A system and method for ECG data classification for use in facilitating diagnosis of cardiac rhythm disorders is provided. ECG data is obtained via an electrocardiography monitor with a patient button. A press of the patient button is identified within the ECG data. A button window with a segment of data prior to and after the button press is defined within the ECG data. The ECG data is divided into blocks. Noise detection analysis is applied to the data blocks. A classification of noise or valid data is assigned to each data block based on the noise detection analysis. At least one data block that overlaps the button window is assigned the noise classification. The at least one data block is trimmed to align with one of the start and end of the button window. The trimmed blocks assigned with the noise classification are removed from the data.