A medical device for determining sensing vectors, comprising: a plurality of electrodes (18, 20, 22) capable of forming a plurality of sensing vectors for sensing cardiac signals; a sense amplifier configured to sense a cardiac signal obtained from the plurality of electrodes; and characterised by: a processor configured to: set a blanking period and a blanking period adjustment window in response to the sensed cardiac signal for the plurality of sensing vectors; and further characterised in that said processor is further configured to determine, for each of the plurality of sensing vectors, first minimum signal differences between the sensed cardiac signal as sensed for the sensing vector and a sensing threshold during the blanking period adjustment window; set a quality metric window extending subsequent to the blanking period adjustment window, determine, for each of the plurality of sensing vectors, second minimum signal differences between the sensed cardiac signal as sensed for the sensing vector and the sensing threshold during the quality metric window, rank the sensing vectors of the plurality of sensing vectors based on the determined second minimum signal differences, and select one or more sensing vectors of the plurality of sensing vectors in response to the determined rankings. a plurality of electrodes (18, 20, 22) capable of forming a plurality of sensing vectors for sensing cardiac signals; a sense amplifier configured to sense a cardiac signal obtained from the plurality of electrodes; and characterised by: a processor configured to: set a blanking period and a blanking period adjustment window in response to the sensed cardiac signal for the plurality of sensing vectors; and further characterised in that said processor is further configured to determine, for each of the plurality of sensing vectors, first minimum signal differences between the sensed cardiac signal as sensed for the sensing vector and a sensing threshold during the blanking period adjustment window; set a quality metric window extending subsequent to the blanking period adjustment window, determine, for each of the plurality of sensing vectors, second minimum signal differences between the sensed cardiac signal as sensed for the sensing vector and the sensing threshold during the quality metric window, rank the sensing vectors of the plurality of sensing vectors based on the determined second minimum signal differences, and select one or more sensing vectors of the plurality of sensing vectors in response to the determined rankings. determine, for each of the plurality of sensing vectors, first minimum signal differences between the sensed cardiac signal as sensed for the sensing vector and a sensing threshold during the blanking period adjustment window; set a quality metric window extending subsequent to the blanking period adjustment window, determine, for each of the plurality of sensing vectors, second minimum signal differences between the sensed cardiac signal as sensed for the sensing vector and the sensing threshold during the quality metric window, rank the sensing vectors of the plurality of sensing vectors based on the determined second minimum signal differences, and select one or more sensing vectors of the plurality of sensing vectors in response to the determined rankings.