Techniques for determining reliability of electrocardiogram (ECG) data are disclosed. ECG data, including waveform data relating to a detected heartbeat for a patient, is received. A peak amplitude associated with an R-wave in the waveform data is determined. First and second baseline regions in the waveform data are identified. The first baseline region precedes the R-wave and the second baseline region follows the R-wave. A signal-to-noise ratio (SNR) is determined, based on the peak amplitude, the first baseline region, and the second baseline region. A confidence metric relating to the waveform data is determined, based on the determined SNR. The confidence metric is used in medical treatment related to the patient.
