a 68-year - old male with a history of palpitations was referred to our hospital for further evaluation . baseline ecg showed sinus rhythm and frequent premature ventricular extrasystoles ( pves ) with a relatively narrow qrs complex ( 115  ms ) , an inferior axis ( tall r waves in leads ii , iii , and avf ) , a qr pattern in lead v1 with no transition zone , and absence of s wave in lead v5 or v6 ( figure 1(a ) ) . an electrophysiological study was then carried out , where a detailed activation mapping of the pves was performed using a 3-dimentional electroanatomical mapping system ( carto 3 , biosense webster , inc . , diamond bar , calif , usa ) . left ventricular ( lv ) mapping was performed using a 4 mm tip deflectable catheter ( navistar , biosense webster ) . the earliest local activation site of the pves ( preceding the onset of the surface qrs by 40  ms ) was identified at the aortomitral continuity of the basal lv ( figure 1(b ) ) . ( 12 of 12 leads ) with the morphology of the pves ( figure 1(c ) ) . the first radiofrequency ( rf ) energy application ( target temperature of 60c , 30  w , 60  s , and impedance drop of 510  ohms ) abolished all the pvbs arising from the aortomitral continuity ( figure 2 ) . additional rf applications ( total ablation time up to 180  s ) were delivered at this region in order to ensure a long - term success ( red dots in figure 2 ) . lv outflow tract ventricular arrhythmias originating from the aortomitral continuity , the left coronary cusp , the superior basal septum , and the epicardial left ventricular summit display common electrocardiographic and electrophysiological features , probably due to the close proximity of those locations [ 13 ] . data regarding ventricular arrhythmias arising from the aortomitral continuity are limited and conflicting [ 13 ] . have shown that pves arising from the aortomitral continuity display narrow qrs complexes , tall r waves in inferior leads ( particularly in lead ii ) , predominantly positive forces in lead i ( where superior and lateral basal sites display negative forces ) , and a qr pattern in lead v1 . have demonstrated the occurrence of a qr pattern in lead v1 and s wave in lead v5 or v6 in 50% of patients with pves arising from aortomitral continuity . the absence of s wave in lead v5 or v6 favours the diagnosis of pves originating from the left coronary cusp or the epicardial left ventricular summit . in a different study , kumagai et al . have shown that all patients with pves arising from the aortomitral continuity exhibit monophasic r waves without s waves in almost all precordial leads . these investigators failed to demonstrate a qr pattern in lead v1 or s wave in lead v6 .