A cardiac rhythm management system may include an implantable cardiac rhythm management device. Such devices may provide therapy, such as to treat bradyarrhythmias and/or tachyarrhythmias. In addition to adjusting heart rate, such a device may also improve cardiac output by providing cardiac resynchronization therapy (CRT). Such CRT assists in spatially coordinating heart contractions. Different arrhythmias and/or pathological conditions may require different therapies. For example, a supraventricular tachyarrhythmia (SVT) may be treated differently from a ventricular tachyarrhythmia (VT). Therefore, it may be desirable for the system to distinguish SVT from VT.
One factor useful for identifying VT (such as for discriminating between SVT and VT, or otherwise) is detecting atrioventricular (AV) dissociation, in which the ventricular heart rhythm doesn't track the atrial heart rhythm. The existence of AV dissociation during a tachyarrhythmia is often an indicator of the existence of VT rather than SVT, particularly where the VT or SVT occurs during a regular heart rhythm.