**2.1 Time domain of an ECG signal**

P, Q, R, S, T and U are specific wave forms identified in the time domain of an ECG signal. The QRS complex, formed by Q, R and S waves, represents a relevant wave form because the heart rate can be identified locating two successive QRS complex. Figure 2 presents typical waves in an ECG signal.

Fig. 2. Typical wave forms of an ECG signal record
