Apparatus and methods are described including sensing a phase of a cyclic activity of a subject. In a first cycle of the cyclic activity, at a given phase of the cycle, movement of a distal portion of a tool toward an occlusion in the subject's blood vessel is allowed. Following the given phase in the first cycle, and prior to an occurrence of the given phase in a subsequent cycle, movement of the tool is inhibited. In a second cycle of the cyclic activity, at the given phase of the cycle, the occlusion is at least partially penetrated by the tool, by allowing movement of the distal portion of the tool through at least a portion of the occlusion. Other applications are also described.
