Differential response to right ventricular extrastimuli from the base and apex during long RP ′ supraventricular tachycardia

Figures

• 

  FIGURE 1. (A) A ventricular extrastimulus delivered from RVA during the HB refractory period. (B) Ventricular overdrive pacing from RVA. A, atrial potential; CS, coronary sinus; d, distal; F, fusion QRS; H, His potential; HIS, a bundle of His; p, proximal; P, paced QRS; RA, right atrium; RVA, apex of right ventricle; RVB, base of right ventricular; St, programmed stimulation.

• 

  FIGURE 2. (A) A ventricular extrastimulus delivered from the RVB during the HB refractory period also reset the tachycardia, resulting in a prolongation of both the A–A interval and the H–H interval. (B) An extrastimulus timed slightly before the HB refractory period from the same site resulted in the disappearance of the tachycardia resetting phenomenon. A, atrial potential; CS, coronary sinus; d, distal; F, fusion QRS; H, His potential; HIS, a bundle of His; p, proximal; P, paced QRS; RA, right atrium; RVA, apex of right ventricle; RVB, base of right ventricular; St, programmed stimulation.