Double ventricular response hy a single ventricular extrastimulus to the inner loop of reentry in a patient without apparent heart disease

In a patient without apparent heart disease, a ventricular extrastimulus de livered from the deft ventricular apex where the electrogram was recorded 3 0 ms after the onset of the QRS complex during VT advanced the second QRS c omplex, but not the first QRS complex. The morphology of the second QRS com plex was the same as that of VT. The post-pacing interval was the same as t he cycle length of the VT. These findings indicated that the site of stimul ation was at the inner loop of the reentry circuit of the VT. A ventricular extrastimulus with a shorter coupling interval advanced the first and seco nd QRS complexes, indicating that the ventricle was activated by antidromic and orthodromic activation from the extrastimulus. Radiofrequency ablation at that site of stimulation terminated the VT and no further VT could be i nduced.