CATHETER ABLATION OF VENTRICULAR-TACHYCARDIA AFTER MYOCARDIAL-INFARCTION - RELATION OF ENDOCARDIAL SINUS RHYTHM LATE POTENTIALS TO THE REENTRY CIRCUIT

Objectives. We sought to determine whether endocardial late potentials during sinus rhythm are associated with reentry circuit sites during ventricular tachycardia (VT). Background. During sinus rhythm, slow co nduction through an old infarct region may depolarize tissue after the end of the QRS complex. Such slow conduction regions can cause reentr y. Methods. Endocardial catheter mapping and radiofrequency ablation w ere performed in 24 patients vith VT late after myocardial infarction. We selected for analysis a total of 103 sites where the electrogram w as recorded during sinus rhythm and, without moving the catheter, VT w as initiated and radiofrequency current applied in an attempt to termi nate VT. Results. Late potentials were present at 34 sites (33%). Duri ng pace mapping, the stimulus-QRS complex was longer at late potential sites, consistent with slow conduction, than at sites without late po tentials (p < 0.0001). Late potentials were present at 15 (71%) of 21 sites classified as central or proximal in the reentry circuit based o n entrainment, but also occurred frequently at bystander sites (13 [33 %] of 39) and were often absent at the reentry circuit exit (3 [23%] o f 13). Late potentials were present at 20 (54%) of 37 sites where abla tion terminated VT, compared with 14 (21%) of 66 sites where ablation did not terminate VT (p = 0.004). Ablation decreased the amplitude of the late potentials present at sites where ablation terminated VT. Con clusions. Although sites,with sinus rhythm late potentials often parti cipate in VT reentry circuits, many reentry circuit sites do not have late potentials. Late potentials can also arise from bystander regions , Late potentials may help identify abnormal regions in sinus rhythm b ut cannot replace mapping during induced VT to guide ablation. (C) 199 7 by the American College of Cardiology.