EP tracing of ventricular premature complexThe first two complexes are sinus beats. The A in these beats seen the coronary sinus electrode channels (CS910 to CS12) precede the V recorded in the HISP (His bundle proximal) channel. The QRS complexes of these beats are narrow as seen in the surface ECG recordings at the top (I, AVF, V1, V6). The third complex (VPC) is a ventricular premature complex. It is not preceded by A in the coronary sinus channels. Instead there is atrial activity after the V, indicating retrograde activation sequence (A’).