results: The endothelium allowed keeping E, V, W_E and W_V in low levels, and a high CF (p<0,05). The reduction in the afterload determinants was higher at higher levels of frequency (p<0,05). Conclusions: The endothelium regulates the arterial viscoelasticity, with a reduction in the dynamic afterload; at the time it allows keeping the CF at high levels, and does  not change the arterial auto-protection. The higher reduction in the afterload at high frequencies (increased oxigen demand), represents an additional beneficial effect in the ventricle function.

Palabras clave : ARTERY; BIOMECHANIC; ENDOTHELIUM; HEART RATE.

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