An implantable flat blood pressure sensing cuff structure and an implantable blood pressure monitoring device use a first portion of the cuff structure that comprises a sidewall that extends from a surface and contains a pressure sensor, and a second portion of the cuff structure that is configured to overlie and be removably relative to the first portion. The first and second portions of the cuff structure are configured to provide an aperture extending transversely through the cuff structure for receiving a blood vessel therein generally sandwiched between the first portion and the second portion when the second portion is positioned on the first portion such that the pressure sensor is operative to detect vessel expansion and contraction.