Systems and methods for detecting atrial tachyarrhythmias such as atrial fibrillation (AF) are disclosed. A medical system can sense a heart rate (HR) output and a hemodynamic status output. An AF detector circuit automatically determines a first detection criterion and a different second detection criterion. The first detection criterion can be more sensitive to the presence of the AF episode than the second detection criterion, and the second detection criterion can be more specific to the AF episode than the first detection criterion. The AF detector circuit detects an AF onset event using the first detection criterion and at least one of the heart rate output or the hemodynamic status output, and detects an AF termination event using the second detection criterion and at least one of the heart rate output or the hemodynamic status output.
