**1.3 Long RP interval vs. short RP interval**

The third step would be to determine the RP interval. SVT can be classified into two categories based on RP interval: Short RP (RP interval less than half of RR interval) and long RP (RP interval greater than half of RR interval) **Figures 4** and **5**. The RP interval is defined as the time interval between ventricular and atrial activation. On an ECG, an RP interval is the distance between the onset of the QRS complex and the end of the P wave. An approximate assumption would be that rhythms which originate from the AV node or perinodal tissue have a short RP interval and rhythms that originate elsewhere would have a long RP interval.
