A cardiac pacemaker and method of operation of such pacemaker is disclosed comprising a single lead having conventional ventricular pacing and sensing electrode means as well as atrial sensors adapted to be positioned in the patient's atrim without any contact with the atrial wall, for sensing atrial wall movement and for generating information signals representative of the atrial wall movement. The free-floating atrial sensor is utilized in providing information for making a determination of a number of cardiac conditions, including analysis of direction of P waves to determine whether sensed signals are anterograde or retrograde.