Figure 4. Susceptibility to the onset of ventricular tachyarrhythmias assessed during programmed electrical stimulation.

A: Programmed electrical stimulation (PES) was performed with a dedicated bipolar catheter, which was advanced anterogradely into the right ventricle. A train of N=20 impulses at 100ms of basal cycle length followed by three extrastimuli at 50ms was used in each case; no arrhythmias were inducible in rats from neither SHAM nor SHAM+ VAL groups. B: R-on-T phenomena before and after stimulation in hypertrophied rat hearts with the induction of a sustained ventricular tachycardia at the end of stimulation. C: In contrast, after valsartan administration only ventricular extra beats were inducible in hypertrophied rats in which stable sinus rhythm was restored at the end of stimulation. Central strips from each panel start from previously recorded 1000ms of respective upper strips, as for bottom strips from panels A and C, whereas bottom strip from panel B is postponed of 24 seconds due to induction of sustained ventricular tachycardia.