Patent ID: 8239011

Claim:
An apparatus comprising: an implantable impedance sensing circuit configured to sense an atrial impedance signal of a subject and adapted to be coupled to a plurality of implantable electrodes; and an impedance signal analyzer circuit, communicatively coupled to the implantable impedance sensing circuit, configured to: detect a sudden change, in a characteristic of the sensed atrial impedance signal, that indicates atrial tachyarrhythmia; classify the atrial tachyarrhythmia indication as sinus tachycardia (ST) when the detected sudden change satisfies an ST threshold value of the characteristic; classify the atrial tachyarrhythmia indication as atrial tachycardia (AT) when the detected sudden change satisfies an AT threshold value of the characteristic that is different from the ST threshold value; classify the atrial tachyarrhythmia indication as atrial fibrillation (AF) when the detected sudden change satisfies an AF threshold value of the characteristic that is different from the ST and AT amplitude threshold values; and provide a classification of the tachyarrhythmia to a user or process.