An implantable cardiac monitoring device includes first and second arms, pivotably attached to one another electronic circuitry and an associated power source of the device are hermetically sealed in a housing formed by one of the arms. A first electrode is carried by the first arm, a second electrode by the second arm, and a third electrode by one of the two arms. The device further includes a tether element, preferably a strut, pivotably attached between the arms and movable between a folded state and an expanded state. When the strut is in the folded state, the device, in a relatively compact form, can be inserted through a relatively small incision and into subcutaneous tissue, after which, the strut is moved to the expanded state where ends of the arms are spaced apart from one another and supported by the strut, and the three electrodes form dual sensing vectors.
