A cardiac device and method thereof for detecting atrial fibrillation within a mean heart signal of a body, wherein the cardiac device includes at least two sensing electrodes. The method includes providing an input heart signal, detecting sense events (VS) and noise events (VN), and generating further noise events (VN) each at a predetermined time interval after a noise event (VN) has been detected and when the noise event (VN) continues. The method includes incrementing a noise counter for each noise event (VN) and each further noise event (VN), and terminating the detection of atrial fibrillation when the noise counter reaches a predetermined limit.
