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Background: Idiopathic premature ventricular complexes (PVCs) usually are considered benign, even when frequent. However, case reports have demonstrated a possible link between frequent PVCs and left ventricular (LV) dysfunction. In addition, frequent PVCs recently were demonstrated to be associated with increased LV dimensions and cardiomyopathy., Methods: Among 60 consecutive patients with idiopathic, frequent PVCs (>10/hour), a reduced LV ejection fraction (EF; mean 34% +/- 13%) was present in 22 (37%) patients. Patients with decreased LV function had a greater PVC burden on a 24-hour Holter monitor than patients with normal EF (37% +/- 13% vs. 11% +/- 10% of all QRS complexes; P <.0001). There was a significant inverse correlation between the PVC burden and the EF before ablation (r = 0.73, P <.0001)., Results: The PVCs originated in the right ventricular outflow tract in 31 (52%) of 60 patients, the LV outflow tract in 9 (15%) of 60 patients, and in other sites in 13 (22%) of 60 patients. The site of PVC origin could not be determined in seven patients. Ablation was completely successful in 48 (80%) patients. In patients with an abnormal EF before ablation, LV function normalized in 18 (82%) of 22 patients from a baseline of 34% to 59% +/- 7% (P <.0001) within 6 months. In the four patients in whom ablation was ineffective, the EF further declined from 34% +/- 10% to 25% +/- 7% (P = .06) during follow-up. In a control group of 11 patients with a similar PVC burden (30% +/- 8%) and a reduced EF (28% +/- 13%) who did not undergo ablation, the EF remained unchanged in 10/11 patients over 19 +/- 17 months of follow-up and one patient underwent heart transplantation., Conclusion: LV dysfunction in the setting of frequent, idiopathic PVCs may represent a form of cardiomyopathy that can be reversed by catheter ablation of the PVCs.

Objectives: The purpose of this study was to identify ventricular tachycardia (VT) isthmus sites by pace-mapping within scar tissue and to identify electrogram characteristics that are helpful in identifying VT isthmus sites during sinus rhythm (SR)., Background: Pace-mapping has been used in the scar border zone to identify the exit site of post-infarction VT., Methods: In 19 consecutive patients (18 men, mean age 66 +/- 9 years, mean ejection fraction 0.24 +/- 0.12) with post-infarction VT, a left ventricular voltage map was generated during SR. Pace-mapping was performed at sites with abnormal electrograms or isolated potentials. Radiofrequency ablation was performed at isthmus sites as defined by pace-mapping (perfect pace-map = 12/12 matching electrocardiogram leads; good pace-map = 10/12 to 11/12 matching electrocardiogram leads) and/or entrainment mapping., Results: A total of 81 VTs (mean cycle length 396 +/- 124 ms) were inducible. In 16 of the 19 patients, a total of 41 distinct isthmus areas of 41 distinct VTs were identified and successfully ablated. All but one displayed isolated potentials during SR. Furthermore, 22 of the 81 VTs (27%) for which no isthmus was identified became noninducible after ablation of a targeted VT. The 16 patients in whom > or =1 isthmus was identified and ablated were free of arrhythmic events during a mean follow-up of 10 months., Conclusions: During SR, excellent or good pace-maps at sites of isolated potentials within areas of scar identify areas of fixed block that are protected and part of the critical isthmus of post-infarction VT. Shared common pathways might explain why non-targeted VTs might become noninducible after ablation of other VTs.

Background: Mapping criteria for hemodynamically tolerated, postinfarction ventricular tachycardia (VT) have been evaluated in only small series of patients., Objectives: The purpose of this study was to evaluate the utility of various mapping criteria for identifying a critical VT circuit isthmus in a post hoc analysis., Methods: Ninety VTs (cycle length 491 +/- 84 ms) were mapped in 48 patients with a prior myocardial infarction. The mapping catheter was positioned within a protected area of the reentrant circuit of the targeted VTs at 176 sites. All sites showed concealed entrainment. The predictive values of the following mapping criteria for a successful ablation site were compared: discrete isolated potential during VT, inability to dissociate the isolated potential from the VT, endocardial activation time >70 ms, matching electrogram-QRS and stimulus-QRS intervals, VT termination without global capture during pacing, stimulus-QRS/VT cycle length ratio

Background: Mechanical trauma has been described as a helpful guide for ablation of atrial tachycardias and accessory pathways. In postinfarction ventricular tachycardia (VT), the reentrant circuit is partly endocardial and therefore may be susceptible to catheter trauma., Objectives: The purpose of this study was to determine the prevalence and significance of VT termination resulting from catheter trauma., Methods: A consecutive series of 39 patients (mean age 68 +/- 7 years, ejection fraction 0.25 +/- 0.02) underwent left ventricular mapping for postinfarction VT. Mapping was performed during 62 hemodynamically tolerated VTs (mean cycle length 451 +/- 88 ms). Only hemodynamically tolerated VTs that did not terminate spontaneously and VTs that were reproducibly inducible were included in the study. VT termination was considered mechanical only if it was not caused by a premature depolarization., Results: In 13 of 62 VTs (21%) in 8 of 39 patients (21%), either VT terminated during catheter placement at a particular site (n = 7) or a previously reproducibly inducible VT became no longer inducible with the mapping catheter located at a particular site (n = 6). The stimulus-QRS interval was significantly shorter at sites where mechanical trauma affected the reentrant circuit compared with sites having concealed entrainment (102 +/- 56 ms vs 253 +/- 134 ms, P = .003). At the site that was susceptible to mechanical trauma, the pace map was identical or highly similar in 13 of 13 VTs. After radiofrequency ablation at these sites, the targeted VTs were no longer inducible. No patient had recurrence of the targeted VT during a mean follow-up of 15 +/- 11 months., Conclusions: Catheter contact at a critical endocardial site can interrupt postinfarction VT or prevent its induction. Radiofrequency ablation at sites of mechanical termination of VT has a high probability of success.