Devices and methods of visualizing and determining depth of penetration in cardiac tissue

Disclosed herein are devices and methods for assessing the surface of a target cardiac tissue and for delivering a tissue anchor to cardiac tissue at a preselected depth within the myocardium in a beating heart procedure. In one variation, an anchor delivery device comprises an elongate body, a tissue anchor disposed within a first longitudinal lumen of the elongate body, and a tissue depth indicator slidable within a second longitudinal lumen of the elongate body. The tissue depth indicator has a first configuration that indicates the boundary of the surface of the target tissue and a second configuration that indicates when the distal tip of the elongate body has been advanced to a preselected depth into the target tissue. In some variations, a tissue depth indicator may also be configured to resist or limit the penetration of the delivery device into tissue after a preselected depth has been reached.