A caster wheel assembly includes at least one hub that has an annularly dished concave region disposed between a pair of cylindrical lips about its outer periphery. The closure catheter carries a plurality of tissue anchors, which may be deployed into tissue surrounding the opening, and used to draw the opening closed. The time interval may be varied, and a characteristic indicative of the return of the valve to the original position may be detected based on a comparison of the pulses. Other configuration include a hollow chamber with an anode outside the chamber located opposite its discharge constriction orifice.