An implantable medical device is provided for detecting transportless ventricular rhythm of a heart lacking atrial transport and comprises a housing, sensors configured to be located proximate to a heart, a sensing module to sense cardiac signals representative of a rhythm originating from the heart and a rhythm detection module. The rhythm detection module determines a change in AV association and identifies a potential ventricular complex with loss of atrial transport (VCLAT) based on the change in AV association.