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Short-term results of substrate mapping and radiofrequency ablation of ischemic ventricular tachycardia using a saline-irrigated catheter

Vivek Y. Reddy, MD, FACC^*,*, Petr Neuzil, MD, Milos Taborsky, MD and Jeremy N. Ruskin, MD, FACC^*

^* Cardiac Arrhythmia Service, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
Electrophysiology Section, Cardiology Division, Na Homolce Hospital, Prague, Czech Republic

View larger version (57K): [in a new window]   Figure 1 Substrate mapping and radiofrequency (RF) ablation in Patient #7. The scale ranges from 0.5 to 1.5 mV in the bipolar voltage map. Purple represents normal tissue, and red represents highly scarred tissue. The localized postero-basal infarction is seen in the postero-anterior view in the bipolar voltage map. The morphologies of the two major induced ventricular tachycardia (VTs) as well as the corresponding pace-mapping sites, are shown (arrows point to sites of stimulation). Pacing between these two sites (red dot) generated a QRS morphology that alternated between VT-1 and VT-2, but with a longer stimulus-QRS latency time. This site likely represented a common pathway for the two VT circuits and was incorporated in the ablation strategy (a geometry/mesh map is shown on the bottom right). No VT was inducible postablation. Each red dot represents a 1-min RF application.

View larger version (65K): [in a new window]   Figure 2 Substrate mapping and radiofrequency (RF) ablation in Patient #5 (a patient with both stable and unstable ventricular tachycardias [VTs]. A large anteroseptal and apical aneurysm is seen in the 30° right anterior oblique view in both the bipolar voltage (top) and EGM duration (middle) maps obtained during sinus rhythm. Pace-mapping (arrow) produced a QRS morphology similar to the predominant VT (cycle length [CL] 643 ms). Concealed entrainment was noted at this point, with a postpacing interval 25 ms greater than the VT CL. Ventricular tachycardia could not be induced when mechanical pressure was applied just inferior to this site (green dot). After the placement of two linear lesions, only an SWVT (CL 311 ms) that rapidly degenerated into VF was induced with programmed stimulation (right ventricular apex: 400/300/290/280).

View larger version (59K): [in a new window]   Figure 3 Substrate mapping and radiofrequency (RF) ablation in Patient #11. A large anterior infarction is noted in the bipolar voltage maps (right anterior oblique view in A and left anterior oblique-cranial view in B). The exit site of the clinically significant ventricular tachycardia (VT) was identified at the septal border of the scar (shown by arrow in A). This and two other VTs (not depicted) were successfully eliminated by the linear ablation strategy shown. Repeat programmed stimulation from two right ventricular sites (using triple extrastimuli and rapid pacing) failed to induce any arrhythmias, but stimulation from the left ventricle induced another hemodynamically unstable VT from the basal-lateral aspect of the scar (exit site shown by arrow in B). Adequate tissue contact could not be achieved using a retrograde aortic approach (as judged by fluoroscopic movement of the catheter within the cardiac silhouette, and by impedance monitoring). During an attempted transseptal puncture, the pericardial space was invaded and the procedure was terminated prematurely. This case was regarded a partial success.

View larger version (53K): [in a new window]   Figure 4 The border between the normal and infarcted/aneurysmal wall contains a stylized ventricular tachycardia (VT) circuit—predominantly endocardial, and partially intramural. The surgical procedures, subendocardial resection, and ventriculotomy are believed to either remove or transect critical endocardial portions of the VT circuit, respectively. After mapping the border zone using the electroanatomic mapping system, the putative exit site of the VT was identified with pace-mapping, and catheter-based linear lesions were placed. Although a single catheter-based linear lesion set along the scar border could potentially interrupt the circuit(s), unlike during surgery, one cannot ensure the lesion’s depth and continuity. Therefore, a second linear lesion set was placed proceeding into the scarred myocardium—with the hope that this empiric lesion set would transect critical portions of the VT circuit(s). LV = left ventricular. Figure reproduced and modified with permission, courtesy of J. Miller, MD, and Williams & Wilkins Inc. (19).