Effect of Lower Body Negative Pressure on Mitral Valve Movement

摘要

This study was designed to investigate the hypothesis that normal mitral valves will prolapse and/or regurgitate in some individuals when their left ventricular volume is reduced with lower body negative pressure (LBNP). The effect of ventricular volume changes on normal mitral valves is not well understood, however, a few studies have suggested that dehydration may cause normal mitral valves to prolapse. Ten men and ten women with normal cardiac findings underwent serial echocardiography with color-flow Doppler and progressive LBNP to -50mmHg from baseline. The data from two subjects (both women) could not be used due to technical difficulties. Of the 18 subjects, 10 had some degrees of mitral regurgitation (MR) at any stage of LBNP. The maximum severity from any of the subjects was mild MR. Five individuals had MR in the pre-LBNP period, but none of these progressed to more significant MR. Five individuals did not have MR in the pre-LBNP period and 4/5 developed trace/mild MR during LBNP. However, the degree of MR during LBNP was not progressive with successive LBNP stages. Although four individuals had anterior leaflet bowing in the apical 4-chamber view during LBNP, these findings alone were not diagnostic of MVP. Conclusions: LBNP is a graded, quickly reversible method of decreasing left ventricular volume in individuals. Further study into volemic state and perhaps individuals' body habitus will help determine the extent to which normal mitral valves may prolapse.