Patent ID: 8403830

Claim:
An apparatus comprising: an implantable cardiac signal sensing circuit, configured to provide a sensed depolarization signal from a ventricle and a sensed depolarization signal from an atrium; and a controller circuit communicatively coupled to the implantable cardiac signal sensing circuit, wherein the controller circuit includes: a one-to-one detector circuit configured to: measure cardiac depolarization intervals of the atrium and the ventricle; and determine whether a relationship of atrial (A-A) depolarizations to ventricular (V-V) depolarizations is substantially one-to-one; a first counter circuit and a second counter circuit; and a tachyarrhythmia discrimination circuit configured to: detect an episode of tachyarrhythmia while the relationship atrial depolarizations to ventricular depolarizations is substantially one-to-one; increment the first counter when detecting one of a shortening or prolonging of a V-V interval that is immediately preceded by the same one of a detected shortening or prolonging of an A-A interval during the episode; increment the second counter when detecting one of a shortening or prolonging of an A-A interval during the episode that is immediately preceded by the same one of a shortening or prolonging of a V-V interval and an interval from a ventricular depolarization to an atrial depolarization (V-A) is greater than a specified threshold V-A interval value; classify the episode as VT when the count of the second counter exceeds the count of the first counter by a specified threshold count; and provide the classification of the tachyarrhythmia episode to a user or process.