A multi-layer method for detecting atrial arrhythmias using ventricular cycle length information that includes performing a base layer algorithm for detecting the onset and offset of an atrial tachyarrhythmia. The multi-layer method further includes one or more higher layer algorithms executed in response to a base layer detection to confirm or reject the base layer detection. The base layer is designed to operate with high sensitivity to atrial fibrillation and/or organized atrial tachycardia and the higher layer is designed to operate with high sensitivity and high specificity to atrial fibrillation and/or organized atrial tachycardia.