Use of a novel fragmentation map to identify the substrate for ventricular tachycardia in postinfarction cardiomyopathy.

BACKGROUND: Substrate ablation is commonly performed in patients with postinfarction cardiomyopathy and ventricular tachycardia (VT). Recognition of fragmented and late potentials during sinus rhythm is a tedious process subject to operator fatigue. OBJECTIVE: The purpose of this study was to assess the value of automated analysis to quantify electrogram fragmentation and to determine the relationship of fragmented regions to the VT isthmus. METHODS: Detailed left ventricular (LV) mapping was performed in 2 groups: (1) 14 patients with previous myocardial infarction and tolerated VT and (2) 14 controls with structurally normal hearts. In patients with VT, mid-isthmus sites were identified using entrainment mapping. Sinus rhythm endocardial LV electrograms underwent time- and frequency-domain analysis and were displayed as fragmentation or frequency maps. The region of fractionated electrograms and their relation to the VT isthmus sites were determined. RESULTS: Cutoffs for abnormal electrogram fragmentation were ventricular fractionation index ≥ 7 and fast Fourier transform ratio ≥ 14%, respectively. In the time domain, LV surface area with fractionated electrograms was significantly smaller than the total scar surface area (27.3% ± 7.1% vs 42.1% ± 12.3%, P <.001), yet contained 100% of VT isthmus sites. In the frequency domain, areas of abnormal fractionation occupied 9.7% ± 6.9% of total LV surface area and included only 60% of the VT isthmus sites. CONCLUSION: Automated electrogram fractionation analysis represents an objective tool to rapidly quantify electrogram fragmentation and guide substrate-based ablation of VT. Empiric ablation of these regions may be a new strategy for substrate-guided VT ablation.

Incremental pacing maneuver for atrial flutter recurrence reduction after ablation: Vallès: yield of incremental pacing after flutter ablation.

BACKGROUND: A < 20 ms increase in the interval between cavo-tricuspid isthmus (CTI) double potentials during incremental pacing (IP) is a highly specific marker differentiating functional from complete CTI block during typical flutter (AFL) ablation. Long-term effects of IP remain unclear. We aimed to assess the impact of IP in reducing AFL recurrences after CTI ablation. METHODS: One hundred and thirty-four patients (age 67 ± 13 years, 78% males) undergoing successful CTI ablation were included and divided into 2 groups: Group 1 (n = 68), in which ablation was performed before the IP maneuver was incorporated, with CTI block confirmed by at least 1 non-local and 1 local electrogram-based previously established criteria; and Group 2 (n = 66), in which IP maneuver was used to confirm complete CTI block. RESULTS: No intergroup differences were noted in baseline characteristics, ablation settings and fluoroscopy/radiofrequency times. Long-term AFL recurrences were observed in 14 out of 134 patients (10.4%), and were more common in Group 1 (19%, vs 1.5% among Group 2 patients, p < 0,001). Despite a longer follow-up period among the former group (1603 ± 734 vs. 964 ± 289 days, respectively), the adjusted AFL recurrence rate was still higher among Group 1 patients (4.3%/year vs. 0.6%/year, p < 0,001). Cox-regression analysis confirmed inclusion in Group 1 as the only predictor of AFL recurrences (HR = 8.2, CI 1.04-64.7, p = 0.046). CONCLUSIONS: The addition of the IP maneuver for the diagnosis of complete CTI block reduces AFL long-term recurrences after ablation.

Incremental His-to-coronary sinus maneuver: a nonlocal electrogram-based technique to assess complete cavotricuspid isthmus block during typical flutter ablation.

BACKGROUND: Achievement of complete cavotricuspid isthmus (CTI) conduction block reduces typical atrial flutter recurrences after ablation. The lack of increase in the His-to-coronary sinus ostium atrial interval during incremental pacing (IP) from the low lateral right atrium may distinguish slow conduction from complete CTI conduction block. METHODS AND RESULTS: Sixty-six consecutive patients (age, 65±13 years; 18% female) were prospectively included. A <10 ms increase in the His-to-coronary sinus ostium atrial timing during low lateral right atrium IP at cycle length of 600 ms through 300 ms was compared with the previously reported IP maneuver for the confirmation of complete CTI block. On the basis of the IP maneuver, complete CTI block (phase 2) was achieved in 59 patients, in 13 of whom an intermediate phase of functional CTI block (phase 1) was observed. In the remaining 7 patients, the IP maneuver did not allow for assessment of complete CTI block because of the presence of inconclusive potentials in the CTI ablation line. As compared with the IP maneuver, the incremental His-to-coronary sinus ostium maneuver was consistent with functional CTI block during phase 1 in all cases and conclusive of complete CTI block in 98% of cases during phase 2. CONCLUSIONS: The incremental His-to-coronary sinus ostium maneuver is analogous to the IP maneuver in distinguishing complete CTI block from persistent CTI conduction. This maneuver may provide confirmation of CTI block in those patients in whom assessment of local electrogram-based criteria is not feasible because of inconclusive potentials in the CTI ablation line.

New unipolar electrogram criteria to identify irreversibility of nonischemic left ventricular cardiomyopathy.

OBJECTIVES: This study sought to assess the value of left ventricular (LV) endocardial unipolar electroanatomical mapping (EAM) in identifying irreversibility of LV systolic dysfunction in patients with left ventricular nonischemic cardiomyopathy (LVCM). BACKGROUND: Identifying irreversibility of LVCM would be helpful but cannot be reliably accomplished by bipolar EAM or cardiac magnetic resonance identification of macroscopic scar. METHODS: Detailed endocardial LV EAM was performed in 3 groups: 1) 24 patients with irreversible LVCM (I-LVCM) but with no or minimal macroscopic scar (<15% LV surface) evidenced on bipolar voltage EAM and/or cardiac magnetic resonance; 2) 14 patients with reversible ventricular premature depolarization-mediated LVCM (R-LVCM); and 3) 17 patients with structurally normal hearts. LV endocardial unipolar electrogram amplitude and area of unipolar amplitude abnormality were defined after excluding macroscopic scar. RESULTS: Unipolar amplitude differed in the 3 groups: median of 7.6 (interquartile range [IQR]: 5.5 to 9.7) mV in I-LVCM group, 13.2 (IQR: 10.4 to 16.2) mV in R-LVCM group, and 16.3 (IQR: 13.6 to 19.8) mV in structurally normal hearts group (p < 0.001). Areas of unipolar abnormality represented a large proportion of total LV surface in I-LVCM, 64.7% (IQR: 47.5% to 75.9%) compared with R-LVCM, 5.2% (IQR: 0.0% to 19.1%) and structurally normal hearts, 0.1% (IQR: 0.0% to 0.9%), groups (p < 0.001). A unipolar abnormality area cutoff of 32% of total LV surface was 96% sensitive and 100% specific in identifying irreversible cardiomyopathy among patients with LV dysfunction (I-LVCM and R-LVCM), p < 0.001. CONCLUSIONS: Detailed unipolar voltage mapping can identify irreversible myocardial dysfunction consistent with fibrosis, even in the absence of bipolar EAM or cardiac magnetic resonance abnormalities, and may serve as valuable prognostic tool in patients presenting with LVCM to facilitate clinical decision making.

Use of a novel endoscopic catheter for direct visualization and ablation in an ovine model of chronic myocardial infarction.

BACKGROUND: Defining the arrhythmogenic substrate is essential for successful ablation of scar-related ventricular tachycardia. The visual characteristics of endocardial ischemic scar have not been described in vivo. The goal of this study was (1) to quantify the visual characteristics of normal tissue, scar border zone, and dense scar in vivo with the use of a novel endoscopic catheter that allows direct endocardial visualization and (2) to correlate visual attributes of myocardial scar with bipolar voltage. METHODS AND RESULTS: Percutaneous transient balloon occlusion (150 minutes) of the mid left anterior descending coronary artery was performed in an ovine model. Animals survived for 41.5±0.7 days. Detailed bipolar voltage maps of the left ventricle were acquired with the use of NavX. Video snapshots of the endocardium were acquired at sites distributed throughout the left ventricle. Visual tissue characteristics of normal (>1.5 mV), border (0.5-1.5 mV), and dense scar (<0.5 mV) were quantified with the use of image processing. Radiofrequency lesions (10-20 W, 30 seconds) were delivered under direct visualization. Mean white-threshold pixel area was lowest in normal tissue (189 969±41 478 pixels(2)), intermediate in scar border zone (255 979±36 016 pixels(2)), and highest in dense scar (324 452±30 152 pixels(2); P<0.0001 for all pairwise comparisons). Tissue whiteness, characteristic of scar, was inversely correlated with bipolar voltage (P<0.0001). During radiofrequency lesions, there was a significant increase in white-thresholded pixel area of the visual field after ablation (average increase, 85 381±52 618 pixels(2); P<0.001). CONCLUSIONS: Visual characteristics of chronic infarct scar in vivo observed with the use of a novel endoscopic catheter correlate with bipolar electrogram voltage. Irrigated radiofrequency lesions in normal endocardial tissue and postinfarction zone can be visualized and quantified with the use of image processing. This technology shows promise for visually based delivery of radiofrequency lesions for the treatment of scar-based ventricular tachycardia.